VLA observations of a complete sample of extragalactic X-ray sources. II

NASA Technical Reports Server (NTRS)

Schild, R.; Zamorani, G.; Gioia, I. M.; Feigelson, E. D.; Maccacaro, T.

1983-01-01

A complete sample of 35 X-ray selected sources found with the Einstein Observatory has been observed with the Very Large Array at 6 cm to investigate the relationship between radio and X-ray emission in extragalactic objects. Detections include three active galactic nuclei (AGNs), two clusters or groups of galaxies, two individual galaxies, and two BL Lac objects. The frequency of radio emission in X-ray selected AGNs is compared with that of optically selected quasars using the integral radio-optical luminosity function. The result suggests that the probability for X-ray selected quasars to be radio sources is higher than for those optically selected. No obvious correlation is found in the sample between the richness of X-ray luminosity of the cluster and the presence of a galaxy with radio luminosity at 5 GHz larger than 10 to the 30th ergs/s/Hz.

A Synthesis Of Cosmic X-ray And Infrared Background

NASA Astrophysics Data System (ADS)

Shi, Yong; Helou, G.; Armus, L.; Stierwalt, S.

2012-01-01

We present a synthesis model of cosmic IR and X-ray background, with the goal to derive a complete census of cosmic evolution of star formation (SF) and black-hole (BH) growth by complementing advantages of X-ray and IR surveys to each other. By assuming that individual galaxies are experiencing both SF and BH accretion, our model decomposes the total IR LF into SF and BH components while taking into account the luminosity-dependent SED and its dispersion of the SF component, and the extinction-dependent SED of the BH component. The best-fit parameters are derived by fitting to the number counts and redshift distributions at X-ray including both hard and soft bands, and mid-IR to submm bands including IRAS, Spitzer, Herschel, SCUBA, Aztec and MAMBO. Based on the fit result, our models provide a series of predictions on galaxy evolution and black-hole growth. For evolution of infrared galaxies, the model predicts that the total infrared luminosity function is best described through evolution in both luminosity and density. For evolution of AGN populations, the model predicts that the evolution of X-ray LF also shows luminosity and density dependent, that the type-1/type-2 AGN fraction is a function of both luminosity and redshift, and that the Compton-thick AGN number density evolves strongly with redshift, contributing about 20% to the total cosmic BH growth. For BH growth in IR galaxies, the model predicts that the majority of BH growth at z>1 occurs in infrared luminous galaxies and the AGN fraction as a function of IR survey is a strong function of the survey depth, ranging from >50% at bright end to below 10% at faint end. We also evaluates various AGN selection techniques at X-ray and IR wavelengths and offer predictions for future missions at X-ray and IR.

The 5-10 keV AGN luminosity function at 0.01 < z < 4.0

NASA Astrophysics Data System (ADS)

Fotopoulou, S.; Buchner, J.; Georgantopoulos, I.; Hasinger, G.; Salvato, M.; Georgakakis, A.; Cappelluti, N.; Ranalli, P.; Hsu, L. T.; Brusa, M.; Comastri, A.; Miyaji, T.; Nandra, K.; Aird, J.; Paltani, S.

2016-03-01

The active galactic nuclei (AGN) X-ray luminosity function traces actively accreting supermassive black holes and is essential for the study of the properties of the AGN population, black hole evolution, and galaxy-black hole coevolution. Up to now, the AGN luminosity function has been estimated several times in soft (0.5-2 keV) and hard X-rays (2-10 keV). AGN selection in these energy ranges often suffers from identification and redshift incompleteness and, at the same time, photoelectric absorption can obscure a significant amount of the X-ray radiation. We estimate the evolution of the luminosity function in the 5-10 keV band, where we effectively avoid the absorbed part of the spectrum, rendering absorption corrections unnecessary up to NH ~ 1023 cm-2. Our dataset is a compilation of six wide, and deep fields: MAXI, HBSS, XMM-COSMOS, Lockman Hole, XMM-CDFS, AEGIS-XD, Chandra-COSMOS, and Chandra-CDFS. This extensive sample of ~1110 AGN (0.01 < z < 4.0, 41 < log Lx < 46) is 98% redshift complete with 68% spectroscopic redshifts. For sources lacking a spectroscopic redshift estimation we use the probability distribution function of photometric redshift estimation specifically tuned for AGN, and a flat probability distribution function for sources with no redshift information. We use Bayesian analysis to select the best parametric model from simple pure luminosity and pure density evolution to more complicated luminosity and density evolution and luminosity-dependent density evolution (LDDE). We estimate the model parameters that describe best our dataset separately for each survey and for the combined sample. We show that, according to Bayesian model selection, the preferred model for our dataset is the LDDE. Our estimation of the AGN luminosity function does not require any assumption on the AGN absorption and is in good agreement with previous works in the 2-10 keV energy band based on X-ray hardness ratios to model the absorption in AGN up to redshift three. Our sample does not show evidence of a rapid decline of the AGN luminosity function up to redshift four.

Studies of the evolution of the x ray emission of clusters of galaxies

NASA Technical Reports Server (NTRS)

Henry, J. Patrick

1990-01-01

The x ray luminosity function of clusters of galaxies was determined at different cosmic epoches using data from the Einstein Observatory Extended Medium Survey. The sample consisted of 67 x ray selected clusters that were grouped into three redshift shells. Evolution was detected in the x ray properties of clusters. The present volume density of high luminosity clusters was found to be greater than it was in the past. This result is the first convincing evidence for evolution in the x ray properties of clusters. Investigations into the constraints provided by these data on various Cold Dark Matter models are underway.

X-ray emission at the low-mass end - Results from an extensive Einstein Observatory survey

NASA Technical Reports Server (NTRS)

Barbera, M.; Micela, G.; Sciortino, S.; Harnden, F. R., Jr.; Rosner, R.

1993-01-01

We have used available IPC data and a critical compilation of cataloged optical data to measure the 0.16-3.5 keV X-ray emission from 88 K and 169 M stars of luminosity classes IV, V, and VI within 25 pc from the Sun. The IPC detected 54 out of the 88 K stars, 70 out of the 138 M stars with M(v) less than 13.4, and 15 out of the 31 fainter M stars. We have identified a subsample of surveyed stars that is statistically representative of the population of K and M stars in the solar neighborhood. On the basis of this subsample (1) we have shown the occurrence of a drop in the level of X-ray emission for M stars later than approximately M5; (2) we have built unbiased maximum likelihood X-ray luminosity functions for the K, early M, and late M stars; (3) we have confirmed, both for K and M stars, the decrease of X-ray luminosity with increasing stellar age in the range of ages of disk population stars: and (4) we have shown that no obvious correlation is present between X-ray and bolometric luminosities in the entire representative samples of K and M stars, but only within flare stars which also seem to mark a saturation in X-ray luminosity level.

Hard X-ray luminosity function of tidal disruption events: First results from the MAXI extragalactic survey

NASA Astrophysics Data System (ADS)

Kawamuro, Taiki; Ueda, Yoshihiro; Shidatsu, Megumi; Hori, Takafumi; Kawai, Nobuyuki; Negoro, Hitoshi; Mihara, Tatehiro

2016-08-01

We derive the first hard X-ray luminosity function (XLF) of stellar tidal disruption events (TDEs) by supermassive black holes (SMBHs), which gives an occurrence rate of TDEs per unit volume as a function of peak luminosity and redshift, utilizing an unbiased sample observed by the Monitor of All-sky X-ray Image (MAXI). On the basis of the light curves characterized by a power-law decay with an index of -5/3, a systematic search using the MAXI data detected four TDEs in the first 37 months of observations, all of which have been found in the literature. To formulate the TDE XLF, we consider the mass function of SMBHs, that of disrupted stars, the specific TDE rate as a function of SMBH mass, and the fraction of TDEs with relativistic jets. We perform an unbinned maximum likelihood fit to the MAXI TDE list and check the consistency with the observed TDE rate in the ROSAT all-sky survey. The results suggest that the intrinsic fraction of the jet-accompanying events is 0.0007%-34%. We confirm that at z ≲ 1.5 the contamination of the hard X-ray luminosity functions of active galactic nuclei by TDEs is not significant and hence that their contribution to the growth of SMBHs is negligible at the redshifts.

Supernova remnants in M33: X-ray properties as observed by XMM-Newton

NASA Astrophysics Data System (ADS)

Garofali, Kristen; Williams, Benjamin F.; Plucinsky, Paul P.; Gaetz, Terrance J.; Wold, Brian; Haberl, Frank; Long, Knox S.; Blair, William P.; Pannuti, Thomas G.; Winkler, P. Frank; Gross, Jacob

2017-11-01

We have carried out a study of the X-ray properties of the supernova remnant (SNR) population in M33 with XMM-Newton, comprising deep observations of eight fields in M33 covering all of the area within the D25 contours, and with a typical luminosity of 7.1 × 1034 erg s-1 (0.2-2.0 keV). Here, we report our work to characterize the X-ray properties of the previously identified SNRs in M33, as well as our search for new X-ray detected SNRs. With our deep observations and large field of view we have detected 105 SNRs at the 3σ level, of which 54 SNRs are newly detected in X-rays, and three are newly discovered SNRs. Combining XMM-Newton data with deep Chandra survey data allows detailed spectral fitting of 15 SNRs, for which we have measured temperatures, ionization time-scales and individual abundances. This large sample of SNRs allows us to construct an X-ray luminosity function, and compare its shape to luminosity functions from host galaxies of differing metallicities and star formation rates to look for environmental effects on SNR properties. We conclude that while metallicity may play a role in SNR population characteristics, differing star formation histories on short time-scales, and small-scale environmental effects appear to cause more significant differences between X-ray luminosity distributions. In addition, we analyse the X-ray detectability of SNRs, and find that in M33 SNRs with higher [S II]/H α ratios, as well as those with smaller galactocentric distances, are more detectable in X-rays.

X-ray Point Source Populations in Spiral and Elliptical Galaxies

NASA Astrophysics Data System (ADS)

Colbert, E.; Heckman, T.; Weaver, K.; Ptak, A.; Strickland, D.

2001-12-01

In the years of the Einstein and ASCA satellites, it was known that the total hard X-ray luminosity from non-AGN galaxies was fairly well correlated with the total blue luminosity. However, the origin of this hard component was not well understood. Some possibilities that were considered included X-ray binaries, extended upscattered far-infrared light via the inverse-Compton process, extended hot 107 K gas (especially in ellipitical galaxies), or even an active nucleus. Now, for the first time, we know from Chandra images that a significant amount of the total hard X-ray emission comes from individual X-ray point sources. We present here spatial and spectral analyses of Chandra data for X-ray point sources in a sample of ~40 galaxies, including both spiral galaxies (starbursts and non-starbursts) and elliptical galaxies. We shall discuss the relationship between the X-ray point source population and the properties of the host galaxies. We show that the slopes of the point-source X-ray luminosity functions are different for different host galaxy types and discuss possible reasons why. We also present detailed X-ray spectral analyses of several of the most luminous X-ray point sources (i.e., IXOs, a.k.a. ULXs), and discuss various scenarios for the origin of the X-ray point sources.

Measuring the X-ray luminosities of SDSS DR7 clusters from ROSAT All Sky Survey

NASA Astrophysics Data System (ADS)

Wang, Lei; Yang, Xiaohu; Shen, Shiyin; Mo, H. J.; van den Bosch, Frank C.; Luo, Wentao; Wang, Yu; Lau, Erwin T.; Wang, Q. D.; Kang, Xi; Li, Ran

2014-03-01

We use ROSAT All Sky Survey broad-band X-ray images and the optical clusters identified from Sloan Digital Sky Survey Data Release 7 to estimate the X-ray luminosities around ˜65 000 candidate clusters with masses ≳ 1013 h- 1 M⊙ based on an optical to X-ray (OTX) code we develop. We obtain a catalogue with X-ray luminosity for each cluster. This catalogue contains 817 clusters (473 at redshift z ≤ 0.12) with signal-to-noise ratio >3 in X-ray detection. We find about 65 per cent of these X-ray clusters have their most massive member located near the X-ray flux peak; for the rest 35 per cent, the most massive galaxy is separated from the X-ray peak, with the separation following a distribution expected from a Navarro-Frenk-White profile. We investigate a number of correlations between the optical and X-ray properties of these X-ray clusters, and find that the cluster X-ray luminosity is correlated with the stellar mass (luminosity) of the clusters, as well as with the stellar mass (luminosity) of the central galaxy and the mass of the halo, but the scatter in these correlations is large. Comparing the properties of X-ray clusters of similar halo masses but having different X-ray luminosities, we find that massive haloes with masses ≳ 1014 h- 1 M⊙ contain a larger fraction of red satellite galaxies when they are brighter in X-ray. An opposite trend is found in central galaxies in relative low-mass haloes with masses ≲ 1014 h- 1 M⊙ where X-ray brighter clusters have smaller fraction of red central galaxies. Clusters with masses ≳ 1014 h- 1 M⊙ that are strong X-ray emitters contain many more low-mass satellite galaxies than weak X-ray emitters. These results are also confirmed by checking X-ray clusters of similar X-ray luminosities but having different characteristic stellar masses. A cluster catalogue containing the optical properties of member galaxies and the X-ray luminosity is available at http://gax.shao.ac.cn/data/Group.html.

Luminosity correlations in quasars

NASA Technical Reports Server (NTRS)

Chanan, G. A.

1983-01-01

Simulations are conducted with and without flux thresholds in an investigation of quasar luminosity correlations by means of a Monte Carlo analysis, for various model distributions of quasars in X-rays and optical luminosity. For the case where the X-ray photons are primary, an anticorrelation between X-ray-to-optical luminosity ratio and optical luminosity arises as a natural consequence which resembles observations. The low optical luminosities of X-ray selected quasars can be understood as a consequence of the same effect, and similar conclusions may hold if the X-ray and optical luminosities are determined independently by a third parameter, although they do not hold if the optical photons are primary. The importance of such considerations is demonstrated through a reanalysis of the published X-ray-to-optical flux ratios for the 3CR sample.

Clustering, Cosmology and a New Era of Black Hole Demographics: The Conditional Luminosity Function of AGNs

NASA Astrophysics Data System (ADS)

Ballantyne, David R.

2016-04-01

Deep X-ray surveys have provided a comprehensive and largely unbiased view of AGN evolution stretching back to z˜5. However, it has been challenging to use the survey results to connect this evolution to the cosmological environment that AGNs inhabit. Exploring this connection will be crucial to understanding the triggering mechanisms of AGNs and how these processes manifest in observations at all wavelengths. In anticipation of upcoming wide-field X-ray surveys that will allow quantitative analysis of AGN environments, we present a method to observationally constrain the Conditional Luminosity Function (CLF) of AGNs at a specific z. Once measured, the CLF allows the calculation of the AGN bias, mean dark matter halo mass, AGN lifetime, halo occupation number, and AGN correlation function - all as a function of luminosity. The CLF can be constrained using a measurement of the X-ray luminosity function and the correlation length at different luminosities. The method is demonstrated at z ≈0 and 0.9, and clear luminosity dependence in the AGN bias and mean halo mass is predicted at both z. The results support the idea that there are at least two different modes of AGN triggering: one, at high luminosity, that only occurs in high mass, highly biased haloes, and one that can occur over a wide range of halo masses and leads to luminosities that are correlated with halo mass. This latter mode dominates at z<0.9. The CLFs for Type 2 and Type 1 AGNs are also constrained at z ≈0, and we find evidence that unobscured quasars are more likely to be found in higher mass halos than obscured quasars. Thus, the AGN unification model seems to fail at quasar luminosities.

Evolution of the X-ray luminosity in young HII galaxies

NASA Astrophysics Data System (ADS)

Rosa González, D.; Terlevich, E.; Jiménez Bailón, E.; Terlevich, R.; Ranalli, P.; Comastri, A.; Laird, E.; Nandra, K.

2009-10-01

In an effort to understand the correlation between X-ray emission and present star formation rate, we obtained XMM-Newton data to estimate the X-ray luminosities of a sample of actively star-forming HII galaxies. The obtained X-ray luminosities are compared to other well-known tracers of star formation activity such as the far-infrared and the ultraviolet luminosities. We also compare the obtained results with empirical laws from the literature and with recently published analysis applying synthesis models. We use the time delay between the formation of the stellar cluster and that of the first X-ray binaries, in order to put limits on the age of a given stellar burst. We conclude that the generation of soft X-rays, as well as the Hα or infrared luminosities is instantaneous. The relation between the observed radio and hard X-ray luminosities, on the other hand, points to the existence of a time delay between the formation of the stellar cluster and the explosion of the first massive stars and the consequent formation of supernova (SN) remnants and high-mass X-ray binaries, which originate the radio and hard X-ray fluxes, respectively. When comparing hard X-rays with a star formation indicator that traces the first million years of evolution (e.g. Hα luminosities), we found a deficit in the expected X-ray luminosity. This deficit is not found when the X-ray luminosities are compared with infrared luminosities, a star formation tracer that represents an average over the last 108yr. The results support the hypothesis that hard X-rays are originated in X-ray binaries which, as SN remnants, have a formation time delay of a few mega years after the star-forming burst. Partially based on observations obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA. E-mail: danrosa@inaoep.mx ‡ Visiting Fellow, IoA, Cambridge, UK.

A deep survey of the X-ray binary populations in the SMC

NASA Astrophysics Data System (ADS)

Zezas, A.; Antoniou, V.

2017-10-01

The Small Magellanic Cloud (SMC) has been the subject of systematic X-ray surveys over the past two decades, which have yielded a rich population of high-mass X-ray binaries consisting predominantly of Be/X-ray binaries. We present results from our deep Chandra survey of the SMC which targeted regions with stellar populations ranging between ˜10-100 Myr. X-ray luminosities down to ˜3×10^{32} erg/s were reached, probing all active accreting binaries and extending well into the regime of quiescent accreting binaries and X-ray emitting normal stars. We measure the dependence of the formation efficiency of X-ray binaries on age. We also detect pulsations from 19 known and one new candidate pulsar. We construct the X-ray luminosity function in different regions of the SMC, which shows clear evidence for the propeller effect the centrifugal inhibition of accretion due to the interaction of the accretion flow with the pulsar's magnetic field. Finally we compare these results with predictions for the formation efficiency of X-ray binaries as a function of age from X-ray binary population synthesis models.

Hard X-Ray Emission and the Ionizing Source in LINERs

NASA Technical Reports Server (NTRS)

Terashima, Yuichi; Ho, Luis C.; Ptak, Andrew F.

2000-01-01

We report X-ray fluxes in the 2-10 keV band from LINERs (low-ionization nuclear emission-line regions) and low-luminosity Seyfert galaxies obtained with the ASCA satellite. Observed X-ray luminosities are in the range between 4 x 10(exp 39) and 5 x 10(exp 41) ergs/s, which are significantly smaller than that of the "classical" low-luminosity Seyfert 1 galaxy NGC 4051. We found that X-ray luminosities in 2-10 keV of LINERs with broad H.alpha emission in their optical spectra (LINER 1s) are proportional to their Ha luminosities. This correlation strongly supports the hypothesis that the dominant ionizing source in LINER 1s is photoionization by hard photons from low-luminosity AGNs. On the other hand, the X-ray luminosities of most LINERs without broad H.alpha emission (LINER 2s) in our sample are lower than LINER 1s at a given H.alpha luminosity. The observed X-ray luminosities in these objects are insufficient to power their H.alpha luminosities, suggesting that their primary ionizing source is other than an AGN, or that an AGN, if present, is obscured even at energies above 2 keV.

Clustering, Cosmology and a New Era of Black Hole Demographics: The Conditional Luminosity Function of AGNs

NASA Astrophysics Data System (ADS)

Ballantyne, David R.

2017-01-01

Deep X-ray surveys have provided a comprehensive and largely unbiased view of active galactic nuclei (AGN) evolution stretching back to z~5. However, it has been challenging to use the survey results to connect this evolution to the cosmological environment that AGNs inhabit. Exploring this connection will be crucial to understanding the triggering mechanisms of AGNs and how these processes manifest in observations at all wavelengths. In anticipation of upcoming wide-field X-ray surveys that will allow quantitative analysis of AGN environments, we present a method to observationally constrain the Conditional Luminosity Function (CLF) of AGNs at a specific z. Once measured, the CLF allows the calculation of the AGN bias, mean dark matter halo mass, AGN lifetime, halo occupation number, and AGN correlation function -- all as a function of luminosity. The CLF can be constrained using a measurement of the X-ray luminosity function and the correlation length at different luminosities. The method is illustrated at z≈0 and 0.9 using the limited data that is currently available, and a clear luminosity dependence in the AGN bias and mean halo mass is predicted at both, supporting the idea that there are at least two different modes of AGN triggering. In addition, the CLF predicts that z≈0.9 quasars may be commonly hosted by haloes with Mh ~ 1014 M⊙. These `young cluster' environments may provide the necessary interactions between gas-rich galaxies to fuel luminous accretion. The results derived from this method will be useful to populate AGNs of different luminosities in cosmological simulations.

Accounting for the dispersion in the x ray properties of early-type galaxies

NASA Technical Reports Server (NTRS)

White, Raymond E., III; Sarazin, Craig L.

1990-01-01

The x ray luminosities of early-type galaxies are correlated with their optical (e.g., blue) luminosities (L sub X approx. L sub B exp 1.6), but the x ray luminosities exhibit considerable scatter for a given optical luminosity L sub B. This dispersion in x ray luminosity is much greater than the dispersion of other properties of early-type galaxies (for a given L sub B), such as luminosity scale-length, velocity dispersion, color, and metallicity. Here, researchers consider several possible sources for the dispersion in x ray luminosity. Some of the scatter in x ray luminosity may result from stellar population variations between galaxies with similar L sub B. Since the x ray emitting gas is from accumulated stellar mass loss, the L sub X dispersion may be due to variations in integrated stellar mass loss rates. Another possible cause of the L sub X dispersion may be variations in the amount of cool material in the galaxies; cool gas may act as an energy sink for the hot gas. Infrared emission may be used to trace such cool material, so researchers look for a correlation between the infrared emission and the x ray emission of early-type galaxies at fixed L sub B. Velocity dispersion variations between galaxies of similar L sub B may also contribute to the L sub X dispersion. The most likely a priori source of the dispersion in L sub X is probably the varying amount of ram-pressure stripping in a range of galaxy environments. The hot gaseous halos of early-type galaxies can be stripped in encounters with other galaxies or with ambient cluster gas if the intracluster gas is sufficiently dense. Researchers find that the most likely cause of dispersion in the x ray properties of early type galaxies is probably the ram-pressure stripping of gaseous halos from galaxies. For a sample of 81 early-type galaxies with x ray luminosities or upper limits derived from Einstein Observatory observations (CFT) researchers calculated the cumulative distribution of angular distances between the x ray sample members and bright galaxies from the Revised Shapley - Ames catalog. Collectively, galaxies with low x ray luminosities (for a given L sub B) tend to be in denser environments than galaxies with higher x ray luminosities.

On the X-ray spectrum of the volume emissivity arising from Abell clusters

NASA Technical Reports Server (NTRS)

Stottlemyer, A. R.; Boldt, E. A.

1984-01-01

HEAO 1 A-2 X-ray spectra (2-15 keV) for an optically selected sample of Abell clusters of galaxies with z less than 0.1 have been analyzed to determine the energy dependence of the cosmological X-ray volume emissivity arising from such clusters. This spectrum is well fitted by an isothermal-bremsstrahlung model with kT = 7.4 + or - 1.5 KeV. This result is a test of the isothermal-volume-emissivity spectrum to be inferred from the conjecture that all contributing clusters may be characterized by kT = 7 keV, as assumed by McKee et al. (1980) in estimating the underlying luminosity function for the same sample. Although satisfied at the statistical level indicated, the analysis of a low-luminosity subsample suggests that this assumption of identical isothermal spectra would lead to a systematic error for a more statistically precise determination of the luminosity function's form.

X-rays across the galaxy population - I. Tracing the main sequence of star formation

NASA Astrophysics Data System (ADS)

Aird, J.; Coil, A. L.; Georgakakis, A.

2017-03-01

We use deep Chandra imaging to measure the distribution of X-ray luminosities (LX) for samples of star-forming galaxies as a function of stellar mass and redshift, using a Bayesian method to push below the nominal X-ray detection limits. Our luminosity distributions all show narrow peaks at LX ≲ 1042 erg s-1 that we associate with star formation, as opposed to AGN that are traced by a broad tail to higher LX. Tracking the luminosity of these peaks as a function of stellar mass reveals an 'X-ray main sequence' with a constant slope ≈0.63 ± 0.03 over 8.5 ≲ log {M}_{ast }/M_{⊙} ≲ 11.5 and 0.1 ≲ z ≲ 4, with a normalization that increases with redshift as (1 + z)3.79 ± 0.12. We also compare the peak X-ray luminosities with UV-to-IR tracers of star formation rates (SFRs) to calibrate the scaling between LX and SFR. We find that LX ∝ SFR0.83 × (1 + z)1.3, where the redshift evolution and non-linearity likely reflect changes in high-mass X-ray binary populations of star-forming galaxies. Using galaxies with a broader range of SFR, we also constrain a stellar-mass-dependent contribution to LX, likely related to low-mass X-ray binaries. Using this calibration, we convert our X-ray main sequence to SFRs and measure a star-forming main sequence with a constant slope ≈0.76 ± 0.06 and a normalization that evolves with redshift as (1 + z)2.95 ± 0.33. Based on the X-ray emission, there is no evidence for a break in the main sequence at high stellar masses, although we cannot rule out a turnover given the uncertainties in the scaling of LX to SFR.

A complete X-ray sample of the high latitude sky from HEAO-1 A-2: log N lo S and luminosity functions

NASA Technical Reports Server (NTRS)

Piccinotti, G.; Mushotzky, R. F.; Boldt, E. A.; Holt, S. S.; Marshall, F. E.; Serlemitsos, P. J.; Shafer, R. A.

1981-01-01

An experiment was performed in which a complete X-ray survey of the 8.2 steradians of the sky at galactic latitudes where the absolute value of b is 20 deg down to a limiting sensitivity of 3.1 x ten to the minus 11th power ergs/sq cm sec in the 2-10 keV band. Of the 85 detected sources 17 were identified with galactic objects, 61 were identified with extragalactic objects, and 7 remain unidentified. The log N - log S relation for the non-galactic objects is well fit by the Euclidean relationship. The X-ray spectra of these objects were used to construct log N - log S in physical units. The complete sample of identified sources was used to construct X-ray luminosity functions, using the absolute maximum likelihood method, for clusters galaxies and active galactic nuclei.

Clustering, cosmology and a new era of black hole demographics- I. The conditional luminosity function of active galactic nuclei

NASA Astrophysics Data System (ADS)

Ballantyne, D. R.

2017-01-01

Deep X-ray surveys have provided a comprehensive and largely unbiased view of active galactic nuclei (AGN) evolution stretching back to z ˜ 5. However, it has been challenging to use the survey results to connect this evolution to the cosmological environment that AGN inhabit. Exploring this connection will be crucial to understanding the triggering mechanisms of AGN and how these processes manifest in observations at all wavelengths. In anticipation of upcoming wide-field X-ray surveys that will allow quantitative analysis of AGN environments, this paper presents a method to observationally constrain the conditional luminosity function (CLF) of AGN at a specific z. Once measured, the CLF allows the calculation of the AGN bias, mean dark matter halo mass, AGN lifetime, halo occupation number, and AGN correlation function- all as a function of luminosity. The CLF can be constrained using a measurement of the X-ray luminosity function and the correlation length at different luminosities. The method is illustrated at z ≈ 0 and 0.9 using the limited data that are currently available, and a clear luminosity dependence in the AGN bias and mean halo mass is predicted at both z, supporting the idea that there are at least two different modes of AGN triggering. In addition, the CLF predicts that z ≈ 0.9 quasars may be commonly hosted by haloes with Mh ˜ 1014 M⊙. These `young cluster' environments may provide the necessary interactions between gas-rich galaxies to fuel luminous accretion. The results derived from this method will be useful to populate AGN of different luminosities in cosmological simulations.

High redshift QSOs and the x ray background

NASA Technical Reports Server (NTRS)

Impey, Chris

1993-01-01

ROSAT pointed observations were made of 9 QSO's from the Large Bright Quasar Survey (LBQS). The LBQS is based on machine measurement of objective prism plates taken with the UK Schmidt Telescope. Software has been used to select QSO's by both color and by the presence of spectral features and continuum breaks. The probability of detection can be calculated as a function of magnitude, redshift and spectral features, and the completeness of the survey can be accurately estimated. Nine out of 1040 QSO's in the LBQS have z greater than 3. The observations will provide an important data point in the X-ray luminosity function of QSO's at high redshift. The QSO's with z greater than 3 span less than a magnitude in M(sub B), so can be combined as a homogeneous sample. This analysis is only possible with a sample drawn from a large and complete catalog such as the LBQS. Four of the 9 QSO's that were observed with the ROSAT PSPC for this proposal were detected, including one of the most luminous X-ray sources ever observed. The April 1992 version of the PROS DETECT package was used to reduce the data. The results have been used to search for evolution of the X-ray properties of QSO's in redshift. The 9 QSO's lie in the range -28.7 less than M(sub B) less than -27.8. When combined with data for 16 QSO's in a similar luminosity range at lower redshift correlations with luminosity and redshift can be separated out. The LBQS sample also yields a new constraint on the contribution of high redshift QSO's to the X-ray background. An initial requirement is knowledge of the X-ray properties (alpha(sub OX)) as a function of redshift. Integration over the evolving luminosity function of the LBQS then gives the QSO contribution to the source counts.

Continuum radiation from active galactic nuclei: A statistical study

NASA Technical Reports Server (NTRS)

Isobe, T.; Feigelson, E. D.; Singh, K. P.; Kembhavi, A.

1986-01-01

The physics of the continuum spectrum of active galactic nuclei (AGNs) was examined using a large data set and rigorous statistical methods. A data base was constructed for 469 objects which include radio selected quasars, optically selected quasars, X-ray selected AGNs, BL Lac objects, and optically unidentified compact radio sources. Each object has measurements of its radio, optical, X-ray core continuum luminosity, though many of them are upper limits. Since many radio sources have extended components, the core component were carefully selected out from the total radio luminosity. With survival analysis statistical methods, which can treat upper limits correctly, these data can yield better statistical results than those previously obtained. A variety of statistical tests are performed, such as the comparison of the luminosity functions in different subsamples, and linear regressions of luminosities in different bands. Interpretation of the results leads to the following tentative conclusions: the main emission mechanism of optically selected quasars and X-ray selected AGNs is thermal, while that of BL Lac objects is synchrotron; radio selected quasars may have two different emission mechanisms in the X-ray band; BL Lac objects appear to be special cases of the radio selected quasars; some compact radio sources show the possibility of synchrotron self-Compton (SSC) in the optical band; and the spectral index between the optical and the X-ray bands depends on the optical luminosity.

X-ray studies of coeval star samples. II - The Pleiades cluster as observed with the Einstein Observatory

NASA Technical Reports Server (NTRS)

Micela, G.; Sciortino, S.; Vaiana, G. S.; Harnden, F. R., Jr.; Rosner, R.

1990-01-01

Coronal X-ray emission of the Pleiades stars is investigated, and maximum likelihood, integral X-ray luminosity functions are computed for Pleiades members in selected color-index ranges. A detailed search is conducted for long-term variability in the X-ray emission of those stars observed more than once. An overall comparison of the survey results with those of previous surveys confirms the ubiquity of X-ray emission in the Pleiades cluster stars and its higher rate of emission with respect to older stars. It is found that the X-ray emission from dA and early dF stars cannot be proven to be dissimilar to that of Hyades and field stars of the same spectral type. The Pleiades cluster members show a real rise of the X-ray luminosity from dA stars to early dF stars. X-ray emission for the young, solarlike Pleiades stars is about two orders of magnitude more intense than for the nearby solarlike stars.

Does the obscured AGN fraction really depend on luminosity?

NASA Astrophysics Data System (ADS)

Sazonov, S.; Churazov, E.; Krivonos, R.

2015-12-01

We use a sample of 151 local non-blazar active galactic nuclei (AGN) selected from the INTEGRAL all-sky hard X-ray survey to investigate if the observed declining trend of the fraction of obscured (i.e. showing X-ray absorption) AGN with increasing luminosity is mostly an intrinsic or selection effect. Using a torus-obscuration model, we demonstrate that in addition to negative bias, due to absorption in the torus, in finding obscured AGN in hard X-ray flux-limited surveys, there is also positive bias in finding unobscured AGN, due to Compton reflection in the torus. These biases can be even stronger taking into account plausible intrinsic collimation of hard X-ray emission along the axis of the obscuring torus. Given the AGN luminosity function, which steepens at high luminosities, these observational biases lead to a decreasing observed fraction of obscured AGN with increasing luminosity even if this fraction has no intrinsic luminosity dependence. We find that if the central hard X-ray source in AGN is isotropic, the intrinsic (i.e. corrected for biases) obscured AGN fraction still shows a declining trend with luminosity, although the intrinsic obscured fraction is significantly larger than the observed one: the actual fraction is larger than ˜85 per cent at L ≲ 1042.5 erg s-1 (17-60 keV), and decreases to ≲60 per cent at L ≳ 1044 erg s-1. In terms of the half-opening angle θ of an obscuring torus, this implies that θ ≲ 30° in lower luminosity AGN, and θ ≳ 45° in higher luminosity ones. If, however, the emission from the central supermassive black hole is collimated as dL/dΩ ∝ cos α, the intrinsic dependence of the obscured AGN fraction is consistent with a luminosity-independent torus half-opening angle θ ˜ 30°.

Gamma-Ray Burst Host Galaxies Have "Normal" Luminosities.

PubMed

Schaefer

2000-04-10

The galactic environment of gamma-ray bursts can provide good evidence about the nature of the progenitor system, with two old arguments implying that the burst host galaxies are significantly subluminous. New data and new analysis have now reversed this picture: (1) Even though the first two known host galaxies are indeed greatly subluminous, the next eight hosts have absolute magnitudes typical for a population of field galaxies. A detailed analysis of the 16 known hosts (10 with redshifts) shows them to be consistent with a Schechter luminosity function with R*=-21.8+/-1.0, as expected for normal galaxies. (2) Bright bursts from the Interplanetary Network are typically 18 times brighter than the faint bursts with redshifts; however, the bright bursts do not have galaxies inside their error boxes to limits deeper than expected based on the luminosities for the two samples being identical. A new solution to this dilemma is that a broad burst luminosity function along with a burst number density varying as the star formation rate will require the average luminosity of the bright sample (>6x1058 photons s-1 or>1.7x1052 ergs s-1) to be much greater than the average luminosity of the faint sample ( approximately 1058 photons s-1 or approximately 3x1051 ergs s-1). This places the bright bursts at distances for which host galaxies with a normal luminosity will not violate the observed limits. In conclusion, all current evidence points to gamma-ray burst host galaxies being normal in luminosity.

The Very Local Universe in X-Rays

NASA Technical Reports Server (NTRS)

Ptak, A.

2011-01-01

There are many open questions in X-ray observations of the Galactic neighborhood and nearby galaxies, such as the properties of the hot ISM and accreting sources, the X-ray/star-formation rate correlation and how the X-ray luminosity function of starburst galaxies. We discuss how these would be addressed by very wide-area (> 100 sq. deg.) X-ray surveys and upcoming X-ray missions. In particular planned NuStar observations of the Galaxy and nearby galaxies will be highlighted.

The WISSH quasars project. III. X-ray properties of hyper-luminous quasars

NASA Astrophysics Data System (ADS)

Martocchia, S.; Piconcelli, E.; Zappacosta, L.; Duras, F.; Vietri, G.; Vignali, C.; Bianchi, S.; Bischetti, M.; Bongiorno, A.; Brusa, M.; Lanzuisi, G.; Marconi, A.; Mathur, S.; Miniutti, G.; Nicastro, F.; Bruni, G.; Fiore, F.

2017-12-01

We performed a survey of the X-ray properties of 41 objects from the WISE/SDSS selected hyper-luminous (WISSH) quasars sample, which includes 86 broad-line quasars with bolometric luminosity LBol ≳ 2 × 1047 erg s-1 shining at z 2-4. We used both proprietary and archival Chandra and XMM-Newton observations. Twenty-one quasars have sufficient quality data to perform a spectroscopic analysis, while for the remaining sources, X-ray properties are derived through hardness-ratio analysis (apart for six sources that result to be undetected). The bulk ( 70%) of the detected WISSH quasars exhibit NH <5 × 1022 cm-2, in agreement with their optical Type 1 AGN classification. All but three quasars show unabsorbed 2-10 keV luminosities L2-10≥ 1045 erg s-1. Thanks to their extreme radiative output across the mid-IR-to-X-ray range, WISSH quasars therefore offer the opportunity to significantly extend and validate the existing relations involving L2-10. Specifically, we studied the X-ray luminosity as a function of (i) X-ray-to-optical (X/O) flux ratio; (ii) mid-IR luminosity (LMIR); (iii) LBol, and (iv) αOX versus 2500 Å luminosity. We find that the WISSH quasars show (i) unreported very low X/O ( <0.1) compared to typical AGN values; (ii) L2-10/LMIR ratios that are significantly smaller than those derived for AGN with lower luminosity; (iii) a large X-ray bolometric correction, kBol,X ≈ 100-1000; and (iv) steep -2≳αOX≳-1.7. These results lead to a scenario in which the X-ray emission of hyper-luminous quasars is relatively weaker compared to lower luminosity AGN. Models predict that such an X-ray weakness can be relevant for the acceleration of powerful high-ionization, emission-line-driven winds, which are commonly detected in the UV spectra of WISSH quasars and can, in turn, perturb the X-ray corona and weaken its emission. Accordingly, hyper-luminous quasars represent the ideal laboratory to study the link between the AGN energy output and wind acceleration. Additionally, WISSH quasars exhibit very large SMBH masses (log [MBH/M⊙]≳ 9.5). This enables a more robust modeling of the Γ-MBH relation by increasing the statistics at high masses. We derive a flatter Γ dependence than previously found over the broad range 5 ≲log (MBH/M⊙)≲ 11. Finally, we estimate that only 300 ks observations of X-IFU on board Athena will offer a detailed view of the properties of absorption features associated with powerful X-ray SMBH winds for a representative sample of WISSH quasars.

Bright end of the luminosity function of high-mass X-ray binaries: contributions of hard, soft and supersoft sources

NASA Astrophysics Data System (ADS)

Sazonov, S.; Khabibullin, I.

2017-04-01

Using a spectral analysis of bright Chandra X-ray sources located in 27 nearby galaxies and maps of star-formation rate (SFR) and interstellar medium surface densities for these galaxies, we constructed the intrinsic X-ray luminosity function (XLF) of luminous high-mass X-ray binaries (HMXBs), taking into account absorption effects and the diversity of HMXB spectra. The XLF per unit SFR can be described by a power-law dN/dlog LX,unabs ≈ 2.0(LX,unabs/1039 erg s-1)-0.6 (M⊙ yr-1)-1 from LX,unabs = 1038 to 1040.5 erg s-1, where LX,unabs is the unabsorbed luminosity at 0.25-8 keV. The intrinsic number of luminous HMXBs per unit SFR is a factor of ˜2.3 larger than the observed number reported before. The intrinsic XLF is composed of hard, soft and supersoft sources (defined here as those with the 0.25-2 keV to 0.25-8 keV flux ratio of <0.6, 0.6-0.95 and >0.95, respectively) in ˜ 2:1:1 proportion. We also constructed the intrinsic HMXB XLF in the soft X-ray band (0.25-2 keV). Here, the numbers of hard, soft and supersoft sources prove to be nearly equal. The cumulative present-day 0.25-2 keV emissivity of HMXBs with luminosities between 1038 and 1040.5 erg s-1 is ˜5 × 1039 erg s-1(M⊙ yr-1)-1, which may be relevant for studying the X-ray preheating of the early Universe.

Seven years with the Swift Supergiant Fast X-ray Transients project

NASA Astrophysics Data System (ADS)

Romano, P.

2015-09-01

Supergiant Fast X-ray Transients (SFXTs) are HMXBs with OB supergiant companions. I review the results of the Swift SFXT project, which since 2007 has been exploiting Swift's capabilities in a systematic study of SFXTs and supergiant X-ray binaries (SGXBs) by combining follow-ups of outbursts, when detailed broad-band spectroscopy is possible, with long-term monitoring campaigns, when the out-of-outburst fainter states can be observed. This strategy has led us to measure their duty cycles as a function of luminosity, to extract their differential luminosity distributions in the soft X-ray domain, and to compare, with unprecedented detail, the X-ray variability in these different classes of sources. I also discuss the ;seventh year crisis;, the challenges that the recent Swift observations are making to the prevailing models attempting to explain the SFXT behavior.

X-ray-selected galaxy groups in Boötes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vajgel, Bruna; Lopes, Paulo A. A.; Jones, Christine

2014-10-10

We present the X-ray and optical properties of the galaxy groups selected in the Chandra X-Boötes survey. We used follow-up Chandra observations to better define the group sample and their X-ray properties. Group redshifts were measured from the AGN and Galaxy Evolution Survey spectroscopic data. We used photometric data from the NOAO Deep Wide Field Survey to estimate the group richness (N {sub gals}) and the optical luminosity (L {sub opt}). Our final sample comprises 32 systems at z < 1.75 with 14 below z = 0.35. For these 14 systems, we estimate velocity dispersions (σ {sub gr}) and performmore » a virial analysis to obtain the radii (R {sub 200} and R {sub 500}) and total masses (M {sub 200} and M {sub 500}) for groups with at least 5 galaxy members. We use the Chandra X-ray observations to derive the X-ray luminosity (L{sub X} ). We examine the performance of the group properties σ{sub gr}, L {sub opt}, and L{sub X} , as proxies for the group mass. Understanding how well these observables measure the total mass is important to estimate how precisely the cluster/group mass function is determined. Exploring the scaling relations built with the X-Boötes sample and comparing these with samples from the literature, we find a break in the L{sub X} -M {sub 500} relation at approximately M {sub 500} = 5 × 10{sup 13} M {sub ☉} (for M {sub 500} > 5 × 10{sup 13} M {sub ☉}, M{sub 500}∝L{sub X}{sup 0.61±0.02}, while for M {sub 500} ≤ 5 × 10{sup 13} M {sub ☉}, M{sub 500}∝L{sub X}{sup 0.44±0.05}). Thus, the mass-luminosity relation for galaxy groups cannot be described by the same power law as galaxy clusters. A possible explanation for this break is the dynamical friction, tidal interactions, and projection effects that reduce the velocity dispersion values of the galaxy groups. By extending the cluster luminosity function to the group regime, we predict the number of groups that new X-ray surveys, particularly eROSITA, will detect. Based on our cluster/group luminosity function estimates, eROSITA will identify ∼1800 groups (L{sub X} = 10{sup 41}-10{sup 43} erg s{sup –1}) within a distance of 200 Mpc. Since groups lie in large-scale filaments, this group sample will map the large-scale structure of the local universe.« less

X-Ray Properties of K-Selected Galaxies at 0.5 Less than z Less than 2.0: Investigating Trends with Stellar Mass, Redshift and Spectral Type

NASA Technical Reports Server (NTRS)

Jones, Therese M.; Kriek, Mariska; vanDokkum, Peter G.; Brammer, Gabriel; Franx, Marijn; Greene, Jenny E.; Labbe, Ivo; Whitaker, Katherine E.

2014-01-01

We examine how the total X-ray luminosity correlates with stellar mass, stellar population, and redshift for a K-band limited sample of approximately 3500 galaxies at 0.5 < z < 2.0 from the NEWFIRM Medium Band Survey in the COSMOS field. The galaxy sample is divided into 32 different galaxy types, based on similarities between the spectral energy distributions. For each galaxy type, we further divide the sample into bins of redshift and stellar mass, and perform an X-ray stacking analysis using the Chandra COSMOS data. We find that full band X-ray luminosity is primarily increasing with stellar mass, and at similar mass and spectral type is higher at larger redshifts. When comparing at the same stellar mass, we find that the X-ray luminosity is slightly higher for younger galaxies (i.e., weaker 4000 angstrom breaks), but the scatter in this relation is large. We compare the observed X-ray luminosities to those expected from low- and high-mass X-ray binaries (XRBs). For blue galaxies, XRBs can almost fully account for the observed emission, while for older galaxies with larger 4000 angstrom breaks, active galactic nuclei (AGN) or hot gas dominate the measured X-ray flux. After correcting for XRBs, the X-ray luminosity is still slightly higher in younger galaxies, although this correlation is not significant. AGN appear to be a larger component of galaxy X-ray luminosity at earlier times, as the hardness ratio increases with redshift. Together with the slight increase in X-ray luminosity this may indicate more obscured AGNs or higher accretion rates at earlier times.

X-ray emission at low-mass end of the MS - Results from an extensive Einstein Observatory survey

NASA Technical Reports Server (NTRS)

Barbera, M.; Micela, G.; Sciortino, S.; Vaiana, G. S.; Harnden, F. R., Jr.; Rosner, R.

1992-01-01

The 0.16-4.0 keV X-ray emission from K and M stars of luminosity classes IV, V, and VI within 25 parsec of the sun was measured using all available Einstein Observatory IPC data and a critical compilation of catalogued optical data. Fifty four of 88 stars were detected, 70 of 138 M stars with Mv less than 13.4 (corresponding to M6) and 15 or 31 fainter M stars. The surveyed stars were grouped, on the basis of U, V, W space velocity components, into old-disk, young-disk, and halo population stars. Then, a subsample was selected which is statistically representative of the population of K and M stars in the solar neighborhood, on the basis of which unbiased Maximum Likelihood X-ray luminosity functions were constructed for K, early M, and late M stars. The investigation revealed a decrease of X-ray luminosity with increasing stellar age in the range of ages of disk population stars.

The cosmic X-ray background-IRAS galaxy correlation and the local X-ray volume emissivity

NASA Technical Reports Server (NTRS)

Miyaji, Takamitsu; Lahav, Ofer; Jahoda, Keith; Boldt, Elihu

1994-01-01

We have cross-correlated the galaxies from the IRAS 2 Jy redshift survey sample and the 0.7 Jy projected sample with the all-sky cosmic X-ray background (CXB) map obtained from the High Energy Astronomy Observatory (HEAO) 1 A-2 experiment. We have detected a significant correlation signal between surface density of IRAS galaxies and the X-ray background intensity, with W(sub xg) = (mean value of ((delta I)(delta N)))/(mean value of I)(mean value of N)) of several times 10(exp -3). While this correlation signal has a significant implication for the contribution of the local universe to the hard (E greater than 2 keV) X-ray background, its interpretation is model-dependent. We have developed a formulation to model the cross-correlation between CXB surface brightness and galaxy counts. This includes the effects of source clustering and the X-ray-far-infrared luminosity correlation. Using an X-ray flux-limited sample of active galactic nuclei (AGNs), which has IRAS 60 micrometer measurements, we have estimated the contribution of the AGN component to the observed CXB-IRAS galaxy count correlations in order to see whether there is an excess component, i.e., contribution from low X-ray luminosity sources. We have applied both the analytical approach and Monte Carlo simulations for the estimations. Our estimate of the local X-ray volume emissivity in the 2-10 keV band is rho(sub x) approximately = (4.3 +/- 1.2) x 10(exp 38) h(sub 50) ergs/s/cu Mpc, consistent with the value expected from the luminosity function of AGNs alone. This sets a limit to the local volume emissivity from lower luminosity sources (e.g., star-forming galaxies, low-ionization nuclear emission-line regions (LINERs)) to rho(sub x) less than or approximately = 2 x 10(exp 38) h(sub 50) ergs/s/cu Mpc.

On two new X-ray sources in the SMC and the high luminosities of the Magellanic X-ray sources

NASA Technical Reports Server (NTRS)

Clark, G.; Doxsey, R.; Li, F.; Jernigan, J. G.; Van Paradijs, J.

1978-01-01

The discovery of two new X-ray sources, SMC X-2 and SMC X-3, in the Small Magellanic Cloud is reported. They have hard spectra, and their luminosities in the energy range 2-11 keV are 1.0 and 0.7 by 10 to the 38th power erg/sq cm per sec, respectively. It is shown that the luminosity distribution of the known Magellanic X-ray sources, which are now nine in number, is shifted toward higher luminosities with respect to that of similar sources in the Galaxy, and that the cause of the shift is probably an underabundance of heavy elements in the material accreted by the X-ray sources.

Einstein X-ray observations of M101

NASA Technical Reports Server (NTRS)

Trinchieri, G.; Fabbiano, G.; Romaine, S.

1990-01-01

The Einstein X-ray observations of the face-on spiral galaxy M101 are presented. The global X-ray luminosity L(x) of M101 is about 1.2 x 10 to the 40th ergs/s for D = 7.2 Mpc, consistent with the expected X-ray luminosity of normal spiral galaxies of its optical magnitude. The X-ray emission is mostly due to very luminous individual sources, with L(x) greater than 10 to the 38th ergs/s each, most likely very massive accreting binary systems. The data suggest a deficiency of sources in the luminosity range of L(x) from about 10 to the 37th to about 10 to the 38th ergs/s, which would indicate that the luminosity distribution of the X-ray sources in M101 might be different from that of M31 or M33.

X-ray emission from a complete sample of Abell clusters of galaxies

NASA Astrophysics Data System (ADS)

Briel, Ulrich G.; Henry, J. Patrick

1993-11-01

The ROSAT All-Sky Survey (RASS) is used to investigate the X-ray properties of a complete sample of Abell clusters with measured redshifts and accurate positions. The sample comprises the 145 clusters within a 561 square degree region at high galactic latitude. The mean redshift is 0.17. This sample is especially well suited to be studied within the RASS since the mean exposure time is higher than average and the mean galactic column density is very low. These together produce a flux limit of about 4.2 x 10-13 erg/sq cm/s in the 0.5 to 2.5 keV energy band. Sixty-six (46%) individual clusters are detected at a significance level higher than 99.7% of which 7 could be chance coincidences of background or foreground sources. At redshifts greater than 0.3 six clusters out of seven (86%) are detected at the same significance level. The detected objects show a clear X-ray luminosity -- galaxy count relation with a dispersion consistent with other external estimates of the error in the counts. By analyzing the excess of positive fluctuations of the X-ray flux at the cluster positions, compared with the fluctuations of randomly drawn background fields, it is possible to extend these results below the nominal flux limit. We find 80% of richness R greater than or = 0 and 86% of R greater than or = 1 clusters are X-ray emitters with fluxes above 1 x 10-13 erg/sq cm/s. Nearly 90% of the clusters meeting the requirements to be in Abell's statistical sample emit above the same level. We therefore conclude that almost all Abell clusters are real clusters and the Abell catalog is not strongly contaminated by projection effects. We use the Kaplan-Meier product limit estimator to calculate the cumulative X-ray luminosity function. We show that the shape of the luminosity functions are similiar for different richness classes, but the characteristic luminosities of richness 2 clusters are about twice those of richness 1 clusters which are in turn about twice those of richness 0 clusters. This result is another manifestation of the luminosity -- richness elation for Abell clusters.

X-ray studies of coeval star samples. II. The Pleiades cluster as observed with the Einstein Observatory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Micela, G.; Sciortino, S.; Vaiana, G.S.

1990-01-01

Coronal X-ray emission of the Pleiades stars is investigated, and maximum likelihood, integral X-ray luminosity functions are computed for Pleiades members in selected color-index ranges. A detailed search is conducted for long-term variability in the X-ray emission of those stars observed more than once. An overall comparison of the survey results with those of previous surveys confirms the ubiquity of X-ray emission in the Pleiades cluster stars and its higher rate of emission with respect to older stars. It is found that the X-ray emission from dA and early dF stars cannot be proven to be dissimilar to that ofmore » Hyades and field stars of the same spectral type. The Pleiades cluster members show a real rise of the X-ray luminosity from dA stars to early dF stars. X-ray emission for the young, solarlike Pleiades stars is about two orders of magnitude more intense than for the nearby solarlike stars. 77 refs.« less

A study of the discrepant QSO X-ray luminosity function from the HEAO-2 data archive

NASA Technical Reports Server (NTRS)

Margon, B.

1986-01-01

Sensitive X-ray information for approximately 90 previously uncataloged Quasi-Stellar Objects (QSOs) in the redshift range 1.8 is less than or equal to z which is less than or equal to 3. Even with the longest esixting Einstein Observatory X-ray exposures, only 25% of these objects are positively detected in X-rays. The data were used to investigate the ensemble X-ray properties of high redshift QSOs, and the QSO population in general.

The clustering amplitude of X-ray-selected AGN at z ˜ 0.8: evidence for a negative dependence on accretion luminosity

NASA Astrophysics Data System (ADS)

Mountrichas, G.; Georgakakis, A.; Menzel, M.-L.; Fanidakis, N.; Merloni, A.; Liu, Z.; Salvato, M.; Nandra, K.

2016-04-01

The northern tile of the wide-area and shallow XMM-XXL X-ray survey field is used to estimate the average dark matter halo mass of relatively luminous X-ray-selected active galactic nucleus (AGN) [log {L}_X (2-10 keV)= 43.6^{+0.4}_{-0.4} erg s^{-1}] in the redshift interval z = 0.5-1.2. Spectroscopic follow-up observations of X-ray sources in the XMM-XXL field by the Sloan telescope are combined with the VIMOS Public Extragalactic Redshift Survey spectroscopic galaxy survey to determine the cross-correlation signal between X-ray-selected AGN (total of 318) and galaxies (about 20 000). We model the large scales (2-25 Mpc) of the correlation function to infer a mean dark matter halo mass of log M / (M_{{⊙}} h^{-1}) = 12.50 ^{+0.22} _{-0.30} for the X-ray-selected AGN sample. This measurement is about 0.5 dex lower compared to estimates in the literature of the mean dark matter halo masses of moderate-luminosity X-ray AGN [LX(2-10 keV) ≈ 1042-1043 erg s- 1] at similar redshifts. Our analysis also links the mean clustering properties of moderate-luminosity AGN with those of powerful ultraviolet/optically selected QSOs, which are typically found in haloes with masses few times 1012 M⊙. There is therefore evidence for a negative luminosity dependence of the AGN clustering. This is consistent with suggestions that AGN have a broad dark matter halo mass distribution with a high mass tail that becomes subdominant at high accretion luminosities. We further show that our results are in qualitative agreement with semi-analytic models of galaxy and AGN evolution, which attribute the wide range of dark matter halo masses among the AGN population to different triggering mechanisms and/or black hole fuelling modes.

X-Ray Properties of Lyman Break Galaxies in the Hubble Deep Field North Region

NASA Technical Reports Server (NTRS)

Nandra, K.; Mushotzky, R. F.; Arnaud, K.; Steidel, C. C.; Adelberger, K. L.; Gardner, J. P.; Teplitz, H. I.; Windhorst, R. A.; White, Nicholas E. (Technical Monitor)

2002-01-01

We describe the X-ray properties of a large sample of z approximately 3 Lyman Break Galaxies (LBGs) in the region of the Hubble Deep Field North, derived from the 1 Ms public Chandra observation. Of our sample of 148 LBGs, four are detected individually. This immediately gives a measure of the bright AGN (active galactic nuclei) fraction in these galaxies of approximately 3 per cent, which is in agreement with that derived from the UV (ultraviolet) spectra. The X-ray color of the detected sources indicates that they are probably moderately obscured. Stacking of the remainder shows a significant detection (6 sigma) with an average luminosity of 3.5 x 10(exp 41) erg/s per galaxy in the rest frame 2-10 keV band. We have also studied a comparison sample of 95 z approximately 1 "Balmer Break" galaxies. Eight of these are detected directly, with at least two clear AGN based on their high X-ray luminosity and very hard X-ray spectra respectively. The remainder are of relatively low luminosity (< 10(exp 42) erg/s, and the X-rays could arise from either AGN or rapid star-formation. The X-ray colors and evidence from other wavebands favor the latter interpretation. Excluding the clear AGN, we deduce a mean X-ray luminosity of 6.6 x 10(exp 40) erg/s, a factor approximately 5 lower than the LBGs. The average ratio of the UV and X-ray luminosities of these star forming galaxies L(sub UV)/L (sub X), however, is approximately the same at z = 1 as it is at z = 3. This scaling implies that the X-ray emission follows the current star formation rate, as measured by the UV luminosity. We use our results to constrain the star formation rate at z approximately 3 from an X-ray perspective. Assuming the locally established correlation between X-ray and far-IR (infrared) luminosity, the average inferred star formation rate in each Lyman break galaxy is found to be approximately 60 solar mass/yr, in excellent agreement with the extinction-corrected UV estimates. This provides an external check on the UV estimates of the star formation rates, and on the use of X-ray luminosities to infer these rates in rapidly starforming galaxies at high redshift.

Complete Hard X-Ray Surveys, AGN Luminosity Functions and the X-Ray Background

NASA Technical Reports Server (NTRS)

Tueller, Jack

2011-01-01

AGN are believed to make up most of the Cosmic X-Ray Background (CXB) above a few keV, but this background cannot be fully resolved at energies less than 10 keV due to absorption. The Swift/BAT and INTEGRAL missions are performing the first complete hard x-ray surveys with minimal bias due to absorption. The most recent results for both missions will be presented. Although the fraction of the CXB resolved by these surveys is small, it is possible to derive unbiased number counts and luminosity functions for AGN in the local universe. The survey energy range from 15-150 keV contains the important reflection and cutoff spectral features dominate the shape of the AGN contribution to the CXB. Average spectral characteristics of survey detected AGN will be presented and compared with model distributions. The numbers of hard x-ray blazars detected in these surveys are finally sufficient to estimate this important component's contribution the cosmic background. Constraints on CXB models and their significance will be discussed.

Spectral Properties, Generation Order Parameters, and Luminosities for Spin-powered X-Ray Pulsars

NASA Astrophysics Data System (ADS)

Wang, Wei; Zhao, Yongheng

2004-02-01

We show the spectral properties of 15 spin-powered X-ray pulsars, and the correlation between the average power-law photon index and spin-down rate. Generation order parameters (GOPs) based on polar cap models are introduced to characterize the X-ray pulsars. We calculate three definitions of generation order parameters arising from the different effects of magnetic and electric fields on photon absorption during cascade processes, and study the relations between the GOPs and spectral properties of X-ray pulsars. There exists a possible correlation between the photon index and GOP in our pulsar sample. Furthermore, we present a method stemming from the concept of GOPs to estimate the nonthermal X-ray luminosity for spin-powered pulsars. Then X-ray luminosity is calculated in the context of our polar cap accelerator model, which is consistent with most observed X-ray pulsar data. The ratio between the X-ray luminosity estimated by our method and the pulsar's spin-down power is consistent with the LX~10-3Lsd feature.

An X-Ray Survey of the Open Cluster NGC 6475 (M7) with ROSAT

NASA Technical Reports Server (NTRS)

Prosser, Charles F.; Stauffer, John R.; Caillault, J.-P.; Balachandran, Suchitra; Stern, Robert A.; Randich, Sofia

1995-01-01

A ROSAT x-ray survey, with complimentary optical photometry, of the open cluster NGC 6475 has enabled the detection of approx. 50 late-F to K0 and approx. 70 K/M dwarf new candidate members, providing the first reliable detection of low-mass stars in this low. galactic latitude, 220 Myr old cluster. The x-ray observations reported here have a typical limiting sensitivity of L(sub x) approx. equal to 10(exp 29) erg/s. The detection frequency of early type cluster members is consistent with the hypothesis that the x-ray emitting early type stars are binary systems with an unseen, low-mass secondary producing the x rays. The ratio between x-ray and bolometric luminosity among NGC 6475 members saturates at a spectral-type/color which is intermediate between that in much younger and in much older clusters, consistent with rotational spindown of solar-type stars upon their arrival on the ZAMS. The upper envelope of x-ray luminosity as a function of spectral type is comparable to that of the Pleiades, with the observed spread in x-ray luminosity among low-mass members being likely due to the presence of binaries and relatively rapid rotators. However, the list of x-ray selected candidate members is likely biased against low-mass, slowly rotating single stars. While some preliminary spectroscopic information is given in an appendix, further spectroscopic observations of the new candidate members will aid in interpreting the coronal activity among solar-type NGC 6475 members and their relation to similar stars in older and younger open clusters.

The black hole candidate MAXI J1659-152 in and towards quiescence in X-ray and radio

NASA Astrophysics Data System (ADS)

Jonker, P. G.; Miller-Jones, J. C. A.; Homan, J.; Tomsick, J.; Fender, R. P.; Kaaret, P.; Markoff, S.; Gallo, E.

2012-07-01

In this paper we report on Expanded Very Large Array radio and Chandra and Swift X-ray observations of the outburst decay of the transient black hole candidate MAXI J1659-152 in 2011. We discuss the distance to the source taking the high inclination into account and conclude that the source distance is probably 6 ± 2 kpc. The lowest observed flux corresponds to a luminosity of ? erg s-1. This, together with the orbital period of 2.4 h reported in the literature, suggests that the quiescent X-ray luminosity is higher than predicted on the basis of the orbital period-quiescent X-ray luminosity relationship. It is more in line with that expected for a neutron star, although the outburst spectral and timing properties reported in the literature strongly suggest that MAXI J1659-152 harbours a black hole. This conclusion is subject to confirmation of the lowest observed flux as the quiescent flux. The relation between the accretion and ejection mechanisms can be studied using the observed correlation between the radio and X-ray luminosities as these evolve over an outburst. We determine the behaviour of MAXI J1659-152 in the radio-X-ray diagram at low X-ray luminosities using the observations reported in this paper and at high X-ray luminosities using values reported in the literature. At high X-ray luminosities, the source lies closer to the sources that follow a correlation index steeper than 0.6-0.7. However, when compared to other sources that follow a steeper correlation index, the X-ray luminosity in MAXI J1659-152 is also lower. The latter can potentially be explained by the high inclination of MAXI J1659-152 if the X-ray emission comes from close to the source and the radio emission is originating in a more extended region. However, it is probable that the source was not in the canonical low-hard state during these radio observations and this may affect the behaviour of the source as well. At intermediate X-ray luminosities, the source makes the transition from the radio underluminous sources in the direction of the relation traced by the 'standard' correlation similar to what has been reported for H 1743-322 in the literature. However, MAXI J1659-152 remains underluminous with respect to this 'standard' correlation.

Hard state neutron star and black hole X-ray binaries in the radio:X-ray luminosity plane

NASA Astrophysics Data System (ADS)

Gallo, Elena; Degenaar, Nathalie; van den Eijnden, Jakob

2018-07-01

Motivated by the large body of literature around the phenomenological properties of accreting black hole (BH) and neutron star (NS) X-ray binaries in the radio:X-ray luminosity plane, we carry out a comparative regression analysis on 36 BHs and 41 NSs in hard X-ray states, with data over 7 dex in X-ray luminosity for both. The BHs follow a radio to X-ray (logarithmic) luminosity relation with slope β = 0.59 ± 0.02, consistent with the NSs' slope (β =0.44^{+0.05}_{-0.04}) within 2.5σ. The best-fitting intercept for the BHs significantly exceeds that for the NSs, cementing BHs as more radio loud, by a factor ˜22. This discrepancy cannot be fully accounted for by the mass or bolometric correction gap, or by the NS boundary layer contribution to the X-rays, and is likely to reflect physical differences in the accretion flow efficiency, or the jet powering mechanism. Once importance sampling is implemented to account for the different luminosity distributions, the slopes of the non-pulsating and pulsating NS subsamples are formally inconsistent (>3σ), unless the transitional millisecond pulsars (whose incoherent radio emission mechanism is not firmly established) are excluded from the analysis. We confirm the lack of a robust partitioning of the BH data set into separate luminosity tracks.

Hard state neutron star and black hole X-ray binaries in the radio:X-ray luminosity plane

NASA Astrophysics Data System (ADS)

Gallo, Elena; Degenaar, Nathalie; van den Eijnden, Jakob

2018-05-01

Motivated by the large body of literature around the phenomenological properties of accreting black hole (BH) and neutron star (NS) X-ray binaries in the radio:X-ray luminosity plane, we carry out a comparative regression analysis on 36 BHs and 41 NSs in hard X-ray states, with data over 7 dex in X-ray luminosity for both. The BHs follow a radio to X-ray (logarithmic) luminosity relation with slope β = 0.59 ± 0.02, consistent with the NSs' slope (β =0.44^{+0.05}_{-0.04}) within 2.5σ. The best-fitting intercept for the BHs significantly exceeds that for the NSs, cementing BHs as more radio loud, by a factor ˜22. This discrepancy can not be fully accounted for by the mass or bolometric correction gap, nor by the NS boundary layer contribution to the X-rays, and is likely to reflect physical differences in the accretion flow efficiency, or the jet powering mechanism. Once importance sampling is implemented to account for the different luminosity distributions, the slopes of the non-pulsating and pulsating NS subsamples are formally inconsistent (>3σ), unless the transitional millisecond pulsars (whose incoherent radio emission mechanism is not firmly established) are excluded from the analysis. We confirm the lack of a robust partitioning of the BH data set into separate luminosity tracks.

Soft X-ray observations of pre-main sequence stars in the chamaeleon dark cloud

NASA Technical Reports Server (NTRS)

Feigelson, Eric D.; Kriss, Gerard A.

1987-01-01

Einstein IPC observations of the nearby Chamaeleon I star forming cloud show 22 well-resolved soft X-ray sources in a 1x2 deg region. Twelve are associated with H-alpha emission line pre-main sequence (PMS) stars, and four with optically selected PMS stars. Several X-ray sources have two or more PMS stars in their error circles. Optical spectra were obtained at CTIO of possible stellar counterparts of the remaining X-ray sources. They reveal 5 probable new cloud members, K7-MO stars with weak or absent emission lines. These naked X-ray selected PMS stars are similar to those found in the Taurus-Auriga cloud. The spatial distributions and H-R diagrams of the X-ray and optically selected PMS stars in the cloud are very similar. Luminosity functions indicate the Chamaeleon stars are on average approximately 5 times more X-ray luminous than Pleiad dwarfs. A significant correlation between L sub x and optical magnitude suggests this trend may continue within the PMS phase of stellar evolution. The relation of increasing X-ray luminosity with decreasing stellar ages is thus extended to stellar ages as young as 1 million years.

Up and Down the Black Hole Radio/X-Ray Correlation: The 2017 Mini-outbursts from Swift J1753.5-0127

NASA Astrophysics Data System (ADS)

Plotkin, R. M.; Bright, J.; Miller-Jones, J. C. A.; Shaw, A. W.; Tomsick, J. A.; Russell, T. D.; Zhang, G.-B.; Russell, D. M.; Fender, R. P.; Homan, J.; Atri, P.; Bernardini, F.; Gelfand, J. D.; Lewis, F.; Cantwell, T. M.; Carey, S. H.; Grainge, K. J. B.; Hickish, J.; Perrott, Y. C.; Razavi-Ghods, N.; Scaife, A. M. M.; Scott, P. F.; Titterington, D. J.

2017-10-01

The candidate black hole X-ray binary Swift J1753.5-0127 faded to quiescence in 2016 November after a prolonged outburst that was discovered in 2005. Nearly three months later, the system displayed renewed activity that lasted through 2017 July. Here, we present radio and X-ray monitoring over ≈ 3 months of the renewed activity to study the coupling between the jet and the inner regions of the disk/jet system. Our observations cover low X-ray luminosities that have not historically been well-sampled ({L}{{X}}≈ 2× {10}33{--}{10}36 {erg} {{{s}}}-1; 1-10 keV), including time periods when the system was both brightening and fading. At these low luminosities, Swift J1753.5-0127 occupies a parameter space in the radio/X-ray luminosity plane that is comparable to “canonical” systems (e.g., GX 339-4), regardless of whether the system was brightening or fading, even though during its ≳11 year outburst, Swift J1753.5-0127 emitted less radio emission from its jet than expected. We discuss implications for the existence of a single radio/X-ray luminosity correlation for black hole X-ray binaries at the lowest luminosities ({L}{{X}}≲ {10}35 {erg} {{{s}}}-1), and we compare to supermassive black holes. Our campaign includes the lowest luminosity quasi-simultaneous radio/X-ray detection to date for a black hole X-ray binary during its rise out of quiescence, thanks to early notification from optical monitoring combined with fast responses from sensitive multiwavelength facilities.

Correlations of the IR Luminosity and Eddington Ratio with a Hard X-ray Selected Sample of AGN

NASA Technical Reports Server (NTRS)

Mushotzy, Richard F.; Winter, Lisa M.; McIntosh, Daniel H.; Tueller, Jack

2008-01-01

We use the SWIFT Burst Alert Telescope (BAT) sample of hard x-ray selected active galactic nuclei (AGN) with a median redshift of 0.03 and the 2MASS J and K band photometry to examine the correlation of hard x-ray emission to Eddington ratio as well as the relationship of the J and K band nuclear luminosity to the hard x-ray luminosity. The BAT sample is almost unbiased by the effects of obscuration and thus offers the first large unbiased sample for the examination of correlations between different wavelength bands. We find that the near-IR nuclear J and K band luminosity is related to the BAT (14 - 195 keV) luminosity over a factor of 10(exp 3) in luminosity (L(sub IR) approx.equals L(sub BAT)(sup 1.25) and thus is unlikely to be due to dust. We also find that the Eddington ratio is proportional to the x-ray luminosity. This new result should be a strong constraint on models of the formation of the broad band continuum.

STELLAR X-RAY SOURCES IN THE CHANDRA COSMOS SURVEY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wright, N. J.; Drake, J. J.; Civano, F., E-mail: nwright@cfa.harvard.ed

2010-12-10

We present an analysis of the X-ray properties of a sample of solar- and late-type field stars identified in the Chandra Cosmic Evolution Survey (COSMOS), a deep (160 ks) and wide ({approx}0.9 deg{sup 2}) extragalactic survey. The sample of 60 sources was identified using both morphological and photometric star/galaxy separation methods. We determine X-ray count rates, extract spectra and light curves, and perform spectral fits to determine fluxes and plasma temperatures. Complementary optical and near-IR photometry is also presented and combined with spectroscopy for 48 of the sources to determine spectral types and distances for the sample. We find distancesmore » ranging from 30 pc to {approx}12 kpc, including a number of the most distant and highly active stellar X-ray sources ever detected. This stellar sample extends the known coverage of the L{sub X}-distance plane to greater distances and higher luminosities, but we do not detect as many intrinsically faint X-ray sources compared to previous surveys. Overall the sample is typically more luminous than the active Sun, representing the high-luminosity end of the disk and halo X-ray luminosity functions. The halo population appears to include both low-activity spectrally hard sources that may be emitting through thermal bremsstrahlung, as well as a number of highly active sources in close binaries.« less

SWIFT BAT Survey of AGN

NASA Technical Reports Server (NTRS)

Tueller, J.; Mushotzky, R. F.; Barthelmy, S.; Cannizzo, J. K.; Gehrels, N.; Markwardt, C. B.; Skinner, G. K.; Winter, L. M.

2008-01-01

We present the results1 of the analysis of the first 9 months of data of the Swift BAT survey of AGN in the 14-195 keV band. Using archival X-ray data or follow-up Swift XRT observations, we have identified 129 (103 AGN) of 130 objects detected at [b] > 15deg and with significance > 4.8-delta. One source remains unidentified. These same X-ray data have allowed measurement of the X-ray properties of the objects. We fit a power law to the logN - log S distribution, and find the slope to be 1.42+/-0.14. Characterizing the differential luminosity function data as a broken power law, we find a break luminosity logL*(ergs/s)= 43.85+/-0.26. We obtain a mean photon index 1.98 in the 14-195 keV band, with an rms spread of 0.27. Integration of our luminosity function gives a local volume density of AGN above 10(exp 41) erg/s of 2.4x10(exp -3) Mpc(sup -3), which is about 10% of the total luminous local galaxy density above M* = -19.75. We have obtained X-ray spectra from the literature and from Swift XRT follow-up observations. These show that the distribution of log nH is essentially flat from nH = 10(exp 20)/sq cm to 10(exp 24)/sq cm, with 50% of the objects having column densities of less than 10(exp 22)/sq cm. BAT Seyfert galaxies have a median redshift of 0.03, a maximum log luminosity of 45.1, and approximately half have log nH > 22.

An unbiased X-ray sampling of stars within 25 parsecs of the Sun

NASA Technical Reports Server (NTRS)

Johnson, H. M.

1985-01-01

A search of all of the Einstein Observatory IPC and HRI fields for untargeted stars in the Woolley, et al., Catalogue of the nearby stars is reported. Optical data and IPC coordinates, flux density F sub x, and luminosity L sub x, or upper limits, are tabulated for 126 single or blended systems, and HRI results for a few of them. IPC luminosity functions are derived for the systems, for 193 individual stars in the systems (with L sub x shared equally among blended components), and for 63 individual M dwarfs. These stars have relatively large X-ray flux densities that are free of interstellar extinction, because they are nearby, but they are otherwise unbiased with respect to the X-ray properties that are found in a defined small space around the Sun.

LUMINOSITY FUNCTIONS OF LMXBs IN CENTAURUS A: GLOBULAR CLUSTERS VERSUS THE FIELD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Voss, Rasmus; Gilfanov, Marat; Sivakoff, Gregory R.

2009-08-10

We study the X-ray luminosity function (XLF) of low-mass X-ray binaries (LMXB) in the nearby early-type galaxy Centaurus A, concentrating primarily on two aspects of binary populations: the XLF behavior at the low-luminosity limit and the comparison between globular cluster and field sources. The 800 ksec exposure of the deep Chandra VLP program allows us to reach a limiting luminosity of {approx}8 x 10{sup 35} erg s{sup -1}, about {approx}2-3 times deeper than previous investigations. We confirm the presence of the low-luminosity break of the overall LMXB XLF at log(L{sub X} ) {approx} 37.2-37.6, below which the luminosity distribution followsmore » a dN/d(ln L) {approx} const law. Separating globular cluster and field sources, we find a statistically significant difference between the two luminosity distributions with a relative underabundance of faint sources in the globular cluster population. This demonstrates that the samples are drawn from distinct parent populations and may disprove the hypothesis that the entire LMXB population in early-type galaxies is created dynamically in globular clusters. As a plausible explanation for this difference in the XLFs, we suggest an enhanced fraction of helium-accreting systems in globular clusters, which are created in collisions between red giants and neutron stars. Due to the four times higher ionization temperature of He, such systems are subject to accretion disk instabilities at {approx}20 times higher mass accretion rate and, therefore, are not observed as persistent sources at low luminosities.« less

X-raying the most luminous quasars at cosmic noon

NASA Astrophysics Data System (ADS)

Piconcelli, E.; Martocchia, S.; Zappacosta, L.

2017-10-01

The WISE/SDSS hyper-luminous (log L_Bol > 47) quasar (WISSH) survey is performing a multi-band systematic exploration of the most luminous AGN shining at the golden epoch of AGN activity (i.e. z ˜ 2-4). This gives the opportunity of overcoming the luminosity bias in the exploration of the accretion phenomenon and the impact of AGN radiative output on the host. In this talk, I present the results of our study of the X-ray spectra of 40 WISSH quasars. I report on the correlations between the X-ray and Optical, UV and MIR properties, and the behavior of the X-ray bolometric correction at the brightest end of the luminosity function. I discuss the relative X-ray weakness of these very powerful quasars compared to less luminous AGN. This X-ray weakness can be a key ingredient for accelerating powerful ionized outflows (ubiquitously revealed in the UV/optical spectra of WISSH quasars) and, furthermore, radiation-driven winds can be effective in destroying the X-ray corona and quenching the X-ray emission. The potential offered by Athena in studying this extreme class of AGN is also discussed.

Efficiency of Synchrotron Radiation from Rotation-powered Pulsars

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kisaka, Shota; Tanaka, Shuta J., E-mail: kisaka@phys.aoyama.ac.jp, E-mail: sjtanaka@center.konan-u.ac.jp

2017-03-01

Synchrotron radiation is widely considered to be the origin of the pulsed non-thermal emissions from rotation-powered pulsars in optical and X-ray bands. In this paper, we study the synchrotron radiation emitted by the created electron and positron pairs in the pulsar magnetosphere to constrain the energy conversion efficiency from the Poynting flux to the particle energy flux. We model two pair creation processes, two-photon collision, which efficiently works in young γ -ray pulsars (≲10{sup 6} year), and magnetic pair creation, which is the dominant process to supply pairs in old pulsars (≳10{sup 6} year). Using the analytical model, we derivemore » the maximum synchrotron luminosity as a function of the energy conversion efficiency. From the comparison with observations, we find that the energy conversion efficiency to the accelerated particles should be an order of unity in the magnetosphere, even though we make a number of the optimistic assumptions to enlarge the synchrotron luminosity. In order to explain the luminosity of the non-thermal X-ray/optical emission from pulsars with low spin-down luminosity L {sub sd} ≲ 10{sup 34} erg s{sup −1}, non-dipole magnetic field components should be dominant at the emission region. For the γ -ray pulsars with L {sub sd} ≲ 10{sup 35} erg s{sup −1}, observed γ -ray to X-ray and optical flux ratios are much higher than the flux ratio between curvature and the synchrotron radiations. We discuss some possibilities such as the coexistence of multiple accelerators in the magnetosphere as suggested from the recent numerical simulation results. The obtained maximum luminosity would be useful to select observational targets in X-ray and optical bands.« less

The Cambridge-Cambridge X-ray Serendipity Survey: I X-ray luminous galaxies

NASA Technical Reports Server (NTRS)

Boyle, B. J.; Mcmahon, R. G.; Wilkes, B. J.; Elvis, M.

1994-01-01

We report on the first results obtained from a new optical identification program of 123 faint X-ray sources with S(0.5-2 keV) greater than 2 x 10(exp -14) erg/s/sq cm serendipitously detected in ROSAT PSPC pointed observations. We have spectroscopically identified the optical counterparts to more than 100 sources in this survey. Although the majority of the sample (68 objects) are QSO's, we have also identified 12 narrow emission line galaxies which have extreme X-ray luminosities (10(exp 42) less than L(sub X) less than 10(exp 43.5) erg/s). Subsequent spectroscopy reveals them to be a mixture of star-burst galaxies and Seyfert 2 galaxies in approximately equal numbers. Combined with potentially similar objects identified in the Einstein Extended Medium Sensitivity Survey, these X-ray luminous galaxies exhibit a rate of cosmological evolution, L(sub X) varies as (1 + z)(exp 2.5 +/- 1.0), consistent with that derived for X-ray QSO's. This evolution, coupled with the steep slope determined for the faint end of the X-ray luminosity function (Phi(L(sub X)) varies as L(sub X)(exp -1.9)), implies that such objects could comprise 15-35% of the soft (1-2 keV) X-ray background.

Constraints on Omega_0 and cluster evolution using the ROSAT log N-log S relation

NASA Astrophysics Data System (ADS)

Mathiesen, B.; Evrard, A. E.

1998-04-01

We examine the likelihoods of different cosmological models and cluster evolutionary histories by comparing semi-analytical predictions of X-ray cluster number counts with observational data from the ROSAT satellite. We model cluster abundance as a function of mass and redshift using a Press-Schechter distribution, and assume that the temperature T(M,z) and bolometric luminosity L_X(M,z) scale as power laws in mass and epoch, in order to construct expected counts as a function of X-ray flux. The L_X-M scaling is fixed using the local luminosity function, while the degree of evolution in the X-ray luminosity with redshift L_X~(1+z)^s is left open, with s an interesting free parameter which we investigate. We examine open and flat cosmologies with initial, scale-free fluctuation spectra having indices n=0, -1 and -2. An independent constraint arising from the slope of the luminosity-temperature relation strongly favours the n=-2 spectrum. The expected counts demonstrate a strong dependence on Omega_0 and s, with lesser dependence on lambda_0 and n. Comparison with the observed counts reveals a `ridge' of acceptable models in the Omega_0-s plane, roughly following the relation s~6Omega_0 and spanning low-density models with a small degree of evolution to Omega=1 models with strong evolution. Models with moderate evolution are revealed to have a strong lower limit of Omega_0>~0.3, and low-evolution models imply that Omega_0<1 at a very high confidence level. We suggest observational tests for breaking the degeneracy along this ridge, and discuss implications for evolutionary histories of the intracluster medium.

Mini Survey of SDSS [OIII] AGN with Swift: Testing the Hypothesis that L(sub [OIII]) Traces AGN Luminosity

NASA Technical Reports Server (NTRS)

2007-01-01

The number of AGN and their luminosity distribution are crucial parameters for our understanding of the AGN phenomenon. Recent work strongly suggests every massive galaxy has a central black hole. However most of these objects either are not radiating or have been very difficult to detect We are now in the era of large surveys, and the luminosity function (LF] of AGN has been estimated in various ways. In the X-ray band. Chandra and XMM surveys have revealed that the LF of hard X-ray selected AGN shows a strong luminosity-dependent evolution with a dramatic break towards low L(sub x) (at all z). This is seen for all types of AGN, but is stronger for the broad-line objects. In sharp contrast, the local LF of optically-selected samples shows no such break and no differences between narrow and broad-line objects. If as been suggested, hard X ray and optical emission line can both can be fair indicators of AGN activity, it is important to first understand how reliable these characteristics are if we hope to understand the apparent discrepancy in the LFs.

Young and Old X-ray Binary and IXO Populations in Spiral and Elliptical Galaxies

NASA Astrophysics Data System (ADS)

Colbert, E.; Heckman, T.; Ptak, A.; Strickland, D.; Weaver, K.

2003-03-01

We have analyzed Chandra ACIS observations of 32 nearby spiral and elliptical galaxies and present the results of 1441 X-ray point sources, which are presumed to be mostly X-ray binaries (XRBs) and Intermediate-luminosity X-ray Objects (IXOs, a.k.a. ULXs). The X-ray luminosity functions (XLFs) of the point sources show that the slope of the elliptical galaxy XLFs are significantly steeper than the spiral galaxy XLFs, indicating grossly different types of point sources, or different stages in their evolution. Since the spiral galaxy XLF is so shallow, the most luminous points sources (usually the IXOs) dominate the total X-ray point source luminosity LXP. We show that the galaxy total B-band and K-band light (proxies for the stellar mass) are well correlated with LXP for both spirals and ellipticals, but the FIR and UV emission is only correlated for the spirals. We deconvolve LXP into two components, one that is proportional to the galaxy stellar mass (pop II), and another that is proportional to the galaxy SFR (pop I). We also note that IXOs (and nearly all of the other point sources) in both spirals and ellipticals have X-ray colors that are most consistent with power-law slopes of Gamma ˜ 1.5--3.0, which is inconsistent with high-mass XRBS (HMXBs). Thus, HMXBs are not important contributors to LXP. We have also found that IXOs in spiral galaxies may have a slightly harder X-ray spectrum than those in elliptical galaxies. The implications of these findings will be discussed.

A Deep Chandra ACIS Survey of M51

NASA Astrophysics Data System (ADS)

Kuntz, K. D.; Long, Knox S.; Kilgard, Roy E.

2016-08-01

We have obtained a deep X-ray image of the nearby galaxy M51 using Chandra. Here we present the catalog of X-ray sources detected in these observations and provide an overview of the properties of the point-source population. We find 298 sources within the D 25 radii of NGC 5194/5, of which 20% are variable, a dozen are classical transients, and another half dozen are transient-like sources. The typical number of active ultraluminous X-ray sources in any given observation is ˜5, and only two of those sources persist in an ultraluminous state over the 12 yr of observations. Given reasonable assumptions about the supernova remnant population, the luminosity function is well described by a power law with an index between 1.55 and 1.7, only slightly shallower than that found for populations dominated by high-mass X-ray binaries (HMXBs), which suggests that the binary population in NGC 5194 is also dominated by HMXBs. The luminosity function of NGC 5195 is more consistent with a low-mass X-ray binary dominated population. Based on observations made with NASA's Chandra X-ray Observatory, which is operated by the Smithsonian Astrophysical Observatory under contract #NAS83060, and the data were obtained through program GO1-12115.

CHANDRA ACIS SURVEY OF X-RAY POINT SOURCES IN NEARBY GALAXIES. II. X-RAY LUMINOSITY FUNCTIONS AND ULTRALUMINOUS X-RAY SOURCES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Song; Qiu, Yanli; Liu, Jifeng

Based on the recently completed Chandra /ACIS survey of X-ray point sources in nearby galaxies, we study the X-ray luminosity functions (XLFs) for X-ray point sources in different types of galaxies and the statistical properties of ultraluminous X-ray sources (ULXs). Uniform procedures are developed to compute the detection threshold, to estimate the foreground/background contamination, and to calculate the XLFs for individual galaxies and groups of galaxies, resulting in an XLF library of 343 galaxies of different types. With the large number of surveyed galaxies, we have studied the XLFs and ULX properties across different host galaxy types, and confirm withmore » good statistics that the XLF slope flattens from lenticular ( α ∼ 1.50 ± 0.07) to elliptical (∼1.21 ± 0.02), to spirals (∼0.80 ± 0.02), to peculiars (∼0.55 ± 0.30), and to irregulars (∼0.26 ± 0.10). The XLF break dividing the neutron star and black hole binaries is also confirmed, albeit at quite different break luminosities for different types of galaxies. A radial dependency is found for ellipticals, with a flatter XLF slope for sources located between D {sub 25} and 2 D {sub 25}, suggesting the XLF slopes in the outer region of early-type galaxies are dominated by low-mass X-ray binaries in globular clusters. This study shows that the ULX rate in early-type galaxies is 0.24 ± 0.05 ULXs per surveyed galaxy, on a 5 σ confidence level. The XLF for ULXs in late-type galaxies extends smoothly until it drops abruptly around 4 × 10{sup 40} erg s{sup −1}, and this break may suggest a mild boundary between the stellar black hole population possibly including 30 M {sub ⊙} black holes with super-Eddington radiation and intermediate mass black holes.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mineo, S.; Rappaport, S.; Levine, A.

We present a comprehensive study of the total X-ray emission from the colliding galaxy pair NGC 2207/IC 2163, based on Chandra, Spitzer, and GALEX data. We detect 28 ultraluminous X-ray sources (ULXs), 7 of which were not detected previously because of X-ray variability. Twelve sources show significant long-term variability, with no correlated spectral changes. Seven sources are transient candidates. One ULX coincides with an extremely blue star cluster (B – V = –0.7). We confirm that the global relation between the number and luminosity of ULXs and the integrated star-formation rate (SFR) of the host galaxy also holds on local scales. We investigatemore » the effects of dust extinction and age on the X-ray binary (XRB) population on subgalactic scales. The distributions of N {sub X} and L {sub X} are peaked at L {sub IR}/L {sub NUV} ∼ 1, which may be associated with an age of ∼10 Myr for the underlying stellar population. We find that approximately one-third of the XRBs are located in close proximity to young star complexes. The luminosity function of the XRBs is consistent with that typical for high-mass XRBs and appears unaffected by variability. We disentangle and compare the X-ray diffuse spectrum with that of the bright XRBs. The hot interstellar medium dominates the diffuse X-ray emission at E ≲ 1 keV and has a temperature kT=0.28{sub −0.04}{sup +0.05} keV and intrinsic 0.5-2 keV luminosity of 7.9×10{sup 40} erg s{sup −1}, a factor of ∼2.3 higher than the average thermal luminosity produced per unit SFR in local star-forming galaxies. The total X-ray output of NGC 2207/IC 2163 is 1.5×10{sup 41} erg s{sup −1}, and the corresponding total integrated SFR is 23.7 M {sub ☉} yr{sup –1}.« less

Simultaneous Chandra and VLA Observations of the Transitional Millisecond Pulsar PSR J1023+0038: Anti-correlated X-Ray and Radio Variability

NASA Astrophysics Data System (ADS)

Bogdanov, Slavko; Deller, Adam T.; Miller-Jones, James C. A.; Archibald, Anne M.; Hessels, Jason W. T.; Jaodand, Amruta; Patruno, Alessandro; Bassa, Cees; D’Angelo, Caroline

2018-03-01

We present coordinated Chandra X-ray Observatory and Karl G. Jansky Very Large Array observations of the transitional millisecond pulsar PSR J1023+0038 in its low-luminosity accreting state. The unprecedented five hours of strictly simultaneous X-ray and radio continuum coverage for the first time unambiguously show a highly reproducible, anti-correlated variability pattern. The characteristic switches from the X-ray high mode into a low mode are always accompanied by a radio brightening with a duration that closely matches the X-ray low mode interval. This behavior cannot be explained by a canonical inflow/outflow accretion model where the radiated emission and the jet luminosity are powered by, and positively correlated with, the available accretion energy. We interpret this phenomenology as alternating episodes of low-level accretion onto the neutron star during the X-ray high mode that are interrupted by rapid ejections of plasma by the active rotation-powered pulsar, possibly initiated by a reconfiguration of the pulsar magnetosphere, that cause a transition to a less X-ray luminous mode. The observed anti-correlation between radio and X-ray luminosity has an additional consequence: transitional MSPs can make excursions into a region of the radio/X-ray luminosity plane previously thought to be occupied solely by black hole X-ray binary sources. This complicates the use of this luminosity relation for identifying candidate black holes, suggesting the need for additional discriminants when attempting to establish the true nature of the accretor.

The dependence of the soft X ray spectral slope with radio property, luminosity, and redshift, for a large sample of AGN from the Einstein IPC data base

NASA Technical Reports Server (NTRS)

Brunner, H.; Worrall, D. M.; Wilkes, Belinda J.; Elvis, Martin

1989-01-01

The dependence of the soft X-ray spectral slope on radio, optical and X-ray properties, and on redshift are reported for a large sample of Active Galactic Nuclei (AGN). The sample includes 317 optically and radio-selected AGN from a preliminary version of the Einstein Imaging Proportional Counter (IPC) quasar and AGN data base. The main results are: the difference in X-ray slope between radio-loud and radio-quiet AGN were confirmed for an independent and much larger sample of sources; a difference in X-ray slope between flat and steep radio spectrum AGN is observed only in high luminosity sub-sample; in flat radio spectrum AGNs there is an indication for a dependence of the X-ray spectral index on X-ray luminosity redshift and alpha sub 0x.

The Hard X-ray 20-40 keV AGN Luminosity Function

NASA Technical Reports Server (NTRS)

Beckmann, V.; Soldi, S.; Shrader, C. R.; Gehrels, N.; Produit, N.

2006-01-01

We have compiled a complete, significance limited extragalactic sample based on approximately 25,000 deg(sup 2) to a limiting flux of 3 x 10(exp -11) ergs per square centimeter per second. (approximately 7,000 deg(sup 2)) to a flux limit of 10(exp -11) ergs per square centimeter per second)) in the 20 - 40 keV band with INTEGRAL. We have constructed a detailed exposure map to compensate for effects of non-uniform exposure. The flux-number relation is best described by a power-law with a slope of alpha = 1.66 plus or minus 0.11. The integration of the cumulative flux per unit area leads to f(sub 20-40 keV) = 2.6 x 10(exp -10) ergs per square centimeter per second per sr(sup -1) which is about 1% of the known 20-40 keV X-ray background. We present the first luminosity function of AGN in the 20-40 keV energy range, based on 68 extragalactic objects detected by the imager IBIS/ISGRI on-board INTEGRAL. The luminosity function shows a smoothly connected two power-law form, with an index of gamma (sub 1) = 0.9 below, and gamma (sub 2) = 2.2 above the turn-over luminosity of L(sub *), = 4.6 x 10(sup 43) ergs per second. The emissivity of all INTEGRAL AGNs per unit volume is W(sub 20-40keV)(greater than 10(sup 41) ergs per second) = 2.8 x 10(sup 38) ergs per second h(sup 3)(sub 70) Mpc(sup -3). These results are consistent with those derived in the 2-20keV energy band and do not show a significant contribution by Compton-thick objects. Because the sample used in this study is truly local (z(raised bar) = 0.022)), only limited conclusions can be drawn for the evolution of AGNs in this energy band. But the objects explaining the peak in the cosmic X-ray background are likely to be either low luminosity AGN (L(sub x) less than 10(sup 41) ergs per second) or of other type, such as intermediate mass black holes, clusters, and star forming regions.

The high-energy X-ray spectrum of black hole candidate GX 339-4 during a transition

NASA Technical Reports Server (NTRS)

Dolan, J. F.; Crannell, C. J.; Dennis, B. R.; Orwig, L. E.

1987-01-01

The X-ray emitting system GX 339-4 contains one of the prime candidates for a stellar mass-sized black hole. Determining the observational similarities and differences between the members of this group is of value in specifying which characteristics can be used to identify systems containing a black hole, especially those for which no mass determination can be made. The first observations of the E greater than 20 keV spectrum of GX 339-4 during a transition between luminosity states are reported here. The hard spectral state is the lower luminosity state of the system. GX 339-4 has a power-low spectrum above 20 keV which pivots during transitions between distinct luminosity states. The only other X-ray sources known to exhibit this behavior, Cyg XR-1 and (probably) A0620-00, are leading candidates for systems containing a black hole component based on their measured spectrocopic mass function.

ROSAT all-sky survey on the Einstein EMSS sample

NASA Technical Reports Server (NTRS)

Maccacaro, Tomasso

1992-01-01

The cosmological evolution and the luminosity function (XLF) of X ray selected Active Galactic Nuclei (AGN's) are discussed. The sample used is extracted from the Einstein Observatory Extended Medium Sensitivity Surveys (EMSS) and consists of more than 420 objects. Preliminary results from the ROSAT All-Sky Survey data confirm the correctness of the optical identification of the EMSS sources, thus giving confidence to the results obtained from the analysis of the AGN's sample. The XLF observed at different redshifts (up to z approx. 2) gives direct evidence of cosmological evolution. Data have been analyzed within the framework of luminosity evolution models and the two most common evolutionary forms, L sub x(Z) = L sub x(0) x e(sup Cr) and L sub x(Z) = L sub x(0) x (1 + z)(exp C), have been considered. Luminosity dependent evolution is required if the evolution function has the exponential form, whereas the simpler pure luminosity evolution model is still acceptable if the evolution function has the power law form. Using the whole sample of objects the number-counts and the de-evolved (z = 0) XLF have been derived. A comparison of the EMSS data with preliminary ROSAT results presented at this meeting indicates an overall agreement.

X-ray Observations of Neutron Stars

NASA Astrophysics Data System (ADS)

Enoto, Teruaki

A large diversity of neutron stars has been discovered by recent multi-wavelength observations from the radio band to the X-ray and gamma-ray energy range. Among different manifestation of neutron stars, magnetars are strongly magnetised objects with the magnetic field strength of B = 1014-15 G. Some of magnetars exhibit transient behaviours, in which activated state the magnetars radiate sporadic short bursts and enhanced persistent X-ray emission for a couple of weeks or more. The Suzaku X-ray satellite has observed 15 magnetars among 23 known sources in 2006-2013, including persistently bright sources and transient objects. We showed that the broadband magnetar spectra, including both of surface emission below 10 keV and magnetospheric power-law radiation above 10 keV, follow spectral evolution as a function of the magnetic field, in terms of wide-band spectral hardness ratio and of power-law photon index. Magnetars are also compared with other rotation powered pulsars on the correlation between X-ray luminosity and the spin-down luminosity. I will address future missions related with investigation of the nature of neutron stars.

Discovery of low-redshift X-ray selected quasars - New clues to the QSO phenomenon

NASA Technical Reports Server (NTRS)

Grindlay, J. E.; Forman, W. R.; Steiner, J. E.; Canizares, C. R.; Mcclintock, J. E.

1980-01-01

The identification of six X-ray sources discovered by the Einstein Observatory with X-ray quasars is reported, and the properties of these X-ray selected quasars are discussed. The four high-latitude fields of 1 sq deg each in which the Einstein imaging proportional counter detected serendipitous X-ray sources at intermediate exposures of 10,000 sec were observed by 4-m and 1.5-m telescopes, and optical sources with uv excesses and emission line spectra typical of many low-redshift quasars and Seyfert 1 galaxies were found within the 1-arcsec error boxes of the X-ray sources. All six quasars identified were found to be radio quiet, with low redshift and relatively faint optical magnitudes, and to be similar in space density, colors and magnitude versus redshift relation to an optically selected sample at the same mean magnitude. X-ray luminosity was found to be well correlated with both continuum and broad-line emission luminosities for the known radio-quiet quasars and Seyfert 1 galaxies, and it was observed that the five objects with the lowest redshifts have very similar X-ray/optical luminosity ratios despite tenfold variations in X-ray luminosity. It is concluded that photoionization by a continuum extending to X-ray energies is the dominant excitation mechanism in radio-quiet quasars.

An X-ray Investigation of the NGC 346 Field in the SMC (2): The Field Population

NASA Technical Reports Server (NTRS)

Naze, Y.; Hartwell, J. M.; Stevens, I. R.; Manfroid, J.; Marchenko, S.; Corcoran, M. F.; Moffat, A. F. J.; Skalkowski, G.

2003-01-01

We present results from a Chandra observation of the NGC 346 cluster, which is the ionizing source of N66, the most luminous HII region and the largest star formation region in the SMC. In the first part of this investigation, we have analysed the X-ray properties of the cluster itself and the remarkable star HD 5980. But the field contains additional objects of interest. In total, 79 X-ray point sources were detected in the Chandra observation: this is more than five times the number of sources detected by previous X-ray surveys. We investigate here their characteristics in detail. The sources possess rather high hardness ratios, and their cumulative luminosity function is steeper than that for the rest of the SMC at higher .luminosities. Their absorption columns suggest that most of the sources belong to NGC346. Using new UBV RI imaging with the ESO 2.2m telescope, we also discovered possible counterparts for 36 of these X-ray sources and estimated a B spectral type for a large number of these counterparts. This tends to suggest that most of the X-ray sources in the field are in fact X-ray binaries. Finally, some objects show X-ray and/or optical variability, with a need for further monitoring.

New Constraints on Dark Energy from the ObservedGrowth of the Most X-ray Luminous Galaxy Clusters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mantz, A.; Allen, S.W.; Ebeling, H.

We present constraints on the mean matter density, {Omega}{sub m}, normalization of the density fluctuation power spectrum, {sigma}{sub 8}, and dark energy equation of state parameter, w, obtained from the X-ray luminosity function of the Massive Cluster Survey (MACS) in combination with the local BCS and REFLEX galaxy cluster samples. Our analysis incorporates the mass function predictions of Jenkins et al. (2001), a mass-luminosity relation calibrated using the data of Reiprich and Bohringer (2002), and standard priors on the Hubble constant, H{sub 0}, and mean baryon density, {Omega}{sub b} h{sup 2}. We find {Omega}{sub m}=0.27 {sup +0.06} {sub -0.05} andmore » {sigma}{sub 8}=0.77 {sup +0.07} {sub -0.06} for a spatially flat, cosmological constant model, and {Omega}{sub m}=0.28 {sup +0.08} {sub -0.06}, {sigma}{sub 8}=0.75 {+-} 0.08 and w=-0.97 {sup +0.20} {sub -0.19} for a flat, constant-w model. Our findings constitute the first precise determination of the dark energy equation of state from measurements of the growth of cosmic structure in galaxy clusters. The consistency of our result with w=-1 lends strong additional support to the cosmological constant model. The constraints are insensitive to uncertainties at the 10-20 percent level in the mass function and in the redshift evolution o the mass-luminosity relation; the constraint on dark energy is additionally robust against our choice of priors and known X-ray observational biases affecting the mass-luminosity relation. Our results compare favorably with those from recent analyses of type Ia supernovae, cosmic microwave background anisotropies, the X-ray gas mass fraction of relaxed galaxy clusters and cosmic shear. A simplified combination of the luminosity function data with supernova, cosmic microwave background and cluster gas fraction data using importance sampling yields the improved constraints {Omega}{sub m}=0.263 {+-} 0.014, {sigma}{sub 8}=0.79 {+-} 0.02 and w=-1.00 +- 0.05.« less

X-Ray Luminosity Functions of Normal Galaxies in the Great Observatories Origins Deep Survey

NASA Astrophysics Data System (ADS)

Ptak, Andrew; Mobasher, Bahram; Hornschemeier, Ann; Bauer, Franz; Norman, Colin

2007-10-01

We present soft (0.5-2 keV) X-ray luminosity functions (XLFs) in the Great Observatories Origins Deep Survey (GOODS) fields derived for galaxies at z~0.25 and 0.75. SED fitting was used to estimate photometric redshifts and separate galaxy types, resulting in a sample of 40 early-type galaxies and 46 late-type galaxies. We estimate k-corrections for both the X-ray/optical and X-ray/NIR flux ratios, which facilitates the separation of AGNs from the normal/starburst galaxies. We fit the XLFs with a power-law model using both traditional and Markov-Chain Monte Carlo (MCMC) procedures. A key advantage of the MCMC approach is that it explicitly takes into account upper limits and allows errors on ``derived'' quantities, such as luminosity densities, to be computed directly (i.e., without potentially questionable assumptions concerning the propagation of errors). The slopes of the early-type galaxy XLFs tend to be slightly flatter than the late-type galaxy XLFs, although the effect is significant at only the 90% and 97% levels for z~0.25 and 0.75. The XLFs differ between z<0.5 and z>0.5 at >99% significance levels for early-type, late-type, and all (early- and late-type) galaxies. We also fit Schechter and lognormal models to the XLFs, fitting the low- and high-redshift XLFs for a given sample simultaneously assuming only pure luminosity evolution. In the case of lognormal fits, the results of MCMC fitting of the local FIR luminosity function were used as priors for the faint- and bright-end slopes (similar to ``fixing'' these parameters at the FIR values, except here the FIR uncertainty is included). The best-fit values of the change in logL* with redshift were ΔlogL*=0.23+/-0.16 dex (for early-type galaxies) and 0.34+/-0.12 dex (for late-type galaxies), corresponding to (1+z)1.6 and (1+z)2.3. These results were insensitive to whether the Schechter or lognormal function was adopted.

A Search for Low-Luminosity BL Lacertae Objects

NASA Astrophysics Data System (ADS)

Rector, Travis A.; Stocke, John T.; Perlman, Eric S.

1999-05-01

Many properties of BL Lacs have become explicable in terms of the ``relativistic beaming'' hypothesis, whereby BL Lacs are FR 1 radio galaxies viewed nearly along the jet axis. However, a possible problem with this model is that a transition population between beamed BL Lacs and unbeamed FR 1 galaxies has not been detected. A transition population of ``low-luminosity BL Lacs'' was predicted to exist in abundance in X-ray-selected samples such as the Einstein Extended Medium Sensitivity Survey (EMSS) by Browne & Marcha. However, these BL Lacs may have been misidentified as clusters of galaxies. We have conducted a search for such objects in the EMSS with the ROSAT High-Resolution Imager (HRI) here we present ROSAT HRI images, optical spectra, and VLA radio maps for a small number of BL Lacs that were previously misidentified in the EMSS catalog as clusters of galaxies. While these objects are slightly lower in luminosity than other EMSS BL Lacs, their properties are too similar to the other BL Lacs in the EMSS sample to ``bridge the gap'' between BL Lacs and FR 1 radio galaxies. Also, the number of new BL Lacs found is too low to alter significantly the X-ray luminosity function or value for the X-ray-selected EMSS BL Lac sample. Thus, these observations do not explain fully the discrepancy between the X-ray- and radio-selected BL Lac samples.

Starburst galaxies

NASA Technical Reports Server (NTRS)

Weedman, Daniel W.

1987-01-01

The infrared properties of star-forming galaxies, primarily as determined by the Infrared Astronomy Satellite (IRAS), are compared to X-ray, optical, and radio properties. Luminosity functions are reviewed and combined with those derived from optically discovered samples using 487 Markarian galaxies with redshifts and published IRAS 60 micron fluxes, and 1074 such galaxies in the Center for Astrophysics redshift survey. It is found that the majority of infrared galaxies which could be detected are low luminosity sources already known from the optical samples, but non-infrared surveys have found only a very small fraction of the highest luminosity sources. Distributions of infrared to optical fluxes and available spectra indicate that the majority of IRAS-selected galaxies are starburst galaxies. Having a census of starburst galaxies and associated dust allow severl important global calculations. The source counts are predicted as a function of flux limits for both infrared and radio fluxes. These galaxies are found to be important radio sources at faint flux limits. Taking the integrated flux to z = 3 indicates that such galaxies are a significant component of the diffuse X-ray background, and could be the the dominant component depending on the nature of the X-ray spectra and source evolution.

The Ultra-Luminous X-ray Source Population from the Chandra Archive of Galaxies

NASA Technical Reports Server (NTRS)

Swartz, Douglas A.; Ghosh, Kajal K.; Tennant, Allen F.; Wu, Kinwah

2004-01-01

One hundred fifty-four discrete non-nuclear Ultra-Luminous X-ray (ULX) sources, with spectroscopically-determined intrinsic X-ray luminosities greater than 1 e39 ergs/s, are identified in 82 galaxies observed with Chandra's Advanced CCD Imaging Spectrometer. Source positions, X-ray luminosities, and spectral and timing characteristics are tabulated. Statistical comparisons between these X-ray properties and those of the weaker discrete sources in the same fields (mainly neutron star and stellar-mass black hole binaries) are made. Sources above approximately le38 ergs per second display similar spatial, spectral, color, and variability distributions. In particular, there is no compelling evidence in the sample for a new and distinct class of X-ray object such as the intermediate-mass black holes. 83% of ULX candidates have spectra that can be described as absorbed power laws with index = 1.74 and column density = 2.24e21 l per square centimeter, or approximately 5 times the average Galactic column. About 20% of the ULX's have much steeper indices indicative of a soft, and likely thermal, spectrum. The locations of ULXs in their host galaxies are strongly peaked towards their galaxy centers. The deprojected radial distribution of the ULX candidates is somewhat steeper than an exponential disk, indistinguishable from that of the weaker sources. About 5--15% of ULX candidates are variable during the Chandra observations (which average 39.5 ks). Comparison of the cumulative X-ray luminosity functions of the ULXs to Chandra Deep Field results suggests approximately 25% of the sources may be background objects including 14% of the ULX candidates in the sample of spiral galaxies and 44% of those in elliptical galaxies implying the elliptical galaxy ULX population is severely compromised by background active galactic nuclei. Correlations with host galaxy properties confirm the number and total X-ray luminosity of the ULXs are associated with recent star formation and with galaxy merging and interactions. The preponderance of ULXs in star-forming galaxies as well as their similarities to less-luminous sources suggest they originate in a young but short-lived population such as the high-mass X-ray binaries with a smaller contribution (based on spectral slope) from recent supernovae. The number of ULXs in elliptical galaxies scales with host galaxy mass and can be explained most simply as the high-luminosity end of the low-mass X-ray binary population.

TRACING THE REVERBERATION LAG IN THE HARD STATE OF BLACK HOLE X-RAY BINARIES

DOE Office of Scientific and Technical Information (OSTI.GOV)

De Marco, B.; Ponti, G.; Nandra, K.

2015-11-20

We report results obtained from a systematic analysis of X-ray lags in a sample of black hole X-ray binaries, with the aim of assessing the presence of reverberation lags and studying their evolution during outburst. We used XMM-Newton and simultaneous Rossi X-ray Timing Explorer (RXTE) observations to obtain broadband energy coverage of both the disk and the hard X-ray Comptonization components. In most cases the detection of reverberation lags is hampered by low levels of variability-power signal-to-noise ratio (typically when the source is in a soft state) and/or short exposure times. The most detailed study was possible for GX 339-4more » in the hard state, which allowed us to characterize the evolution of X-ray lags as a function of luminosity in a single source. Over all the sampled frequencies (∼0.05–9 Hz), we observe the hard lags intrinsic to the power-law component, already well known from previous RXTE studies. The XMM-Newton soft X-ray response allows us to detail the disk variability. At low frequencies (long timescales) the disk component always leads the power-law component. On the other hand, a soft reverberation lag (ascribable to thermal reprocessing) is always detected at high frequencies (short timescales). The intrinsic amplitude of the reverberation lag decreases as the source luminosity and the disk fraction increase. This suggests that the distance between the X-ray source and the region of the optically thick disk where reprocessing occurs gradually decreases as GX 339-4 rises in luminosity through the hard state, possibly as a consequence of reduced disk truncation.« less

Relationship between optical and X-ray properties of O-type stars surveyed with the Einstein Observatory

NASA Technical Reports Server (NTRS)

Sciortino, S.; Vaiana, G. S.; Harnden, F. R., Jr.; Ramella, M.; Morossi, C.

1990-01-01

An X-ray luminosity function is derived for a representative volume-limited sample of O-type stars selected from the catalog of Galactic O stars surveyed with the Einstein Observatory. It was found that, for the stars of this sample which is ten times larger than any previously analyzed, the level of X-ray emission is strongly correlated with bolometric luminosity, confirming previous findings of an Lx-L(bol) relationship (e.g., Harnden et al., 1979; Pallavicini et al., 1981). Correlations between the Lx and the mass loss rate with the wind terminal velocity or with the rotation rate were weak. However, there was a strong correlation with wind momentum flux as well as with the wind kinetic energy flux.

The X-ray cluster Abell 744

NASA Technical Reports Server (NTRS)

Kurtz, M. J.; Huchra, J. P.; Beers, T. C.; Geller, M. J.; Gioia, I. M.

1985-01-01

X-ray and optical observations of the cluster of galaxies Abell 744 are presented. The X-ray flux (assuming H(0) = 100 km/s per Mpc) is about 9 x 10 to the 42nd erg/s. The X-ray source is extended, but shows no other structure. Photographic photometry (in Kron-Cousins R), calibrated by deep CCD frames, is presented for all galaxies brighter than 19th magnitude within 0.75 Mpc of the cluster center. The luminosity function is normal, and the isopleths show little evidence of substructure near the cluster center. The cluster has a dominant central galaxy, which is classified as a normal brightest-cluster elliptical on the basis of its luminosity profile. New redshifts were obtained for 26 galaxies in the vicinity of the cluster center; 20 appear to be cluster members. The spatial distribution of redshifts is peculiar; the dispersion within the 150 kpc core radius is much greater than outside. Abell 744 is similar to the nearby cluster Abell 1060.

Low-Luminosity AGN As Analogues of Galactic Black Holes in the Low/Hard State: Evidence from X-Ray Timing of NGC 4258

NASA Technical Reports Server (NTRS)

Markowitz, A.; Uttley, P.

2005-01-01

We present a broadband power spectral density function (PSD) measured from extensive RXTE monitoring data of the low-luminosity AGN NGC 4258, which has an accurate, maser-determined black hole mass of (3.9 plus or minus 0.1) x 10(exp 7) solar mass. We constrain the PSD break time scale to be greater than 4.5 d at greater than 90% confidence, which appears to rule out the possibility that NGC 4258 is an analogue of black hole X-ray binaries (BHXRBs) in the high/soft state. In this sense, the PSD of NGC 4258 is different to that of some more-luminous Seyferts, which appear similar to the PSDs of high/soft state X-ray binaries. This result supports previous analogies between LLAGN and X-ray binaries in the low/hard state based on spectral energy distributions, indicating that the AGN/BHXRB analogy is valid across a broad range of accretion rates.

Exploring the Overabundance of ULXs in Metal- and Dust-Poor Local Lyman Break Analogs

NASA Technical Reports Server (NTRS)

Basu-Zych, Antara R.; Lehmer, Bret; Fragos, Tassos; Hornschemeier, Ann; Yukita, Mihoko; Zezas, Andreas; Ptak, Andy

2016-01-01

We have studied high-mass X-ray binary (HMXB) populations within two low-metallicity, starburst galaxies, Haro 11 and VV 114. These galaxies serve as analogs to high-redshift (z greater than 2) Lyman break galaxies and, within the larger sample of Lyman break analogs (LBAs), they are sufficiently nearby (less than 87 Mpc) to be spatially resolved by Chandra. Previous studies of the X-ray emission in LBAs have found that the 2-10 keV luminosity per star formation rate (SFR) in these galaxies is elevated, potentially because of their low metallicities (12 + log[O/H] = 8.3-8.4). Theoretically, the progenitors of XRBs forming in lower metallicity environments lose less mass from stellar winds over their lifetimes, producing more massive compact objects (i.e., neutron stars and black holes), and thus resulting in more numerous and luminous HMXBs per SFR. In this paper, we have performed an in-depth study of the only two LBAs that have spatially resolved 2-10 keV emission with Chandra to present the bright end of the X-ray luminosity distribution of HMXBs (L(sub X) approximately greater than 10(exp 39) erg s(exp -1); ultraluminous X-ray sources, ULXs) in these low-metallicity galaxies, based on eight detected ULXs. Compared with the star-forming galaxy X-ray luminosity function (XLF) presented by Mineo et al., Haro 11 and VV 114 host approximately equal to 4 times more L(sub X) greater than 10(exp 40) erg s(exp -1) sources than expected given their SFRs. We simulate the effects of source blending from crowded lower-luminosity HMXBs using the star-forming galaxy XLF and then vary the XLF normalizations and bright-end slopes until we reproduce the observed point source luminosity distributions. We find that these LBAs have a shallower bright-end slope (gamma(sub 2) = 1.90) than the standard XLF (gamma(sub 2) 2.73). If we conservatively assume that the brightest X-ray source from each galaxy is powered by an accreting supermassive black hole rather than an HMXB and eliminate these sources from consideration, the luminosity distribution becomes poorly constrained but does appear to be consistent with a standard XLF.

On the surface density of X-ray selected BL Lacertae objects

NASA Technical Reports Server (NTRS)

Maccacaro, T.; Gioia, I. M.; Maccagni, D.; Stocke, J. T.

1984-01-01

Only a handful of BL Lac objects have been found as a result of systematic optical identification of serendipitous Einstein X-ray sources. By combining the data from two flux-limited complete X-ray surveys (the HEAO 1 A-2 and the Einstein Observatory Medium Sensitivity Survey) the surface density of X-ray emitting BL Lac objects is evaluated as a function of their X-ray flux. It is found that a single power law is not an acceptable representation of the BL Lac objects' X-ray log N-log S. The number-flux relationship is consistent with the Euclidean slope at 'high' flux levels but shows a drastic flattnring below fluxes of the order of 10 to the -12th ergs per sq cm/s. The implications of this result are briefly discussed with respect to the luminosity function, the cosmological evolution, and the X-ray to optical flux ratio in BL Lac objects.

Amuse-Virgo: Downsizing In Black Hole Accretion

NASA Astrophysics Data System (ADS)

Gallo, Elena

2010-03-01

An issue of fundamental importance in understanding the galaxy-black hole connection is the duty cycle of accretion. If black holes are indeed ubiquitous in galactic nuclei, little is known about the frequency and intensity of their activity, the more so at the low-mass/low-luminosity end. I will present new results from AMUSE-Virgo, a Chandra survey of (formally) inactive early type galaxies in the Virgo cluster. Out of 100 objects, 32 show a nuclear X-ray source, including 6 hybrid nuclei which also host a massive nuclear cluster as visible from archival HST images. After carefully accounting for contamination from nuclear low mass X-ray binaries based on the shape and normalization of their X-ray luminosity function, we conclude that between 24-34% of the galaxies in our sample host a X-ray active super-massive black hole. This sets a firm lower limit to the black hole occupation fraction in nearby bulges within a cluster environment. At face value, the active fraction is found to increase with host stellar mass. However, taking into account selection effects, we find that the average Eddington-scaled X-ray luminosity scales with black hole mass to the power -0.62, with an intrinsic scatter of 0.46 dex. This represents the first observational evidence for down-sizing of black hole accretion in local early types, that is, the fraction of active galaxies, defined as those above a fixed X-ray Eddington ratio, decreases with increasing host galaxy mass.

High-redshift Extremely Red Quasars in X-Rays

NASA Astrophysics Data System (ADS)

Goulding, Andy D.; Zakamska, Nadia L.; Alexandroff, Rachael M.; Assef, Roberto J.; Banerji, Manda; Hamann, Fred; Wylezalek, Dominika; Brandt, William N.; Greene, Jenny E.; Lansbury, George B.; Pâris, Isabelle; Richards, Gordon; Stern, Daniel; Strauss, Michael A.

2018-03-01

Quasars may have played a key role in limiting the stellar mass of massive galaxies. Identifying those quasars in the process of removing star formation fuel from their hosts is an exciting ongoing challenge in extragalactic astronomy. In this paper, we present X-ray observations of 11 extremely red quasars (ERQs) with L bol ∼ 1047 erg s‑1 at z = 1.5–3.2 with evidence for high-velocity (v ≥slant 1000 km s‑1) [O III] λ5007 outflows. X-rays allow us to directly probe circumnuclear obscuration and to measure the instantaneous accretion luminosity. We detect 10 out of 11 ERQs available in targeted and archival data. Using a combination of X-ray spectral fitting and hardness ratios, we find that all of the ERQs show signs of absorption in the X-rays with inferred column densities of N H ≈ 1023 cm‑2, including four Compton-thick candidates (N H ≥slant 1024 cm‑2). We stack the X-ray emission of the seven weakly detected sources, measuring an average column density of N H ∼ 8 × 1023 cm‑2. The absorption-corrected (intrinsic) 2–10 keV X-ray luminosity of the stack is 2.7 × 1045 erg s‑1, consistent with X-ray luminosities of type 1 quasars of the same infrared luminosity. Thus, we find that ERQs are a highly obscured, borderline Compton-thick population, and based on optical and infrared data we suggest that these objects are partially hidden by their own equatorial outflows. However, unlike some quasars with known outflows, ERQs do not appear to be intrinsically underluminous in X-rays for their bolometric luminosity. Our observations indicate that low X-rays are not necessary to enable some types of radiatively driven winds.

Resolving the X-ray emission from the Lyman-continuum emitting galaxy Tol 1247-232

NASA Astrophysics Data System (ADS)

Kaaret, P.; Brorby, M.; Casella, L.; Prestwich, A. H.

2017-11-01

Chandra observations of the nearby, Lyman-continuum (LyC) emitting galaxy Tol 1247-232 resolve the X-ray emission and show that it is dominated by a point-like source with a hard spectrum (Γ = 1.6 ± 0.5) and a high luminosity [(9 ± 2) × 1040 erg s- 1]. Comparison with an earlier XMM-Newton observation shows flux variation of a factor of 2. Hence, the X-ray emission likely arises from an accreting X-ray source: a low-luminosity active galactic nucleus or one or a few X-ray binaries. The Chandra X-ray source is similar to the point-like, hard spectrum (Γ = 1.2 ± 0.2), high-luminosity (1041 erg s- 1) source seen in Haro 11, which is the only other confirmed LyC-emitting galaxy that has been resolved in X-rays. We discuss the possibility that accreting X-ray sources contribute to LyC escape.

The X-Ray and Mid-infrared Luminosities in Luminous Type 1 Quasars

NASA Astrophysics Data System (ADS)

Chen, Chien-Ting J.; Hickox, Ryan C.; Goulding, Andrew D.; Stern, Daniel; Assef, Roberto; Kochanek, Christopher S.; Brown, Michael J. I.; Harrison, Chris M.; Hainline, Kevin N.; Alberts, Stacey; Alexander, David M.; Brodwin, Mark; Del Moro, Agnese; Forman, William R.; Gorjian, Varoujan; Jones, Christine; Murray, Stephen S.; Pope, Alexandra; Rovilos, Emmanouel

2017-03-01

Several recent studies have reported different intrinsic correlations between the active galactic nucleus (AGN) mid-IR luminosity ({L}MIR}) and the rest-frame 2–10 keV luminosity (L X) for luminous quasars. To understand the origin of the difference in the observed {L}{{X}}{--}{L}MIR} relations, we study a sample of 3247 spectroscopically confirmed type 1 AGNs collected from Boötes, XMM-COSMOS, XMM-XXL-North, and the Sloan Digital Sky Survey quasars in the Swift/XRT footprint spanning over four orders of magnitude in luminosity. We carefully examine how different observational constraints impact the observed {L}{{X}}{--}{L}MIR} relations, including the inclusion of X-ray-nondetected objects, possible X-ray absorption in type 1 AGNs, X-ray flux limits, and star formation contamination. We find that the primary factor driving the different {L}{{X}}{--}{L}MIR} relations reported in the literature is the X-ray flux limits for different studies. When taking these effects into account, we find that the X-ray luminosity and mid-IR luminosity (measured at rest-frame 6 μ {{m}}, or {L}6μ {{m}}) of our sample of type 1 AGNs follow a bilinear relation in the log–log plane: {log}{L}{{X}}=(0.84+/- 0.03)× {log}{L}6μ {{m}}/{10}45 erg s‑1 + (44.60 ± 0.01) for {L}6μ {{m}}< {10}44.79 erg s‑1, and {log}{L}{{X}}=(0.40+/- 0.03)× {log}{L}6μ {{m}}/{10}45 erg s‑1 + (44.51 ± 0.01) for {L}6μ {{m}} ≥slant {10}44.79 erg s‑1. This suggests that the luminous type 1 quasars have a shallower {L}{{X}}{--}{L}6μ {{m}} correlation than the approximately linear relations found in local Seyfert galaxies. This result is consistent with previous studies reporting a luminosity-dependent {L}{{X}}{--}{L}MIR} relation and implies that assuming a linear {L}{{X}}{--}{L}6μ {{m}} relation to infer the neutral gas column density for X-ray absorption might overestimate the column densities in luminous quasars.

X-RAY EMISSION FROM MAGNETIC MASSIVE STARS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nazé, Yaël; Petit, Véronique; Rinbrand, Melanie

2014-11-01

Magnetically confined winds of early-type stars are expected to be sources of bright and hard X-rays. To clarify the systematics of the observed X-ray properties, we have analyzed a large series of Chandra and XMM-Newton observations, corresponding to all available exposures of known massive magnetic stars (over 100 exposures covering ∼60% of stars compiled in the catalog of Petit et al.). We show that the X-ray luminosity is strongly correlated with the stellar wind mass-loss rate, with a power-law form that is slightly steeper than linear for the majority of the less luminous, lower- M-dot B stars and flattens formore » the more luminous, higher- M-dot O stars. As the winds are radiatively driven, these scalings can be equivalently written as relations with the bolometric luminosity. The observed X-ray luminosities, and their trend with mass-loss rates, are well reproduced by new MHD models, although a few overluminous stars (mostly rapidly rotating objects) exist. No relation is found between other X-ray properties (plasma temperature, absorption) and stellar or magnetic parameters, contrary to expectations (e.g., higher temperature for stronger mass-loss rate). This suggests that the main driver for the plasma properties is different from the main determinant of the X-ray luminosity. Finally, variations of the X-ray hardnesses and luminosities, in phase with the stellar rotation period, are detected for some objects and they suggest that some temperature stratification exists in massive stars' magnetospheres.« less

Hydrogen line ratios in Seyfert galaxies and low redshift quasars

NASA Technical Reports Server (NTRS)

Kriss, G. R.

1984-01-01

New observations of the Lymal alpha radiation/hydrogen alpha radiation ratio in a set of X-ray selected active galactic nuclei and an archival study of International Ultraviolet Explorer (IUE) observations of Lymal alpha low redshift quasars and Seyfert galaxies have been used to form a large sample for studying the influence of soft X-rays on the enhancement of Balmer emission in the broad line region. In common models of broad line clouds, the Balmer lines are formed deep in the interior, largely by collisional excitation. Heating within the clouds is provided by soft X-ray radiation, while Lymal alpha is formed mainly by recombination after photoionization. The ratio Lymal alpha/Halpha is expected to depend weakly on the ratio of ionizing ultraviolet luminosity to X-ray luminosity (L sub UV/l sub x). If the Lymal alpha luminosity is used as a measure of L sub UV' a weak dependence of Lymal/H alpha on the X-ray luminosity is found similar to previous results.

A statistical analysis of the Einstein normal galaxy sample. III - Radio and X-ray properties of elliptical and S0 galaxies

NASA Technical Reports Server (NTRS)

Fabbiano, G.; Klein, U.; Trinchieri, G.; Wielebinski, R.

1987-01-01

Radioastronomy, optical and X-ray data were used to probe the cause of high X-ray luminosities of 28 radio-quiet elliptical galaxies (RQE) and S0 galaxies previously scanned by the Einstein Observatory. Comparisons were made with similar data on double-lobed 3CR galaxies. Radio luminosities were highly correlated with the X-ray luminosities, agreeing with models of radio nuclear sources in early-type galaxies as accreting compact objects. Additionally, 3CR galaxies seemed to be large-scale versions of normal RQE. The significance of interstellar medium/intracluster medium interactions for high correlations between the core and total radio power from X-ray emitting galaxies is discussed.

A deeper look at the X-ray point source population of NGC 4472

NASA Astrophysics Data System (ADS)

Joseph, T. D.; Maccarone, T. J.; Kraft, R. P.; Sivakoff, G. R.

2017-10-01

In this paper we discuss the X-ray point source population of NGC 4472, an elliptical galaxy in the Virgo cluster. We used recent deep Chandra data combined with archival Chandra data to obtain a 380 ks exposure time. We find 238 X-ray point sources within 3.7 arcmin of the galaxy centre, with a completeness flux, FX, 0.5-2 keV = 6.3 × 10-16 erg s-1 cm-2. Most of these sources are expected to be low-mass X-ray binaries. We finding that, using data from a single galaxy which is both complete and has a large number of objects (˜100) below 1038 erg s-1, the X-ray luminosity function is well fitted with a single power-law model. By cross matching our X-ray data with both space based and ground based optical data for NGC 4472, we find that 80 of the 238 sources are in globular clusters. We compare the red and blue globular cluster subpopulations and find red clusters are nearly six times more likely to host an X-ray source than blue clusters. We show that there is evidence that these two subpopulations have significantly different X-ray luminosity distributions. Source catalogues for all X-ray point sources, as well as any corresponding optical data for globular cluster sources, are also presented here.

Obscuration-dependent Evolution of Active Galactic Nuclei

NASA Astrophysics Data System (ADS)

Buchner, Johannes; Georgakakis, Antonis; Nandra, Kirpal; Brightman, Murray; Menzel, Marie-Luise; Liu, Zhu; Hsu, Li-Ting; Salvato, Mara; Rangel, Cyprian; Aird, James; Merloni, Andrea; Ross, Nicholas

2015-04-01

We aim to constrain the evolution of active galactic nuclei (AGNs) as a function of obscuration using an X-ray-selected sample of ~2000 AGNs from a multi-tiered survey including the CDFS, AEGIS-XD, COSMOS, and XMM-XXL fields. The spectra of individual X-ray sources are analyzed using a Bayesian methodology with a physically realistic model to infer the posterior distribution of the hydrogen column density and intrinsic X-ray luminosity. We develop a novel non-parametric method that allows us to robustly infer the distribution of the AGN population in X-ray luminosity, redshift, and obscuring column density, relying only on minimal smoothness assumptions. Our analysis properly incorporates uncertainties from low count spectra, photometric redshift measurements, association incompleteness, and the limited sample size. We find that obscured AGNs with N H > 1022 cm-2 account for {77}+4-5% of the number density and luminosity density of the accretion supermassive black hole population with L X > 1043 erg s-1, averaged over cosmic time. Compton-thick AGNs account for approximately half the number and luminosity density of the obscured population, and {38}+8-7% of the total. We also find evidence that the evolution is obscuration dependent, with the strongest evolution around N H ≈ 1023 cm-2. We highlight this by measuring the obscured fraction in Compton-thin AGNs, which increases toward z ~ 3, where it is 25% higher than the local value. In contrast, the fraction of Compton-thick AGNs is consistent with being constant at ≈35%, independent of redshift and accretion luminosity. We discuss our findings in the context of existing models and conclude that the observed evolution is, to first order, a side effect of anti-hierarchical growth.

A Search for Periodicity in the X-Ray Spectrum of Black Hole Candidate A0620-00

DTIC Science & Technology

1991-06-01

They are observed as radio pulsars and as the X-ray emitting components of binary X-ray sources. The limits of stability of neutron stars are not...4 Lo ). The three candidates are CYG X-1, LMC X-3, and A0620. In this section all data such as mass functions, luminosities, distances, periods, etc...1.4. Finally, we discard data for which a/ lo > 1. Such a point is of little statistical significance since its error bars are so large. Figure 2.2d

Toward An Understanding of Cluster Evolution: A Deep X-Ray Selected Cluster Catalog from ROSAT

NASA Technical Reports Server (NTRS)

Jones, Christine; Oliversen, Ronald (Technical Monitor)

2002-01-01

In the past year, we have focussed on studying individual clusters found in this sample with Chandra, as well as using Chandra to measure the luminosity-temperature relation for a sample of distant clusters identified through the ROSAT study, and finally we are continuing our study of fossil groups. For the luminosity-temperature study, we compared a sample of nearby clusters with a sample of distant clusters and, for the first time, measured a significant change in the relation as a function of redshift (Vikhlinin et al. in final preparation for submission to Cape). We also used our ROSAT analysis to select and propose for Chandra observations of individual clusters. We are now analyzing the Chandra observations of the distant cluster A520, which appears to have undergone a recent merger. Finally, we have completed the analysis of the fossil groups identified in ROM observations. In the past few months, we have derived X-ray fluxes and luminosities as well as X-ray extents for an initial sample of 89 objects. Based on the X-ray extents and the lack of bright galaxies, we have identified 16 fossil groups. We are comparing their X-ray and optical properties with those of optically rich groups. A paper is being readied for submission (Jones, Forman, and Vikhlinin in preparation).

A deep x-ray survey of the Pleiades cluster and the B6-A3 main sequence stars in Orion

NASA Technical Reports Server (NTRS)

Caillault, Jean-Pierre

1993-01-01

We have obtained deep ROSAT images of three regions within the Pleiades open cluster. We have detected 317 X-ray sources in these ROSAT PSPC images, 171 of which we associate with certain probable members of the Pleiades cluster. We detect nearly all Pleiades members with spectral types later than G0 and within 25 arcminutes of our three field centers where our sensitivity is highest. This has allowed us to derive for the first time the luminosity function for the G, K, and M dwarfs of an open cluster without the need to use statistical techniques to account for the presence of upper limits in the data sample. Because of our high X-ray detection frequency down to the faint limit of the optical catalog, we suspect that some of our unidentified X-ray sources are previously unknown, very low-mass members of the Pleiades. A large fraction of the Pleiades members detected with ROSAT have published rotational velocities. Plots of L(sub x)/L(sub bol) versus spectroscopic rotational velocity show tightly correlated 'saturation' type relations for stars with (B - V)(sub O) greater than 0.60. For each of several color ranges, X-ray luminosities rise rapidly with increasing rotation rate until v sin i approximately equals 15 km/s, and then remain essentially flat for rotation rates up to at least v sin i approximately equal to 100 km/s. The dispersion in rotation among low-mass stars in the Pleiades is by far the dominant contributor to the dispersion in L(subx) at a given mass. Only about 35 percent of the B.A. and early F stars in the Pleiades are detected as X-ray sources in our survey. There is no correlation between X-ray flux and rotation for these stars. The X-ray luminosity function for the early-type Pleiades stars appears to be bimodal, with only a few exceptions. We either detect these stars at fluxes in the range found for low-mass stars or we derive X-ray limits below the level found for most Pleiades dwarfs. The X-ray spectra for the early-type Pleiades stars detected by ROSAT are indistinguishable from the spectra of the low-mass Pleiades members. We believe that the simple explanation for this behavior is that the early-type Pleiades stars are not themselves intrinsic X-ray sources and that the X-ray sources and that the X-ray emission actually arises from low-mass companions to these stars.

The X-ray properties of the young open cluster around alpha Persei

NASA Technical Reports Server (NTRS)

Randich, S.; Schmitt, J. H. M. M.; Prosser, C. F.; Stauffer, J. R.

1995-01-01

The observations of the 50 Myr old alpha Persei open cluster, performed by the Rosat's position sensitive proportional counter (PSPC), are discussed. The X-ray observations cover an area of about 10 sq deg. A total of 160 X-ray sources were detected. The comparison between the X-ray luminosity distribution functions of the alpha Persei sample and the Pleiades indicated that F and G-type stars in the alpha Persei are more X-ray luminous than their older counterparts in the Pleiades. No significant difference was found between the distributions of the K and M-type dwarfs in the two clusters.

The x-ray luminosity-redshift relationship of quasars

PubMed Central

Segal, I. E.; Segal, W.

1980-01-01

Chronometric cosmology provides an excellent fit for the phenomenological x-ray luminosity-redshift relationship for 49 quasars observed by the Einstein satellite. Analysis of the data on the basis of the Friedmann cosmology leads to a correlation of absolute x-ray luminosity with redshift of >0.8, which is increased to ∼1 in the bright envelope. Although the trend might be ascribed a priori to an observational magnitude bias, it persists after nonparametric, maximum-likelihood removal of this bias. PMID:16592826

Quasi-spherical accretion in High Mass X-ray Binaries

NASA Astrophysics Data System (ADS)

Postnov, Konstantin

2016-07-01

Quasi-spherical accreion onto magnetized neutron stars from stellar winds in high-mass X-ray binaries is discussed. Depending on the X-ray luminosity of the neutron star, the accretion can proceed in two regimes (modes): at L_x ≳ 4× 10^{36} erg/s, Compton cooling of accreting matter near magnetosphere leads to a supersonic (Bondi) accretion, while at smaller X-ray luminosity the Compton cooling is ineffective, and subsonic settling accretion regime sets in. In this regime, a hot convective shell is formed around the magnetosphere, and the plasma entry rate into magnetosphere is controlled by less effective radiative plasma cooling. The shell mediates the angular momentum transfer from/to the neutron star magnetosphere. Observational evidences for the different accretion regimes in slowly rotating X-ray pulsars with moderate and low X-ray luminosity, as well as possible manifestations of non-stationary quasi-spherical settling accretion due to the magnetospheric shell instability in Supergiant Fast X-ray Transients will be presented.

Recurrent Outbursts Revealed in 3XMM J031820.8-663034

NASA Astrophysics Data System (ADS)

Zhao, Hai-Hui; Weng, Shan-Shan; Wang, Jun-Xian

2018-06-01

3XMM J031820.8-663034, first detected by ROSAT in NGC 1313, is one of a few known transient ultraluminous X-ray sources (ULXs). In this paper, we present decades of X-ray data of this source from ROSAT, XMM-Newton, Chandra, and the Neil Gehrels Swift Observatory. We find that its X-ray emission experienced four outbursts since 1992, with a typical recurrent time ∼1800 days, an outburst duration ∼240–300 days, and a nearly constant peak X-ray luminosity ∼1.5 × 1039 erg s‑1. The upper limit of X-ray luminosity at the quiescent state is ∼5.6 × 1036 erg s‑1, and the total energy radiated during one outburst is ∼1046 erg. The spectra at the high luminosity states can be described with an absorbed disk blackbody, and the disk temperature increases with the X-ray luminosity. We compare its outburst properties with other known transient ULXs including ESO 243-49 HLX-1. As its peak luminosity only marginally puts it in the category of ULXs, we also compare it with normal transient black hole binaries. Our results suggest that the source is powered by an accreting massive stellar-mass black hole, and the outbursts are triggered by the thermal-viscous instability.

Introductory Overview of Intermediate-luminosity X-ray Objects

NASA Astrophysics Data System (ADS)

Colbert, E. J. M.

2001-05-01

Intermediate-luminosity X-ray Objects (IXOs) are defined as compact objects having X-ray luminosities between those of X-ray binaries and low-luminosity AGNs (i.e., 1039.0 erg s-1 < ~ LX [IXOs] < ~ 1041.0 erg s-1). It is not currently known if these objects are intermediate-mass (M ~ 102-104 Msun) black holes accreting near the Eddington limit, near-solar-mass black holes in a super-Eddington state, or are, in some cases, just supermassive black holes accreting at very low rates. However, the first idea has been popularized by recent press coverage. IXOs are quite common (present in about half of spiral galaxies) and are typically found displaced from the optical nucleus, reducing the likelihood that they are low-luminosity AGN. Nearly all of our knowledge of these objects comes from X-ray observations, as observations of optical, NIR and radio counterparts are not widely known. In this session, we will address (1) the phenomenology of the objects, (2) possible geometry and accretion mechanisms for these objects (i.e., are they more similar to black hole X-ray binaries or AGNs), (3) the central black hole masses, and (4) the formation mechanism for these black holes, if they are of intermediate mass. In this talk, I will focus primarily on giving background information of these fascinating objects.

Chandra reveals a black hole X-ray binary within the ultraluminous supernova remnant MF 16

NASA Astrophysics Data System (ADS)

Roberts, T. P.; Colbert, E. J. M.

2003-06-01

We present evidence, based on Chandra ACIS-S observations of the nearby spiral galaxy NGC 6946, that the extraordinary X-ray luminosity of the MF 16 supernova remnant actually arises in a black hole X-ray binary. This conclusion is drawn from the point-like nature of the X-ray source, its X-ray spectrum closely resembling the spectrum of other ultraluminous X-ray sources thought to be black hole X-ray binary systems, and the detection of rapid hard X-ray variability from the source. We briefly discuss the nature of the hard X-ray variability, and the origin of the extreme radio and optical luminosity of MF 16 in light of this identification.

A luminous hot accretion flow in the low-luminosity active galactic nucleus NGC 7213

NASA Astrophysics Data System (ADS)

Xie, Fu-Guo; Zdziarski, Andrzej A.; Ma, Renyi; Yang, Qi-Xiang

2016-12-01

The active galactic nucleus (AGN) NGC 7213 shows a complex correlation between the monochromatic radio luminosity LR and the 2-10 keV X-ray luminosity LX, I.e. the correlation is unusually weak with p ˜ 0 (in the form L_R∝ L_X^p) when LX is below a critical luminosity, and steep with p > 1 when LX is above that luminosity. Such a hybrid correlation in individual AGNs is unexpected as it deviates from the Fundamental Plane of AGN activity. Interestingly, a similar correlation pattern is observed in the black hole X-ray binary H1743-322, where it has been modelled by switching between different modes of accretion. We propose that the flat LR-LX correlation of NGC 7213 is due to the presence of a luminous hot accretion flow, an accretion model whose radiative efficiency is sensitive to the accretion rate. Given the low luminosity of the source, LX ˜ 10-4 of the Eddington luminosity, the viscosity parameter is determined to be small, α ≈ 0.01. We also modelled the broad-band spectrum from radio to γ-rays, the time lag between the radio and X-ray light curves, and the implied size and the Lorentz factor of the radio jet. We predict that NGC 7213 will enter into a two-phase accretion regime when LX ≳ 1.5 × 1042 erg s- 1. When this happens, we predict a softening of the X-ray spectrum with the increasing flux and a steep radio/X-ray correlation.

An ultraluminous X-ray source powered by an accreting neutron star.

PubMed

Bachetti, M; Harrison, F A; Walton, D J; Grefenstette, B W; Chakrabarty, D; Fürst, F; Barret, D; Beloborodov, A; Boggs, S E; Christensen, F E; Craig, W W; Fabian, A C; Hailey, C J; Hornschemeier, A; Kaspi, V; Kulkarni, S R; Maccarone, T; Miller, J M; Rana, V; Stern, D; Tendulkar, S P; Tomsick, J; Webb, N A; Zhang, W W

2014-10-09

The majority of ultraluminous X-ray sources are point sources that are spatially offset from the nuclei of nearby galaxies and whose X-ray luminosities exceed the theoretical maximum for spherical infall (the Eddington limit) onto stellar-mass black holes. Their X-ray luminosities in the 0.5-10 kiloelectronvolt energy band range from 10(39) to 10(41) ergs per second. Because higher masses imply less extreme ratios of the luminosity to the isotropic Eddington limit, theoretical models have focused on black hole rather than neutron star systems. The most challenging sources to explain are those at the luminous end of the range (more than 10(40) ergs per second), which require black hole masses of 50-100 times the solar value or significant departures from the standard thin disk accretion that powers bright Galactic X-ray binaries, or both. Here we report broadband X-ray observations of the nuclear region of the galaxy M82 that reveal pulsations with an average period of 1.37 seconds and a 2.5-day sinusoidal modulation. The pulsations result from the rotation of a magnetized neutron star, and the modulation arises from its binary orbit. The pulsed flux alone corresponds to an X-ray luminosity in the 3-30 kiloelectronvolt range of 4.9 × 10(39) ergs per second. The pulsating source is spatially coincident with a variable source that can reach an X-ray luminosity in the 0.3-10 kiloelectronvolt range of 1.8 × 10(40) ergs per second. This association implies a luminosity of about 100 times the Eddington limit for a 1.4-solar-mass object, or more than ten times brighter than any known accreting pulsar. This implies that neutron stars may not be rare in the ultraluminous X-ray population, and it challenges physical models for the accretion of matter onto magnetized compact objects.

Hidden Active Galactic Nuclei in Early-type Galaxies

NASA Astrophysics Data System (ADS)

Paggi, Alessandro; Fabbiano, Giuseppina; Civano, Francesca; Pellegrini, Silvia; Elvis, Martin; Kim, Dong-Woo

2016-06-01

We present a stacking analysis of the complete sample of early-type galaxies (ETGs) in the Chandra COSMOS (C-COSMOS) survey, to explore the nature of the X-ray luminosity in the redshift and stellar luminosity ranges 0\\lt z\\lt 1.5 and {10}9\\lt {L}K/{L}⊙ \\lt {10}13. Using established scaling relations, we subtract the contribution of X-ray binary populations to estimate the combined emission of hot ISM and active galactic nuclei (AGNs). To discriminate between the relative importance of these two components, we (1) compare our results with the relation observed in the local universe {L}X,{gas}\\propto {L}K4.5 for hot gaseous halos emission in ETGs, and (2) evaluate the spectral signature of each stacked bin. We find two regimes where the non-stellar X-ray emission is hard, consistent with AGN emission. First, there is evidence of hard, absorbed X-ray emission in stacked bins including relatively high z (˜1.2) ETGs with average high X-ray luminosity ({L}X {- {LMXB}}≳ 6× {10}42 {{erg}} {{{s}}}-1). These luminosities are consistent with the presence of highly absorbed “hidden” AGNs in these ETGs, which are not visible in their optical-IR spectra and spectral energy distributions. Second, confirming the early indication from our C-COSMOS study of X-ray detected ETGs, we find significantly enhanced X-ray luminosity in lower stellar mass ETGs ({L}K≲ {10}11{L}⊙ ), relative to the local {L}X,{gas}\\propto {L}K4.5 relation. The stacked spectra of these ETGs also suggest X-ray emission harder than expected from gaseous hot halos. This emission is consistent with inefficient accretion {10}-5-{10}-4{\\dot{M}}{Edd} onto {M}{BH}˜ {10}6-{10}8 {M}⊙ .

Soft X-ray characterisation of the long-term properties of supergiant fast X-ray transients

NASA Astrophysics Data System (ADS)

Romano, P.; Ducci, L.; Mangano, V.; Esposito, P.; Bozzo, E.; Vercellone, S.

2014-08-01

Context. Supergiant fast X-ray transients (SFXTs) are high mass X-ray binaries (HMXBs) that are characterised by a hard X-ray (≥ 15 keV) flaring behaviour. These flares reach peak luminosities of 1036-1037 erg s-1 and last a few hours in the hard X-rays. Aims: We investigate the long-term properties of SFXTs by examining the soft (0.3-10 keV) X-ray emission of the three least active SFXTs in the hard X-ray and by comparing them with the remainder of the SFXT sample. Methods: We performed the first high-sensitivity soft X-ray long-term monitoring with Swift/XRT of three relatively unexplored SFXTs, IGR J08408-4503, IGR J16328-4726, and IGR J16465-4507, whose hard X-ray duty cycles are the lowest measured among the SFXT sample. We assessed how long each source spends in each flux state and compared their properties with those of the prototypical SFXTs. Results: The behaviour of IGR J08408-4503 and IGR J16328-4726 resembles that of other SFXTs, and it is characterised by a relatively high inactivity duty cycle (IDC) and pronounced dynamic range (DR) in the X-ray luminosity. We found DR ~ 7400, IDC ~ 67% for IGR J08408-4503, and DR ~ 750, IDC ~ 61% for IGR J16328-4726 (in all cases the IDC is given with respect to the limiting flux sensitivity of XRT, that is 1-3 × 10-12 erg cm-2 s-1). In common with all the most extreme SFXT prototypes (IGR J17544-2619, XTE J1739-302, and IGR J16479-4514), IGR J08408-4503 shows two distinct flare populations. The first one is associated with the brightest outbursts (X-ray luminosity LX ≳ 1035 - 36 erg s-1), while the second comprises dimmer events with typical luminosities of LX ≲ 1035 erg s-1. This double-peaked distribution of the flares as a function of the X-ray luminosity seems to be a ubiquitous feature of the extreme SFXTs. The lower DR of IGR J16328-4726 suggests that this is an intermediate SFXT. IGR J16465-4507 is characterised by a low IDC ~ 5% and a relatively narrow DR ~ 40, reminiscent of classical supergiant HMXBs. The duty cycles measured with XRT are found to be comparable with those reported previously by BAT and INTEGRAL, when the higher limiting sensitivities of these instruments are taken into account and sufficiently long observational campaigns are available. By making use of these new results and those we reported previously, we prove that no clear correlation exists between the duty cycles of the SFXTs and their orbital periods. Conclusions: The unique sensitivity and scheduling flexibility of Swift/XRT allowed us to carry out an efficient long-term monitoring of the SFXTs, following their activity across more than 4 orders of magnitude in X-ray luminosity. While it is not possible to exclude that particular distributions of the clump and wind parameters may produce double-peaked differential distributions in the X-ray luminosities of the SFXTs, the lack of a clear correlation between the duty cycles and orbital periods of these sources make it difficult to interpret their peculiar variability by only using arguments related to the properties of supergiant star winds. Our findings favour the idea that a correct interpretation of the SFXT phenomenology requires a mechanism to strongly reduce the mass accretion rate onto the compact object during most of its orbit around the companion, as proposed in a number of theoretical works. Tables 1-4 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/568/A55

Gamma-Ray Bursts and Cosmology

NASA Technical Reports Server (NTRS)

Norris, Jay P.

2003-01-01

The unrivalled, extreme luminosities of gamma-ray bursts (GRBs) make them the favored beacons for sampling the high redshift Universe. To employ GRBs to study the cosmic terrain -- e.g., star and galaxy formation history -- GRB luminosities must be calibrated, and the luminosity function versus redshift must be measured or inferred. Several nascent relationships between gamma-ray temporal or spectral indicators and luminosity or total energy have been reported. These measures promise to further our understanding of GRBs once the connections between the luminosity indicators and GRB jets and emission mechanisms are better elucidated. The current distribution of 33 redshifts determined from host galaxies and afterglows peaks near z $\\sim$ 1, whereas for the full BATSE sample of long bursts, the lag-luminosity relation predicts a broad peak z $\\sim$ 1--4 with a tail to z $\\sim$ 20, in rough agreement with theoretical models based on star formation considerations. For some GRB subclasses and apparently related phenomena -- short bursts, long-lag bursts, and X-ray flashes -- the present information on their redshift distributions is sparse or entirely lacking, and progress is expected in Swift era when prompt alerts become numerous.

Testing the Paradigm that Ultra-Luminous X-Ray Sources as a Class Represent Accreting Intermediate

NASA Technical Reports Server (NTRS)

Berghea, C. T.; Weaver, K. A.; Colbert, E. J. M.; Roberts, T. P.

2008-01-01

To test the idea that ultraluminous X-ray sources (ULXs) in external galaxies represent a class of accreting Intermediate-Mass Black Holes (IMBHs), we have undertaken a program to identify ULXs and a lower luminosity X-ray comparison sample with the highest quality data in the Chandra archive. We establish a general property of ULXs that the most X-ray luminous objects possess the fattest X-ray spectra (in the Chandra band pass). No prior sample studies have established the general hardening of ULX spectra with luminosity. This hardening occurs at the highest luminosities (absorbed luminosity > or equals 5x10(exp 39) ergs/s) and is in line with recent models arguing that ULXs are actually stellar-mass black holes. From spectral modeling, we show that the evidence originally taken to mean that ULXs are IMBHs - i.e., the "simple IMBH model" - is nowhere near as compelling when a large sample of ULXs is looked at properly. During the last couple of years, XMM-Newton spectroscopy of ULXs has to some large extent begun to negate the simple IMBH model based on fewer objects. We confirm and expand these results, which validates the XMM-Newton work in a broader sense with independent X-ray data. We find (1) that cool disk components are present with roughly equal probability and total flux fraction for any given ULX, regardless of luminosity, and (2) that cool disk components extend below the standard ULX luminosity cutoff of 10(exp 39) ergs/s, down to our sample limit of 10(exp 38:3) ergs/s. The fact that cool disk components are not correlated with luminosity damages the argument that cool disks indicate IMBHs in ULXs, for which a strong statistical support was never made.

An Ultradeep Chandra Catalog of X-Ray Point Sources in the Galactic Center Star Cluster

NASA Astrophysics Data System (ADS)

Zhu, Zhenlin; Li, Zhiyuan; Morris, Mark R.

2018-04-01

We present an updated catalog of X-ray point sources in the inner 500″ (∼20 pc) of the Galactic center (GC), where the nuclear star cluster (NSC) stands, based on a total of ∼4.5 Ms of Chandra observations taken from 1999 September to 2013 April. This ultradeep data set offers unprecedented sensitivity for detecting X-ray sources in the GC, down to an intrinsic 2–10 keV luminosity of 1.0 × 1031 erg s‑1. A total of 3619 sources are detected in the 2–8 keV band, among which ∼3500 are probable GC sources and ∼1300 are new identifications. The GC sources collectively account for ∼20% of the total 2–8 keV flux from the inner 250″ region where detection sensitivity is the greatest. Taking advantage of this unprecedented sample of faint X-ray sources that primarily traces the old stellar populations in the NSC, we revisit global source properties, including long-term variability, cumulative spectra, luminosity function, and spatial distribution. Based on the equivalent width and relative strength of the iron lines, we suggest that in addition to the arguably predominant population of magnetic cataclysmic variables (CVs), nonmagnetic CVs contribute substantially to the detected sources, especially in the lower-luminosity group. On the other hand, the X-ray sources have a radial distribution closely following the stellar mass distribution in the NSC, but much flatter than that of the known X-ray transients, which are presumably low-mass X-ray binaries (LMXBs) caught in outburst. This, together with the very modest long-term variability of the detected sources, strongly suggests that quiescent LMXBs are a minor (less than a few percent) population.

An XMM-Newton spectral survey of 12 μm selected galaxies - II. Implications for AGN selection and unification

NASA Astrophysics Data System (ADS)

Brightman, Murray; Nandra, Kirpal

2011-07-01

We present a multi-waveband analysis of a 126-galaxy sub-sample of the 12 μm galaxy sample (12MGS), for which we have carried out a detailed X-ray spectral analysis in a previous paper. We determine the activity class of the galaxies by way of optical-line ratio diagnostics and characterize the optical classes by their X-ray, 12 μm and [O III] luminosities and X-ray spectral properties. Our most interesting results from this investigation are as follows. (i) Seyfert (Sy) 1s and Sy2s show a significantly different X-ray luminosity distributions from each other. (ii) Sy2 galaxies with a detection of a hidden broad-line region show a significantly higher X-ray luminosity than those without a detection, supporting the findings of Tran. (iii) Sy1s also present a significantly different 12 μm luminosity distribution from both intermediate Sy types and Sy2s. (iv) The Sy2 fraction decreases towards high X-ray luminosities. (v) X-ray indications of active galactic nuclei (AGN) power agree well with the optical classifications. (vi) There is X-ray evidence for the presence of an AGN in 17 per cent of H II/AGN composite galaxies and 40 per cent of LINERs. (vii) We advocate the use of a 2-10 keV X-ray luminosity of 1041 erg s-1 in the X-ray selection of AGN, rather than 1042 erg s-1, which we find gives a contamination rate of only 3 per cent from star-forming galaxies. (viii) From an analysis of the X-ray power-law index, Γ, we find that Sy1s and Sy2 have the same intrinsic distributions, implying that the central engines are the same, in support of AGN unification schemes. (ix) In 24 per cent of cases the absorption measured in the X-ray spectra does not correspond directly to that implied in the optical band from the visibility of the broad-line regions (BLRs), which is in conflict with AGN unification schemes. (x) We confirm the previous work showing that the obscured fraction in AGN declines at high X-ray luminosity, but also find a decrease at low luminosity having peaked at LX˜ 1042 erg s-1, suggesting that source luminosity has a large effect on the obscuring material, therefore also calling for a modification to unified schemes. (xi) The average obscured and Compton-thick fractions for this sample are 62 ± 5 per cent and 20 ± 4 per cent, respectively, which are higher than hard X-ray and optically selected samples, therefore supporting mid-infrared (MIR) selection as a relatively unbiased method of selecting AGN. (xii) We assess the use of the 'T' ratio (?) for selecting Compton-thick candidates. We conclude here that this quantity can often be unreliable due to uncertainties in the extinction corrections to the [O III] flux. These results have important impacts on AGN selection and unification, and the results from the 12MGS are particularly useful as a local analogue to Spitzer/MIPS 24 μm samples selected at z= 1, as observed 24 μm emission originates at rest-frame 12 μm in sources at this redshift.

Accretion geometry in the persistent Be/X-ray binary RXJ0440.9+4431

NASA Astrophysics Data System (ADS)

Ferrigno, C.; Farinelli, R.; Bozzo, E.; Pottschmidt, K.; Klochkov, D.; Kretschmar, P.

2014-01-01

The persistent Be/X-ray binary RXJ0440.9+4431 flared in 2010 and 2011 and has been followed by various X-ray facilities (Swift, RXTE, XMM-Newton, and INTEGRAL). We studied the source timing and spectral properties as a function of its X-ray luminosity to investigate the transition from normal to flaring activity. The source spectrum can always be described by a bulk-motion Comptonization model of black body seed photons attenuated by a moderate photoelectric absorption. At the highest luminosity, we measured a curvature of the spectrum, which we attribute to a significant contribution of the radiation pressure in the accretion process. This allows us to estimate that the transition from a bulk-motion-dominated flow to a radiatively dominated one happens at a luminosity of ~ 2 × 1036 erg s-1. The luminosity dependency of the size of the black body emission region is found to be rBB ∝ LX0.39±0.02. This suggests that either matter accreting onto the neutron star hosted in RXJ0440.9+4431 penetrates through closed magnetic field lines at the border of the compact object magnetosphere or that the size of the black-body emitting hotspot is larger than the footprint of the accretion column. This phenomenon can be due to illumination of the surface by a growing column or by a a structure of the neutron star magnetic field more complicated than a simple dipole at least close to the surface.

Simulating the X-ray luminosity of Be X-ray binaries: the case for black holes versus neutron stars

NASA Astrophysics Data System (ADS)

Brown, R. O.; Ho, W. C. G.; Coe, M. J.; Okazaki, A. T.

2018-04-01

There are over 100 Be stars that are known to have neutron star companions but only one such system with a black hole. Previous theoretical work suggests this is not due to their formation but due to differences in X-ray luminosity. It has also been proposed that the truncation of the Be star's circumstellar disc is dependent on the mass of the compact object. Hence, Be star discs in black hole binaries are smaller. Since accretion onto the compact object from the Be star's disc is what powers the X-ray luminosity, a smaller disc in black hole systems leads to a lower luminosity. In this paper, simulations are performed with a range of eccentricities and compact object mass. The disc's size and density are shown to be dependent on both quantities. Mass capture and, in turn, X-ray luminosity are heavily dependent on the size and density of the disc. Be/black hole binaries are expected to be up to ˜10 times fainter than Be/neutron star binaries when both systems have the same eccentricity and can be 100 times fainter when comparing systems with different eccentricity.

The X-Ray Luminosity Functions of Field Low-Mass X-Ray Binaries in Early-Type Galaxies: Evidence for a Stellar Age Dependence

NASA Technical Reports Server (NTRS)

Lehmer, B. D.; Berkeley, M.; Zezas, A.; Alexander, D. M.; Basu-Zych, A.; Bauer, F. E.; Brandt, W. N.; Fragos, T.; Hornschemeier, A. E.; Kalogera, V.;

High-energy neutrino fluxes from AGN populations inferred from X-ray surveys

NASA Astrophysics Data System (ADS)

Jacobsen, Idunn B.; Wu, Kinwah; On, Alvina Y. L.; Saxton, Curtis J.

2015-08-01

High-energy neutrinos and photons are complementary messengers, probing violent astrophysical processes and structural evolution of the Universe. X-ray and neutrino observations jointly constrain conditions in active galactic nuclei (AGN) jets: their baryonic and leptonic contents, and particle production efficiency. Testing two standard neutrino production models for local source Cen A (Koers & Tinyakov and Becker & Biermann), we calculate the high-energy neutrino spectra of single AGN sources and derive the flux of high-energy neutrinos expected for the current epoch. Assuming that accretion determines both X-rays and particle creation, our parametric scaling relations predict neutrino yield in various AGN classes. We derive redshift-dependent number densities of each class, from Chandra and Swift/BAT X-ray luminosity functions (Silverman et al. and Ajello et al.). We integrate the neutrino spectrum expected from the cumulative history of AGN (correcting for cosmological and source effects, e.g. jet orientation and beaming). Both emission scenarios yield neutrino fluxes well above limits set by IceCube (by ˜4-106 × at 1 PeV, depending on the assumed jet models for neutrino production). This implies that: (i) Cen A might not be a typical neutrino source as commonly assumed; (ii) both neutrino production models overestimate the efficiency; (iii) neutrino luminosity scales with accretion power differently among AGN classes and hence does not follow X-ray luminosity universally; (iv) some AGN are neutrino-quiet (e.g. below a power threshold for neutrino production); (v) neutrino and X-ray emission have different duty cycles (e.g. jets alternate between baryonic and leptonic flows); or (vi) some combination of the above.

X-Ray Emission from a Merger Remnant, NGC 7252 (the ``Atoms-for-Peace'' Galaxy)

NASA Astrophysics Data System (ADS)

Awaki, Hisamitsu; Matsumoto, Hironori; Tomida, Hiroshi

2002-03-01

We observed a nearby merger remnant NGC 7252 with the X-ray satellite ASCA and detected X-ray emission with the X-ray flux of (1.8+/-0.3)×10-13 ergs s-1 cm-2 in the 0.5-10 keV band. This corresponds to the X-ray luminosity of 8.1×1040 ergs s-1. The X-ray emission is well described with a two-component model: a soft component with kT=0.72+/-0.13 keV and a hard component with kT>5.1 keV. Although NGC 7252 is referred to as a dynamically young protoelliptical, the 0.5-4 keV luminosity of the soft component is about 2×1040 ergs s-1, which is low for an early-type galaxy. The ratio of LX/LFIR suggests that the soft component originated from the hot gas due to star formation. Its low luminosity can be explained by the gas ejection from the galaxy as galaxy winds. Our observation reveals the existence of hard X-ray emission with the 2-10 keV luminosity of 5.6×1040 ergs s-1. This may indicate the existence of nuclear activity or an intermediate-mass black hole in NGC 7252.

The Swift Supergiant Fast X-ray Transient Project

NASA Astrophysics Data System (ADS)

Romano, P.; Barthelmy, S.; Bozzo, E.; Burrows, D.; Ducci, L.; Esposito, P.; Evans, P.; Kennea, J.; Krimm, H.; Vercellone, S.

2017-10-01

We present the Swift Supergiant Fast X-ray Transients project, a systematic study of SFXTs and classical supergiant X-ray binaries (SGXBs) through efficient long-term monitoring of 17 sources including SFXTs and classical SGXBs across more than 4 orders of magnitude in X-ray luminosity on timescales from hundred seconds to years. We derived dynamic ranges, duty cycles, and luminosity distributions to highlight systematic differences that help discriminate between different theoretical models proposed to explain the differences between the wind accretion processes in SFXTs and classical SGXBs. Our follow-ups of the SFXT outbursts provide a steady advancement in the comprehension of the mechanisms triggering the high X-ray level emission of these sources. In particular, the observations of the outburst of the SFXT prototype IGR J17544-2619, when the source reached a peak X-ray luminosity of 3×10^{38} erg s^{-1}, challenged for the first time the maximum theoretical luminosity achievable by a wind-fed neutron star high mass X-ray binary. We propose that this giant outburst was due to the formation of a transient accretion disc around the compact object. We also created a catalogue of over 1000 BAT flares which we use to predict the observability and perspectives with future missions.

RXJ0440.9+4431: a Persistent Be-x-ray Binary in Outburst

NASA Technical Reports Server (NTRS)

Ferrigno, C.; Farinelli, R.; Bozzo, E.; Pottschmidt, K.; Klochkov, D.; Kretschmar, P.

2013-01-01

The persistent Be/X-ray binary RXJ0440.9+4431 flared in 2010 and 2011 and has been followed by various X-ray facilities (Swift, RXTE, XMM-Newton, and INTEGRAL).We studied the source timing and spectral properties as a function of its X-ray luminosity to investigate the transition from normal to flaring activity and the dynamical properties of the system. We have determined the orbital period from the long-term Swift/BAT light curve, but our determinations of the spin-period are not precise enough to constrain any orbital solution. The source spectrum can always be described by a bulk-motion Comptonization model of black body seed photons attenuated by a moderate photoelectric absorption. At the highest luminosity, we measured a curvature of the spectrum, which we attribute to a significant contribution of the radiation pressure in the accretion process. This allows us to estimate that the transition from a bulk-motion-dominated flow to a radiatively dominated one happens at a luminosity of approx 2 × 10(exp 36) erg/ s. The luminosity dependency of the size of the black body emission region is found to be r(sub BB) varies as L(sub x) (exp 0.39 +/- 0.02). This suggests that either matter accreting onto the neutron star hosted in RXJ0440.9+4431 penetrates through closed magnetic field lines at the border of the compact object magnetosphere or that the structure of the Neutron star magnetic field is more complicated than a simple dipole close to the surface.

A deep imaging survey of the Pleiades with ROSAT

NASA Technical Reports Server (NTRS)

Stauffer, J. R.; Caillault, J.-P.; Gagne, M.; Prosser, C. F.; Hartmann, L. W.

1994-01-01

We have obtained deep ROSAT images of three regions within the Pleiades open cluster. We have detected 317 X-ray sources in these ROSAT Position Sensitive Proportional Counter (PSPC) images, 171 of which we associate with certain or probable members of the Pleiades cluster. We detect nearly all Pleiades members with spectral types later than G0 and within 25 arcminutes of our three field centers where our sensitivity is highest. This has allowed us to derive for the first time the luminosity function for the G, K, amd M dwarfs of an open cluster without the need to use statistical techniques to account for the presence of upper limits in the data sample. Because of our high X-ray detection frequency down to the faint limit of the optical catalog, we suspect that some of our unidentified X-ray sources are previously unknown, very low-mass members of Pleiades. A large fraction of the Pleiades members detected with ROSAT have published rotational velocities. Plots of L(sub X)/L(sub Bol) versus spectroscopic rotational velocity show tightly correlated `saturation' type relations for stars with ((B - V)(sub 0)) greater than or equal to 0.60. For each of several color ranges, X-ray luminosities rise rapidly with increasing rotation rate until c sin i approximately equal to 15 km/sec, and then remains essentially flat for rotation rates up to at least v sin i approximately equal to 100 km/sec. The dispersion in rotation among low-mass stars in the Pleiades is by far the dominant contributor to the dispersion in L(sub X) at a given mass. Only about 35% of the B, A, and early F stars in the Pleiades are detected as X-ray sources in our survey. There is no correlation between X-ray flux and rotation for these stars. The X-ray luminosity function for the early-type Pleiades stars appears to be bimodal -- with only a few exceptions, we either detect these stars at fluxes in the range found for low-mass stars or we derive X-ray limits below the level found for most Pleiades dwarfs. The X-ray spectra for the early-type Pleiades stars detected by ROSAT are indistinguishable from the spectra of the low-mass Pleiades members. We believe that the simplest explanation for this behavior is that the early-type Pleiades stars are not themselves intrinsic X-ray sources and that the X-ray emission actually arises from low-mass companions to these stars.

VizieR Online Data Catalog: Intermediate-luminosity X-ray objects catalog (Colbert+, 2002)

NASA Astrophysics Data System (ADS)

Colbert, E. J. M.; Ptak, A. F.

2002-11-01

ROSAT, and now Chandra, X-ray images allow studies of extranuclear X-ray point sources in galaxies other than our own. X-ray observations of normal galaxies with ROSAT and Chandra have revealed that off-nuclear, compact, intermediate-luminosity (LX[2-10keV]>=1039erg/s) X-ray objects (IXOs, a.k.a. ULXs [ultraluminous X-ray sources]) are quite common. Here we present a catalog and finding charts for 87 IXOs in 54 galaxies, derived from all of the ROSAT HRI imaging data for galaxies with cz<=5000km/s from the Third Reference Catalog of Bright Galaxies. (2 data files).

Testing the Paradigm that Ultraluminous X-Ray Sources as a Class Represent Accreting Intermediate-Mass Black Holes

NASA Astrophysics Data System (ADS)

Berghea, C. T.; Weaver, K. A.; Colbert, E. J. M.; Roberts, T. P.

2008-11-01

To test the idea that ultraluminous X-ray sources (ULXs) in external galaxies represent a class of accreting intermediate-mass black holes (IMBHs), we have undertaken a program to identify ULXs and a lower luminosity X-ray comparison sample with the highest quality data in the Chandra archive. We establish as a general property of ULXs that the most X-ray-luminous objects possess the flattest X-ray spectra (in the Chandra bandpass). No prior sample studies have established the general hardening of ULX spectra with luminosity. This hardening occurs at the highest luminosities (absorbed luminosity >=5 × 1039 erg s-1) and is in line with recent models arguing that ULXs are actually stellar mass black holes. From spectral modeling, we show that the evidence originally taken to mean that ULXs are IMBHs—i.e., the "simple IMBH model"—is nowhere near as compelling when a large sample of ULXs is looked at properly. During the last couple of years, XMM-Newton spectroscopy of ULXs has to a large extent begun to negate the simple IMBH model based on fewer objects. We confirm and expand these results, which validates the XMM-Newton work in a broader sense with independent X-ray data. We find that (1) cool-disk components are present with roughly equal probability and total flux fraction for any given ULX, regardless of luminosity, and (2) cool-disk components extend below the standard ULX luminosity cutoff of 1039 erg s-1, down to our sample limit of 1038.3 erg s-1. The fact that cool-disk components are not correlated with luminosity damages the argument that cool disks indicate IMBHs in ULXs, for which strong statistical support was never found.

A Deep NuSTAR Survey of M31: Compact object types in our Nearest Neighbor Galaxy

NASA Astrophysics Data System (ADS)

Hornschemeier, Ann E.; Wik, Daniel R.; Yukita, Mihoko; Ptak, Andrew; Venters, Tonia M.; Lehmer, Bret; Maccarone, Thomas J.; Zezas, Andreas; Harrison, Fiona; Stern, Daniel; Williams, Benjamin F.; Vulic, Neven

2017-08-01

X-ray binaries (XRBs) trace young and old stellar populations in galaxies, and thus star formation rate and star formation history/stellar mass. X-ray emission from XRBs may be responsible for significant amounts of heating of the early Intergalactic Medium at Cosmic Dawn and may also play a significant role in reionization. Until recently, the E>10 keV (hard X-ray) emission from these populations could only be studied for XRBs in our own galaxy, where it is often difficult to measure accurate distances and thus luminosities. We have observed M31 in 4 NuSTAR fields for a total exposure of 1.4 Ms, covering the young stellar population in a swath of the disk (within the footprint of the Panchromatic Hubble Andromeda Treasury (PHAT) Survey) and older populations in the bulge. We detected more than 100 sources in the 4-25 keV band, where hard band (12-25 keV) emission has allowed us to discriminate between black holes and neutron stars in different accretion states. The luminosity function of the hard band detected sources are compared to Swift/BAT and INTEGRAL-derived luminosity functions of the Milky Way population, which reveals an excess of luminous sources in M31 when correcting for star formation rate and stellar mass.

Simulations of the Formation and Evolution of X-ray Clusters

NASA Astrophysics Data System (ADS)

Bryan, G. L.; Klypin, A.; Norman, M. L.

1994-05-01

We describe results from a set of Omega = 1 Cold plus Hot Dark Matter (CHDM) and Cold Dark Matter (CDM) simulations. We examine the formation and evolution of X-ray clusters in a cosmological setting with sufficient numbers to perform statistical analysis. We find that CDM, normalized to COBE, seems to produce too many large clusters, both in terms of the luminosity (dn/dL) and temperature (dn/dT) functions. The CHDM simulation produces fewer clusters and the temperature distribution (our numerically most secure result) matches observations where they overlap. The computed cluster luminosity function drops below observations, but we are almost surely underestimating the X-ray luminosity. Because of the lower fluctuations in CHDM, there are only a small number of bright clusters in our simulation volume; however we can use the simulated clusters to fix the relation between temperature and velocity dispersion, allowing us to use collisionless N-body codes to probe larger length scales with correspondingly brighter clusters. The hydrodynamic simulations have been performed with a hybrid particle-mesh scheme for the dark matter and a high resolution grid-based piecewise parabolic method for the adiabatic gas dynamics. This combination has been implemented for massively parallel computers, allowing us to achive grids as large as 512(3) .

ROSAT X-ray observations of late-type evolved stars: On the relationship between coronal temperatures and luminosities

NASA Technical Reports Server (NTRS)

Maggio, A.; Sciortino, S.; Harnden, F. R., Jr.

1994-01-01

We present ROSAT Position Sensitive Proportional Counters (PSPC) X-ray observations of three near-solar-mass stars, in different evolutionary phases beyond the main sequence: eta Sco (F3 III-IV), iota Vir (F6 III), and HD 74772 (G5 III). All three of these nearby, presumably single stars have been detected, and we have collected enough counts to perform a detailed analysis of their soft X-ray spectra. While the X-ray spectra of eta Sco and HD 74772 can be fitted with Raymond-Smith thermal models with temperatures around 2 x 10(exp 6) K, the high signal-to-noise spectrum of iota Vir provides unambiguous evidence of a multitemperature plasma, with a two-temperature best-fit model with components at approximately 2 x 10(exp 6) K and 8 x 10(exp 6) K. Evidence of some hot plasma (T approximately 10(exp 7) K) has been also found for HD 74772. The present data, compared with spectral fitting results for other late-type stars observed with the Einstein Observatory, indicate that the low X-ray luminosity giants (L(sub x) is less than 5 x 10(exp 28) ergs/s) do not share with the higher X-ray luminosity stars of the same class the property of having substantial amount of 10(exp 7) K plasma. Moreover, our results confirm the trend of increasing X-ray luminosities with increasing coronal temperatures.

Broadband X-Ray Spectral Analysis of the Double-nucleus Luminous Infrared Galaxy Mrk 463

NASA Astrophysics Data System (ADS)

Yamada, Satoshi; Ueda, Yoshihiro; Oda, Saeko; Tanimoto, Atsushi; Imanishi, Masatoshi; Terashima, Yuichi; Ricci, Claudio

2018-05-01

We present a broadband (0.4–70 keV) X-ray spectral analysis of the luminous infrared galaxy (LIRG) system Mrk 463 observed with Nuclear Spectroscopic Telescope Array (NuSTAR), Chandra, and XMM-Newton, which contains double active galactic nuclei (AGNs; Mrk 463E and Mrk 463W) with a separation of ∼3.8 kpc. Detecting their transmitted hard X-ray >10 keV continua with NuSTAR, we confirm that Mrk 463E and Mrk 463W have AGNs with intrinsic luminosities of (1.6–2.2) × 1043 and (0.5–0.6) × 1043 erg s‑1 (2–10 keV) obscured by hydrogen column densities of 8 × 1023 and 3 × 1023 cm‑2, respectively. Both nuclei show strong reflection components from cold matter. The luminosity ratio between X-ray (2–10 keV) and [O IV] 25.89 μm of Mrk 463E is ∼5 times smaller than those of normal Seyfert galaxies, suggesting that the intrinsic SED is X-ray weak relative to the UV luminosity. In fact, the bolometric AGN luminosity of Mrk 463E estimated from L‧-band (3.8 μm), [O IV] 25.89 μm, and [Ne V] 14.32 μm lines indicate a large bolometric-to-X-ray luminosity ratio, κ 2–10 keV ≈ 110–410, and a high Eddington ratio, λ Edd ∼ 0.4–0.8. We suggest that the merger triggered a rapid growth of the black hole in Mrk 463E, which is not yet deeply “buried” by circumnuclear dust. By contrast, the L‧-band luminosity of Mrk 463W is unusually small relative to the X-ray luminosity, suggesting that the Eddington ratio is low (<10‑3) and it might be still in an early phase of merger-driven AGN activity.

The X-Ray Globular Cluster Population in NGC 1399

NASA Technical Reports Server (NTRS)

Angelini, Lorella; Loewenstein, Michael; Mushotzky, Richard F.; White, Nicholas E. (Technical Monitor)

2001-01-01

We report on X-ray sources detected in the Chandra images of the elliptical galaxy NGC 1399 and identified with globular clusters (GCs). The 8'x 8' Chandra image shows that a large fraction of the 2-10 keV X-ray emission is resolved into point sources, with a luminosity threshold of 5 x 10 (exp 37) ergs s-1. These sources are most likely Low Mass X-ray Binaries (LMXBs). More than 70% of the X-ray sources, in a region imaged by Hubble Space Telescope (HST), are located within GCs. Many of these sources have super-Eddington luminosity (for an accreting neutron star) and their average luminosity is higher than the remaining sources. This association suggests that, in giant elliptical galaxies, luminous X-ray binaries preferentially form in GCs. The spectral properties of the GC and non-GC sources are in most cases similar to those of LMXBs in our galaxy. Two of the brightest sources, one of which is in GC, have a much softer spectra as seen in the high state black hole. The "apparent" super-Eddington luminosity in many cases may be due to multiple LMXB systems within individual GC, but with some of the most extreme luminous systems containing massive black holes.

X-ray binary formation in low-metallicity blue compact dwarf galaxies

NASA Astrophysics Data System (ADS)

Brorby, M.; Kaaret, P.; Prestwich, A.

2014-07-01

X-rays from binaries in small, metal-deficient galaxies may have contributed significantly to the heating and reionization of the early Universe. We investigate this claim by studying blue compact dwarfs (BCDs) as local analogues to these early galaxies. We constrain the relation of the X-ray luminosity function (XLF) to the star formation rate (SFR) using a Bayesian approach applied to a sample of 25 BCDs. The functional form of the XLF is fixed to that found for near-solar metallicity galaxies and is used to find the probability distribution of the normalization that relates X-ray luminosity to SFR. Our results suggest that the XLF normalization for low-metallicity BCDs (12+log(O/H) < 7.7) is not consistent with the XLF normalization for galaxies with near-solar metallicities, at a confidence level 1-5 × 10- 6. The XLF normalization for the BCDs is found to be 14.5± 4.8 ({M}_{⊙}^{-1} yr), a factor of 9.7 ± 3.2 higher than for near-solar metallicity galaxies. Simultaneous determination of the XLF normalization and power-law index result in estimates of q = 21.2^{+12.2}_{-8.8} ({M}_{⊙}^{-1} yr) and α = 1.89^{+0.41}_{-0.30}, respectively. Our results suggest a significant enhancement in the population of high-mass X-ray binaries in BCDs compared to the near-solar metallicity galaxies. This suggests that X-ray binaries could have been a significant source of heating in the early Universe.

Modeling X-Ray Binary Evolution in Normal Galaxies: Insights from SINGS

NASA Technical Reports Server (NTRS)

Tzanavaris, P.; Fragos, T.; Tremmel, M.; Jenkins, L.; Zezas, A.; Lehmer, B. D.; Hornschemeier, A.; Kalogera, V.; Ptak, A; Basu-Zych, A.

2013-01-01

We present the largest-scale comparison to date between observed extragalactic X-ray binary (XRB) populations and theoretical models of their production. We construct observational X-ray luminosity functions (oXLFs) using Chandra observations of 12 late-type galaxies from the Spitzer Infrared Nearby Galaxy Survey (SINGS). For each galaxy, we obtain theoretical XLFs (tXLFs) by combining XRB synthetic models, constructed with the population synthesis code StarTrack, with observational star formation histories (SFHs). We identify highest-likelihood models both for individual galaxies and globally, averaged over the full galaxy sample. Individual tXLFs successfully reproduce about half of oXLFs, but for some galaxies we are unable to find underlying source populations, indicating that galaxy SFHs and metallicities are not well matched and/or XRB modeling requires calibration on larger observational samples. Given these limitations, we find that best models are consistent with a product of common envelope ejection efficiency and central donor concentration approx.. = 0.1, and a 50% uniform - 50% "twins" initial mass-ratio distribution. We present and discuss constituent subpopulations of tXLFs according to donor, accretor and stellar population characteristics. The galaxy-wide X-ray luminosity due to low-mass and high-mass XRBs, estimated via our best global model tXLF, follows the general trend expected from the L(sub X) - star formation rate and L(sub X) - stellar mass relations of Lehmer et al. Our best models are also in agreement with modeling of the evolution both of XRBs over cosmic time and of the galaxy X-ray luminosity with redshift.

Examining the X-ray Properties of Lenticular Galaxies: Rollins S0 X-ray Sample (RS0X)

NASA Astrophysics Data System (ADS)

Fuse, Christopher R.; Malespina, Alysa

2017-01-01

Lenticular galaxies represent a complex morphology in which many questions remain. The S0 morphology possesses spiral galaxy attributes, such as a disk, while also displaying the luminosity and old stellar population indicative of an elliptical galaxy. The proposed formation mechanisms for lenticulars are also varied, with the absence of gas suggesting a faded spiral and the high masses and luminosities implying a merger formation. The star formation and high-energy emission from a sample of S0s will be used to better understand the properties and formation mechanisms of this unique subset of galaxies.We use the Chandra X-ray Observatory archives cycle 1 - 16 to identify a sample of seventeen lenticular galaxies residing in a variety of environments. Data was analyzed using the CIAO software to produce true color images, radial profiles of the halo gas, gas contours, as well as determine the X-ray luminosities of the point sources and gas.The X-ray gas temperature of the sample S0s varied over a narrow range between 0.61 and 0.96 keV, with one outlier, NGC 4382 at 2.0 keV. The X-ray luminosity of the halo gas varies by four dex. The gas temperatures and X-ray luminosities do not vary by environment, with the majority of sample S0s displaying values of typical elliptical galaxies. The S0 sample is X-ray under-luminous relative to the optical luminosity as compared to the sample of early-type galaxies of Ellis & O’Sullivan (2006).The halo gas exhibited some distinct morphological features, such as multiple X-ray peaks, which may indicate a merger event, and highly concentrated gas, suggesting limited gravitational disturbance. Isolated S0, NGC 4406, displays an asymmetric halo, which could be interpreted as gas stripping. An isolated lenticular experiencing gas redistribution due to gravitational perturbation or a cluster-like medium could be interpreted as NGC 4406 forming in a higher galactic density environment than the field.

Superwind evolution: the young starburst-driven wind galaxy NGC 2782

NASA Astrophysics Data System (ADS)

Bravo-Guerrero, Jimena; Stevens, Ian R.

2017-06-01

We present results from a 30-ks Chandra observation of the important starburst galaxy NGC 2782, covering the 0.3-10 keV energy band. We find evidence of a superwind of small extent, which is likely in an early stage of development. We find a total of 27 X-ray point sources within a region of radius 2D25 of the galaxy centre and that are likely associated with the galaxy. Of these, 13 are ultraluminous X-ray point sources (ULXs; LX ≥ 1039 erg s- 1) and a number have likely counterparts. The X-ray luminosities of the ULX candidates are 1.2-3.9 × 1039 erg s- 1. NGC 2782 seems to have an unusually large number of ULXs. Central diffuse X-ray emission extending to ˜3 kpc from the nuclear region has been detected. We also find an X-ray structure to the south of the nucleus, coincident with Hα filaments and with a 5-GHz radio source. We interpret this as a blow-out region of a forming superwind. This X-ray bubble has a total luminosity (0.3-10 keV) of 5 × 1039 erg s-1 (around 15 per cent of the total luminosity of the extended emission), and an inferred wind mass of 1.5 × 106 M⊙ . We also discuss the nature of the central X-ray source in NGC 2782, and conclude that it is likely a low-luminosity active galactic nucleus, with a total X-ray luminosity of LX = 6 × 1040 erg s-1, with strong Fe line emission at 6.4 keV.

ROSAT observations of Coma Cluster galaxies

NASA Technical Reports Server (NTRS)

Dow, K. L.; White, S. D. M.

1995-01-01

The approximately 86 ks ROSAT Position Sensitive Proportional Counter (PSPC) image of the Coma Cluster is deeper than any previous X-ray observation of a galaxy cluster. We search for X-ray emission from 35 individual galaxies in a magnitude-limited sample, all of which lie within 20 arcmins of the optical axis in at least one of the four Coma pointings. We detect seven galaxies in the 0.4-2.4 keV band at a significance level exceeding 3 sigma, and a further four at above 2 sigma. Although we can set only upper limits on the individual flux from each of the other galaxies, we are able to measure their mean flux by stacking the observations. The X-ray luminosities of the seven detections range from 6.2 x 10(exp 40) to 1.5 x 10(exp 42) ergs/s (0.4-2.4 keV for H(sub 0) = 50 km/s/Mpc). For galaxies with a blue absolute magnitude of about -21 we find a mean X-ray luminosity of 1.3 x 10(exp 40) ergs/s. The ratio of X-ray to optical luminosity is substantially smaller for such subjects than for the brightest galaxies in the cluster. The X-ray luminosities of the four brightest galaxies are ill-defined, however, because of ambiguity in distinguishing galaxy emission from cluster emission. Each object appears to be related to significant structure in the diffuse intracluster medium. We also investigate emission in the softer 0.2-0.4 keV band where detections are less significant because of the higher background, and we discuss the properties of a number of interesting individual sources. The X-ray luminosities of the Coma galaxies are similar to those of galaxies in the Virgo Cluster and in other regions with relatively low galaxy density. We conclude that large-scale environmental effects do not significantly enhance or suppress the average X-ray emission from galaxies, but that individual objects vary in luminosity substantially in a way which may depend on the detailed history of their environment.

Very Luminous X-ray Point Sources in Starburst Galaxies

NASA Astrophysics Data System (ADS)

Colbert, E.; Heckman, T.; Ptak, A.; Weaver, K. A.; Strickland, D.

Extranuclear X-ray point sources in external galaxies with luminosities above 1039.0 erg/s are quite common in elliptical, disk and dwarf galaxies, with an average of ~ 0.5 and dwarf galaxies, with an average of ~0.5 sources per galaxy. These objects may be a new class of object, perhaps accreting intermediate-mass black holes, or beamed stellar mass black hole binaries. Starburst galaxies tend to have a larger number of these intermediate-luminosity X-ray objects (IXOs), as well as a large number of lower-luminosity (1037 - 1039 erg/s) point sources. These point sources dominate the total hard X-ray emission in starburst galaxies. We present a review of both types of objects and discuss possible schemes for their formation.

X-ray constraints on the fraction of obscured active galactic nuclei at high accretion luminosities

NASA Astrophysics Data System (ADS)

Georgakakis, A.; Salvato, M.; Liu, Z.; Buchner, J.; Brandt, W. N.; Ananna, T. Tasnim; Schulze, A.; Shen, Yue; LaMassa, S.; Nandra, K.; Merloni, A.; McGreer, I. D.

2017-08-01

The wide-area XMM-XXL X-ray survey is used to explore the fraction of obscured active galactic nuclei (AGNs) at high accretion luminosities, LX(2-10 keV) ≳ 1044 erg s - 1, and out to redshift z ≈ 1.5. The sample covers an area of about 14 deg2 and provides constraints on the space density of powerful AGNs over a wide range of neutral hydrogen column densities extending beyond the Compton-thick limit, NH ≈ 1024 cm - 2. The fraction of obscured Compton-thin (NH = 1022-1024 cm - 2) AGNs is estimated to be ≈0.35 for luminosities LX(2-10 keV) > 1044 erg s - 1, independent of redshift. For less luminous sources, the fraction of obscured Compton-thin AGNs increases from 0.45 ± 0.10 at z = 0.25 to 0.75 ± 0.05 at z = 1.25. Studies that select AGNs in the infrared via template fits to the observed spectral energy distribution of extragalactic sources estimate space densities at high accretion luminosities consistent with the XMM-XXL constraints. There is no evidence for a large population of AGNs (e.g. heavily obscured) identified in the infrared and missed at X-ray wavelengths. We further explore the mid-infrared colours of XMM-XXL AGNs as a function of accretion luminosity, column density and redshift. The fraction of XMM-XXL sources that lie within the mid-infrared colour wedges defined in the literature to select AGNs is primarily a function of redshift. This fraction increases from about 20-30 per cent at z = 0.25 to about 50-70 per cent at z = 1.5.

Narrow vs. Broad line Seyfert 1 galaxies: X-ray, optical and mid-infrared AGN characteristics

NASA Astrophysics Data System (ADS)

Lakićević, Maša; Popović, Luka Č.; Kovačević-Dojčinović, Jelena

2018-05-01

We investigated narrow line Seyfert 1 galaxies (NLS1s) at optical, mid-infrared (MIR) and X-ray wavelengths, comparing them to the broad line active galactic nuclei (BLAGNs). We found that black hole mass, coronal line luminosities, X-ray hardness ratio and X-ray, optical and MIR luminosities are higher for the BLAGNs than for NLS1s, while policyclic aromatic hydrocarbon (PAH) contribution and the accretion rates are higher for the NLS1s. Furthermore, we found some trends among spectral parameters that NLS1s have and BLAGNs do not have. The evolution of FWHM(Hβ) with the luminosities of MIR and coronal lines, continuum luminosities, PAH contribution, Hβ broad line luminosity, FWHM[O III] and EW(HβNLR), are important trends found for NLS1s. That may contribute to the insight that NLS1s are developing AGNs, growing their black holes, while their luminosities and FWHM(Hβ) consequently grow, and that BLAGNs are mature, larger objects of slower and/or different evolution. Black hole mass is related to PAH contribution only for NLS1s, which may suggest that PAHs are more efficiently destroyed in NLS1s.

A Radio Frequency Study of the Accreting Millisecond X-ray Pulsar, IGR J16597–3704, in the Globular Cluster NGC 6256

NASA Astrophysics Data System (ADS)

Tetarenko, A. J.; Bahramian, A.; Wijnands, R.; Heinke, C. O.; Maccarone, T. J.; Miller-Jones, J. C. A.; Strader, J.; Chomiuk, L.; Degenaar, N.; Sivakoff, G. R.; Altamirano, D.; Deller, A. T.; Kennea, J. A.; Li, K. L.; Plotkin, R. M.; Russell, T. D.; Shaw, A. W.

2018-02-01

We present Karl G. Jansky Very Large Array radio frequency observations of the new accreting millisecond X-ray pulsar (AMXP), IGR J16597‑3704, located in the globular cluster NGC 6256. With these data, we detect a radio counterpart to IGR J16597‑3704, and determine an improved source position. Pairing our radio observations with quasi-simultaneous Swift/XRT X-ray observations, we place IGR J16597‑3704 on the radio–X-ray luminosity plane, where we find that IGR J16597‑3704 is one of the more radio-quiet neutron star low-mass X-ray binaries known to date. We discuss the mechanisms that may govern radio luminosity (and in turn jet production and evolution) in AMXPs. Furthermore, we use our derived radio position to search for a counterpart in archival Hubble Space Telescope and Chandra X-ray Observatory data, and estimate an upper limit on the X-ray luminosity of IGR J16597‑3704 during quiescence.

X-ray pulsars in nearby irregular galaxies

NASA Astrophysics Data System (ADS)

Yang, Jun

2018-01-01

The Small Magellanic Cloud (SMC), Large Magellanic Cloud (LMC) and Irregular Galaxy IC 10 are valuable laboratories to study the physical, temporal and statistical properties of the X-ray pulsar population with multi-satellite observations, in order to probe fundamental physics. The known distance of these galaxies can help us easily categorize the luminosity of the pulsars and their age difference can be helpful for for studying the origin and evolution of compact objects. Therefore, a complete archive of 116 XMM-Newton PN, 151 Chandra (Advanced CCD Imaging Spectrometer) ACIS, and 952 RXTE PCA observations for the pulsars in the Small Magellanic Cloud (SMC) were collected and analyzed, along with 42 XMM-Newton and 30 Chandra observations for the Large Magellanic Cloud, spanning 1997-2014. From a sample of 67 SMC pulsars we generate a suite of products for each pulsar detection: spin period, flux, event list, high time-resolution light-curve, pulse-profile, periodogram, and X-ray spectrum. Combining all three satellites, I generated complete histories of the spin periods, pulse amplitudes, pulsed fractions and X-ray luminosities. Many of the pulsars show variations in pulse period due to the combination of orbital motion and accretion torques. Long-term spin-up/down trends are seen in 28/25 pulsars respectively, pointing to sustained transfer of mass and angular momentum to the neutron star on decadal timescales. The distributions of pulse detection and flux as functions of spin period provide interesting findings: mapping boundaries of accretion-driven X-ray luminosity, and showing that fast pulsars (P<10 s) are rarely detected, which yet are more prone to giant outbursts. In parallel we compare the observed pulse profiles to our general relativity (GR) model of X-ray emission in order to constrain the physical parameters of the pulsars.In addition, we conduct a search for optical counterparts to X-ray sources in the local dwarf galaxy IC 10 to form a comparison sample for Magellanic Cloud X-ray pulsars.

An X-ray survey of nine historical novae. [HEAO 2 observations

NASA Technical Reports Server (NTRS)

Becker, R. H.; Marshall, F. E.

1980-01-01

The Einstein Observatory imaging proportional counter was used to search for X-ray emission from nine nearby historical novae. Six of the novae were detected with estimated X-ray intensities between .1 to 4 keV of 10 to the -13th power to 10 to the -11th power ergs/sq cm-s, comparable to the intensities of previously detected cataclysmic variables. The X-ray intensity of one of the novae, V603 Aql, varies over times of several hundred seconds. The data suggest a correlation between the decay rate of the historical outburst and the current X-ray luminosity. Alternatively, the X-ray luminosity may be related to the inclination of the binary system.

Anti-correlated X-ray and Radio Variability in the Transitional Millisecond Pulsar PSR J1023+0038

NASA Astrophysics Data System (ADS)

Bogdanov, Slavko; Deller, Adam; Miller-Jones, James; Archibald, Anne; Hessels, Jason W. T.; Jaodand, Amruta; Patruno, Alessandro; Bassa, Cees; D'Angelo, Caroline

2018-01-01

The PSR J1023+0038 binary system hosts a 1.69-ms neutron star and a low-mass, main-sequence-like star. The system underwent a transformation from a rotation-powered to a low-luminosity accreting state in 2013 June, in which it has remained since. We present an unprecedented set of strictly simultaneous Chandra X-ray Observatory and Karl G. Jansky Very Large Array observations, which for the first time reveal a highly reproducible, anti-correlated variability pattern. Rapid declines in X-ray flux are always accompanied by a radio brightening with duration that closely matches the low X-ray flux mode intervals. We discuss these findings in the context of accretion and jet outflow physics and their implications for using the radio/X-ray luminosity plane to distinguish low-luminosity candidate black hole binary systems from accreting transitional millisecond pulsars.

An accreting pulsar with extreme properties drives an ultraluminous x-ray source in NGC 5907.

PubMed

Israel, Gian Luca; Belfiore, Andrea; Stella, Luigi; Esposito, Paolo; Casella, Piergiorgio; De Luca, Andrea; Marelli, Martino; Papitto, Alessandro; Perri, Matteo; Puccetti, Simonetta; Castillo, Guillermo A Rodríguez; Salvetti, David; Tiengo, Andrea; Zampieri, Luca; D'Agostino, Daniele; Greiner, Jochen; Haberl, Frank; Novara, Giovanni; Salvaterra, Ruben; Turolla, Roberto; Watson, Mike; Wilms, Joern; Wolter, Anna

2017-02-24

Ultraluminous x-ray sources (ULXs) in nearby galaxies shine brighter than any x-ray source in our Galaxy. ULXs are usually modeled as stellar-mass black holes (BHs) accreting at very high rates or intermediate-mass BHs. We present observations showing that NGC 5907 ULX is instead an x-ray accreting neutron star (NS) with a spin period evolving from 1.43 seconds in 2003 to 1.13 seconds in 2014. It has an isotropic peak luminosity of [Formula: see text]1000 times the Eddington limit for a NS at 17.1 megaparsec. Standard accretion models fail to explain its luminosity, even assuming beamed emission, but a strong multipolar magnetic field can describe its properties. These findings suggest that other extreme ULXs (x-ray luminosity [Formula: see text] 10 41 erg second[Formula: see text]) might harbor NSs. Copyright © 2017, American Association for the Advancement of Science.

Do X-ray dark or underluminous galaxy clusters exist?

NASA Astrophysics Data System (ADS)

Andreon, S.; Moretti, A.

2011-12-01

We study the X-ray properties of a color-selected sample of clusters at 0.1 < z < 0.3, to quantify the real aboundance of the population of X-ray dark or underluminous clusters and at the same time the spurious detection contamination level of color-selected cluster catalogs. Starting from a local sample of color-selected clusters, we restrict our attention to those with sufficiently deep X-ray observations to probe their X-ray luminosity down to very faint values and without introducing any X-ray bias. This allowed us to have an X-ray- unbiased sample of 33 clusters to measure the LX-richness relation. Swift 1.4 Ms X-ray observations show that at least 89% of the color-detected clusters are real objects with a potential well deep enough to heat and retain an intracluster medium. The percentage rises to 94% when one includes the single spectroscopically confirmed color-selected cluster whose X-ray emission is not secured. Looking at our results from the opposite perspective, the percentage of X-ray dark clusters among color-selected clusters is very low: at most about 11 per cent (at 90% confidence). Supplementing our data with those from literature, we conclude that X-ray- and color- cluster surveys sample the same population and consequently that in this regard we can safely use clusters selected with any of the two methods for cosmological purposes. This is an essential and promising piece of information for upcoming surveys in both the optical/IR (DES, EUCLID) and X-ray (eRosita). Richness correlates with X-ray luminosity with a large scatter, 0.51 ± 0.08 (0.44 ± 0.07) dex in lgLX at a given richness, when Lx is measured in a 500 (1070) kpc aperture. We release data and software to estimate the X-ray flux, or its upper limit, of a source with over-Poisson background fluctuations (found in this work to be ~20% on cluster angular scales) and to fit X-ray luminosity vs richness if there is an intrinsic scatter. These Bayesian applications rigorously account for boundaries (e.g., the X-ray luminosity and the richness cannot be negative).

Quasar X-Ray Spectra At z=1.5

NASA Technical Reports Server (NTRS)

Siemiginowska, Aneta

2001-01-01

The predicted counts for ASCA observation was much higher than actually observed counts in the quasar. However, there are three weak hard x-ray sources in the GIS field. We are adding them to the source counts in modeling of hard x-ray background. The work is in progress. We have published a paper in Ap.J. on the luminosity function and the quasar evolution. Based on the theory described in this paper we are predicting a number of sources and their contribution to the x-ray background at different redshifts. These model predictions will be compared to the observed data in the final paper.

Globular cluster x-ray sources

PubMed Central

Pooley, David

2010-01-01

Globular clusters and x-ray astronomy have a long and fruitful history. Uhuru and OSO-7 revealed highly luminous (> 1036 ergs-1) x-ray sources in globular clusters, and Einstein and ROSAT revealed a larger population of low-luminosity (< 1033 ergs-1) x-ray sources. It was realized early on that the high-luminosity sources were low-mass x-ray binaries in outburst and that they were orders of magnitude more abundant per unit mass in globular clusters than in the rest of the galaxy. However, the low-luminosity sources proved difficult to classify. Many ideas were put forth—low-mass x-ray binaries in quiescence (qLMXBs), cataclysmic variables (CVs), active main-sequence binaries (ABs), and millisecond pulsars (MSPs)—but secure identifications were scarce. In ROSAT observations of 55 clusters, about 25 low-luminosity sources were found. Chandra has now observed over 80 Galactic globular clusters, and these observations have revealed over 1,500 x-ray sources. The superb angular resolution has allowed for many counterpart identifications, providing clues to the nature of this population. It is a heterogeneous mix of qLMXBs, CVs, ABs, and MSPs, and it has been shown that the qLMXBs and CVs are both, in part, overabundant like the luminous LMXBs. The number of x-ray sources in a cluster correlates very well with its encounter frequency. This points to dynamical formation scenarios for the x-ray sources and shows them to be excellent tracers of the complicated internal dynamics. The relation between the encounter frequency and the number of x-ray sources has been used to suggest that we have misunderstood the dynamical states of globular clusters. PMID:20404204

Extended X-Ray Emission around Quasars at Intermediate Redshift

NASA Technical Reports Server (NTRS)

Fiore, Fabrizio

1998-01-01

We compare the optical to soft X-ray spectral energy distribution (SED) of a sample of bright low-redshift (0.048 less than z less than 0.155), radio-quiet quasars, with a range of thermal models which have been proposed to explain the optical/UV/soft X-ray quasar emission: (a) optically thin emission from an ionized plasma, (b) optically thick emission from the innermost regions of an accretion disk in Schwarzschild and Kerr geometries. We presented ROSAT PSPC observations of these quasars in an earlier paper. Here our goals are to search for the signature of thermal emission in the quasar SED, and to investigate whether a single component is dominating at different frequencies. We find that isothermal optically thin plasma models can explain the observed soft X-ray color and the mean OUV color. However, they predict an ultraviolet (1325 Angstrom) luminosity a factor of 3 to 10 times lower than observed. Pure disk models, even in a Kerr geometry, do not have the necessary flexibility to account for the observed OUV and soft X-ray luminosities. Additional components are needed both in the optical and in the soft X-rays (e.g. a hot corona can explain the soft X-ray color). The most constrained modification of pure disk models, is the assumption of an underlying power law component extending from the infrared (3 micrometers) to the X-ray. This can explain both the OUV and soft X-ray colors and luminosities and does not exceed the 3 micrometers luminosity, where a contribution from hot dust is likely to be important. We also discuss the possibility that the observed soft X-ray color and luminosity are dominated by reflection from the ionized surface of the accretion disk. While modifications of both optically thin plasma models and pure disk models might account for the observed SED, we do not find any strong evidence that the OUV bump and soft X-ray emission are one and the same component. Likewise, we do not find any strong argument which definitely argues in favor of thermal models.

Distant Cluster Hunting. II; A Comparison of X-Ray and Optical Cluster Detection Techniques and Catalogs from the ROSAT Optical X-Ray Survey

NASA Technical Reports Server (NTRS)

Donahue, Megan; Scharf, Caleb A.; Mack, Jennifer; Lee, Y. Paul; Postman, Marc; Rosait, Piero; Dickinson, Mark; Voit, G. Mark; Stocke, John T.

2002-01-01

We present and analyze the optical and X-ray catalogs of moderate-redshift cluster candidates from the ROSA TOptical X-Ray Survey, or ROXS. The survey covers the sky area contained in the fields of view of 23 deep archival ROSA T PSPC pointings, 4.8 square degrees. The cross-correlated cluster catalogs were con- structed by comparing two independent catalogs extracted from the optical and X-ray bandpasses, using a matched-filter technique for the optical data and a wavelet technique for the X-ray data. We cross-identified cluster candidates in each catalog. As reported in Paper 1, the matched-filter technique found optical counter- parts for at least 60% (26 out of 43) of the X-ray cluster candidates; the estimated redshifts from the matched filter algorithm agree with at least 7 of 1 1 spectroscopic confirmations (Az 5 0.10). The matched filter technique. with an imaging sensitivity of ml N 23, identified approximately 3 times the number of candidates (155 candidates, 142 with a detection confidence >3 u) found in the X-ray survey of nearly the same area. There are 57 X-ray candidates, 43 of which are unobscured by scattered light or bright stars in the optical images. Twenty-six of these have fairly secure optical counterparts. We find that the matched filter algorithm, when applied to images with galaxy flux sensitivities of mI N 23, is fairly well-matched to discovering z 5 1 clusters detected by wavelets in ROSAT PSPC exposures of 8000-60,000 s. The difference in the spurious fractions between the optical and X-ray (30%) and IO%, respectively) cannot account for the difference in source number. In Paper I, we compared the optical and X-ray cluster luminosity functions and we found that the luminosity functions are consistent if the relationship between X-ray and optical luminosities is steep (Lx o( L&f). Here, in Paper 11, we present the cluster catalogs and a numerical simulation of the ROXS. We also present color-magnitude plots for several of the cluster candidates, and examine the prominence of the red sequence in each. We find that the X-ray clusters in our survey do not all have a prominent red sequence. We conclude that while the red sequence may be a distinct feature in the color-magnitude plots for virialized massive clusters, it may be less distinct in lower mass clusters of galaxies at even moderate redshifts. Multiple, complementary methods of selecting and defining clusters may be essential, particularly at high redshift where all methods start to run into completeness limits, incomplete understanding of physical evolution, and projection effects.

Near-infrared Variability of Obscured and Unobscured X-Ray-selected AGNs in the COSMOS Field

NASA Astrophysics Data System (ADS)

Sánchez, P.; Lira, P.; Cartier, R.; Pérez, V.; Miranda, N.; Yovaniniz, C.; Arévalo, P.; Milvang-Jensen, B.; Fynbo, J.; Dunlop, J.; Coppi, P.; Marchesi, S.

2017-11-01

We present our statistical study of near-infrared (NIR) variability of X-ray-selected active galactic nuclei (AGNs) in the COSMOS field, using UltraVISTA data. This is the largest sample of AGN light curves in YJHKs bands, making it possible to have a global description of the nature of AGNs for a large range of redshifts and for different levels of obscuration. To characterize the variability properties of the sources, we computed the structure function. Our results show that there is an anticorrelation between the structure function A parameter (variability amplitude) and the wavelength of emission and a weak anticorrelation between A and the bolometric luminosity. We find that broad-line (BL) AGNs have a considerably larger fraction of variable sources than narrow-line (NL) AGNs and that they have different distributions of the A parameter. We find evidence that suggests that most of the low-luminosity variable NL sources correspond to BL AGNs, where the host galaxy could be damping the variability signal. For high-luminosity variable NL sources, we propose that they can be examples of “true type II” AGNs or BL AGNs with limited spectral coverage, which results in missing the BL emission. We also find that the fraction of variable sources classified as unobscured in the X-ray is smaller than the fraction of variable sources unobscured in the optical range. We present evidence that this is related to the differences in the origin of the obscuration in the optical and X-ray regimes.

Ensemble X-ray variability of active galactic nuclei. II. Excess variance and updated structure function

NASA Astrophysics Data System (ADS)

Vagnetti, F.; Middei, R.; Antonucci, M.; Paolillo, M.; Serafinelli, R.

2016-09-01

Context. Most investigations of the X-ray variability of active galactic nuclei (AGN) have been concentrated on the detailed analyses of individual, nearby sources. A relatively small number of studies have treated the ensemble behaviour of the more general AGN population in wider regions of the luminosity-redshift plane. Aims: We want to determine the ensemble variability properties of a rich AGN sample, called Multi-Epoch XMM Serendipitous AGN Sample (MEXSAS), extracted from the fifth release of the XMM-Newton Serendipitous Source Catalogue (XMMSSC-DR5), with redshift between ~0.1 and ~5, and X-ray luminosities in the 0.5-4.5 keV band between ~1042 erg/s and ~1047 erg/s. Methods: We urge caution on the use of the normalised excess variance (NXS), noting that it may lead to underestimate variability if used improperly. We use the structure function (SF), updating our previous analysis for a smaller sample. We propose a correction to the NXS variability estimator, taking account of the light curve duration in the rest frame on the basis of the knowledge of the variability behaviour gained by SF studies. Results: We find an ensemble increase of the X-ray variability with the rest-frame time lag τ, given by SF ∝ τ0.12. We confirm an inverse dependence on the X-ray luminosity, approximately as SF ∝ LX-0.19. We analyse the SF in different X-ray bands, finding a dependence of the variability on the frequency as SF ∝ ν-0.15, corresponding to a so-called softer when brighter trend. In turn, this dependence allows us to parametrically correct the variability estimated in observer-frame bands to that in the rest frame, resulting in a moderate (≲15%) shift upwards (V-correction). Conclusions: Ensemble X-ray variability of AGNs is best described by the structure function. An improper use of the normalised excess variance may lead to an underestimate of the intrinsic variability, so that appropriate corrections to the data or the models must be applied to prevent these effects. Full Table 1 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/593/A55

Coronal Activity in Low-Mass Pre-Main Sequence Stars: NGC 2264

NASA Technical Reports Server (NTRS)

Tebbe, H. J.; Patten, B. M.

2000-01-01

We present the preliminary results of an analysis of ROSAT images in the region of the populous young (age approx. 3 Myr) star-forming region NGC 2264. The cluster was imaged with the ROSAT HRI in two sets of pointings -- one set near the central region of the cluster, centered on the star LW Mon, and the other set in the southern part of the cluster, centered near the star V428 Mon, just south of the Cone Nebula. In total 113 unique X-ray sources have been identified in the ROSAT images with signal-to-noise ratios greater than 3. The limiting luminosities (log Lx(ergs/sec)) for 3-sigma detections are estimated to be 30.18, 30.23, and 30.08 for the northern field, southern field, and overlap region between the two fields respectively. Extensive optical photometry, classification spectroscopy, and proper motions, obtained from recent ground-based surveys of this region, were used to identify the most likely optical counterpart to each X-ray source. Although most of our X-ray selected sample appears to be associated with NGC 2264 members, we find that the vast majority of the cluster membership was undetected in the ROSAT HRI survey. The X-ray cumulative luminosity function for solar-mass stars in NGC 2264 shows that most of the low-mass members probably have X-ray luminosities similar to those seen for the X-ray brightest members of older clusters such as IC 2391/IC 2602 (age approx. 50 Myr) and the Pleiades (age approx. 100 Myr). This research was funded in part by the SAO Summer Intern Program and NASA grant NAG5-8120.

Disentangling AGN and Star Formation in Soft X-Rays

NASA Technical Reports Server (NTRS)

LaMassa, Stephanie M.; Heckman, T. M.; Ptak, A.

2012-01-01

We have explored the interplay of star formation and active galactic nucleus (AGN) activity in soft X-rays (0.5-2 keV) in two samples of Seyfert 2 galaxies (Sy2s). Using a combination of low-resolution CCD spectra from Chandra and XMM-Newton, we modeled the soft emission of 34 Sy2s using power-law and thermal models. For the 11 sources with high signal-to-noise Chandra imaging of the diffuse host galaxy emission, we estimate the luminosity due to star formation by removing the AGN, fitting the residual emission. The AGN and star formation contributions to the soft X-ray luminosity (i.e., L(sub x,AGN) and L(sub x,SF)) for the remaining 24 Sy2s were estimated from the power-law and thermal luminosities derived from spectral fitting. These luminosities were scaled based on a template derived from XSINGS analysis of normal star-forming galaxies. To account for errors in the luminosities derived from spectral fitting and the spread in the scaling factor, we estimated L(sub x,AGN) and L(sub x,SF))from Monte Carlo simulations. These simulated luminosities agree with L(sub x,AGN) and L(sub x,SF) derived from Chandra imaging analysis within a 3sigma confidence level. Using the infrared [Ne ii]12.8 micron and [O iv]26 micron lines as a proxy of star formation and AGN activity, respectively, we independently disentangle the contributions of these two processes to the total soft X-ray emission. This decomposition generally agrees with L(sub x,SF) and L(sub x,AGN) at the 3 sigma level. In the absence of resolvable nuclear emission, our decomposition method provides a reasonable estimate of emission due to star formation in galaxies hosting type 2 AGNs.

Multiwavelength Study of Active Galaxies

NASA Astrophysics Data System (ADS)

Singh, Veeresh

2010-08-01

Seyfert galaxies are a subclass of active galaxies and are categorized as nearby, low luminosity, radio-quiet Active Galactic Nuclei (AGN) hosted in spiral or lenticular galaxies. Demographically, Seyfert galaxies may account for ~ 10% of the entire population of active galaxies in the nearby universe. Seyfert galaxies are classified mainly into two subclasses named as `type 1' and `type 2' Seyferts, based on the presence and absence of broad permitted emission lines in their optical spectra, respectively. Detection of broad permitted emission lines in some Seyfert type 2s observed in the polarized light laid the foundation of the Seyfert unification scheme, which hypothesizes that Seyfert type 1s and type 2s belong to the same parent population and appear different solely due to the differing orientations of the obscuring material having a torus-like geometry around the AGN (Antonucci and Miller 1985; Antonucci 1993). The primary objective of this thesis work is to examine the validity and limitations of the orientation and obscuration based Seyfert unification scheme using multiwavelength (mainly X-ray and radio) observations. The key issue in testing the Seyfert unification scheme has been acquiring a well defined rigorously selected Seyfert sample. I have argued that the Seyfert samples based on flux limited surveys at optical, IR, UV and X-ray are likely to be biased against obscured and faint sources. In order to test the predictions of Seyfert unification scheme I use a sample based on properties (i.e., cosmological redshift, [OIII] emission line luminosity, absolute bulge magnitude, absolute stellar magnitude of the host galaxy and the Hubble stage of the host galaxy) that are independent to the orientation of the obscuring torus, host galaxy and the AGN axis. Furthermore, two Seyfert subtypes of our sample have matched distributions in the orientation-independent properties and this ensures the intrinsic similarity between two Seyfert subtypes within the framework of the unification scheme. In other words, it is ensured that the two subtypes being compared are not selected from entirely different parts of the evolution function (redshift, luminosity, bulge magnitude, stellar luminosity of the host galaxy and Hubble type of the host galaxy). To study the X-ray spectral properties of two Seyfert subtypes I use the XMM-Newton pn data. The 0.5 - 10 keV X-ray spectra of Seyfert galaxies are generally best fitted with a model consists of: an absorbed power law with exponential cut-off which contains cold absorption from the Galactic hydrogen column density together with absorption from neutral gas at the redshift of the source; a narrow Gaussian line fitted to the Fe K_alpha line at 6.4 keV; a soft excess component characterized by either a steep power law and/or a thermal plasma model with temperature kT and in some cases, reflection component characterized by the reflection from an isotropically illuminated cold slab, (model `pexrav' in XSPEC) is required. Partial covering of the primary AGN power law component is also required for the best fit in some sources. There are several type 2 sources in our sample in which the hard (2.0 - 10.0 keV) part of the X-ray spectrum is best fitted with a reflection component alone (`pexrav' model). The statistical comparisons of the X-ray spectral properties show that in compared to Seyfert type 1s, the type 2s exhibit lower X-ray luminosities in soft (0.5 - 2.0 keV) and hard (2.0 - 10.0) X-ray bands, higher X-ray absorbing column densities, higher equivalent widths of Fe K line, and lower flux ratios of hard X-ray (2.0 - 10.0 keV) to [OIII]. In both the Seyfert subtypes, the X-ray luminosity is moderately correlated with the pc-scale, kpc-scale radio luminosities and [OIII] line luminosity, in a similar fashion. A large fraction ~ 60 - 70% of type 2 Seyferts of our sample are likely to be Compton-thick and as a case study of a Compton-thick AGN, we studied the broad-band 0.5 - 50 keV X-ray spectral properties of NGC 5135 using Suzaku (XIS and HID) data to unveil the nature and geometry of obscuring torus. To test the predictions of the Seyfert unification scheme in the radio regime, I studied the radio properties of Seyfert galaxies using Giant Meterwave Radio Telescope (GMRT) observations carried out at 240 MHz/610 MHz, and NRAO VLA Sky Survey observations at 1.4 GHz and VLA 5 GHz observations from the literature. The four point (240 MHz, 610 MHz, 1.4 GHz, 5.0 GHz) integrated radio spectra of the two Seyfert subtypes are similar and fairly steep (i.e., spectral index ~ -0.7). Radio luminosity distributions at 240 MHz, 610 MHz, 1.4 GHz and 5.0 GHz are also similar for the Seyfert type 1s and type 2s. The study on radio - IR luminosity correlations shows that for both the Seyfert subtypes, the total 610 MHz and 240 MHz radio luminosities are moderately correlated with near-IR, mid-IR luminosities while the correlation becomes poorer with far-IR luminosities. Furthermore, the 12 micron, 25 micron, 60 micron and 100 micron IR luminosity distributions are also statistically simil! ar for the Seyfert type 1s and type 2s. I conclude that the statistical comparisons of the X-ray, radio and IR properties of the two Seyfert subtypes of our sample are consistent with the obscuration and orientation based unification scheme.

Exploring anti-correlated radio/X-ray modes in transitional millisecond pulsars

NASA Astrophysics Data System (ADS)

Jaodand, Amruta

2017-09-01

Recently, using coordinated VLA+Chandra observations, Bogdanov et al.(2017) have uncovered a stunning anti-correlation in the LMXB state of the tMSP PSR J1023+0038. They see that radio luminosity consistently peaks during the X-ray `low' luminosity modes. Also, we have found a promising candidate tMSP, 3FGL J1544-1125(J1544) (Bogdanov and Halpern 2015; currently only tMSP candidate apart from J1023 in a persistent LMXB state). Using VLA and simultaneous Swift observations we see that it lies on the proposed tMSP track in radio vs. X-ray luminosity (L_ R/L_X) diagram. This finding strengthens its classification as a tMSP and provides an excellent opportunity to a)determine universality of radio/X-ray brightness anti-correlatio and b)understand jet/outflow formation in tMSPs.

Early-type galaxies in the Chandra cosmos survey

DOE Office of Scientific and Technical Information (OSTI.GOV)

Civano, F.; Fabbiano, G.; Kim, D.-W.

2014-07-20

We study a sample of 69 X-ray detected early-type galaxies (ETGs), selected from the Chandra COSMOS survey, to explore the relation between the X-ray luminosity of hot gaseous halos (L{sub X,{sub gas}}) and the integrated stellar luminosity (L{sub K} ) of the galaxies, in a range of redshift extending out to z = 1.5. In the local universe, a tight, steep relationship has been established between these two quantities (L{sub X,gas}∼L{sub K}{sup 4.5}), suggesting the presence of largely virialized halos in X-ray luminous systems. We use well-established relations from the study of local universe ETGs, together with the expected evolutionmore » of the X-ray emission, to subtract the contribution of low-mass X-ray binary populations from the X-ray luminosity of our sample. Our selection minimizes the presence of active galactic nuclei (AGNs), yielding a sample representative of normal passive COSMOS ETGs; therefore, the resulting luminosity should be representative of gaseous halos, although we cannot exclude other sources such as obscured AGNs or enhanced X-ray emission connected with embedded star formation in the higher-z galaxies. We find that most of the galaxies with estimated L{sub X} < 10{sup 42} erg s{sup –1} and z < 0.55 follow the L{sub X,{sub gas}}-L{sub K} relation of local universe ETGs. For these galaxies, the gravitational mass can be estimated with a certain degree of confidence from the local virial relation. However, the more luminous (10{sup 42} erg s{sup –1}« less

X-raying supernova remnants in the Magellanic Clouds

NASA Astrophysics Data System (ADS)

Maggi, P.; Hirschi, R.; Haberl, F.; Vasilopoulos, G.; Pietsch, W.; Greiner, J.; Kavanagh, J. P.; Sasaki, M.; Bozzetto, M. L.; Filipovic, M. D.; Points, S. D.; Chu, Y.-H.; Dickel, J.; Ehle, M.; Williams, R.

2016-06-01

The Magellanic Clouds (MCs) offer an ideal laboratory for the study of the SNR population in star-forming galaxies, since they are relatively nearby and free of large absorption. Both the LMC and SMC have been targeted by large XMM-Newton surveys, which, combined with archival observations, provide the best dataset to systematically study the X-ray emission of their numerous SNRs (˜ 60 in the LMC, ˜ 20 in the SMC). In this talk, I will highlight the results from this homogeneous analysis, which allows for the first time meaningful comparisons of temperature, chemical composition, and luminosity of SNRs in the MCs. The SNRs can be used as probes of their host galaxies: We measured chemical abundances in the hot phase of the LMC, and constrained the ratio of core-collapse to type Ia SN rates. The X-ray luminosity function of SNRs in the MCs are compared to those in other Local Group galaxies with different metallicities and star formation properties. Finally, we present a new population of evolved type Ia SNRs that was discovered recently in the MCs via their iron-rich X-ray emission.

The high-energy X-ray spectrum of Centaurus XR-3 observed from OSO 8

NASA Technical Reports Server (NTRS)

Dolan, J. F.; Crannell, C. J.; Dennis, B. R.; Frost, K. J.; Orwig, L. E.

1984-01-01

Observations of the X-ray binary Cen XR-3 in the 20-120 keV energy range by means of OSO 8's high energy X-ray spectrometer, during July 16-19, 1975, and July 5-14 and 28-29, 1978, indicate that the source was in a high luminosity state during 1975 and a low luminosity one in 1978. While mean orbital light curves appear similar in shape in both years, orbit-to-orbit intensity variations are noted. Spectral, luminosity, and the 4.84 sec modulation are characterized. Cen XR-3 may be a system in which mass transfer by Roche lobe overflow, and by accretion from a stellar wind, are both effective in the production of observable X-ray radiation.

X-ray and multiwavelength insights into the inner structure of high-luminosity disc-like emitters

NASA Astrophysics Data System (ADS)

Luo, B.; Brandt, W. N.; Eracleous, M.; Wu, Jian; Hall, P. B.; Rafiee, A.; Schneider, D. P.; Wu, Jianfeng

2013-02-01

We present X-ray and multiwavelength studies of a sample of eight high-luminosity active galactic nuclei (AGN) with disc-like Hβ emission-line profiles selected from the Sloan Digital Sky Survey Data Release 7. These sources have higher redshift (z ≈ 0.6) than the majority of the known disc-like emitters, and they occupy a largely unexplored space in the luminosity-redshift plane. Seven sources have typical AGN X-ray spectra with power-law photon indices of Γ ≈ 1.4-2.0; two of them show some X-ray absorption (column density NH ≈ 1021-1022 cm-2 for neutral gas). The other source, J0850+4451, has only three hard X-ray photons detected and is probably heavily obscured (NH ≳ 3 × 1023 cm-2). This object is also identified as a low-ionization broad absorption line (BAL) quasar based on Mg II λ2799 absorption; it is the first disc-like emitter reported that is also a BAL quasar. The infrared-to-ultraviolet (UV) spectral energy distributions (SEDs) of these eight sources are similar to the mean SEDs of typical quasars with a UV `bump', suggestive of standard accretion discs radiating with high efficiency, which differs from low-luminosity disc-like emitters. Studies of the X-ray-to-optical power-law slope parameters (αOX) indicate that there is no significant excess X-ray emission in these high-luminosity disc-like emitters. Energy budget analysis suggests that for disc-like emitters in general, the inner disc must illuminate and ionize the outer disc efficiently (≈15 per cent of the nuclear ionizing radiation is required on average) via direct illumination and/or scattering. Warped accretion discs are probably needed for direct illumination to work in high-luminosity objects, as their geometrically thin inner discs decrease the amount of direct illumination possible for a flat disc.

The joint fit of the BHMF and ERDF for the BAT AGN Sample

NASA Astrophysics Data System (ADS)

Weigel, Anna K.; Koss, Michael; Ricci, Claudio; Trakhtenbrot, Benny; Oh, Kyuseok; Schawinski, Kevin; Lamperti, Isabella

2018-01-01

A natural product of an AGN survey is the AGN luminosity function. This statistical measure describes the distribution of directly measurable AGN luminosities. Intrinsically, the shape of the luminosity function depends on the distribution of black hole masses and Eddington ratios. To constrain these fundamental AGN properties, the luminosity function thus has to be disentangled into the black hole mass and Eddington ratio distribution function. The BASS survey is unique as it allows such a joint fit for a large number of local AGN, is unbiased in terms of obscuration in the X-rays and provides black hole masses for type-1 and type-2 AGN. The black hole mass function at z ~ 0 represents an essential baseline for simulations and black hole growth models. The normalization of the Eddington ratio distribution function directly constrains the AGN fraction. Together, the BASS AGN luminosity, black hole mass and Eddington ratio distribution functions thus provide a complete picture of the local black hole population.

ROSAT X-ray sources embedded in the rho Ophiuchi cloud core

NASA Astrophysics Data System (ADS)

Casanova, Sophie; Montmerle, Thierry; Feigelson, Eric D.; Andre, Philippe

1995-02-01

We present a deep ROSAT Position Sensitive Proportional Counter (PSPC) image of the central region of the rho Oph star-forming region. The selected area, about 35 x 35 arcmins in size, is rich with dense molecular cores and young stellar objects (YSOs). Fifty-five reliable X-ray sources are detected (and up to 50 more candidates may be present) above approximately 1 keV,, doubling the number of Einstein sources in this area. These sources are cross-identified with an updated list of 88 YSOs associated with the rho Oph cloud core. A third of the reliable X-ray sources do not have optical counterparts on photographic plates. Most can be cross-identified wth Class II and Class III infrared (IR) sources, which are embedded T Tauri stars, but three reliable X-ray sources and up to seven candidate sources are tentatively identified with Class I protostars. Eighteen reliable, and up to 20 candidate, X-ray sources are probably new cloud members. The overall detection rate of the bona fide cloud population is very high (73% for the Class II and Class III objects). The spatial distribution of the X-ray sources closely follows that of the moleclar gas. The visual extinctions Av estimated from near-IR data) of the ROSAT sources can be as high as 50 or more, confirming that most are embedded in the cloud core and are presumably very young. Using bolometric luminosities Lbol estimated from J-magnitudes a tight correlation between Lx and Lbol is found, similar to that seen for older T Tauri stars in the Cha I cloud: Lx approximately 10-4 Lbol. A general relation Lxproportional to LbolLj seems to apply to all T Tauri-like YSOs. The near equality of the extintion in the IR J band and in the keV X-ray rage implies that this relation is valid for the detected fluxes as well as for the dereddened fluxes. The X-ray luminosity function of the embedded sourced in rho Oph spans a range of Lx approximately 1028.5 to approximately equal to or greater than 1031.5 ergs/s and is statistically indistinguishable from that of X-ray-detected visile T Tauri stars. We estimate a total X-ray luminosity Lx, Oph approximately equal to or greater than 6 x 10 32 ergs/s from approximately equal to 200 X-ray sources in the cloud core, down to Lbol approximately 0.1 solar luminosity or Mstar approximately 0.3 solar mass. We discuss several consequences of in situ irradiation of molecular clouds by X-rays from embedded YSOs. These X-rays must partially ionize the inner regions of circumstellar disk coronae, possibly playing an important role in coupling magnetic ionize the fields and wind or bipolar outflows. Photon-stimulated deportion of large molecules by YSO X-rays may be partly responsible for the bright 12 micrometer halos seen in some molecular clouds.

The First Simultaneous X-Ray/Radio Detection of the First Be/BH System MWC 656

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ribó, M.; Paredes, J. M.; Marcote, B.

2017-02-01

MWC 656 is the first known Be/black hole (BH) binary system. Be/BH binaries are important in the context of binary system evolution and sources of detectable gravitational waves because they are possible precursors of coalescing neutron star/BH binaries. X-ray observations conducted in 2013 revealed that MWC 656 is a quiescent high-mass X-ray binary (HMXB), opening the possibility to explore X-ray/radio correlations and the accretion/ejection coupling down to low luminosities for BH HMXBs. Here we report on a deep joint Chandra /VLA observation of MWC 656 (and contemporaneous optical data) conducted in 2015 July that has allowed us to unambiguously identifymore » the X-ray counterpart of the source. The X-ray spectrum can be fitted with a power law with Γ ∼ 2, providing a flux of ≃4 × 10{sup −15} erg cm{sup −2} s{sup −1} in the 0.5–8 keV energy range and a luminosity of L {sub X} ≃ 3 × 10{sup 30} erg s{sup −1} at a 2.6 kpc distance. For a 5 M{sub ⊙} BH this translates into ≃5 × 10{sup −9} L {sub Edd}. These results imply that MWC 656 is about 7 times fainter in X-rays than it was two years before and reaches the faintest X-ray luminosities ever detected in stellar-mass BHs. The radio data provide a detection with a peak flux density of 3.5 ± 1.1 μ Jy beam{sup −1}. The obtained X-ray/radio luminosities for this quiescent BH HMXB are fully compatible with those of the X-ray/radio correlations derived from quiescent BH low-mass X-ray binaries. These results show that the accretion/ejection coupling in stellar-mass BHs is independent of the nature of the donor star.« less

Tracing the Far-Infrared Roles of AGN in Dusty Star-Forming Galaxies

NASA Astrophysics Data System (ADS)

Brown, Arianna; Nayyeri, Hooshang; Cooray, Asantha R.; Mitchell-Wynne, Ketron

2017-01-01

Active galactic nuclei (AGNs) are suggested to play an important role in quenching their host galaxy’s star formation rate (SFR) by heating up and/or consuming the cool gas necessary to create stars. This mechanism is theorized as a critical step in AGN evolutionary models. The efforts to study this effect suffer in part from low-number statistics at high x-ray luminosities (LXR > 1044 ergs/s) for AGNs at z≈1-3, and a lack of separately estimated SFRs for AGN in dusty, star-forming galaxies (DSFGs). In this work, we extend our analysis to build a more complete picture using the variety of available multi-wavelength data in the XBoötes region. The Chandra XBoötes Survey is a 5-ks X-ray survey of the 9.3 square degree Boötes Field of the NOAO Deep Wide-Field Survey, a survey imaged from the optical to the near-IR. We estimate AGN spectral energy distributions and SFRs for ~400 x-ray sources using available data in all four Spitzer IRAC bands, the Spitzer MIPS 24µm band, all five Herschel SPIRE and PACS bands, along with NEWFIRM optical bands. Preliminary results show an exponential correlation between x-ray luminosity and star formation. As a comparison, we will use a stacking technique for the ~500 x-ray sources that were not detected at submillimeter wavelengths, where sources are binned by x-ray luminosity. We will compare these two samples and expect to see a difference in slope. Using these techniques, we hope to place tighter constraints on the mean SFRs of high-luminosity AGNs inside DSFGs, and determine if x-ray luminosities are independent of average SFRs for our sample in the Boötes field.

Einstein Observations of X-ray emission from A stars

NASA Astrophysics Data System (ADS)

Golub, L.; Harnden, F. R., Jr.; Maxson, C. W.; Rosner, R.; Vaiana, G. S.; Cash, W., Jr.; Snow, T. P., Jr.

1983-08-01

Results are reported from the combined CfA Stellar Survey of selected bright A stars and an Einstein Guest Observer program for Ap and Am stars. In an initial report of results from the CfA Stellar Surveys by Vaiana et al. (1981) it was noted that the spread in observed X-ray luminosities among the few A stars observed was quite large. The reasons for this large spread was studied by Pallavicini et al. (1981). It was found that the X-ray emission from normal stars is related very strongly to bolometric luminosity for early-type stars and to rotation rate for late-type stars. However, an exception to this rule has been the apparently anomalous behavior of A star X-ray emission, for which the large spread in luminosity showed no apparent correlation with either bolometric luminosity or stellar rotation rate. In the present study, it is shown that the level of emission from normal A stars agrees with the correlation observed for O and B stars.

Classification of X-ray sources in the direction of M31

NASA Astrophysics Data System (ADS)

Vasilopoulos, G.; Hatzidimitriou, D.; Pietsch, W.

2012-01-01

M31 is our nearest spiral galaxy, at a distance of 780 kpc. Identification of X-ray sources in nearby galaxies is important for interpreting the properties of more distant ones, mainly because we can classify nearby sources using both X-ray and optical data, while more distant ones via X-rays alone. The XMM-Newton Large Project for M31 has produced an abundant sample of about 1900 X-ray sources in the direction of M31. Most of them remain elusive, giving us little signs of their origin. Our goal is to classify these sources using criteria based on properties of already identified ones. In particular we construct candidate lists of high mass X-ray binaries, low mass X-ray binaries, X-ray binaries correlated with globular clusters and AGN based on their X-ray emission and the properties of their optical counterparts, if any. Our main methodology consists of identifying particular loci of X-ray sources on X-ray hardness ratio diagrams and the color magnitude diagrams of their optical counterparts. Finally, we examined the X-ray luminosity function of the X-ray binaries populations.

CXOGBS J173620.2-293338: A candidate symbiotic X-ray binary associated with a bulge carbon star

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hynes, Robert I.; Britt, C. T.; Johnson, C. B.

2014-01-01

The Galactic Bulge Survey (GBS) is a wide but shallow X-ray survey of regions above and below the Plane in the Galactic Bulge. It was performed using the Chandra X-ray Observatory's ACIS camera. The survey is primarily designed to find and classify low luminosity X-ray binaries. The combination of the X-ray depth of the survey and the accessibility of optical and infrared counterparts makes this survey ideally suited to identification of new symbiotic X-ray binaries (SyXBs) in the Bulge. We consider the specific case of the X-ray source CXOGBS J173620.2-293338. It is coincident to within 1 arcsec with a verymore » red star, showing a carbon star spectrum and irregular variability in the Optical Gravitational Lensing Experiment data. We classify the star as a late C-R type carbon star based on its spectral features, photometric properties, and variability characteristics, although a low-luminosity C-N type cannot be ruled out. The brightness of the star implies it is located in the Bulge, and its photometric properties are overall consistent with the Bulge carbon star population. Given the rarity of carbon stars in the Bulge, we estimate the probability of such a close chance alignment of any GBS source with a carbon star to be ≲ 10{sup –3}, suggesting that this is likely to be a real match. If the X-ray source is indeed associated with the carbon star, then the X-ray luminosity is around 9 × 10{sup 32} erg s{sup –1}. Its characteristics are consistent with a low luminosity SyXB, or possibly a low accretion rate white dwarf symbiotic.« less

X-Ray Emission from Active Galactic Nuclei with Intermediate-Mass Black Holes

NASA Astrophysics Data System (ADS)

Dewangan, G. C.; Mathur, S.; Griffiths, R. E.; Rao, A. R.

2008-12-01

We present a systematic X-ray study of eight active galactic nuclei (AGNs) with intermediate-mass black holes (MBH ~ 8-95 × 104 M⊙) based on 12 XMM-Newton observations. The sample includes the two prototype AGNs in this class—NGC 4395 and POX 52 and six other AGNs discovered with the Sloan Digitized Sky Survey. These AGNs show some of the strongest X-ray variability, with the normalized excess variances being the largest and the power density break timescales being the shortest observed among radio-quiet AGNs. The excess-variance-luminosity correlation appears to depend on both the BH mass and the Eddington luminosity ratio. The break timescale-black hole mass relations for AGN with IMBHs are consistent with that observed for massive AGNs. We find that the FWHM of the Hβ/Hα line is uncorrelated with the BH mass, but shows strong anticorrelation with the Eddington luminosity ratio. Four AGNs show clear evidence for soft X-ray excess emission (kTin ~ 150-200 eV). X-ray spectra of three other AGNs are consistent with the presence of the soft excess emission. NGC 4395 with lowest L/LEdd lacks the soft excess emission. Evidently small black mass is not the primary driver of strong soft X-ray excess emission from AGNs. The X-ray spectral properties and optical-to-X-ray spectral energy distributions of these AGNs are similar to those of Seyfert 1 galaxies. The observed X-ray/UV properties of AGNs with IMBHs are consistent with these AGNs being low-mass extensions of more massive AGNs, those with high Eddington luminosity ratio looking more like narrow-line Seyfert 1 s and those with low L/LEdd looking more like broad-line Seyfert 1 galaxies.

HIFLUGCS: X-ray luminosity-dynamical mass relation and its implications for mass calibrations with the SPIDERS and 4MOST surveys

NASA Astrophysics Data System (ADS)

Zhang, Yu-Ying; Reiprich, Thomas H.; Schneider, Peter; Clerc, Nicolas; Merloni, Andrea; Schwope, Axel; Borm, Katharina; Andernach, Heinz; Caretta, César A.; Wu, Xiang-Ping

2017-03-01

We present the relation of X-ray luminosity versus dynamical mass for 63 nearby clusters of galaxies in a flux-limited sample, the HIghest X-ray FLUx Galaxy Cluster Sample (HIFLUGCS, consisting of 64 clusters). The luminosity measurements are obtained based on 1.3 Ms of clean XMM-Newton data and ROSAT pointed observations. The masses are estimated using optical spectroscopic redshifts of 13647 cluster galaxies in total. We classify clusters into disturbed and undisturbed based on a combination of the X-ray luminosity concentration and the offset between the brightest cluster galaxy and X-ray flux-weighted center. Given sufficient numbers (I.e., ≥45) of member galaxies when the dynamical masses are computed, the luminosity versus mass relations agree between the disturbed and undisturbed clusters. The cool-core clusters still dominate the scatter in the luminosity versus mass relation even when a core-corrected X-ray luminosity is used, which indicates that the scatter of this scaling relation mainly reflects the structure formation history of the clusters. As shown by the clusters with only few spectroscopically confirmed members, the dynamical masses can be underestimated and thus lead to a biased scaling relation. To investigate the potential of spectroscopic surveys to follow up high-redshift galaxy clusters or groups observed in X-ray surveys for the identifications and mass calibrations, we carried out Monte Carlo resampling of the cluster galaxy redshifts and calibrated the uncertainties of the redshift and dynamical mass estimates when only reduced numbers of galaxy redshifts per cluster are available. The resampling considers the SPIDERS and 4MOST configurations, designed for the follow-up of the eROSITA clusters, and was carried out for each cluster in the sample at the actual cluster redshift as well as at the assigned input cluster redshifts of 0.2, 0.4, 0.6, and 0.8. To follow up very distant clusters or groups, we also carried out the mass calibration based on the resampling with only ten redshifts per cluster, and redshift calibration based on the resampling with only five and ten redshifts per cluster, respectively. Our results demonstrate the power of combining upcoming X-ray and optical spectroscopic surveys for mass calibration of clusters. The scatter in the dynamical mass estimates for the clusters with at least ten members is within 50%.

Modeling X-Ray Binary Evolution in Normal Galaxies: Insights from SINGS

NASA Astrophysics Data System (ADS)

Tzanavaris, P.; Fragos, T.; Tremmel, M.; Jenkins, L.; Zezas, A.; Lehmer, B. D.; Hornschemeier, A.; Kalogera, V.; Ptak, A.; Basu-Zych, A. R.

2013-09-01

We present the largest-scale comparison to date between observed extragalactic X-ray binary (XRB) populations and theoretical models of their production. We construct observational X-ray luminosity functions (oXLFs) using Chandra observations of 12 late-type galaxies from the Spitzer Infrared Nearby Galaxy Survey. For each galaxy, we obtain theoretical XLFs (tXLFs) by combining XRB synthetic models, constructed with the population synthesis code StarTrack, with observational star formation histories (SFHs). We identify highest-likelihood models both for individual galaxies and globally, averaged over the full galaxy sample. Individual tXLFs successfully reproduce about half of the oXLFs, but for some galaxies we are unable to find underlying source populations, indicating that galaxy SFHs and metallicities are not well matched and/or that XRB modeling requires calibration on larger observational samples. Given these limitations, we find that the best models are consistent with a product of common envelope ejection efficiency and central donor concentration ~= 0.1, and a 50% uniform-50% "twins" initial mass-ratio distribution. We present and discuss constituent subpopulations of tXLFs according to donor, accretor, and stellar population characteristics. The galaxy-wide X-ray luminosity due to low-mass and high-mass XRBs, estimated via our best global model tXLF, follows the general trend expected from the LX -star formation rate and LX -stellar mass relations of Lehmer et al. Our best models are also in agreement with modeling of the evolution of both XRBs over cosmic time and of the galaxy X-ray luminosity with redshift.

Inflow Generated X-ray Corona Around Supermassive Black Holes and Unified Model for X-ray Emission

NASA Astrophysics Data System (ADS)

Wang, Lile; Cen, Renyue

2016-01-01

Three-dimensional hydrodynamic simulations, covering the spatial domain from hundreds of Schwarzschild radii to 2 pc around the central supermassive black hole of mass 108 M⊙, with detailed radiative cooling processes, are performed. Generically found is the existence of a significant amount of shock heated, high temperature (≥108 K) coronal gas in the inner (≤104 rsch) region. It is shown that the composite bremsstrahlung emission spectrum due to coronal gas of various temperatures are in reasonable agreement with the overall ensemble spectrum of AGNs and hard X-ray background. Taking into account inverse Compton processes, in the context of the simulation-produced coronal gas, our model can readily account for the wide variety of AGN spectral shape, which can now be understood physically. The distinguishing feature of our model is that X-ray coronal gas is, for the first time, an integral part of the inflow gas and its observable characteristics are physically coupled to the concomitant inflow gas. One natural prediction of our model is the anti-correlation between accretion disk luminosity and spectral hardness: as the luminosity of SMBH accretion disk decreases, the hard X-ray luminosity increases relative to the UV/optical luminosity.

Regulation of the X-ray luminosity of clusters of galaxies by cooling and supernova feedback.

PubMed

Voit, G M; Bryan, G L

2001-11-22

Clusters of galaxies are thought to contain about ten times as much dark matter as baryonic matter. The dark component therefore dominates the gravitational potential of a cluster, and the baryons confined by this potential radiate X-rays with a luminosity that depends mainly on the gas density in the cluster's core. Predictions of the X-rays' properties based on models of cluster formation do not, however, agree with the observations. If the models ignore the condensation of cooling gas into stars and feedback from the associated supernovae, they overestimate the X-ray luminosity because the density of the core gas is too high. An early episode of uniformly distributed supernova feedback could rectify this by heating the uncondensed gas and therefore making it harder to compress into the core, but such a process seems to require an implausibly large number of supernovae. Here we show how radiative cooling of intergalactic gas and subsequent supernova heating conspire to eliminate highly compressible low-entropy gas from the intracluster medium. This brings the core entropy and X-ray luminosities of clusters into agreement with the observations, in a way that depends little on the efficiency of supernova heating in the early Universe.

Mini-Survey Of SDSS of [OIII] AGN With Swift

NASA Technical Reports Server (NTRS)

Angelini, L.; George, I. M.; Hill, J.; Padgett, C. A.; Mushotzky, R. F.

2008-01-01

The number of AGN and their luminosity distribution are crucial parameters for our understanding of the AGN phenomenon. Recent work (e.g. Ferrarese and Merritt 2000) strongly suggests every massive galaxy has a central black hole. However, most of these objects either are not radiating or have been very difficult to detect. We are now in the era of large surveys, and the luminosity function (LF) of AGN has been estimated in various ways. In the X-ray band, Chandra and XMM surveys (e.g., Barger et al. 2005; Hasinger, et al. 2005) have revealed that the LF of Hard X-ray selected AGN shows a strong luminosity-dependent evolution with a dramatic break towards low L(x) (at al z). This is seen for all types of AGN, but is stronger for the broad-line objects (e.g., Steffen et al. 2004). In sharp contrast, the local LF of optically-selected samples shows no such break and no differences between narrow and broad-line objects (Hao et al. 2005). If, as been suggested, hard X-ray and optical emission line can both be fair indicators of AGN activity, it is important to first understand how reliable these characteristics are if we hope to understand the apparent discrepancy in the LFs.

Clumpy wind accretion in supergiant neutron star high mass X-ray binaries

NASA Astrophysics Data System (ADS)

Bozzo, E.; Oskinova, L.; Feldmeier, A.; Falanga, M.

2016-05-01

The accretion of the stellar wind material by a compact object represents the main mechanism powering the X-ray emission in classical supergiant high mass X-ray binaries and supergiant fast X-ray transients. In this work we present the first attempt to simulate the accretion process of a fast and dense massive star wind onto a neutron star, taking into account the effects of the centrifugal and magnetic inhibition of accretion ("gating") due to the spin and magnetic field of the compact object. We made use of a radiative hydrodynamical code to model the nonstationary radiatively driven wind of an O-B supergiant star and then place a neutron star characterized by a fixed magnetic field and spin period at a certain distance from the massive companion. Our calculations follow, as a function of time (on a total timescale of several hours), the transitions of the system through all different accretion regimes that are triggered by the intrinsic variations in the density and velocity of the nonstationary wind. The X-ray luminosity released by the system is computed at each time step by taking into account the relevant physical processes occurring in the different accretion regimes. Synthetic lightcurves are derived and qualitatively compared with those observed from classical supergiant high mass X-ray binaries and supergiant fast X-ray transients. Although a number of simplifications are assumed in these calculations, we show that taking into account the effects of the centrifugal and magnetic inhibition of accretion significantly reduces the average X-ray luminosity expected for any neutron star wind-fed binary. The present model calculations suggest that long spin periods and stronger magnetic fields are favored in order to reproduce the peculiar behavior of supergiant fast X-ray transients in the X-ray domain.

The XMM-Newton Wide Angle Survey (XWAS): the X-ray spectrum of type-1 AGN

NASA Astrophysics Data System (ADS)

Mateos, S.; Carrera, F. J.; Page, M. J.; Watson, M. G.; Corral, A.; Tedds, J. A.; Ebrero, J.; Krumpe, M.; Schwope, A.; Ceballos, M. T.

2010-02-01

Aims: We discuss the broad band X-ray properties of one of the largest samples of X-ray selected type-1 AGN to date (487 objects in total), drawn from the XMM-Newton Wide Angle Survey (XWAS). The objects presented in this work cover 2-10 keV (rest-frame) luminosities from 1042-1045 erg s-1 and are detected up to redshift 4. We constrain the overall properties of the broad band continuum, soft excess and X-ray absorption, along with their dependence on the X-ray luminosity and redshift. We discuss the implications for models of AGN emission. Methods: We fitted the observed 0.2-12 keV broad band spectra with various models to search for X-ray absorption and soft excess. The F-test was used with a significance threshold of 99% to statistically accept the detection of additional spectral components. Results: We constrained the mean spectral index of the broad band X-ray continuum to <Γ> = 1.96 ± 0.02 with intrinsic dispersion {σ< Γ >} = 0.27-0.02+0.01. The continuum becomes harder at faint fluxes and at higher redshifts and hard (2-10 keV) luminosities. The dependence of Γ with flux is likely due to undetected absorption rather than to spectral variation. We found a strong dependence of the detection efficiency of objects on the spectral shape. We expect this effect to have an impact on the measured mean continuum shapes of sources at different redshifts and luminosities. We detected excess absorption in ⪆3% of our objects, with rest-frame column densities a few ×1022 cm-2. The apparent mismatch between the optical classification and X-ray properties of these objects is a challenge for the standard orientation-based AGN unification model. We found that the fraction of objects with detected soft excess is 36%. Using a thermal model, we constrained the soft excess mean rest-frame temperature and intrinsic dispersion to kT 100 eV and σkT 34 eV. The origin of the soft excess as thermal emission from the accretion disk or Compton scattered disk emission is ruled out on the basis of the temperatures detected and the lack of correlation of the soft excess temperature with the hard X-ray luminosity over more than 2 orders of magnitude in luminosity. Furthermore, the high luminosities of the soft excess rule out an origin in the host galaxy.

A Chandra X-ray census of the interacting binaries in old open clusters - NGC 188

NASA Astrophysics Data System (ADS)

Vats, Smriti; Van Den Berg, Maureen

2017-01-01

We present a new X-ray study of NGC 188, one of the oldest open clusters known in the Milky Way (7 Gyr). Our X-ray observation using the Chandra X-ray Observatory is aimed at uncovering the population of close interacting binaries in the cluster. We detect 84 X-ray sources with a limiting X-ray luminosity, LX ~ 4×1029 erg s-1 (0.3-7 keV), of which 28 are within the half-mass radius. Of these, 13 are proper-motion or radial-velocity cluster members, wherein we identify a mix of active binaries (ABs) and blue straggler stars (BSSs). We also identify one tentative cataclysmic variable (CV) candidate which is a known short-period photometric variable, but whose membership to NGC 188 is unknown. We have compared the X-ray luminosity per unit of cluster mass (i.e. the X-ray emissivity) of NGC 188 with those of other old Galactic open clusters and dense globular clusters (47 Tuc, NGC 6397). Our findings confirm the earlier result that old open clusters have higher X-ray emissivities than the globular clusters (LX ≥1×1030 erg s-1). This may be explained by dynamical encounters in globulars, which could have a net effect of destroying binaries, or the typically higher metallicities of open clusters. We find one intriguing X-ray source in NGC 188 that is a BSS and cluster member, whose X-ray luminosity cannot be explained by its currently understood binary configuration. Its X-ray detection invokes the need for a third companion in the system.

A coordinated X-ray, optical, and microwave study of the flare star Proxima Centauri

NASA Technical Reports Server (NTRS)

Haisch, B. M.; Linsky, J. L.; Slee, O. B.; Hearn, D. R.; Walker, A. R.; Rydgren, A. E.; Nicolson, G. D.

1978-01-01

Results are reported for a three-day coordinated observing program to monitor the flare star Proxima Centauri in the X-ray, optical, and radio spectrum. During this interval 30 optical flares and 12 possible radio bursts were observed. The SAS 3 X-ray satellite made no X-ray detections. An upper limit of 0.08 on the X-ray/optical luminosity ratio is derived for the brightest optical flare. The most sensitive of the radio telescopes failed to detect 6-cm emission during one major and three minor optical flares, and on this basis an upper limit on the flare radio emission (1 hundred-thousandth of the optimal luminosity) is derived.

The X-ray emitting gas in poor clusters with central dominant galaxies

NASA Technical Reports Server (NTRS)

Kriss, G. A.; Cioffi, D. F.; Canizares, C. R.

1983-01-01

The 12 clusters detected in the present study by the Einstein Observatory's X-ray imaging proportional counter show X-ray emission centered on the dominant galaxy in all cases. Comparison of the deduced distribution of binding mass with the light distribution of the central galaxies of four clusters indicates that the mass/luminosity ratio rises to over 200 solar masses/solar luminosity in the galaxy halos. These halos must therefore, like the clusters themselves, posses dark matter. The X-ray data clearly show that the dominant galaxies sit at the bottoms of the poor cluster gravitational potential wells, suggesting a similar origin for dominant galaxies in poor and rich clusters, perhaps through the merger and cannibalism of cluster galaxies. It is the luminosity of the distended cD envelope that reflects the relative wealth of the cluster environment.

Relations Between FUV Excess and Coronal Soft X-Ray Emission Among Dwarf Stars

NASA Astrophysics Data System (ADS)

Smith, Graeme H.; Hargrave, Mason; Eckholm, Elliot

2017-11-01

The far-ultraviolet magnitudes of late-F, G and early-K dwarfs with (B - V) ⩾ 0.50 as measured by the GALEX satellite are shown to correlate with soft X-ray luminosity. This result indicates that line and continuum emission from stellar active regions make significant contributions to the flux in the GALEX FUV band for late-F, G and K dwarfs. By contrast, detection of a correlation between FUV brightness and soft X-ray luminosity among early-F dwarfs requires subtraction of the photospheric component from the FUV flux. The range in (B - V) among F and G dwarfs over which a correlation between uncorrected FUV magnitude and X-ray luminosity is detected coincides with the range in colour over which coronal and chromospheric emission correlates with stellar rotation.

X-ray Point Source Populations in Spiral and Elliptical Galaxies

NASA Astrophysics Data System (ADS)

Colbert, E.; Heckman, T.; Weaver, K.; Strickland, D.

2002-01-01

The hard-X-ray luminosity of non-active galaxies has been known to be fairly well correlated with the total blue luminosity since the days of the Einstein satellite. However, the origin of this hard component was not well understood. Some possibilities that were considered included X-ray binaries, extended upscattered far-infrared light via the inverse-Compton process, extended hot 107 K gas (especially in ellipitical galaxies), or even an active nucleus. Chandra images of normal, elliptical and starburst galaxies now show that a significant amount of the total hard X-ray emission comes from individual point sources. We present here spatial and spectral analyses of the point sources in a small sample of Chandra obervations of starburst galaxies, and compare with Chandra point source analyses from comparison galaxies (elliptical, Seyfert and normal galaxies). We discuss possible relationships between the number and total hard luminosity of the X-ray point sources and various measures of the galaxy star formation rate, and discuss possible options for the numerous compact sources that are observed.

Mini-Survey on SDSS OIII AGN with Swift

NASA Technical Reports Server (NTRS)

Angelini, Lorella

2008-01-01

The number of AGN and their luminosity distribution are crucial parameters for our understanding of the AGN phenomenon. There is a common wisdom that every massive galaxy has a massive black hole. However, most of these objects either are not radiating or until recently have been very difficult to detect. The Sloan Digital Sky Survey (SDSS) data, based on the [OIII] line indicate that perhaps up to 20% of all galaxies may be classified as AGN a surprising result that must be checked with independent data. X-ray surveys have revealed that hard X-ray selected AGN show a strong luminosity dependent evolution and their luminosity function (LF) shows a dramatic break towards low $L_X$ (at all $z$). This is seen for all types of AGN, but is stronger for the broad-line objects. In sharp contrast, the local LF of {it optically-selected samples} shows no such break and no differences between narrow and broad-line objects. Assuming both hard X-ray and [O{\\sc iii}] emission are fair indicators of AGN activity, it is important to understand this discrepancy. We present here the results of a min-survey done with Swift on a selected sample of SDSS selected AGN. The objects have been sampled at different L([O{\\sc iii}]) to check the relation with the $L_X$ observed with Swift.

EDDINGTON RATIO DISTRIBUTION OF X-RAY-SELECTED BROAD-LINE AGNs AT 1.0 < z < 2.2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Suh, Hyewon; Hasinger, Günther; Steinhardt, Charles

2015-12-20

We investigate the Eddington ratio distribution of X-ray-selected broad-line active galactic nuclei (AGNs) in the redshift range 1.0 < z < 2.2, where the number density of AGNs peaks. Combining the optical and Subaru/Fiber Multi Object Spectrograph near-infrared spectroscopy, we estimate black hole masses for broad-line AGNs in the Chandra Deep Field South (CDF-S), Extended Chandra Deep Field South (E-CDF-S), and the XMM-Newton Lockman Hole (XMM-LH) surveys. AGNs with similar black hole masses show a broad range of AGN bolometric luminosities, which are calculated from X-ray luminosities, indicating that the accretion rate of black holes is widely distributed. We find a substantial fraction ofmore » massive black holes accreting significantly below the Eddington limit at z ≲ 2, in contrast to what is generally found for luminous AGNs at high redshift. Our analysis of observational selection biases indicates that the “AGN cosmic downsizing” phenomenon can be simply explained by the strong evolution of the comoving number density at the bright end of the AGN luminosity function, together with the corresponding selection effects. However, one might need to consider a correlation between the AGN luminosity and the accretion rate of black holes, in which luminous AGNs have higher Eddington ratios than low-luminosity AGNs, in order to understand the relatively small fraction of low-luminosity AGNs with high accretion rates in this epoch. Therefore, the observed downsizing trend could be interpreted as massive black holes with low accretion rates, which are relatively fainter than less-massive black holes with efficient accretion.« less

Revisiting the "Fundamental Plane" of Black Hole Activity at Extremely Low Luminosities

NASA Astrophysics Data System (ADS)

Yuan, F.; Yu, Z.; Ho, L. C.

2010-10-01

We investigate the origin of the X-ray emission in low-luminosity AGNs (LLAGNs). Yuan & Cui (2005) predicted that the X-ray emission should originate from jets rather than from an advection-dominated accretion flow (ADAF) when the X-ray luminosity LX of the source is below a critical value of LX,crit ≍ 10-6 LEdd. This prediction implies that the X-ray spectrum in such sources should be fitted by jets rather than ADAFs. Furthermore, below LX,crit the correlation between radio (LR) and X-ray (LX) luminosities and the black hole mass (M)—the so-called fundamental plane of black hole activity—should deviate from the general correlation obtained by Merloni, Heinz & Di Matteo (2003) and become steeper. The Merloni et al. correlation is described by logLR = 0.6logLX + 0.78logM + 7.33, while the predicted correlation is logL_R = 1.23logLX + 0.25logM - 13.45. We collect data from the literature to check the validity of these two expectations. We find that among the 16 LLAGNs with good X-ray and radio spectra, 13 are consistent with the Yuan & Cui prediction. For the 22 LLAGNs with LX < LX,crit, the fundamental plane correlation is described by logLR = 1.22logLX + 0.23logM - 12.46, also in excellent agreement with the prediction.

Galactic X-ray emission from pulsars

NASA Technical Reports Server (NTRS)

Harding, A. K.

1981-01-01

The contribution of pulsars to the gamma-ray flux from the galactic plane is examined using data from the most recent pulsar surveys. It is assumed that pulsar gamma-rays are produced by curvature radiation from relativistic particles above the polar cap and attenuated by pair production in the strong magnetic and electric fields. Assuming that all pulsars produce gamma-rays in this way, their luminosities can be predicted as a function of period and magnetic field strength. Using the distribution of pulsars in the galaxy as determined from data on 328 pulsars detected in three surveys, the local gamma-ray production spectrum, the longitude profile, and the latitude profile of pulsar gamma-ray flux are calculated. The largest sources of uncertainty in the size of the pulsar contribution are the value of the mean interstellar electron density, the turnover in the pulsar radio luminosity function, and the average pulsar magnetic field strength. A present estimate is that pulsars contribute from 15 to 20 % of the total flux of gamma-rays from the galactic plane.

Results from the REFLEX Cluster Survey

NASA Astrophysics Data System (ADS)

Bohringer, H.; Guzzo, L.; Collins, C. A.; Neumann, D. M.; Schindler, S.; Schuecker, P.; Cruddace, R.; Chincarini, G.; de Grandi, S.; Edge, A. C.; MacGillivray, H. T.; Shaver, P.; Vettolani, G.; Voges, W.

Based on the ROSAT All-Sky Survey we have conducted a large redshift survey as an ESO key programme to identify and secure redshifts for the X-ray brightest clusters found in the southern hemisphere. We present first results for a highly controlled sample for a flux limit of 3cdot 10^{-12} erg s^{-1} cm^{-2} (0.1 - 2.4 keV) comprising 475 clusters (87% with redshifts). The logN-logS function of the sample shows an almost perfect Euclidian slope and a preliminary X-ray luminosity function is presented.

ROSAT X-ray detection of a young brown dwarf in the chamaeleon I dark cloud

PubMed

Neuhauser; Comeron

1998-10-02

Photometry and spectroscopy of the object Cha Halpha 1, located in the Chamaeleon I star-forming cloud, show that it is a approximately 10(6)-year-old brown dwarf with spectral type M7.5 to M8 and 0.04 +/- 0.01 solar masses. Quiescent x-ray emission was detected in a 36-kilosecond observation with 31.4 +/- 7.7 x-ray photons, obtained with the Rontgen Satellite (ROSAT), with 9final sigma detection significance. This corresponds to an x-ray luminosity of 2.57 x 10(28) ergs per second and an x-ray to bolometric luminosity ratio of 10(-3.44). These are typical values for late M-type stars. Because the interior of brown dwarfs may be similar to that of convective late-type stars, which are well-known x-ray sources, x-ray emission from brown dwarfs may indicate magnetic activity.

Identifying the subtle signatures of feedback from distant AGN using ALMA observations and the EAGLE hydrodynamical simulations

NASA Astrophysics Data System (ADS)

Scholtz, J.; Alexander, D. M.; Harrison, C. M.; Rosario, D. J.; McAlpine, S.; Mullaney, J. R.; Stanley, F.; Simpson, J.; Theuns, T.; Bower, R. G.; Hickox, R. C.; Santini, P.; Swinbank, A. M.

2018-03-01

We present sensitive 870 μm continuum measurements from our ALMA programmes of 114 X-ray selected active galactic nuclei (AGN) in the Chandra Deep Field-South and Cosmic Evolution Survey fields. We use these observations in combination with data from Spitzer and Herschel to construct a sample of 86 X-ray selected AGN, 63 with ALMA constraints at z = 1.5-3.2 with stellar mass >2 × 1010 M⊙. We constructed broad-band spectral energy distributions in the infrared band (8-1000 μm) and constrain star-formation rates (SFRs) uncontaminated by the AGN. Using a hierarchical Bayesian method that takes into account the information from upper limits, we fit SFR and specific SFR (sSFR) distributions. We explore these distributions as a function of both X-ray luminosity and stellar mass. We compare our measurements to two versions of the Evolution and Assembly of GaLaxies and their Environments (EAGLE) hydrodynamical simulations: the reference model with AGN feedback and the model without AGN. We find good agreement between the observations and that predicted by the EAGLE reference model for the modes and widths of the sSFR distributions as a function of both X-ray luminosity and stellar mass; however, we found that the EAGLE model without AGN feedback predicts a significantly narrower width when compared to the data. Overall, from the combination of the observations with the model predictions, we conclude that (1) even with AGN feedback, we expect no strong relationship between the sSFR distribution parameters and instantaneous AGN luminosity and (2) a signature of AGN feedback is a broad distribution of sSFRs for all galaxies (not just those hosting an AGN) with stellar masses above ≈1010 M⊙.

Variability Selected Low-Luminosity Active Galactic Nuclei in the 4 Ms Chandra Deep Field-South

NASA Technical Reports Server (NTRS)

Young, M.; Brandt, W. N.; Xue, Y. Q.; Paolillo, D. M.; Alexander, F. E.; Bauer, F. E.; Lehmer, B. D.; Luo, B.; Shemmer, O.; Schneider, D. P.;

THE OBSCURED FRACTION OF ACTIVE GALACTIC NUCLEI IN THE XMM-COSMOS SURVEY: A SPECTRAL ENERGY DISTRIBUTION PERSPECTIVE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lusso, E.; Hennawi, J. F.; Richards, G. T.

2013-11-10

The fraction of active galactic nucleus (AGN) luminosity obscured by dust and re-emitted in the mid-IR is critical for understanding AGN evolution, unification, and parsec-scale AGN physics. For unobscured (Type 1) AGNs, where we have a direct view of the accretion disk, the dust covering factor can be measured by computing the ratio of re-processed mid-IR emission to intrinsic nuclear bolometric luminosity. We use this technique to estimate the obscured AGN fraction as a function of luminosity and redshift for 513 Type 1 AGNs from the XMM-COSMOS survey. The re-processed and intrinsic luminosities are computed by fitting the 18 bandmore » COSMOS photometry with a custom spectral energy distribution fitting code, which jointly models emission from hot dust in the AGN torus, from the accretion disk, and from the host galaxy. We find a relatively shallow decrease of the luminosity ratio as a function of L{sub bol}, which we interpret as a corresponding decrease in the obscured fraction. In the context of the receding torus model, where dust sublimation reduces the covering factor of more luminous AGNs, our measurements require a torus height that increases with luminosity as h ∝ L{sub bol}{sup 0.3-0.4}. Our obscured-fraction-luminosity relation agrees with determinations from Sloan Digital Sky Survey censuses of Type 1 and Type 2 quasars and favors a torus optically thin to mid-IR radiation. We find a much weaker dependence of the obscured fraction on 2-10 keV luminosity than previous determinations from X-ray surveys and argue that X-ray surveys miss a significant population of highly obscured Compton-thick AGNs. Our analysis shows no clear evidence for evolution of the obscured fraction with redshift.« less

A limit to the X-ray luminosity of nearby normal galaxies

NASA Technical Reports Server (NTRS)

Worrall, D. M.; Marshall, F. E.; Boldt, E. A.

1979-01-01

Emission is studied at luminosities lower than those for which individual discrete sources can be studied. It is shown that normal galaxies do not appear to provide the numerous low luminosity X-ray sources which could make up the 2-60 keV diffuse background. Indeed, upper limits suggest luminosities comparable with, or a little less than, that of the galaxy. This is consistent with the fact that the average optical luminosity of the sample galaxies within approximately 20 Mpc is slightly lower than that of the galaxy. An upper limit of approximately 1% of the diffuse background from such sources is derived.

On the evidence for axionlike particles from active galactic nuclei

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pettinari, Guido Walter; Crittenden, Robert

2010-10-15

Burrage, Davis, and Shaw recently suggested exploiting the correlations between high and low energy luminosities of astrophysical objects to probe possible mixing between photons and axionlike particles (ALP) in magnetic field regions. They also presented evidence for the existence of ALP's by analyzing the optical/UV and x-ray monochromatic luminosities of active galactic nuclei. We extend their work by using the monochromatic luminosities of 320 unobscured active galactic nuclei from the Sloan Digital Sky Survey/Xmm-Newton Quasar Survey which allows the exploration of 18 different combinations of optical/UV and x-ray monochromatic luminosities. However, we do not find compelling evidence for the existencemore » of ALPs. Moreover, it appears that the signal reported by Burrage et al. is more likely due to x-ray absorption rather than to photon-ALP oscillation.« less

A Catalog of Candidate Intermediate-Luminosity X-Ray Objects

NASA Astrophysics Data System (ADS)

Colbert, E. J. M.; Ptak, A. F.

2002-11-01

ROSAT, and now Chandra, X-ray images allow studies of extranuclear X-ray point sources in galaxies other than our own. X-ray observations of normal galaxies with ROSAT and Chandra have revealed that off-nuclear, compact, intermediate-luminosity (LX[2-10keV]>=1039.0 ergs s-1) X-ray objects (IXOs, a.k.a. ULXs [ultraluminous X-ray sources]) are quite common. Here we present a catalog and finding charts for 87 IXOs in 54 galaxies, derived from all of the ROSAT HRI imaging data for galaxies with cz<=5000 km s-1 from the Third Reference Catalog of Bright Galaxies. We have defined the cutoff LX for IXOs so that it is well above the Eddington luminosity of a 1.4 Msolar black hole (1038.3 ergs s-1), so as not to confuse IXOs with ``normal'' black hole X-ray binaries. This catalog is intended to provide a baseline for follow-up work with Chandra and XMM-Newton, and with space- and ground-based survey work at wavelengths other than X-ray. We demonstrate that elliptical galaxies with IXOs have a larger number of IXOs per galaxy than nonelliptical galaxies with IXOs and note that they are not likely to be merely high-mass X-ray binaries with beamed X-ray emission, as may be the case for IXOs in starburst galaxies. Approximately half of the IXOs with multiple observations show X-ray variability, and many (19) of the IXOs have faint optical counterparts in DSS optical B-band images. Follow-up observations of these objects should be helpful in identifying their nature.

A ROSAT Survey of Contact Binary Stars

NASA Astrophysics Data System (ADS)

Geske, M. T.; Gettel, S. J.; McKay, T. A.

2006-01-01

Contact binary stars are common variable stars that are all believed to emit relatively large fluxes of X-rays. In this work we combine a large new sample of contact binary stars derived from the ROTSE-I telescope with X-ray data from the ROSAT All Sky Survey (RASS) to estimate the X-ray volume emissivity of contact binary stars in the Galaxy. We obtained X-ray fluxes for 140 contact binaries from the RASS, as well as two additional stars observed by the XMM-Newton observatory. From these data we confirm the emission of X-rays from all contact binary systems, with typical luminosities of approximately 1.0×1030 ergs s-1. Combining calculated luminosities with an estimated contact binary space density, we find that contact binaries do not have strong enough X-ray emission to account for a significant portion of the Galactic X-ray background.

Heavily Obscured AGN with SIMBOL-X

NASA Astrophysics Data System (ADS)

Della Ceca, R.; Caccianiga, A.; Severgnini, P.

2009-05-01

By comparing an optically selected sample of narrow lines AGN with an X-ray selected sample of AGN we have recently derived an estimate of the intrinsic (i.e. before absorption) 2-10 keV luminosity function (XLF) of Compton Thick AGNs. We will use this XLF to derive the number of Compton Thick AGN that will be found in the SIMBOL-X survey(s).

SphinX Measurements of the 2009 Solar Minimum X-Ray Emission

NASA Astrophysics Data System (ADS)

Sylwester, J.; Kowalinski, M.; Gburek, S.; Siarkowski, M.; Kuzin, S.; Farnik, F.; Reale, F.; Phillips, K. J. H.; Bakała, J.; Gryciuk, M.; Podgorski, P.; Sylwester, B.

2012-06-01

The SphinX X-ray spectrophotometer on the CORONAS-PHOTON spacecraft measured soft X-ray emission in the 1-15 keV energy range during the deep solar minimum of 2009 with a sensitivity much greater than GOES. Several intervals are identified when the X-ray flux was exceptionally low, and the flux and solar X-ray luminosity are estimated. Spectral fits to the emission at these times give temperatures of 1.7-1.9 MK and emission measures between 4 × 1047 cm-3 and 1.1 × 1048 cm-3. Comparing SphinX emission with that from the Hinode X-ray Telescope, we deduce that most of the emission is from general coronal structures rather than confined features like bright points. For one of 27 intervals of exceptionally low activity identified in the SphinX data, the Sun's X-ray luminosity in an energy range roughly extrapolated to that of ROSAT (0.1-2.4 keV) was less than most nearby K and M dwarfs.

ROSAT X-ray luminosity functions of the Hyades dK and dM stars

NASA Astrophysics Data System (ADS)

Pye, John P.; Hodgkin, Simon T.; Stern, Robert A.; Stauffer, John R.

1994-02-01

Long-duration ROSAT PSPC pointed observations of the Hyades open star cluster are performed. The Hyades dK and XLFs from the present observations are compared with published Einstein dK/dM XLFs. The Hyades dK binaries have significantly higher L(X) than the Hyades dK stars. However, all these binaries have relatively long periods (greater than about 1 yr), and hence the L(X) levels cannot be attributed to the enhanced activity expected in short-period, 'BY Dra-type' systems. It is also shown that the effect cannot be due simply to the summed luminosities of the component stars.

Multiwavength Observations of the Black Hole X-Ray Binary A0620-00 in Quiescence

NASA Astrophysics Data System (ADS)

Dinçer, Tolga; Bailyn, Charles D.; Miller-Jones, James C. A.; Buxton, Michelle; MacDonald, Rachel K. D.

2018-01-01

We present results from simultaneous multiwavelength X-ray, radio, and optical/near-infrared observations of the quiescent black hole X-ray binary A0620-00 performed in 2013 December. We find that the Chandra flux has brightened by a factor of 2 since 2005, and by a factor of 7 since 2000. The spectrum has not changed significantly over this time, being consistent with a power law of {{Γ }}=2.07+/- 0.13 and a hydrogen column of {N}H=(3.0+/- 0.5)× {10}21 {{cm}}-2. Very Large Array observations of A0620-00 at three frequencies, over the interval of 5.25–22.0 GHz, have provided us with the first broadband radio spectrum of a quiescent stellar mass black hole system at X-ray luminosities as low as 10‑8 times the Eddington luminosity. Compared to previous observations, the source has moved to lower radio and higher X-ray luminosity, shifting it perpendicular to the standard track of the radio/X-ray correlation for X-ray binaries. The radio spectrum is inverted with a spectral index α =0.74+/- 0.19 ({S}ν \\propto {ν }α ). This suggests that the peak of the spectral energy distribution is likely to be between 1012 and 1014 Hz, and that the near-IR and optical flux contain significant contributions from the star, the accretion flow, and from the outflow. Decomposing these components may be difficult, but holds the promise of revealing the interplay between accretion and jet in low luminosity systems.

Chandra Studies of Unidentified X-ray Sources in the Galactic Bulge

NASA Astrophysics Data System (ADS)

Mori, Hideyuki

2013-09-01

We propose to study a complete X-ray sample in the luminosity range of > 10^34 erg s^-1 in the Galactic bulge, including 5 unidentified sources detected in the ROSAT All Sky Survey. Our goal is to obtain a clear picture about X-ray populations in the bulge, by utilizing the excellent Chandra position accuracy leading to unique optical identification together with the X-ray spectral properties. This is a new step toward understanding the formation history of the bulge. Furthermore, because the luminosity range we observe corresponds to a ``missing link'' region ever studied for a neutron star or blackhole X-ray binary, our results are also unique to test accretion disk theories at intermediate mass accretion rates.

The formation efficiency of different generations of HMXBs in the low metallicity environment of the SMC

NASA Astrophysics Data System (ADS)

Antoniou, Vallia; Zezas, Andreas; Drake, Jeremy J.; Badenes, Carles; Hong, Jaesub; SMC XVP Collaboration

2018-01-01

Nearby star-forming galaxies offer a unique environment to study the populations of young (<100 Myr) X-ray binaries, which consist of a compact object - typically a neutron star or a black hole - powered by accretion from a companion star. These systems are tracers of past populations of massive stars that heavily affect their immediate environment and parent galaxies. The Small Magellanic Cloud (SMC) is the ideal environment for population studies of young X-ray binaries by providing us with what the Milky Way cannot: A complete sample of X-ray sources within a galaxy. Using a Chandra X-ray Visionary program, we investigate the young neutron-star binary population in this low-metallicity, nearby, star-forming galaxy by reaching quiescent X-ray luminosity levels (~few times 1032 erg/s). In this talk, I will present the first measurement of the formation efficiency of high-mass X-ray binaries (HMXBs) as a function of the age of their parent stellar populations. We use three indicators of the formation efficiency of young accreting binaries in the low SMC metallicity: the number ratio of the HMXBs, N(HMXBs), to the number of OB stars, to the star-formation rate (SFR), and to the stellar mass produced during the specific star-formation burst they are associated with, all as a function of the age of their parent stellar populations. In all cases, we find that the HMXB formation efficiency increases as a function of time up to ~40—60 Myr, and then gradually decreases. The peak formation efficiency N(HMXB)/SFR is in good agreement with previous estimates of the average formation efficiency in the broad ~20—60 Myr age range, and a factor of at least ~8 and ~4 higher than the formation efficiency in earlier (~10 Myr) and later (~260 Myr) epochs. I will also present the deepest luminosity function ever recorded for a galaxy, and discuss the X-ray properties of the largest sample of extragalactic accreting pulsars as well.

Inflow Generated X-Ray Corona around Supermassive Black Holes and a Unified Model for X-Ray Emission

NASA Astrophysics Data System (ADS)

Wang, Lile; Cen, Renyue

2016-02-01

Three-dimensional hydrodynamic simulations are performed, which cover the spatial domain from hundreds of Schwarzschild radii to 2 pc around the central supermassive black hole of mass {10}8{M}⊙ , with detailed radiative cooling processes. The existence of a significant amount of shock heated, high temperature (≥slant {10}8 {{K}}) coronal gas in the inner (≤slant {10}4{r}{sch}) region is generally found. It is shown that the composite bremsstrahlung emission spectrum due to coronal gas of various temperatures is in reasonable agreement with the overall ensemble spectrum of active galactic nuclei (AGNs) and hard X-ray background. Taking into account inverse Compton processes, in the context of the simulation-produced coronal gas, our model can readily account for the wide variety of AGN spectral shapes, which can now be understood physically. The distinguishing feature of our model is that X-ray coronal gas is, for the first time, an integral part of the inflow gas and its observable characteristics are physically coupled to the concomitant inflow gas. One natural prediction of our model is the anti-correlation between accretion disk luminosity and spectral hardness: as the luminosity of SMBH accretion disk decreases, the hard X-ray luminosity increases relative to the UV/optical luminosity.

Some Like it Hot: Linking Diffuse X-Ray Luminosity, Baryonic Mass, and Star Formation Rate in Compact Groups of Galaxies

NASA Technical Reports Server (NTRS)

Desjardins, Tyler D.; Gallagher, Sarah C.; Hornschemeier, Ann E.; Mulchaey, John S.; Walker, Lisa May; Brandt, Willian N.; Charlton, Jane C.; Johnson, Kelsey E.; Tzanavaris, Panayiotis

2014-01-01

We present an analysis of the diffuse X-ray emission in 19 compact groups (CGs) of galaxies observed with Chandra. The hottest, most X-ray luminous CGs agree well with the galaxy cluster X-ray scaling relations in L(x-T) and (L(x-sigma), even in CGs where the hot gas is associated with only the brightest galaxy. Using Spitzer photometry, we compute stellar masses and classify Hickson CGs 19, 22, 40, and 42, and RSCGs 32, 44, and 86 as fossil groups using a new definition for fossil systems that includes a broader range of masses. We find that CGs with total stellar and Hi masses are great than or equal to 10(sup (11.3) solar mass are often X-ray luminous, while lower-mass CGs only sometimes exhibit faint, localized X-ray emission. Additionally, we compare the diffuse X-ray luminosity against both the total UV and 24 micron star formation rates of each CG and optical colors of the most massive galaxy in each of the CGs. The most X-ray luminous CGs have the lowest star formation rates, likely because there is no cold gas available for star formation, either because the majority of the baryons in these CGs are in stars or the X-ray halo, or due togas stripping from the galaxies in CGs with hot halos. Finally, the optical colors that trace recent star formation histories of the most massive group galaxies do not correlate with the X-ray luminosities of the CGs, indicating that perhaps the current state of the X-ray halos is independent of the recent history of stellar mass assembly in the most massive galaxies.

High levels of absorption in orientation-unbiased, radio-selected 3CR Active Galaxies

NASA Astrophysics Data System (ADS)

Wilkes, Belinda J.; Haas, Martin; Barthel, Peter; Leipski, Christian; Kuraszkiewicz, Joanna; Worrall, Diana; Birkinshaw, Mark; Willner, Steven P.

2014-08-01

A critical problem in understanding active galaxies (AGN) is the separation of intrinsic physical differences from observed differences that are due to orientation. Obscuration of the active nucleus is anisotropic and strongly frequency dependent leading to complex selection effects for observations in most wavebands. These can only be quantified using a sample that is sufficiently unbiased to test orientation effects. Low-frequency radio emission is one way to select a close-to orientation-unbiased sample, albeit limited to the minority of AGN with strong radio emission.Recent Chandra, Spitzer and Herschel observations combined with multi-wavelength data for a complete sample of high-redshift (1 24.2) = 2.5:1.4:1 in these high-luminosity (log L(0.3-8keV) ~ 44-46) sources. These ratios are consistent with current expectations based on modelingthe Cosmic X-ray Background. A strong correlation with radio orientation constrains the geometry of the obscuring disk/torus to have a ~60 degree opening angle and ~12 degree Compton-thick cross-section. The deduced ~50% obscured fraction of the population contrasts with typical estimates of ~20% obscured in optically- and X-ray-selected high-luminosity samples. Once the primary nuclear emission is obscured, AGN X-ray spectra are frequently dominated by unobscured non-nuclear or scattered nuclear emission which cannot be distinguished from direct nuclear emission with a lower obscuration level unless high quality data is available. As a result, both the level of obscuration and the estimated instrinsic luminosities of highly-obscured AGN are likely to be significantly (*10-1000) underestimated for 25-50% of the population. This may explain the lower obscured fractions reported for optical and X-ray samples which have no independent measure of the AGN luminosity. Correcting AGN samples for these underestimated luminosities would result in flatter derived luminosity functions and potentially change their evolution.

Black Holes in Bulgeless Galaxies: An XMM-Newton Investigation of NGC 3367 AND NGC 4536

NASA Technical Reports Server (NTRS)

McAlpine, W.; Satyapal, S.; Gliozzi, M.; Cheung, C. C.; Sambruna, R. M.; Eracleous, Michael

2012-01-01

The vast majority of optically identified active galactic nuclei (AGNs) in the local Universe reside in host galaxies with prominent bulges, supporting the hypothesis that black hole formation and growth is fundamentally connected to the build-up of galaxy bulges. However, recent mid-infrared spectroscopic studies with Spitzer of a sample of optically "normal" late-type galaxies reveal remarkably the presence of high-ionization [NeV] lines in several sources, providing strong evidence for AGNs in these galaxies. We present follow-up X-ray observations recently obtained with XMM-Newton of two such sources, the late-type optically normal galaxies NGC 3367 and NGC 4536. Both sources are detected in our observations. Detailed spectral analysis reveals that for both galaxies, the 2-10 keV emission is dominated by a power law with an X-ray luminosity in the L(sub 2- 10 keV) approximates 10(exp 39) - 10(exp 40) ergs/s range, consistent with low luminosity AGNs. While there is a possibility that X-ray binaries account for some fraction of the observed X-ray luminosity, we argue that this fraction is negligible. These observations therefore add to the growing evidence that the fraction of late-type galaxies hosting AGNs is significantly underestimated using optical observations alone. A comparison of the midinfrared [NeV] luminosity and the X-ray luminosities suggests the presence of an additional highly absorbed X-ray source in both galaxies, and that the black hole masses are in the range of 10(exp 5) - 10(exp 7) solar M for NGC 3367 and 10(exp 4) - (exp 10) solar M for NGC 4536

Medusa spectroscopy of A400, A576, A1767, and A2124

NASA Technical Reports Server (NTRS)

Hintzen, P.; Hill, J. M.; Lindley, D.; Scott, J. S.; Angel, J. R. P.

1982-01-01

Galaxy velocity data taken with the Steward Observatory multiple aperture fiber optic spectrograph are presented for four Abell clusters. The root-mean-square external errors in these velocities are about 100 km/s; accuracy which compares favorably with that obtained from single-object observations. It is expected that the recent adoption of a CCD detector should decrease external errors to about 50 km/s. All four of the clusters observed are known X-ray sources and the present data agree well with empirically derived velocity dispersion-X-ray luminosity relations for clusters of galaxies. Abell 400 is interesting in this regard, since both its X-ray luminosity and its velocity dispersion are quite small. Such objects are particularly important in determining the slope of the velocity dispersion-X-ray luminosity relation. The large microwave decrement observed in A576 was initially interpreted as due to Compton scattering of the microwave background by the X-ray-emitting intracluster gas. White and Silk have presented Einstein X-ray data which indicate that A576 contains too little gas to produce the observed microwave decrement by Compton scattering. The velocity dispersion obtained here for 47 members of this cluster strengthens their conclusion.

The Swift BAT Hard X-ray Survey - A New Window on the Local AGN Universe

NASA Technical Reports Server (NTRS)

Mushotzky, Richard

2009-01-01

The Swift Burst and Transient telescope (BAT) has surveyed the entire sky for the last 3.5 years obtaining the first sensitive all sky survey of the 14-195 keV sky. At high galactic latitudes the vast majority of the detected sources are AGN. Since hard x-rays penetrate all but Compton thick obscuring material (Column densities of 1.6E24 atms/cm2) this survey is unbiased with respect to obscuration, host galaxy type, optical , radio or IR properties. We will present results on the broad band x-ray properties, the nature of the host galaxies, the luminosity function and will discuss a few of the optical, IR and x-ray results in detail.

XMM TOO Observation

NASA Technical Reports Server (NTRS)

Kong, Albert

2005-01-01

The primary research goal of this project is to perform follow-up observations of a recurrent ultraluminous supersoft X-ray source (SSS) in Ml0l. The source was first discovered by ROSAT and was confirmed as a SSS with a blackbody temperature of about l00eV by Chandra. During 2000 March, Chandra detected it at Lx=4e39 erg per second, and then in 2000 October, its luminosity dropped to around le39 erg per second. During 2004, Chandra is conducting a monitoring program for Ml0l. The SSS was near the detection limit during January, March, and May; the X-ray spectra were harder with a power-law shape, and the X-ray luminosity was about 3e37 erg/second, a factor of greater than 200 fainter than that in the previous high state. The source was found to be in outburst again during the July 5 observation, with an X-ray luminosity of about 7e39 erg/second. Data taken on July 6,7, and 8 show that the source was in a strong outburst with a peak bolometric luminosity of about 7e39 erg/second. In general, the X-ray spectra are best described with an absorbed blackbody model with temperatures of approximately 50-100eV. In addition, we found absorption edges at 0.33, 0.57, 0.66, and 0.88 keV in two of the high state spectra. These features may signal the presence of highly ionized gas in the vicinity of the accretor (e.g., warm absorber). In order to study an ultraluminous SSS in outburst in detail, we proposed a TOO XMM observation to observe the source. The observation was taken on July 23 and the source was fainter with a luminosity of 6e38 ergs, and a harder X-ray spectrum with a power-law tail seen up to 7 keV. This clearly indicates that the source was in the decline stage with spectral change. In addition to the XMM observation, we also arranged radio observation and a simultaneous CFHT observation. The X-ray results were published in ATel and ApJL. There were several more Chandra observations taken after 2004 July. The source was in a low luminosity state but it underwent another X-ray outburst in 2004 December. We are arranging more follow-up observations for this intriguing source.

Star Formation Rate Distribution in the Galaxy NGC 1232

NASA Astrophysics Data System (ADS)

Araújo de Souza, Alexandre; Martins, Lucimara P.; Rodríguez-Ardila, Alberto; Fraga, Luciano

2018-06-01

NGC 1232 is a face-on spiral galaxy and a great laboratory for the study of star formation due to its proximity. We obtained high spatial resolution Hα images of this galaxy, with adaptive optics, using the SAM instrument at the SOAR telescope, and used these images to study its H II regions. These observations allowed us to produce the most complete H II region catalog for it to date, with a total of 976 sources. This doubles the number of H II regions previously found for this object. We used these data to construct the H II luminosity function, and obtained a power-law index lower than the typical values found for Sc galaxies. This shallower slope is related to the presence of a significant number of high-luminosity H II regions (log L > 39 dex). We also constructed the size distribution function, verifying that, as for most galaxies, NGC 1232 follows an exponential law. We also used the Hα luminosity to calculate the star formation rate. An extremely interesting fact about this galaxy is that X-ray diffuse observations suggest that NGC 1232 recently suffered a collision with a dwarf galaxy. We found an absence of star formation around the region where the X-ray emission is more intense, which we interpret as a star formation quenching due to the collision. Along with that, we found an excess of star-forming regions in the northeast part of the galaxy, where the X-ray emission is less intense.

A search for X-ray binary stars in their quiescent phase

NASA Technical Reports Server (NTRS)

Helfand, D. J.

1980-01-01

Fourteen early-type stars representative of systems which may be harboring a neutron star companion and are thus potential progenitors of massive X-ray binaries have been examined for X-ray emission with the HEAO A-1 experiment. Limits on the 0.5-20 keV luminosity for these objects lie in the range 10 to the 31-33 erg/sec. In several cases, the hypothesis of a collapsed companion, in combination with the X-ray limit, places a serious constraint on the mass-loss rate of the primary star. In one instance, an X-ray source was discovered coincident with a candidate star, although the luminosity of 5 x 10 to the 31 is consistent with that expected from a single star of the same spectral type. The prospects for directly observing the quiescent phase of a binary X-ray source with the Einstein Observatory are discussed in the context of these results.

The X-ray spectrum and time variability of narrow emission line galaxies

NASA Technical Reports Server (NTRS)

Mushotzky, R.

1981-01-01

X-ray spectral and temporal observations are reported for six narrow emission line galaxies (NELGs), all of which are fitted by power-law X-ray spectra of energy slope 0.8 and have column densities in the line of sight greater than 1 x 10 to the 22nd atoms/sq cm. Three of the objects, NGC 526a, NGC 2110 and MCG-5-23-16 are variable in their X-ray flux, and the latter two, along with NGC 5506 and NGC 7582, showed detectable variability in at least one observation. The measured X-ray properties of these NELGs, which also included NGC 2992, strongly resemble those of previously-measured type 1 Seyferts of the same X-ray luminosity and lead to the conclusion of great similarity between the NELGs and low-luminosity type 1 Seyferts. The implications of these observations for the optical line-emitting region structure of these galaxies are discussed.

X-RAY OUTBURSTS OF ESO 243-49 HLX-1: COMPARISON WITH GALACTIC LOW-MASS X-RAY BINARY TRANSIENTS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yan, Zhen; Zhang, Wenda; Yu, Wenfei

2015-09-20

We studied the outburst properties of the hyper-luminous X-ray source ESO 243-49 HLX-1, using the full set of Swift monitoring observations. We quantified the increase in the waiting time, recurrence time, and e-folding rise timescale along the outburst sequence, and the corresponding decrease in outburst duration, total radiated energy, and e-folding decay timescale, which confirms previous findings. HLX-1 spends less and less time in outburst and more and more time in quiescence, but its peak luminosity remains approximately constant. We compared the HLX-1 outburst properties with those of bright Galactic low-mass X-ray binary transients (LMXBTs). Our spectral analysis strengthens themore » similarity between state transitions in HLX-1 and those in Galactic LMXBTs. We also found that HLX-1 follows the nearly linear correlations between the hard-to-soft state transition luminosity and the peak luminosity, and between the rate of change of X-ray luminosity during the rise phase and the peak luminosity, which indicates that the occurrence of the hard-to-soft state transition of HLX-1 is similar to those of Galactic LMXBTs during outbursts. We found that HLX-1 does not follow the correlations between total radiated energy and peak luminosity, and between total radiated energy and e-folding rise/decay timescales we had previously identified in Galactic LMXBTs. HLX-1 would follow those correlations if the distance were several hundreds of kiloparsecs. However, invoking a much closer distance for HLX-1 is not a viable solution to this problem, as it introduces other, more serious inconsistencies with the observations.« less

DUSTY EXPLOSIONS FROM DUSTY PROGENITORS: THE PHYSICS OF SN 2008S AND THE 2008 NGC 300-OT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kochanek, C. S.

2011-11-01

SN 2008S and the 2008 NGC 300-OT were explosive transients of stars self-obscured by very dense, dusty stellar winds. An explosive transient with an unobserved shock breakout luminosity of order 10{sup 10} L{sub sun} is required to render the transients little obscured and visible in the optical at their peaks. Such a large breakout luminosity then implies that the progenitor stars were cool, red supergiants, most probably {approx}9 M{sub sun} extreme asymptotic giant branch stars. As the shocks generated by the explosions propagate outward through the dense wind, they produce a shock luminosity in soft X-rays that powers the long-livedmore » luminosity of the transients. Unlike typical cases of transients exploding into a surrounding circumstellar medium, the progenitor winds in these systems are optically thick to soft X-rays, easily absorb radio emission, and rapidly reform dust destroyed by the peak luminosity of the transients. As a result, X-rays are absorbed by the gas and the energy is ultimately radiated by the reformed dust. Three years post-peak, both systems are still significantly more luminous than their progenitor stars, but they are again fully shrouded by the reformed dust and only visible in the mid-IR. The high luminosity and heavy obscuration may make it difficult to determine the survival of the progenitor stars for {approx}10 years. However, our model indicates that SN 2008S, but not the NGC 300-OT, should now be a detectable X-ray source. SN 2008S has a higher estimated shock velocity and a lower density wind, so the X-rays begin to escape at a much earlier phase.« less

Black holes in short period X-ray binaries and the transition to radiatively inefficient accretion

NASA Astrophysics Data System (ADS)

Knevitt, G.; Wynn, G. A.; Vaughan, S.; Watson, M. G.

2014-02-01

By comparing the orbital period distributions of black hole and neutron star low-mass X-ray binaries (LMXBs) in the Ritter-Kolb catalogue we show that there is statistical evidence for a dearth of black hole systems at short orbital periods (Porb < 4 h). This could either be due to a true divergence in orbital period distributions of these two types of system, or to black hole LMXBs being preferentially hidden from view at short orbital periods. We explore the latter possibility, by investigating whether black hole LMXBs could be concealed by a switch to radiatively inefficient accretion at low luminosities. The peak luminosity and the duration of X-ray binary outbursts are related to the disc radius and, hence, the orbital period. At short periods, where the peak outburst luminosity drops close to the threshold for radiatively inefficient accretion, black hole LMXBs have lower outburst luminosities, shorter outburst durations and lower X-ray duty cycles than comparable neutron star systems. These factors can combine to severely reduce the detection probability of short period black hole LMXBs relative to those containing neutron stars. We estimate the outburst properties and orbital period distribution of black hole LMXBs using two models of the transition to radiatively inefficient accretion: an instantaneous drop in accretion efficiency (η) to zero, at a fraction (f) of the Eddington luminosity (LEdd) and a power-law efficiency decrease, η ∝ dot{M}^n, for L < f LEdd. We show that a population of black hole LMXBs at short orbital periods can only be hidden by a sharp drop in efficiency, either instantaneous or for n ≳ 3. This could be achieved by a genuine drop in luminosity or through abrupt spectral changes that shift the accretion power out of a given X-ray band.

Measuring the Impact of AGN Outflows via Intensive UV and X-ray Monitoring Campaigns

NASA Astrophysics Data System (ADS)

Kriss, Gerard

2015-08-01

Observations of AGN outflows have progressed from the era of single-object surveys to intensive monitoring campaigns spanning weeks to months. The combination of multiple observations, improved temporal coverage, multi-wavelength monitoring in both the X-ray and UV bands, and the baseline of prior historical observations has enabled determinations of the locations, mass flux, and kinetic luminosities of the outflowing absorbing gas in several AGN, notably Mrk 509, NGC 5548, Mrk 335, and NGC 985. Another intensive campaign is planned for 2015-2016 on NGC 7469. In all cases, the mass flux and kinetic energy is dominated by the higher-ionization X-ray absorbing gas. But the higher-resolution UV observations give a kinematically resolved picture of the overall outflow. In most cases, the outflowing gas is located at parsec to kpc scales, with insufficient kinetic luminosity to have an evolutionary impact on the host galaxy. Typically, the kinetic luminosity is less than a percent of the Eddington luminosity. In some cases, transient, broad UV absorption troughs have appeared (e.g., Mrk 335 and NGC 5548), with variability timescales suggesting locations near the broad-line region of the AGN. Yet these higher-velocity outflows also have low-impact kinetic luminosities. In the best-studied case of NGC 5548, the strength of the broad UV absorption lines varies with the degree of soft X-ray obscuration first revealed by XMM-Newton spectra. The lower-ionization, narrow associated absorption lines in the UV spectrum of NGC 5548 that appeared concurrently with the soft X-ray obscuration vary in response to the changing UV flux on a daily basis. The intensive monitoring allows us to fit time-dependent photoionization models to the UV-absorbing gas, allowing precise determinations of the locations, mass flux, and kinetic luminosities of the absorbers.

An Expanded Rossi X-Ray Timing Explorer Survey of X-Ray Variability in Seyfert 1 Galaxies

NASA Astrophysics Data System (ADS)

Markowitz, A.; Edelson, R.

2004-12-01

The first seven years of RXTE monitoring of Seyfert 1 active galactic nuclei have been systematically analyzed to yield five homogeneous samples of 2-12 keV light curves, probing hard X-ray variability on successively longer durations from ~1 day to ~3.5 yr. The 2-10 keV variability on timescales of ~1 day, as probed by ASCA, is included. All sources exhibit stronger X-ray variability toward longer timescales, but the increase is greater for relatively higher luminosity sources. Variability amplitudes are anticorrelated with X-ray luminosity and black hole mass, but amplitudes saturate and become independent of luminosity or black hole mass toward the longest timescales. The data are consistent with the models of power spectral density (PSD) movement described by Markowitz and coworkers and McHardy and coworkers, whereby Seyfert 1 galaxies' variability can be described by a single, universal PSD shape whose break frequency scales with black hole mass. The best-fitting scaling relations between variability timescale, black hole mass, and X-ray luminosity imply an average accretion rate of ~5% of the Eddington limit for the sample. Nearly all sources exhibit stronger variability in the relatively soft 2-4 keV band compared to the 7-12 keV band on all timescales. There are indications that relatively less luminous or less massive sources exhibit a greater degree of spectral variability for a given increase in overall flux.

Accretion powered X-ray pulsars

NASA Technical Reports Server (NTRS)

White, N. E.; Swank, J. H.; Holt, S. S.

1982-01-01

A unified description of the properties of 14 X-ray pulsars is presented and compared with the current theoretical understanding of these systems. The sample extends over six orders of magnitude in luminosity, with the only trend in the phase averaged spectra being that the lower luminosity systems appear to have less abrupt high energy cutoffs. There is no correlation of luminosity with power law index, high energy cutoff energy or iron line EW. Detailed pulse phase spectroscopy is given for five systems.

X-ray study of a sample of FR0 radio galaxies: unveiling the nature of the central engine

NASA Astrophysics Data System (ADS)

Torresi, E.; Grandi, P.; Capetti, A.; Baldi, R. D.; Giovannini, G.

2018-06-01

Fanaroff-Riley type 0 radio galaxies (FR0s) are compact radio sources that represent the bulk of the radio-loud active galactic nuclei (AGN) population, but they are still poorly understood. Pilot studies on these sources have been already performed at radio and optical wavelengths: here we present the first X-ray study of a sample of 19 FR0 radio galaxies selected from the Sloan Digital Sky Survey/NRAO VLA Sky Survey/Faint Images of the Radio Sky at Twenty-cm sample of Best & Heckman, with redshift ≤0.15, radio size ≤10 kpc, and optically classified as low-excitation galaxies. The X-ray spectra are modelled with a power-law component absorbed by Galactic column density with, in some cases, a contribution from thermal extended gas. The X-ray photons are likely produced by the jet as attested by the observed correlation between X-ray (2-10 keV) and radio (5 GHz) luminosities, similar to Fanaroff-Riley type I radio galaxies (FRIs). The estimated Eddington-scaled luminosities indicate a low accretion rate. Overall, we find that the X-ray properties of FR0s are indistinguishable from those of FRIs, thus adding another similarity between AGN associated with compact and extended radio sources. A comparison between FR0s and low-luminosity BL Lacs rules out important beaming effects in the X-ray emission of the compact radio galaxies. FR0s have different X-ray properties with respect to young radio sources (e.g. gigahertz-peaked spectrum/compact steep spectrum sources), generally characterized by higher X-ray luminosities and more complex spectra. In conclusion, the paucity of extended radio emission in FR0s is probably related to the intrinsic properties of their jets that prevent the formation of extended structures, and/or to intermittent activity of their engines.

An X-ray halo around Cassiopeia A

NASA Astrophysics Data System (ADS)

Stewart, G. C.; Fabian, A. C.; Seward, F. D.

The large-scale X-ray emission of Cas A is characterized, and mechanisms are proposed to explain it. The Einstein HRI image of Murray et al. (1979) is binned into 16-arcsec pixels, a point-spread function based on the 2.04-keV monochromatic Zr source is applied, and the data are modeled as a series of circularly symmetric rings of emission. A significant excess extending to a radius of 6 arcmin (roughly the size of the optical H II region) is found to have a total 0.5-3-keV luminosity of about 5 x 10 to the 34th erg/s, or about 2 percent of the total luminosity of Cas A, which is assumed to lie at a distance of 3 kpc. Thermal bremsstrahlung, synchrotron radiation, and dust scattering of the main-shell emission are examined and found to be plausible emission mechanisms; further observations are required to identify the one active in Cas A.

On the Spatially Resolved Star Formation History in M51. II. X-Ray Binary Population Evolution

NASA Astrophysics Data System (ADS)

Lehmer, B. D.; Eufrasio, R. T.; Markwardt, L.; Zezas, A.; Basu-Zych, A.; Fragos, T.; Hornschemeier, A. E.; Ptak, A.; Tzanavaris, P.; Yukita, M.

2017-12-01

We present a new technique for empirically calibrating how the X-ray luminosity function (XLF) of X-ray binary (XRB) populations evolves following a star formation event. We first utilize detailed stellar population synthesis modeling of far-UV-to-far-IR photometry of the nearby face-on spiral galaxy M51 to construct maps of the star formation histories (SFHs) on subgalactic (≈400 pc) scales. Next, we use the ≈850 ks cumulative Chandra exposure of M51 to identify and isolate 2-7 keV detected point sources within the galaxy, and we use our SFH maps to recover the local properties of the stellar populations in which each X-ray source is located. We then divide the galaxy into various subregions based on their SFH properties (e.g., star formation rate (SFR) per stellar mass ({M}\\star ) and mass-weighted stellar age) and group the X-ray point sources according to the characteristics of the regions in which they are found. Finally, we construct and fit a parameterized XLF model that quantifies how the XLF shape and normalization evolves as a function of the XRB population age Our best-fit model indicates that the XRB XLF per unit stellar mass declines in normalization, by ˜3-3.5 dex, and steepens in slope from ≈10 Myr to ≈10 Gyr. We find that our technique recovers results from past studies of how XRB XLFs and XRB luminosity scaling relations vary with age and provides a self-consistent picture for how XRB XLFs evolve with age.

Active galactic nucleus X-ray variability in the XMM-COSMOS survey

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lanzuisi, G.; Ponti, G.; Salvato, M.

2014-02-01

We used the observations carried out by XMM in the COSMOS field over 3.5 yr to study the long term variability of a large sample of active galactic nuclei (AGNs) (638 sources) in a wide range of redshifts (0.1 < z < 3.5) and X-ray luminosities (10{sup 41} < L {sub 0.5-10} <10{sup 45.5}). Both a simple statistical method to assess the significance of variability and the Normalized Excess Variance (σ{sub rms}{sup 2}) parameter were used to obtain a quantitative measurement of the variability. Variability is found to be prevalent in most AGNs, whenever we have good statistics to measuremore » it, and no significant differences between type 1 and type 2 AGNs were found. A flat (slope –0.23 ± 0.03) anti-correlation between σ{sub rms}{sup 2} and X-ray luminosity is found when all significantly variable sources are considered together. When divided into three redshift bins, the anti-correlation becomes stronger and evolving with z, with higher redshift AGNs being more variable. We prove, however, that this effect is due to the pre-selection of variable sources: when considering all of the sources with an available σ{sub rms}{sup 2} measurement, the evolution in redshift disappears. For the first time, we were also able to study long term X-ray variability as a function of M {sub BH} and Eddington ratio for a large sample of AGNs spanning a wide range of redshifts. An anti-correlation between σ{sub rms}{sup 2} and M {sub BH} is found, with the same slope of anti-correlation between σ{sub rms}{sup 2} and X-ray luminosity, suggesting that the latter may be a by-product of the former. No clear correlation is found between σ{sub rms}{sup 2} and the Eddington ratio in our sample. Finally, no correlation is found between the X-ray σ{sub rms}{sup 2} and optical variability.« less

The Structure of the Young Star Cluster NGC 6231. I. Stellar Population

NASA Astrophysics Data System (ADS)

Kuhn, Michael A.; Medina, Nicolás; Getman, Konstantin V.; Feigelson, Eric D.; Gromadzki, Mariusz; Borissova, Jordanka; Kurtev, Radostin

2017-09-01

NGC 6231 is a young cluster (age ˜2-7 Myr) dominating the Sco OB1 association (distance ˜1.59 kpc) with ˜100 O and B stars and a large pre-main-sequence stellar population. We combine a reanalysis of archival Chandra X-ray data with multiepoch near-infrared (NIR) photometry from the VISTA Variables in the Vía Lactéa (VVV) survey and published optical catalogs to obtain a catalog of 2148 probable cluster members. This catalog is 70% larger than previous censuses of probable cluster members in NGC 6231. It includes many low-mass stars detected in the NIR but not in the optical and some B stars without previously noted X-ray counterparts. In addition, we identify 295 NIR variables, about half of which are expected to be pre-main-sequence stars. With the more complete sample, we estimate a total population in the Chandra field of 5700-7500 cluster members down to 0.08 {M}⊙ (assuming a universal initial mass function) with a completeness limit at 0.5 {M}⊙ . A decrease in stellar X-ray luminosities is noted relative to other younger clusters. However, within the cluster, there is little variation in the distribution of X-ray luminosities for ages less than 5 Myr. The X-ray spectral hardness for B stars may be useful for distinguishing between early-B stars with X-rays generated in stellar winds and B-star systems with X-rays from a pre-main-sequence companion (>35% of B stars). A small fraction of catalog members have unusually high X-ray median energies or reddened NIR colors, which might be explained by absorption from thick or edge-on disks or being background field stars.

Luminosity Dependence and Search Doppler

NASA Technical Reports Server (NTRS)

VanParadijs, Johannes A.

1998-01-01

The research supported by this grant covered two projects: (1) a study of the luminosity dependence of the properties of atoll sources; and (2) a search for Doppler shifts in the pulse arrival times of the anomalous pulsar 4U 0142+61. Following the discovery of kilohertz quasi-periodic oscillations (QPOS) in Sco X-1 studies of the X-ray properties of atoll sources have been dominated by searches for these QPOS, and the study of their dependence on other source properties, such as X-ray luminosity and spectral state. In the project supported by grant NAG5-3269 we have detected kHz QPOs for several atoll sources. The physical interpretation of these QPO is as yet unclear, but simple models (such as the Keplerian beat frequency model) can probably be excluded. The results of this research have been reported. We have studied the X-ray pulsations of the anomalous X-ray pulsar 4U 0142+61 using the Rossi XTE. A detailed search for Doppler shifts did not lead to a positive detection. The upper limits exclude almost all types of possible companion stars, except white dwarfs. However, the latter can be excluded since anomalous X-ray pulsars are very young objects. We therefore conclude that anomalous X-ray pulsars are single neutron stars.

A Chandra Study of the Stellar X-Ray Emissivity of Globular Clusters in the M31 Bulge

NASA Astrophysics Data System (ADS)

Xu, Xiao-jie; Li, Zhiyuan

2018-03-01

The X-ray emissivity (i.e., luminosity per unit stellar mass) of globular clusters (GCs) is an important indicator of their dynamical evolution history. Based on deep archival Chandra observations, we report a stacking analysis of 44 GCs with 0.5–8 keV luminosities L X ≲ 1035 erg s‑1 in the M31 bulge, which are supposed to be dominated by cataclysmic variables (CVs) and coronally active binaries (ABs). We obtain a significant detection at the 5σ level in 0.5–8 keV band. The average X-ray luminosity per GC and the average X-ray emissivity are determined to be 5.3 ± 1.6 × 1033 erg s‑1 and 13.2 ± 4.3 × 1027 erg s‑1 {M}ȯ -1, respectively. Both of these values are consistent with those of Milky Way GCs. Moreover, the measured emissivity of M31 GCs is also consistent with that of the Milky Way field stars. Massive GCs have X-ray luminosities that are marginally higher than those of less massive ones. Massive GCs also show a lower emissivity (5.0+/- 2.5× {10}27 {erg} {{{s}}}-1 {M}ȯ -1) than less massive ones (26.5+/- 14.3× {10}27 {erg} {{{s}}}-1 {M}ȯ -1), which is consistent with the scenario that the (progenitors of) CVs and ABs were more efficiently destroyed via stellar encounters in the more massive GCs. No dependence of the X-ray emissivity on GC color or on the projected galactocentric distance of GCs is found.

Flaring activity of the SFXT IGR J16418-4532

NASA Astrophysics Data System (ADS)

Poliakov, D.; Aitov, V.; Ikhsanov, N.

2017-12-01

Supergiant fast X-ray transients (SFXTs) are a sub-class of wind-fed High Mass X-ray Binaries (HMXB) in which the normal companion is a supergiant. These systems were collected in a sub-class because of short flares (a few hours duration) in which the X-ray luminosity increases by a few orders of magnitude. One of the members of SFXTs is the X-ray 1212 s pulsar IGR J16418-4532, which is characterized by a high quiescent X-ray luminosity and flaring on a short timescale. We show that the degenerate component of the system is either a magnetar which accretes matter from a Keplerian disk of quasi-spherical flow, or a regularly magnetized neutron star which rotates near spin equilibrium and accretes matter from a non-Keplerian magnetic disk.

GRB 120422A: a Low-Luminosity Gamma-Ray Burst Driven by a Central Engine

NASA Technical Reports Server (NTRS)

Zhang, Bin-Bin; Fan, Yi-Zhong; Shen, Rong-Feng; Xu, Dong; Zhang, Fu-Wen; Wei, Da-Ming; Burrows, David N.; Zhang, Bing; Gehrels, Neil

2012-01-01

GRB 120422A is a low-luminosity gamma-ray burst (GRB) associated with a bright supernova, which distinguishesitself by its relatively short T(sub 90) (approximately 5 s) and an energetic and steep-decaying X-ray tail. We analyze the Swift BurstAlert Telescope and X-ray Telescope data and discuss the physical implications. We show that the steep declineearly in the X-ray light curve can be interpreted as the curvature tail of a late emission episode around 58-86 s,with a curved instantaneous spectrum at the end of the emission episode. Together with the main activity in thefirst 20 s and the weak emission from 40 s to 60 s, the prompt emission is variable, which points to a centralengine origin in contrast to a shock-breakout origin, which is used to interpret some other nearby low-luminosity supernova GRBs. Both the curvature effect model and interpreting the early shallow decay as the coasting externalforward shock emission in a wind medium provide a constraint on the bulk Lorentz factor to be around several.Comparing the properties ofGRB 120422A and other supernova GRBs,we find that themain criterion to distinguish engine-driven GRBs from shock-breakout GRBs is the time-averaged -ray luminosity. Engine-driven GRBs likelyhave a luminosity above approximately 10(sup 48) erg s(sup -1).

X-ray properties of quasars

NASA Technical Reports Server (NTRS)

Ku, W. H.-M.; Helfand, D. J.; Lucy, L. B.

1980-01-01

The X-ray properties of 111 catalogued quasars have been examined with the imaging proportional counter on board the Einstein Observatory. Thirty-five of the objects, of redshift between 0.064 and 3.53, were detected as X-ray sources. The 0.5-4.5-keV X-ray properties of these quasars are correlated with their optical and radio continuum properties and with their redshifts and variability characteristics. The X-ray luminosity of quasars tends to be highest for those objects which are bright in the optical and radio regimes and which exhibit optically violent variability. These observations suggest that quasars should be divided into two classes on the basis of radio luminosities, spectra, evolution and underlying morphology and that quasars can make up a significant portion of the diffuse soft X-ray background only if the slope of the optical quasar log N-log S relation is steeper than 2 to m sub b of about 21.5.

Observations of low luminosity X-ray sources in Vela-Puppis

NASA Technical Reports Server (NTRS)

Pravdo, S. H.; Becker, R. H.; Boldt, E. A.; Holt, S. S.; Erlemitsos, P. J.; Swank, J. H.

1978-01-01

Results of a study of the X-ray emission from a small portion of the galactic plane near galactic longitude 260 deg are presented. This region contains at least six low luminosity X-ray sources within approximately 10 deg. of PSRO833-45, which is near the center of the Gum Nebula. The X-ray source associated with the Vela pulsar, 4U0833-45, is observed at twice its 4U catalogue intensity. The lack of X-ray pulsations at the pulsar period, the non thermal power law spectrum, and models of the X-ray come from an extended source approximately 1 deg in radius. The observation of a high temperature spectrum in a field of view containing only Puppis A among known sources has led to the discovery of a new OSO-8 source, OSO752-39. Other spectra from this region are discussed.

A mass of less than 15 solar masses for the black hole in an ultraluminous X-ray source.

PubMed

Motch, C; Pakull, M W; Soria, R; Grisé, F; Pietrzyński, G

2014-10-09

Most ultraluminous X-ray sources have a typical set of properties not seen in Galactic stellar-mass black holes. They have luminosities of more than 3 × 10(39) ergs per second, unusually soft X-ray components (with a typical temperature of less than about 0.3 kiloelectronvolts) and a characteristic downturn in their spectra above about 5 kiloelectronvolts. Such puzzling properties have been interpreted either as evidence of intermediate-mass black holes or as emission from stellar-mass black holes accreting above their Eddington limit, analogous to some Galactic black holes at peak luminosity. Recently, a very soft X-ray spectrum was observed in a rare and transient stellar-mass black hole. Here we report that the X-ray source P13 in the galaxy NGC 7793 is in a binary system with a period of about 64 days and exhibits all three canonical properties of ultraluminous sources. By modelling the strong optical and ultraviolet modulations arising from X-ray heating of the B9Ia donor star, we constrain the black hole mass to be less than 15 solar masses. Our results demonstrate that in P13, soft thermal emission and spectral curvature are indeed signatures of supercritical accretion. By analogy, ultraluminous X-ray sources with similar X-ray spectra and luminosities of up to a few times 10(40) ergs per second can be explained by supercritical accretion onto massive stellar-mass black holes.

Hard X-Ray View of HCG 16 (Arp 318)

NASA Astrophysics Data System (ADS)

Oda, Saeko; Ueda, Yoshihiro; Tanimoto, Atsushi; Ricci, Claudio

2018-03-01

We report the hard X-ray (3–50 keV) view of the compact group HCG 16 (Arp 318) observed with the Nuclear Spectroscopic Telescope Array (NuSTAR). NGC 838 and NGC 839 are undetected at energies above 8 keV, showing no evidence of heavily obscured active galactic nuclei (AGNs). This confirms that these are starburst-dominant galaxies as previously suggested. We perform a comprehensive broadband (0.3–50 keV) X-ray spectral analysis of the interacting galaxies NGC 833 and NGC 835, using data of NuSTAR, Chandra, and XMM-Newton observed on multiple epochs from 2000 to 2015. NuSTAR detects the transmitted continua of low-luminosity active galactic nuclei (LLAGNs) in NGC 833 and NGC 835 with line-of-sight column densities of ≈3 × 1023 cm‑2 and intrinsic 2–10 keV luminosities of ≈3 × 1041 erg s‑1. The iron-Kα to hard X-ray luminosity ratios of NGC 833 and NGC 835 suggest that their tori are moderately developed, which may have been triggered by the galaxy interactions. We find that NGC 835 underwent long-term variability in both intrinsic luminosity (by a factor of 5) and absorption (by ΔN H ≈ 2 × 1023 cm‑2). We discuss the relation between the X-ray and total infrared luminosities in local LLAGNs hosted by spiral galaxies. The large diversity in their ratios is consistent with the general idea that the mass accretion process in the nucleus and the star-forming activity in the disk are not strongly coupled, regardless of the galaxy environment.

An X-ray/SDSS sample. I. Multi-phase outflow incidence and dependence on AGN luminosity

NASA Astrophysics Data System (ADS)

Perna, M.; Lanzuisi, G.; Brusa, M.; Mignoli, M.; Cresci, G.

2017-07-01

Aims: The connection between the growth of super-massive black holes (SMBHs) and the evolution of their host galaxies is nowadays well established, although the underlying mechanisms explaining their mutual relations are still debated. Multi-phase fast, massive outflows have been postulated to play a crucial role in this process. The aim of this work is to constrain the nature and the fraction of outflowing gas in active galactic nuclei (AGNs) as well as the nuclear conditions possibly at the origin of such phenomena. Methods: We present a large spectroscopic sample of X-ray detected SDSS AGNs at z< 0.8 with a high signal-to-noise ratio in the [O III]λ5007 line to unveil the faint wings of the emission profile associated with AGN-driven outflows. We used X-ray and optical flux ratio diagnostics to select the sample. We derived physical and kinematic characterization by re-analysing optical (and X-ray) spectra. Results: We derive the incidence of ionized ( 40%) and atomic (<1%) outflows covering a wide range of AGN bolometric luminosity from 1042 to 1046 erg/s. We also derive bolometric luminosities and X-ray bolometric corrections to test whether the presence of outflows is associated with an X-ray loudness, as suggested by our recent results obtained by studying high-z QSOs. Conclusions: We study the relations between the outflow velocity inferred from [O III] kinematic analysis and different AGN power tracers, such as black hole mass (MBH), [O III], and X-ray luminosity. We show a well-defined positive trend between outflow velocity and LX, for the first time, over a range of 5 order of magnitudes. Overall, we find that in the QSO-luminosity regime and at MBH> 108M⊙ the fraction of AGNs with outflows becomes >50%. Finally, we discuss our results about X-ray bolometric corrections and outflow incidence in cold and ionized phases in the context of an evolutionary sequence allowing two distinct stages for the feedback phase: first, an initial stage characterized by X-ray/optical obscured AGNs, in which the atomic gas is still present in the ISM and the outflow processes involve all the gas components and, second, a later stage associated with unobscured AGNs, in which the line of sight has been cleaned and the cold components have been heated or exhausted.

The Second Most Distant Cluster of Galaxies in the Extended Medium Sensitivity Survey

NASA Technical Reports Server (NTRS)

Donahue, Megan; Voit, G. Mark; Scharf, Caleb A.; Gioia, Isabella M.; Mullis, Christopher R.; Hughes, John P.; Stocke, John T.

1999-01-01

We report on our ASCA, Keck, and ROSAT observations of MS 1137.5+6625, the second most distant cluster of galaxies in the Einstein Extended Medium Sensitivity Survey (EMSS), at redshift 0.78. We now have a full set of X-ray temperatures, optical velocity dispersions, and X-ray images for a complete, high-redshift sample of clusters of galaxies drawn from the EMSS. Our ASCA observations of MS 1137.5 +6625 yield a temperature of 5.7 (+2.1)(-1.1) keV and a metallicity of 0.43 (+40)(-3.7) solar, with 90% confidence limits. Keck II spectroscopy of 22 cluster members reveals a velocity dispersion of 884 (+185)(-124) km 24/s. This cluster is the most distant in the sample with a detected iron line. We also derive a mean abundance at z = 0.8 by simultaneously fitting X-ray data for the two z = 0.8 clusters, and obtain an abundance of Z(sub Fe) = 0.33 (+.26)(-.23). Our ROSAT observations show that MS 1137.5+6625 is regular and highly centrally concentrated. Fitting of a Beta model to the X-ray surface brightness yields a core radius of only 71/h kpc (q(sub o) = 0.1) with Beta = 0.70(+.45)(-.15) The gas mass interior to 0.5/h Mpc is thus 1.2 (+0.2)(-0.3) X 10(exp 13) h(exp - 5/2) Solar Mass (q(sub o) = 0.1). If the cluster's gas is nearly isothermal and in hydrostatic equilibrium with the cluster potential, the total mass of the cluster within this same region is 2.1(+1.5)(-0.8) X 10exp 14)/h Solar Mass, giving a gas fraction of 0.06 +/-0.04 h (exp -3/2). This cluster is the highest redshift EMSS cluster showing evidence for a possible cooling flow (about 20-400 Solar Mass/yr). The velocity dispersion, temperature, gas fraction, and iron abundance of MS 1137.5+6625 are all statistically the same as those properties in lower red- shift clusters of similar luminosity. With this cluster's temperature now in hand, we derive a high-redshift temperature function for EMSS clusters at 0.5 < z < 0.9 and compare it with temperature functions at lower redshifts, showing that the evolution of the temperature function is relatively modest. Supplementing our high-redshift sample with other data from the literature, we demonstrate that neither the cluster luminosity-temperature relation, nor cluster metallicities, nor the cluster gas evolved with redshift. The very modest degree of evolution in the luminosity-temperature relation inferred from these data is inconsistent with the absence of evolution in the X-ray luminosity functions derived from ROSAT cluster surveys if a critical density structure formation model is assumed.

A deep NuSTAR observation of M51: Investigating its Compton-thick nucleus, LINER companion and ULXs above 10 keV

NASA Astrophysics Data System (ADS)

Brightman, Murray; Annuar, Ady; Alexander, David M.; Earnshaw, Hannah; Gandhi, Poshak; Hornschemeier, Ann E.; Lehmer, Bret; Ptak, Andrew; Rangelov, Blagoy; Roberts, Tim P.; Stern, Daniel; Zezas, Andreas

2017-08-01

We present the results from a deep 200ks observation of M51 with NuSTAR. This observation was taken simultaneously with Chandra to provide soft-X-ray-coverage as well as to resolve the different point sources. We detect the Compton-thick nucleus of M51a, the LINER nucleus of M51b and several ultraluminous X-ray sources located in the galaxies above 10 keV. From X-ray torus modeling, we find that the covering factor of the torus in the nucleus of M51a is ~40% and supports a decline in the obscured fration at low X-ray luminosities. We find that the X-ray spectrum of the intermediate mass black hole candidate, ULX-7, is consistent with a power-law up to high energies, supporting its IMBH status. We further resolve the nucleus of M51b into two X-ray sources with Chandra, and measure its X-ray luminosity.

Observations of low-luminosity X-ray sources in Vela-Puppis

NASA Technical Reports Server (NTRS)

Pravdo, S. H.; Becker, R. H.; Boldt, E. A.; Holt, S. S.; Serlemitsos, P. J.; Swank, J. H.

1978-01-01

Results are presented for a study of the X-ray emission from a small portion of the galactic plane near galactic longitude 260 deg. This region contains at least six low-luminosity X-ray sources within about 10 deg of PSR 0833-45, which is near the center of the Gum nebula. The X-ray source 4U 0833-45, associated with the Vela pulsar, is observed at twice its 4U catalog intensity. The lack of X-ray pulsations at the pulsar period (greater than 99% nonpulsed), the nonthermal power-law spectrum, and models of the X-ray source distribution in this region suggest that a large fraction of the X-rays come from an extended source about 1 deg of arc in radius. The observation of a high-temperature (effective temperature at least 100 million K) spectrum in a field of view containing only Puppis A among known sources has led to the discovery of new OSO 8 source, OS 0752-39. Other spectra from this region are discussed.

Two giant outbursts of V0332+53 observed with INTEGRAL

NASA Astrophysics Data System (ADS)

Ferrigno, Carlo; Ducci, Lorenzo; Bozzo, Enrico; Kretschmar, Peter; Kühnel, Matthias; Malacaria, Christian; Pottschmidt, Katja; Santangelo, Andrea; Savchenko, Volodymyr; Wilms, Jörn

2016-10-01

Context. In July 2015, the high-mass X-ray binary V0332+53 underwent a giant outburst, a decade after the previous one. V0332+53 hosts a strongly magnetized neutron star. During the 2004-2005 outburst, an anti-correlation between the centroid energy of its fundamental cyclotron resonance scattering features (CRSFs) and the X-ray luminosity was observed. Aims: The long (≈100 d) and bright (Lx ≈ 1038 erg s-1) 2015 outburst provided the opportunity to study the unique properties of the fundamental CRSF during another outburst and to study its dependence on the X-ray luminosity. Methods: The source was observed by the INTEGRAL satellite for ~330 ks. We exploit the spectral resolution at high energies of the SPectrometer on INTEGRAL (SPI) and the Joint European X-ray Monitors to characterize its spectral properties, focusing in particular on the CRSF-luminosity dependence. We complement the data of the 2015 outburst with those collected by SPI in 2004-2005, which have so far been left unpublished. Results: We find a highly significant anti-correlation of the centroid energy of the fundamental CRSF and the 3-100 keV luminosity of E1 ∝ -0.095(8)L37 keV. This trend is observed for both outbursts. We confirm the correlation between the width of the fundamental CRSF and the X-ray luminosity previously found in the JEM-X and IBIS dataset of the 2004-2005 outburst. By exploiting the RXTE/ASM and Swift/BAT monitoring data, we also report on the detection of a ~34 d modulation superimposed on the mean profiles and roughly consistent with the orbital period of the pulsar. We discuss possible interpretations of such variability.

Chandra Observations of Low Velocity Dispersion Groups

NASA Astrophysics Data System (ADS)

Helsdon, Stephen F.; Ponman, Trevor J.; Mulchaey, J. S.

2005-01-01

Deviations of galaxy groups from cluster scaling relations can be understood in terms of an excess of entropy in groups. The main effect of this excess is to reduce the density and thus the luminosity of the intragroup gas. Given this, groups should also show a steep relationship between X-ray luminosity and velocity dispersion. However, previous work suggests that this is not the case, with many measuring slopes flatter than the cluster relation. Examining the group LX-σ relation shows that much of the flattening is caused by a small subset of groups that show very high X-ray luminosities for their velocity dispersions (or vice versa). Detailed Chandra study of two such groups shows that earlier ROSAT results were subject to significant (~30%-40%) point-source contamination but confirm that a significant hot intergalactic medium is present in these groups, although these are two of the coolest systems in which intergalactic X-ray emission has been detected. Their X-ray properties are shown to be broadly consistent with those of other galaxy groups, although the gas entropy in NGC 1587 is unusually low, and its X-ray luminosity is correspondingly high for its temperature when compared with most groups. This leads us to suggest that the velocity dispersion in these systems has been reduced in some way, and we consider how this might have come about.

MAXI observations of long X-ray bursts

NASA Astrophysics Data System (ADS)

Serino, Motoko; Iwakiri, Wataru; Tamagawa, Toru; Sakamoto, Takanori; Nakahira, Satoshi; Matsuoka, Masaru; Yamaoka, Kazutaka; Negoro, Hitoshi

2016-12-01

We report nine long X-ray bursts from neutron stars, detected with the Monitor of All-sky X-ray Image (MAXI). Some of these bursts lasted for hours, and hence are qualified as superbursts, which are prolonged thermonuclear flashes on neutron stars and are relatively rare events. MAXI observes roughly 85% of the whole sky every 92 minutes in the 2-20 keV energy band, and has detected nine bursts with a long e-folding decay time, ranging from 0.27 to 5.2 hr, since its launch in 2009 August until 2015 August. The majority of the nine events were found to originate from transient X-ray sources. The persistent luminosities of the sources, when these prolonged bursts were observed, were lower than 1% of the Eddington luminosity for five of them and lower than 20% for the rest. This trend is contrastive to the 18 superbursts observed before MAXI, all but two of which originated from bright persistent sources. The distribution of the total emitted energy, i.e., the product of e-folding time and luminosity, of these bursts clusters around 1041-1042 erg, whereas both the e-folding time and luminosity ranges for an order of magnitude. Among the nine events, two were from 4U 1850-086 during phases of relatively low persistent flux, whereas it usually exhibits standard short X-ray bursts during outbursts.

Soft X-ray spectral observations of quasars and high X-ray luminosity Seyfert galaxies

NASA Technical Reports Server (NTRS)

Petre, R.; Mushotzky, R. F.; Krolik, J. H.; Holt, S. S.

1983-01-01

Results of the analysis of 28 Einstein SSS observations of 15 high X-ray luminosity (L(x) 10 to the 435 power erg/s) quasars and Seyfert type 1 nuclei are presented. The 0.75-4.5 keV spectra are in general well fit by a simple model consisting of a power law plus absorption by cold gas. The averager spectral index alpha is 0.66 + or - .36, consistent with alpha for the spectrum of these objects above 2 keV. In all but one case, no evidence was found for intrinsic absorption, with an upper limit of 2 x 10 to the 21st power/sq cm. Neither was evidence found for partial covering of the active nucleus by dense, cold matter (N(H) 10 to the 22nd power/sq cm; the average upper limit on the partial covering fraction is 0.5. There is no obvious correlation between spectral index and 0175-4.5 keV X-ray luminosity (which ranges from 3 x 10 to the 43rd to 47th powers erg/s or with other source properties. The lack of intrinsic X-ray absorption allows us to place constraints on the density and temperature of the broad-line emission region, and narrow line emission region, and the intergalactic medium.

Anti-correlation between X-ray luminosity and pulsed fraction in the Small Magellanic Cloud pulsar SXP 1323

NASA Astrophysics Data System (ADS)

Yang, Jun; Zezas, Andreas; Coe, Malcolm J.; Drake, Jeremy J.; Hong, JaeSub; Laycock, Silas G. T.; Wik, Daniel R.

2018-05-01

We report the evidence for the anti-correlation between pulsed fraction (PF) and luminosity of the X-ray pulsar SXP 1323, found for the first time in a luminosity range 1035-1037 erg s-1 from observations spanning 15 years. The phenomenon of a decrease in X-ray PF when the source flux increases has been observed in our pipeline analysis of other X-ray pulsars in the Small Magellanic Cloud (SMC). It is expected that the luminosity under a certain value decreases as the PF decreases due to the propeller effect. Above the propeller region, an anti-correlation between the PF and flux might occur either as a result of an increase in the un-pulsed component of the total emission or a decrease of the pulsed component. Additional modes of accretion may also be possible, such as spherical accretion and a change in emission geometry. At higher mass accretion rates, the accretion disk could also extend closer to the neutron star (NS) surface, where a reduced inner radius leads to hotter inner disk emission. These modes of plasma accretion may affect the change in the beam configuration to fan-beam dominant emission.

Astrophysical parameters and orbital solution of the peculiar X-ray transient IGR J00370+6122

NASA Astrophysics Data System (ADS)

González-Galán, A.; Negueruela, I.; Castro, N.; Simón-Díaz, S.; Lorenzo, J.; Vilardell, F.

2014-06-01

Context. BD + 60° 73 is the optical counterpart of the X-ray source IGR J00370+6122, a probable accretion-powered X-ray pulsar. The X-ray light curve of this binary system shows clear periodicity at 15.7 d, which has been interpreted as repeated outbursts around the periastron of an eccentric orbit. Aims: We aim to characterise the binary system IGR J00370+6122 by deriving its orbital and physical parameters. Methods: We obtained high-resolution spectra of BD + 60° 73 at different epochs. We used the fastwind code to generate a stellar atmosphere model to fit the observed spectrum and obtain physical magnitudes. The synthetic spectrum was used as a template for cross-correlation with the observed spectra to measure radial velocities. The radial velocity curve provided an orbital solution for the system. We also analysed the RXTE/ASM and Swift/BAT light curves to confirm the stability of the periodicity. Results: BD + 60° 73 is a BN0.7 Ib low-luminosity supergiant located at a distance ~3.1 kpc, in the Cas OB4 association. We derive Teff = 24 000 K and log gc = 3.0, and chemical abundances consistent with a moderately high level of evolution. The spectroscopic and evolutionary masses are consistent at the 1-σ level with a mass M∗ ≈ 15 M⊙. The recurrence time of the X-ray flares is the orbital period of the system. The neutron star is in a high-eccentricity (e = 0.56 ± 0.07) orbit, and the X-ray emission is strongly peaked around orbital phase φ = 0.2, though the observations are consistent with some level of X-ray activity happening at all orbital phases. Conclusions: The X-ray behaviour of IGR J00370+6122 is reminiscent of "intermediate" supergiant X-ray transients, though its peak luminosity is rather low. The orbit is somewhat wider than those of classical persistent supergiant X-ray binaries, which when combined with the low luminosity of the mass donor, explains the low X-ray luminosity. IGR J00370+6122 will very likely evolve towards a persistent supergiant system, highlighting the evolutionary connection between different classes of wind-accreting X-ray sources.

Probing the X-Ray Binary Populations of the Ring Galaxy NGC 1291

NASA Technical Reports Server (NTRS)

Luo, B.; Fabbiano, G.; Fragos, T.; Kim, D. W.; Belczynski, K.; Brassington, N. J.; Pellegrini, S.; Tzanavaris, P.; Wang, J.; Zezas, A.

2012-01-01

We present Chandra studies of the X-ray binary (XRB) populations in the bulge and ring regions of the ring galaxy NGC 1291. We detect 169 X-ray point sources in the galaxy, 75 in the bulge and 71 in the ring, utilizing the four available Chandra observations totaling an effective exposure of 179 ks. We report photometric properties of these sources in a point-source catalog. There are approx. 40% of the bulge sources and approx. 25% of the ring sources showing > 3(sigma) long-term variability in their X-ray count rate. The X-ray colors suggest that a significant fraction of the bulge (approx. 75%) and ring (approx. 65%) sources are likely low-mass X-ray binaries (LMXBs). The spectra of the nuclear source indicate that it is a low-luminosity AGN with moderate obscuration; spectral variability is observed between individual observations. We construct 0.3-8.0 keV X-ray luminosity functions (XLFs) for the bulge and ring XRB populations, taking into account the detection incompleteness and background AGN contamination. We reach 90% completeness limits of approx.1.5 x 10(exp 37) and approx. 2.2 x 10(exp 37) erg/s for the bulge and ring populations, respectively. Both XLFs can be fit with a broken power-law model, and the shapes are consistent with those expected for populations dominated by LMXBs. We perform detailed population synthesis modeling of the XRB populations in NGC 1291 , which suggests that the observed combined XLF is dominated by aD old LMXB population. We compare the bulge and ring XRB populations, and argue that the ring XRBs are associated with a younger stellar population than the bulge sources, based on the relative over-density of X-ray sources in the ring, the generally harder X-ray color of the ring sources, the overabundance of luminous sources in the combined XLF, and the flatter shape of the ring XLF.

Clustering, cosmology and a new era of black hole demographics- II. The conditional luminosity functions of Type 2 and Type 1 active galactic nuclei

NASA Astrophysics Data System (ADS)

Ballantyne, D. R.

2017-01-01

The orientation-based unification model of active galactic nuclei (AGNs) posits that the principle difference between obscured (Type 2) and unobscured (Type 1) AGNs is the line of sight into the central engine. If this model is correct then there should be no difference in many of the properties of AGN host galaxies (e.g. the mass of the surrounding dark matter haloes). However, recent clustering analyses of Type 1 and Type 2 AGNs have provided some evidence for a difference in the halo mass, in conflict with the orientation-based unified model. In this work, a method to compute the conditional luminosity function (CLF) of Type 2 and Type 1 AGNs is presented. The CLF allows many fundamental halo properties to be computed as a function of AGN luminosity, which we apply to the question of the host halo masses of Type 1 and 2 AGNs. By making use of the total AGN CLF, the Type 1 X-ray luminosity function, and the luminosity-dependent Type 2 AGN fraction, the CLFs of Type 1 and 2 AGNs are calculated at z ≈ 0 and 0.9. At both z, there is no statistically significant difference in the mean halo mass of Type 2 and 1 AGNs at any luminosity. There is marginal evidence that Type 1 AGNs may have larger halo masses than Type 2s, which would be consistent with an evolutionary picture where quasars are initially obscured and then subsequently reveal themselves as Type 1s. As the Type 1 lifetime is longer, the host halo will increase somewhat in mass during the Type 1 phase. The CLF technique will be a powerful way to study the properties of many AGNs subsets (e.g. radio-loud, Compton-thick) as future wide-area X-ray and optical surveys substantially increase our ability to place AGNs in their cosmological context.

"A Richness Study of 14 Distant X-Ray Clusters from the 160 Square Degree Survey"

NASA Technical Reports Server (NTRS)

Jones, Christine; West, Donald (Technical Monitor)

2001-01-01

We have measured the surface density of galaxies toward 14 X-ray-selected cluster candidates at redshifts z(sub i) 0.46, and we show that they are associated with rich galaxy concentrations. These clusters, having X-ray luminosities of Lx(0.5-2 keV) approx. (0.5 - 2.6) x 10(exp 44) ergs/ sec are among the most distant and luminous in our 160 deg(exp 2) ROSAT Position Sensitive Proportional Counter cluster survey. We find that the clusters range between Abell richness classes 0 and 2 and have a most probable richness class of 1. We compare the richness distribution of our distant clusters to those for three samples of nearby clusters with similar X-ray luminosities. We find that the nearby and distant samples have similar richness distributions, which shows that clusters have apparently not evolved substantially in richness since redshift z=0.5. There is, however, a marginal tendency for the distant clusters to be slightly poorer than nearby clusters, although deeper multicolor data for a large sample would be required to confirm this trend. We compare the distribution of distant X-ray clusters in the L(sub X)-richness plane to the distribution of optically selected clusters from the Palomar Distant Cluster Survey. The optically selected clusters appear overly rich for their X-ray luminosities, when compared to X-ray-selected clusters. Apparently, X-ray and optical surveys do not necessarily sample identical mass concentrations at large redshifts. This may indicate the existence of a population of optically rich clusters with anomalously low X-ray emission, More likely, however, it reflects the tendency for optical surveys to select unvirialized mass concentrations, as might be expected when peering along large-scale filaments.

X-Ray Emissions from Accreting White Dwarfs: A Review

NASA Technical Reports Server (NTRS)

Mukai, K.

2017-01-01

Interacting binaries in which a white dwarf accretes material from a companion-cataclysmic variables (CVs) in which the mass donor is a Roche-lobe filling star on or near the main sequence, and symbiotic stars in which the mass donor is a late type giant-are relatively commonplace. They display a wide range of behaviors in the optical, X-rays, and other wavelengths, which still often baffle observers and theorists alike. Here I review the existing body of research on X-ray emissions from these objects for the benefits of both experts and newcomers to the field. I provide introductions to the past and current X-ray observatories, the types of known X-ray emissions from these objects, and the data analysis techniques relevant to this field. I then summarize of our knowledge regarding the X-ray emissions from magnetic CVs, non-magnetic CVs and symbiotic stars, and novae in eruption. I also discuss space density and the X-ray luminosity functions of these binaries and their contribution to the integrated X-ray emission from the Galaxy. I then discuss open questions and future prospects.

Spectral-luminosity evolution of active galactic nuclei (AGN)

NASA Technical Reports Server (NTRS)

Leiter, Darryl; Boldt, Elihu

1992-01-01

The origin of the cosmic X-ray and gamma-ray backgrounds is explained via the mechanism of AGN spectral-luminosity evolution. The spectral evolution of precursor active galaxies into AGN, and Newton-Raphson input and output parameters are discussed.

Cosmological evolution of supermassive black holes in galactic centers unveiled by hard X-ray observations.

PubMed

Ueda, Yoshihiro

2015-01-01

We review the current understanding of the cosmological evolution of supermassive black holes in galactic centers elucidated by X-ray surveys of active galactic nuclei (AGNs). Hard X-ray observations at energies above 2 keV are the most efficient and complete tools to find "obscured" AGNs, which are dominant populations among all AGNs. Combinations of surveys with various flux limits and survey area have enabled us to determine the space number density and obscuration properties of AGNs as a function of luminosity and redshift. The results have essentially solved the origin of the X-ray background in the energy band below ∼10 keV. The downsizing (or anti-hierarchical) evolution that more luminous AGNs have the space-density peak at higher redshifts has been discovered, challenging theories of galaxy and black hole formation. Finally, we summarize unresolved issues on AGN evolution and prospects for future X-ray missions.

Discovery of a 3.6-hr Eclipsing Luminous X-Ray Binary in the Galaxy NGC 4214

NASA Technical Reports Server (NTRS)

Ghosh, Kajal K.; Rappaport, Saul; Tennant, Allyn F.; Swartz, Douglas A.; Pooley, David; Madhusudhan, N.

2006-01-01

We report the discovery of an eclipsing X-ray binary with a 3.62-hr period within 24 arcsec of the center of the dwarf starburst galaxy NGC 4214. The orbital period places interesting constraints on the nature of the binary, and allows for a few very different interpretations. The most likely possibility is that the source lies within NGC 4214 and has an X-ray luminosity of up to 7e38. In this case the binary may well be comprised of a naked He-burning donor star with a neutron-star accretor, though a stellar-mass black-hole accretor cannot be completely excluded. There is no obvious evidence for a strong stellar wind in the X-ray orbital light curve that would be expected from a massive He star; thus, the mass of the He star should be <3-4 solar masses. If correct, this would represent a new class of very luminous X-ray binary----perhaps related to Cyg X-3. Other less likely possibilities include a conventional low-mass X-ray binary that somehow manages to produce such a high X-ray luminosity and is apparently persistent over an interval of years; or a foreground AM Her binary of much lower luminosity that fortuitously lies in the direction of NGC 4214. Any model for this system must accommodate the lack of an optical counterpart down to a limiting magnitude of 22.6 in the visible.

Neutron stars and millisecond pulsars from accretion-induced collapse in globular clusters

NASA Technical Reports Server (NTRS)

Bailyn, Charles D.; Grindlay, Jonathan E.

1990-01-01

This paper examines the limits on the number of millisecond pulsars which could be formed in globular clusters by the generally accepted scenario (in which a neutron star is created by the supernova of an initially massive star and subsequently captures a companion to form a low-mass X-ray binary which eventually becomes a millisecond pulsar). It is found that, while the number of observed low-mass X-ray binaries can be adequately explained in this way, the reasonable assumption that the pulsar luminosity function in clusters extends below the current observational limits down to the luminosity of the faintest millisecond pulsars in the field suggests a cluster population of millisecond pulsars which is substantially larger than the standard model can produce. Alleviating this problem by postulating much shorter lifetimes for the X-ray binaries requires massive star populations sufficiently large that the mass loss resulting from their evolution would be likely to unbind the cluster. It is argued that neutron star formation in globular clusters by accretion-induced collapse of white dwarfs may resolve the discrepancy in birthrates.

The Reverberation Lag in the Low-mass X-ray Binary H1743-322

NASA Astrophysics Data System (ADS)

De Marco, Barbara; Ponti, Gabriele

2016-07-01

The evolution of the inner accretion flow of a black hole X-ray binary during an outburst is still a matter of active research. X-ray reverberation lags are powerful tools for constraining disk-corona geometry. We present a study of X-ray lags in the black hole transient H1743-322. We compared the results obtained from analysis of all the publicly available XMM-Newton observations. These observations were carried out during two different outbursts that occurred in 2008 and 2014. During all the observations the source was caught in the hard state and at similar luminosities ({L}3-10{keV}/{L}{Edd}˜ 0.004). We detected a soft X-ray lag of ˜60 ms, most likely due to thermal reverberation. We did not detect any significant change of the lag amplitude among the different observations, indicating a similar disk-corona geometry at the same luminosity in the hard state. On the other hand, we observe significant differences between the reverberation lag detected in H1743-322 and in GX 339-4 (at similar luminosities in the hard state), which might indicate variations of the geometry from source to source.

Synchrotron X-ray emission from old pulsars

NASA Astrophysics Data System (ADS)

Kisaka, Shota; Tanaka, Shuta J.

2014-09-01

We study the synchrotron radiation as the observed non-thermal emission by the X-ray satellites from old pulsars (≳1-10 Myr) to investigate the particle acceleration in their magnetospheres. We assume that the power-law component of the observed X-ray spectra is caused by the synchrotron radiation from electrons and positrons in the magnetosphere. We consider two pair-production mechanisms of X-ray emitting particles, the magnetic and the photon-photon pair productions. High-energy photons, which ignite the pair production, are emitted via the curvature radiation of the accelerated particles. We use the analytical description for the radiative transfer and estimate the luminosity of the synchrotron radiation. We find that for pulsars with the spin-down luminosity Lsd ≲ 1033 erg s-1, the locations of the particle acceleration and the non-thermal X-ray emission are within ≲107 cm from the centre of the neutron star, where the magnetic pair production occurs. For pulsars with the spin-down luminosity Lsd ≲ 1031 erg s-1 such as J0108-1431, the synchrotron radiation is difficult to explain the observed non-thermal component even if we consider the existence of the strong and small-scale surface magnetic field structures.

The Swift Burst and Transient Telescope (BAT)

NASA Technical Reports Server (NTRS)

Mushotzky, Richard

2008-01-01

The Swift Burst and Transient telescope (BAT) has surveyed the entire sky for the last 3.5 years obtaining the first sensitive all sky survey of the 14-195 kev sky. At high galactic latitudes the vast majority of the detected sources are AGN. Since hard x-rays penetrate all but Compton thick obscuring material (Column densities of 1.6324 atms/sq cm) this survey is unbiased with respect to obscuration, host galaxy type, optical , radio or IR properties. We will present results on the broad band x-ray properties, the nature of the host galaxies, the luminosity function and will discuss a few of the optical, IR and x-ray results in detail.

A multiparametric analysis of the Einstein sample of early-type galaxies. 1: Luminosity and ISM parameters

NASA Technical Reports Server (NTRS)

Eskridge, Paul B.; Fabbiano, Giuseppina; Kim, Dong-Woo

1995-01-01

We have conducted bivariate and multivariate statistical analysis of data measuring the luminosity and interstellar medium of the Einstein sample of early-type galaxies (presented by Fabbiano, Kim, & Trinchieri 1992). We find a strong nonlinear correlation between L(sub B) and L(sub X), with a power-law slope of 1.8 +/- 0.1, steepening to 2.0 +/- if we do not consider the Local Group dwarf galaxies M32 and NGC 205. Considering only galaxies with log L(sub X) less than or equal to 40.5, we instead find a slope of 1.0 +/- 0.2 (with or without the Local Group dwarfs). Although E and S0 galaxies have consistent slopes for their L(sub B)-L(sub X) relationships, the mean values of the distribution functions of both L(sub X) and L(sub X)/L(sub B) for the S0 galaxies are lower than those for the E galaxies at the 2.8 sigma and 3.5 sigma levels, respectively. We find clear evidence for a correlation between L(sub X) and the X-ray color C(sub 21), defined by Kim, Fabbiano, & Trinchieri (1992b), which indicates that X-ray luminosity is correlated with the spectral shape below 1 keV in the sense that low-L(sub X) systems have relatively large contributions from a soft component compared with high-L(sub X) systems. We find evidence from our analysis of the 12 micron IRAS data for our sample that our S0 sample has excess 12 micron emission compared with the E sample, scaled by their optical luminosities. This may be due to emission from dust heated in star-forming regions in S0 disks. This interpretation is reinforced by the existence of a strong L(sub 12)-L(sub 100) correlation for our S0 sample that is not found for the E galaxies, and by an analysis of optical-IR colors. We find steep slopes for power-law relationships between radio luminosity and optical, X-ray, and far-IR (FIR) properties. This last point argues that the presence of an FIR-emitting interstellar medium (ISM) in early-type galaxies is coupled to their ability to generate nonthermal radio continuum, as previously argued by, e.g., Walsh et al. (1989). We also find that, for a given L(sub 100), galaxies with larger L(sub X)/L(sub B) tend to be stronger nonthermal radio sources, as originally suggested by Kim & Fabbiano (1990). We note that, while L(sub B) is most strongly correlated with L(sub 6), the total radio luminosity, both L(sub X) and L(sub X)/L(sub B) are more strongly correlated with L(sub 6 CO), the core radio luminosity. These points support the argument (proposed by Fabbiano, Gioia, & Trinchieri 1989) that radio cores in early-type galaxies are fueled by the hot ISM.

CHANDRA ACIS SURVEY OF X-RAY POINT SOURCES: THE SOURCE CATALOG

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Song; Liu, Jifeng; Qiu, Yanli

The Chandra archival data is a valuable resource for various studies on different X-ray astronomy topics. In this paper, we utilize this wealth of information and present a uniformly processed data set, which can be used to address a wide range of scientific questions. The data analysis procedures are applied to 10,029 Advanced CCD Imaging Spectrometer observations, which produces 363,530 source detections belonging to 217,828 distinct X-ray sources. This number is twice the size of the Chandra Source Catalog (Version 1.1). The catalogs in this paper provide abundant estimates of the detected X-ray source properties, including source positions, counts, colors,more » fluxes, luminosities, variability statistics, etc. Cross-correlation of these objects with galaxies shows that 17,828 sources are located within the D {sub 25} isophotes of 1110 galaxies, and 7504 sources are located between the D {sub 25} and 2 D {sub 25} isophotes of 910 galaxies. Contamination analysis with the log N –log S relation indicates that 51.3% of objects within 2 D {sub 25} isophotes are truly relevant to galaxies, and the “net” source fraction increases to 58.9%, 67.3%, and 69.1% for sources with luminosities above 10{sup 37}, 10{sup 38}, and 10{sup 39} erg s{sup −1}, respectively. Among the possible scientific uses of this catalog, we discuss the possibility of studying intra-observation variability, inter-observation variability, and supersoft sources (SSSs). About 17,092 detected sources above 10 counts are classified as variable in individual observation with the Kolmogorov–Smirnov (K–S) criterion ( P {sub K–S} < 0.01). There are 99,647 sources observed more than once and 11,843 sources observed 10 times or more, offering us a wealth of data with which to explore the long-term variability. There are 1638 individual objects (∼2350 detections) classified as SSSs. As a quite interesting subclass, detailed studies on X-ray spectra and optical spectroscopic follow-up are needed to categorize these SSSs and pinpoint their properties. In addition, this survey can enable a wide range of statistical studies, such as X-ray activity in different types of stars, X-ray luminosity functions in different types of galaxies, and multi-wavelength identification and classification of different X-ray populations.« less

A WEAK LENSING STUDY OF X-RAY GROUPS IN THE COSMOS SURVEY: FORM AND EVOLUTION OF THE MASS-LUMINOSITY RELATION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Leauthaud, Alexie; Finoguenov, Alexis; Cappelluti, Nico

2010-01-20

Measurements of X-ray scaling laws are critical for improving cosmological constraints derived with the halo mass function and for understanding the physical processes that govern the heating and cooling of the intracluster medium. In this paper, we use a sample of 206 X-ray-selected galaxy groups to investigate the scaling relation between X-ray luminosity (L{sub X}) and halo mass (M{sub 200}) where M{sub 200} is derived via stacked weak gravitational lensing. This work draws upon a broad array of multi-wavelength COSMOS observations including 1.64 degrees{sup 2} of contiguous imaging with the Advanced Camera for Surveys to a limiting magnitude of I{submore » F814W} = 26.5 and deep XMM-Newton/Chandra imaging to a limiting flux of 1.0 x 10{sup -15} erg cm{sup -2} s{sup -1} in the 0.5-2 keV band. The combined depth of these two data sets allows us to probe the lensing signals of X-ray-detected structures at both higher redshifts and lower masses than previously explored. Weak lensing profiles and halo masses are derived for nine sub-samples, narrowly binned in luminosity and redshift. The COSMOS data alone are well fit by a power law, M{sub 200} propor to (L{sub X}){sup a}lpha, with a slope of alpha = 0.66 +- 0.14. These results significantly extend the dynamic range for which the halo masses of X-ray-selected structures have been measured with weak gravitational lensing. As a result, tight constraints are obtained for the slope of the M-L{sub X} relation. The combination of our group data with previously published cluster data demonstrates that the M-L{sub X} relation is well described by a single power law, alpha = 0.64 +- 0.03, over two decades in mass, M{sub 200} approx 10{sup 13.5}-10{sup 15.5} h {sup -1}{sub 72} M{sub sun}. These results are inconsistent at the 3.7sigma level with the self-similar prediction of alpha = 0.75. We examine the redshift dependence of the M-L{sub X} relation and find little evidence for evolution beyond the rate predicted by self-similarity from z approx 0.25 to z approx 0.8.« less

X-rays from superbubbles in the Large Magellanic Cloud

NASA Technical Reports Server (NTRS)

Chu, You-Hua; Mac Low, Mordecai-Marc

1990-01-01

Diffuse X-ray emission not associated with known supernova remnants (SNRs) are found in seven Large Magellanic Cloud H II complexes encompassing 10 OB associations: N44, N51D, N57A, N70, N154, N157 (30 Dor), and N158. Their X-ray luminosities range from 7 x 10 to the 34th ergs/s in N57A to 7 x 10 to the 36th ergs/s in 30 Dor. All, except 30 Dor, have simple ring morphologies, indicating shell structures. Modeling these as superbubbles, it is found that the X-ray luminosities expected from their hot interiors fall an order of magnitude below the observed values. SNRs close to the center of a superbubble add very little emission, but it is calculated that off-center SNRs hitting the ionized shell could explain the observed emission.

An extended galactic population of low-luminosity x-ray sources (CVs?) and the diffuse x-ray background

NASA Technical Reports Server (NTRS)

Maoz, Eyal; Grindlay, Jonathan E.

1995-01-01

The incompatibility of the properties of the X-ray background (XRB) with active galactic nuclei (AGNs) contributing approximately greater than 60% at energies of a few keV has often been interpreted as being due to a substantial contribution of a new population of yet unrecognized X-ray sources. The existence of such population has been recently suggested also by an analysis of very deep ROSAT observations which revealed a considerable excess of faint X-ray sources over that expected from QSO evolution models, and that the average spectrum of the resolved sources becomes harder with decreasing flux limit. These sources could be extragalactic in origin, but if they make a substantial contribution to the XRB then they must exhibit much weaker clustering than galaxies or QSOs in order to be consistent with the stringent constraints on source clustering imposed by autocorrelation analyses of the unresolved XRB. We investigate the possibility that the indicated new population of X-ray sources is Galactic in origin. Examining spherical halo and thick disk distributions, we derive the allowed properties of such populations which would resolve the discrepancy found in the number counts of faint sources and be consistent with observational constraints on the total background intensity, the XRB anisotropy, the number of unidentified bright sources, the Galaxy's total X-ray luminosity, and with the results of fluctuation analyses of the unresolved XRB. We find that a flattened Galactic halo (or a thick disk) distribution with a scale height of a few kpc is consistent with all the above requirements. The typical X-ray luminosity of the sources is approximately equal to 10(exp 30-31)ergs/s in the 0.5-2 keV band, the number density of sources in the solar vicinity is approximately 10(exp -4.5)pc(exp -3), their total number in the Galaxy is approximately 10(exp 8.5), and their total contribution to the Galaxy's X-ray luminosity is approximately 10(exp 39) ergs/s. We discuss the possible nature of these soures, including their being subdwarfs, low mass x-ray binaries (LMXBs), massive black holes, and old neutron stars. We argue that the inferred X-ray and optical luminosities of these sources, the slope of their energy spectrum, and the derived local number density and spatial distribution are all consistent with their being intrinsically faint cataclysmic variables with low accretion rates. We suggest a few possibilities for the origin of such population, including an origin from disrupted globular clusters or dark clusters. We make predictions and suggest tests that could either confirm or rule out our proposal in the near future.

Probing BL Lac and Cluster Evolution via a Wide-angle, Deep X-ray Selected Sample

NASA Astrophysics Data System (ADS)

Perlman, E.; Jones, L.; White, N.; Angelini, L.; Giommi, P.; McHardy, I.; Wegner, G.

1994-12-01

The WARPS survey (Wide-Angle ROSAT Pointed Survey) has been constructed from the archive of all public ROSAT PSPC observations, and is a subset of the WGACAT catalog. WARPS will include a complete sample of >= 100 BL Lacs at F_x >= 10(-13) erg s(-1) cm(-2) . A second selection technique will identify ~ 100 clusters at 0.15 = 0.304 +/- 0.062 for XBLs but = 0.60 +/- 0.05 for RBLs. Models of the X-ray luminosity function (XLF) are also poorly constrained. WARPS will allow us to compute an accurate XLF, decreasing the error bars above by over a factor of two. We will also test for low-luminosity BL Lacs, whose non-thermal nuclear sources are dim compared to the host galaxy. Browne and Marcha (1993) claim the EMSS missed most of these objects and is incomplete. If their predictions are correct, 20-40% of the BL Lacs we find will fall in this category, enabling us to probe the evolution and internal workings of BL Lacs at lower luminosities than ever before. By removing likely QSOs before optical spectroscopy, WARPS requires only modest amounts of telescope time. It will extend measurement of the cluster XLF both to higher redshifts (z>0.5) and lower luminosities (LX<1x10(44) erg s(-1) ) than previous measurements, confirming or rejecting the 3sigma detection of negative evolution found in the EMSS, and constraining Cold Dark Matter cosmologies. Faint NELGs are a recently discovered major contributor to the X-ray background. They are a mixture of Sy2s, starbursts and galaxies of unknown type. Detailed classification and evolution of their XLF will be determined for the first time.

THE XMM-NEWTON WIDE-FIELD SURVEY IN THE COSMOS FIELD (XMM-COSMOS): DEMOGRAPHY AND MULTIWAVELENGTH PROPERTIES OF OBSCURED AND UNOBSCURED LUMINOUS ACTIVE GALACTIC NUCLEI

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brusa, M.; Cappelluti, N.; Merloni, A.

2010-06-10

We report the final optical identifications of the medium-depth ({approx}60 ks), contiguous (2 deg{sup 2}) XMM-Newton survey of the COSMOS field. XMM-Newton has detected {approx}1800 X-ray sources down to limiting fluxes of {approx}5 x 10{sup -16}, {approx}3 x 10{sup -15}, and {approx}7 x 10{sup -15} erg cm{sup -2} s{sup -1} in the 0.5-2 keV, 2-10 keV, and 5-10 keV bands, respectively ({approx}1 x 10{sup -15}, {approx}6 x 10{sup -15}, and {approx}1 x 10{sup -14} erg cm{sup -2} s{sup -1}, in the three bands, respectively, over 50% of the area). The work is complemented by an extensive collection of multiwavelength datamore » from 24 {mu}m to UV, available from the COSMOS survey, for each of the X-ray sources, including spectroscopic redshifts for {approx}>50% of the sample, and high-quality photometric redshifts for the rest. The XMM and multiwavelength flux limits are well matched: 1760 (98%) of the X-ray sources have optical counterparts, 1711 ({approx}95%) have IRAC counterparts, and 1394 ({approx}78%) have MIPS 24 {mu}m detections. Thanks to the redshift completeness (almost 100%) we were able to constrain the high-luminosity tail of the X-ray luminosity function confirming that the peak of the number density of log L{sub X} > 44.5 active galactic nuclei (AGNs) is at z {approx} 2. Spectroscopically identified obscured and unobscured AGNs, as well as normal and star-forming galaxies, present well-defined optical and infrared properties. We devised a robust method to identify a sample of {approx}150 high-redshift (z > 1), obscured AGN candidates for which optical spectroscopy is not available. We were able to determine that the fraction of the obscured AGN population at the highest (L{sub X} > 10{sup 44} erg s{sup -1}) X-ray luminosity is {approx}15%-30% when selection effects are taken into account, providing an important observational constraint for X-ray background synthesis. We studied in detail the optical spectrum and the overall spectral energy distribution of a prototypical Type 2 QSO, caught in a stage transitioning from being starburst dominated to AGN dominated, which was possible to isolate only thanks to the combination of X-ray and infrared observations.« less

Multiwavelength follow-up observations of the tidal disruption event candidate 2XMMi J184725.1-631724

NASA Astrophysics Data System (ADS)

Lin, Dacheng; Strader, Jay; Carrasco, Eleazar R.; Godet, Olivier; Grupe, Dirk; Webb, Natalie A.; Barret, Didier; Irwin, Jimmy A.

2018-03-01

The ultrasoft X-ray flare 2XMMi J184725.1-631724 was serendipitously detected in two XMM-Newton observations in 2006 and 2007, with a peak luminosity of 6 × 1043 erg s-1. It was suggested to be a tidal disruption event (TDE) because its position is consistent with the centre of an inactive galaxy. It is the only known X-ray TDE candidate whose X-ray spectra showed evidence of a weak steep power-law component besides a dominant supersoft thermal disc. We have carried out multiwavelength follow-up observations of the event. Multiple X-ray monitorings show that the X-ray luminosity has decayed significantly after 2011. Especially, in our deep Chandra observation in 2013, we detected a very faint counterpart that supports the nuclear origin of 2XMMi J184725.1-631724 but had an X-ray flux a factor of ˜1000 lower than in the peak of the event. Compared with follow-up ultraviolet (UV) observations, we found that there might be some enhanced UV emission associated with the TDE in the first XMM-Newton observation. We also obtained a high-quality UV-optical spectrum with the Southern Astrophysical Research (SOAR) Telescope and put a very tight constraint on the persistent nuclear activity, with a persistent X-ray luminosity expected to be lower than the peak of the flare by a factor of >2700. Therefore, our multiwavelength follow-up observations strongly support the TDE explanation of the event.

Black Holes across the Mass Spectrum-from Stellar Mass BH to ULXs and AGN

NASA Technical Reports Server (NTRS)

Mushotzky, Richard

2006-01-01

I will discuss the observational characteristics of black holes and how they compare across the 10^8 range in mass and as a function of luminosity and apparent Eddington ratio. I will concentrate on the broad band spectrum, the timing signatures and the energy budget of these objects. In particular I will stress the similarities and differences in the x-ray spectra and power density spectra of AGN, ultraluminous x-ray sources and galactic black holes as a function of 'state'. I will also discuss the nature of the Fe K line and other diagnostics of the regions near the event horizon.

An Archival Chandra and XMM-Newton Survey of Type 2 Quasars

NASA Technical Reports Server (NTRS)

Jia, Jianjun; Ptak, Andrew Francis; Heckman, Timothy; Zakamska, Nadia L.

2013-01-01

In order to investigate obscuration in high-luminosity type 2 active galactic nuclei (AGNs), we analyzed Chandra and XMM-Newton archival observations for 71 type 2 quasars detected at 0.05 < z < 0.73, which were selected based on their [O III] lambda5007 emission lines. For 54 objects with good spectral fits, the observed hard X-ray luminosity ranges from 2 × 10(exp 41) to 5.3 × 10(exp 44) erg s(exp -1), with a median of 1.1 × 10(exp 43) erg s(exp -1). We find that the means of the column density and photon index of our sample are log N(sub H) = 22.9 cm(exp -2) and gamma = 1.87, respectively. From simulations using a more physically realistic model, we find that the absorbing column density estimates based on simple power-law models significantly underestimate the actual absorption in approximately half of the sources. Eleven sources show a prominent Fe K alpha emission line (EW>100 eV in the rest frame) and we detect this line in the other sources through a joint fit (spectral stacking). The correlation between the Fe K alpha and [O III] fluxes and the inverse correlation of the equivalent width of the Fe Ka line with the ratio of hard X-ray and [O III] fluxes is consistent with previous results for lower luminosity Seyfert 2 galaxies. We conclude that obscuration is the cause of the weak hard X-ray emission rather than intrinsically low X-ray luminosities. We find that about half of the population of optically selected type 2 quasars are likely to be Compton thick. We also find no evidence that the amount of X-ray obscuration depends on the AGN luminosity (over a range of more than three orders of magnitude in luminosity).

A Possible X-Ray and Radio Counterpart of the High-Energy Gamma-Ray Source 3EG J2227+6122

NASA Technical Reports Server (NTRS)

Halpern, Jules P.; Gotthelf, E. V.; Helfand, D. J.; Leighly, K. M.; Oliversen, Ronald (Technical Monitor)

2001-01-01

The identity of the persistent EGRET sources in the Galactic plane is largely a mystery. For one of these, 3EG J2227+6122, our complete census of X-ray and radio sources in its error circle reveals a remarkable superposition of an incomplete radio shell with a flat radio spectrum, and a compact, power-law X-ray source with photon index Gamma = 1.5 and with no obvious optical counterpart. The radio shell is polarized at a level of approx. = 25%. The anomalous properties of the radio source prevent us from deriving a completely satisfactory theory as to its nature. Nevertheless, using data from ROSAT, ASCA, the VLA, and optical imaging and spectroscopy, we argue that the X-ray source may be a young pulsar with an associated wind-blown bubble or bow shock nebula, and an example of the class of radio-quiet pulsars which are hypothesized to comprise the majority of EGRET sources in the Galaxy. The distance to this source can be estimated from its X-ray absorption as 3 kpc. At this distance, the X-ray and gamma-ray luminosities would be approx. = 1.7 x 10(exp 33) and approx. = 3.7 x 10(exp 35) erg/s, respectively, which would require an energetic pulsar to power them. If, on the contrary, this X-ray source is not the counterpart of 3EG J2227+6122, then by process of elimination the X-ray luminosity of the latter must be less than 10(exp -4) of its gamma-ray luminosity, a condition not satisfied by any established class of gamma-ray source counterpart. This would require the existence of at least a quantitatively new type of EGRET source, as has been suggested in studies of other EGRET fields.

X-Ray Detection of the Cluster Containing the Cepheid S Mus

NASA Astrophysics Data System (ADS)

Evans, Nancy Remage; Pillitteri, Ignazio; Wolk, Scott; Guinan, Edward; Engle, Scott; Bond, Howard E.; Schaefer, Gail H.; Karovska, Margarita; DePasquale, Joseph; Tingle, Evan

2014-04-01

The galactic Cepheid S Muscae has recently been added to the important list of Cepheids linked to open clusters, in this case the sparse young cluster ASCC 69. Low-mass members of a young cluster are expected to have rapid rotation and X-ray activity, making X-ray emission an excellent way to discriminate them from old field stars. We have made an XMM-Newton observation centered on S Mus and identified a population of X-ray sources whose near-IR Two Micron All Sky Survey counterparts lie at locations in the J, (J - K) color-magnitude diagram consistent with cluster membership at the distance of S Mus. Their median energy and X-ray luminosity are consistent with young cluster members as distinct from field stars. These strengthen the association of S Mus with the young cluster, making it a potential Leavitt law (period-luminosity relation) calibrator.

OSO-8 X-ray spectra of clusters of galaxies. 1. Observations of twenty clusters: Physical correlations

NASA Technical Reports Server (NTRS)

Mushotzky, R. F.; Serlemitsos, P. J.; Smith, B. W.; Boldt, E. A.; Holt, S. S.

1978-01-01

OSO-8 X-ray spectra from 2 to 20 keV were analyzed for 26 clusters of galaxies. Temperature, emission integrals, iron abundances, and low energy absorption measurements are given. Eight clusters have positive iron emission line detections at the 90% confidence level, and all twenty cluster spectra are consistent with Fe/H=0.000014 by number with the possible exception of Virgo. Physical correlations between X-ray spectral parameters and other cluster properties are examined. It is found that: (1) the X-ray temperature is approximately proportional to the square of the velocity dispersion of the galaxies; (2) the emission integral and therefore the bolometric X-ray luminosity is a strong function of the X-ray temperature; (3) the X-ray temperature and emission integral are better correlated with cluster central galaxy density than with richness; (4) temperature and emission integral are separately correlated with Rood-Sastry type; and (5) the fraction of galaxies which are spirals is correlated with the observed ram pressure in the cluster core.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gutiérrez, Carlos M.; Moon, Dae-Sik, E-mail: cgc@iac.es

We present the identification and characterization of the optical counterpart to 2XMM J011942.7+032421, one of the most luminous and distant ultra-luminous X-ray sources (ULXs). The counterpart is located near a star-forming region in a spiral arm of the galaxy NGC 470 with u, g, and r magnitudes of 21.53, 21.69, and 21.71 mag, respectively. The luminosity of the counterpart is much larger than that of a single O-type star, indicating that it may be a stellar cluster. Our optical spectroscopic observations confirm the association of the X-ray source and the optical counterpart with its host galaxy NGC 470, which validates the high,more » ≳10{sup 41} erg s{sup -1}, X-ray luminosity of the source. Its optical spectrum is embedded with numerous emission lines, including H recombination lines, metallic forbidden lines, and more notably the high-ionization He II (λ4686) line. That line shows a large velocity dispersion of ≅410 km s{sup -1}, consistent with the existence of a compact (<5 AU) highly ionized accretion disk rotating around the central X-ray source. The ∼1.4 × 10{sup 37} erg s{sup -1} luminosity of the He II line emission makes the source one of the most luminous ULXs in that emission. This, together with the high X-ray luminosity and the large velocity dispersion of the He II emission, suggests that the source is an ideal candidate for more extensive follow-up observations for understanding the nature of hyper-luminous X-ray sources, a more luminous subgroup of ULXs, and more likely candidates for intermediate-mass black holes.« less

Challenges in Finding AGNs in the Low Luminosity Regime

NASA Astrophysics Data System (ADS)

Satyapal, Shobita; Abel, Nick; Secrest, Nathan; Singh, Amrit; Ellison, Sara

2016-08-01

Low luminosity AGNs are an important component of the AGN population. They are often found in the lowest mass galaxies or galaxies that lack classical bulges, a demographic that places important constraints to models of supermassive black hole seed formation and merger-free models of AGN fueling. The detection of AGNs in this low luminosity regime is challenging both because star formation in the host galaxy can dominate the optical spectrum and gas and dust can obscure the central engine at both optical and X-ray wavelengths. Thus while mid-infrared color selection and X-ray observations at energies <10 keV are often powerful tools in uncovering optically unidentified AGNs at higher luminosities, this is not the case in the low luminosity regime. In this talk, I will review the effectiveness of uncovering AGNs in the low luminosity regime using multiwavength investigations, with a focus on infrared spectroscopic signatures.

AGN host galaxy mass function in COSMOS. Is AGN feedback responsible for the mass-quenching of galaxies?

NASA Astrophysics Data System (ADS)

Bongiorno, A.; Schulze, A.; Merloni, A.; Zamorani, G.; Ilbert, O.; La Franca, F.; Peng, Y.; Piconcelli, E.; Mainieri, V.; Silverman, J. D.; Brusa, M.; Fiore, F.; Salvato, M.; Scoville, N.

2016-04-01

We investigate the role of supermassive black holes in the global context of galaxy evolution by measuring the host galaxy stellar mass function (HGMF) and the specific accretion rate, that is, λSAR, the distribution function (SARDF), up to z ~ 2.5 with ~1000 X-ray selected AGN from XMM-COSMOS. Using a maximum likelihood approach, we jointly fit the stellar mass function and specific accretion rate distribution function, with the X-ray luminosity function as an additional constraint. Our best-fit model characterizes the SARDF as a double power-law with mass-dependent but redshift-independent break, whose low λSAR slope flattens with increasing redshift while the normalization increases. This implies that for a given stellar mass, higher λSAR objects have a peak in their space density at earlier epoch than the lower λSAR objects, following and mimicking the well-known AGN cosmic downsizing as observed in the AGN luminosity function. The mass function of active galaxies is described by a Schechter function with an almost constant M∗⋆ and a low-mass slope α that flattens with redshift. Compared to the stellar mass function, we find that the HGMF has a similar shape and that up to log (M⋆/M⊙) ~ 11.5, the ratio of AGN host galaxies to star-forming galaxies is basically constant (~10%). Finally, the comparison of the AGN HGMF for different luminosity and specific accretion rate subclasses with a previously published phenomenological model prediction for the "transient" population, which are galaxies in the process of being mass-quenched, reveals that low-luminosity AGN do not appear to be able to contribute significantly to the quenching and that at least at high masses, that is, M⋆ > 1010.7 M⊙, feedback from luminous AGN (log Lbol ≳ 46 [erg/s]) may be responsible for the quenching of star formation in the host galaxy.

Models of the hard X-ray spectrum of AM Herculis and implications for the accretion rate

NASA Technical Reports Server (NTRS)

Swank, J. H.; Fabian, A. C.; Ross, R. R.

1983-01-01

Phenomenological fits to the hard X-ray spectrum of AM Herculis left unexplained the high equivalent width (0.8 + or - 0.1 keV) of Fe K alpha emission. A purely thermal origin implies a much steeper spectrum than was observed. With Monte Carlo calculations, scattering and fluorescent line production in a cold or partially ionized accretion column of hard X-rays emitted at the base were investigated. The strength of the iron emission and the flat spectral continuum can be explained by the effects of fluorescence and absorption within the accretion column and the surface of the white dwarf on a thermal X-ray spectrum. Thomson optical depths across the column in the range 0.2 to 0.7 are acceptable. The accretion rate and gravitational power can be deduced from the optical depth across the column, if the column size is known, and, together with the observed hard X-ray and polarized light luminosities, imply a lower limit for the luminosity in the UV to soft X-ray range, for which the observations give model-dependent values. Estimates of the column size differ by a factor of 40. Small spot sizes and low luminosities would be consistent with the soft component being the expected reprocessed bremsstrahlung and cyclotron radiation, although the constraint of matching the spectrum confines one to solutions with fluxes exceeding 20% the Eddington limits.

Bright radio emission from an ultraluminous stellar-mass microquasar in M 31.

PubMed

Middleton, Matthew J; Miller-Jones, James C A; Markoff, Sera; Fender, Rob; Henze, Martin; Hurley-Walker, Natasha; Scaife, Anna M M; Roberts, Timothy P; Walton, Dominic; Carpenter, John; Macquart, Jean-Pierre; Bower, Geoffrey C; Gurwell, Mark; Pietsch, Wolfgang; Haberl, Frank; Harris, Jonathan; Daniel, Michael; Miah, Junayd; Done, Chris; Morgan, John S; Dickinson, Hugh; Charles, Phil; Burwitz, Vadim; Della Valle, Massimo; Freyberg, Michael; Greiner, Jochen; Hernanz, Margarita; Hartmann, Dieter H; Hatzidimitriou, Despina; Riffeser, Arno; Sala, Gloria; Seitz, Stella; Reig, Pablo; Rau, Arne; Orio, Marina; Titterington, David; Grainge, Keith

2013-01-10

A subset of ultraluminous X-ray sources (those with luminosities of less than 10(40) erg s(-1); ref. 1) are thought to be powered by the accretion of gas onto black holes with masses of ∼5-20M cicled dot, probably by means of an accretion disk. The X-ray and radio emission are coupled in such Galactic sources; the radio emission originates in a relativistic jet thought to be launched from the innermost regions near the black hole, with the most powerful emission occurring when the rate of infalling matter approaches a theoretical maximum (the Eddington limit). Only four such maximal sources are known in the Milky Way, and the absorption of soft X-rays in the interstellar medium hinders the determination of the causal sequence of events that leads to the ejection of the jet. Here we report radio and X-ray observations of a bright new X-ray source in the nearby galaxy M 31, whose peak luminosity exceeded 10(39) erg s(-1). The radio luminosity is extremely high and shows variability on a timescale of tens of minutes, arguing that the source is highly compact and powered by accretion close to the Eddington limit onto a black hole of stellar mass. Continued radio and X-ray monitoring of such sources should reveal the causal relationship between the accretion flow and the powerful jet emission.

X-Ray Bolometric Corrections for Compton-thick Active Galactic Nuclei

NASA Astrophysics Data System (ADS)

Brightman, M.; Baloković, M.; Ballantyne, D. R.; Bauer, F. E.; Boorman, P.; Buchner, J.; Brandt, W. N.; Comastri, A.; Del Moro, A.; Farrah, D.; Gandhi, P.; Harrison, F. A.; Koss, M.; Lanz, L.; Masini, A.; Ricci, C.; Stern, D.; Vasudevan, R.; Walton, D. J.

2017-07-01

We present X-ray bolometric correction factors, {κ }{Bol} (≡{L}{Bol}/{L}{{X}}), for Compton-thick (CT) active galactic nuclei (AGNs) with the aim of testing AGN torus models, probing orientation effects, and estimating the bolometric output of the most obscured AGNs. We adopt bolometric luminosities, {L}{Bol}, from literature infrared (IR) torus modeling and compile published intrinsic 2-10 keV X-ray luminosities, {L}{{X}}, from X-ray torus modeling of NuSTAR data. Our sample consists of 10 local CT AGNs, where both of these estimates are available. We test for systematic differences in {κ }{Bol} values produced when using two widely used IR torus models and two widely used X-ray torus models, finding consistency within the uncertainties. We find that the mean {κ }{Bol} of our sample in the range of {L}{Bol}≈ {10}42{--}{10}45 {erg} {{{s}}}-1 is log10 {κ }{Bol} = 1.44 ± 0.12 with an intrinsic scatter of ˜0.2 dex, and that our derived {κ }{Bol} values are consistent with previously established relationships between {κ }{Bol} and {L}{Bol} and {κ }{Bol} and Eddington ratio ({λ }{Edd}). We investigate if {κ }{Bol} is dependent on {N}{{H}} by comparing our results on CT AGNs to published results on less-obscured AGNs, finding no significant dependence. Since many of our sample are megamaser AGNs, known to be viewed edge-on, and furthermore under the assumptions of AGN unification whereby unobscured AGNs are viewed face-on, our result implies that the X-ray emitting corona is not strongly anisotropic. Finally, we present {κ }{Bol} values for CT AGNs identified in X-ray surveys as a function of their observed {L}{{X}}, where an estimate of their intrinsic {L}{{X}} is not available, and redshift, useful for estimating the bolometric output of the most obscured AGNs across cosmic time.

Radio Sources Associated with Intermediate X-ray Luminosity Objects in Merging Galaxy Systems

NASA Technical Reports Server (NTRS)

Neff, S. G.; Ulvestad, J. S.; Oegerle, William R. (Technical Monitor)

2002-01-01

We present new, high-resolution 6, 3.6, and 2 cm radio images of a time-ordered sequence of merging galaxy systems. The new data have a resolution of less than 100pc and a sensitivity comparable to a few x Cas A. We detect compact radio sources in all systems, generally embedded in more diffuse radio emission at the longer wavelengths. Several of the compact radio sources are coincident with compact Intermediate-luminosity X-ray Objects (IXOs) in these systems, and many more are within the 3$/sigma$ Chandra position errors for other IXOs. The fraction of radio identifications and the nature of the radio sources changes as a function of merger stage. These data suggest that the IXOs are associated with complexes of supernova remnants, and therefore with star formation that has occurred within the last $/sim$10$circumflex7$ yr, but are not located in HII regions where copious star formation is occurring currently.

Very old and very young compact objects: X-ray studies of galactic globular clusters and recent core-collapse supernovae

NASA Astrophysics Data System (ADS)

Pooley, David Aaron

2003-09-01

This thesis comprises the results of two distinct areas of research, namely, X-ray studies of Galactic globular clusters and X-ray studies of recent core collapse supernovae. My analyses of the Chandra X-ray Observatory observations of the globular clusters NGC 6752 and NGC 6440 revealed as many low- luminosity X-ray sources as was in the entire census of globular cluster sources with the previous best X-ray imaging instrument, Röntgensatellit. In the observation of NGC 6752, I detect 6 X-ray sources within the 10''.5 core radius and 13 more within the 115' half-mass radius down to a limiting luminosity of Lx ≈ 1030 ergs s -1 for cluster sources. Based on a reanalysis of archival data from the Hubble Space Telescope and the Australia Telescope Compact Array, I make 12 optical identifications and one radio identification. Based on X- ray and optical properties of the identifications, I find 10 likely cataclysmic variables (CVs), 1 3 likely RS CVn or BY Dra systems, and 1 or 2 possible background objects. Of the 7 sources for which no optical identifications were made, one was detected in the archival radio data, and another was found to be a millisecond pulsar. Of the remaining sources, I expect that ˜2 4 are background objects and that the rest are either CVs or millisecond pulsars whose radio emission has not been detected. These and other Chandra results on globular clusters indicate that the dozens of CVs per cluster expected by theoretical arguments are being found. Based upon X-ray luminosities and colors, I conclude that there are 4 5 likely quiescent low-mass X-ray binaries and that most of the other sources are cataclysmic variables. I compare these results to Chandra results from other globular clusters and find the X-ray luminosity functions differ among the clusters. Observations of the Type II-P (plateau) Supernova (SN) 1999em and Type IIn (narrow emission line) SN 1998S have enabled estimation of the profile of the SN ejecta, the structure of the circumstellar medium (CSM) established by the pre-SN stellar wind, and the nature of the shock interaction. SN 1999em is the first Type II-P detected at both X-ray and radio wavelengths. It is the least radio luminous and one of the least X-ray luminous SNe ever detected (except for the unusual and very close SN 1987A). My analysis of the Chandra X- ray data indicate non-radiative interaction of SN ejecta with a power-law density profile (ρ ∝ r-n with n ˜ 7) for a pre-SN wind with a low mass-loss rate of ˜2 × 10-6 M⊙ yr-1 for a wind velocity of 10 km s-1 , in agreement with radio mass-loss rate estimates. The Chandra data show an unexpected, temporary rise in the 0.4 2.0 keV X-ray flux at ˜100 days after explosion. My analysis of SN 1998S yielded the first X-ray spectrum of a supernova in which numerous heavy element emission features (Ne, Al, Si, S, Ar, Fe) were present. Spectral fits to the Chandra data show that these heavy elements are overabundant with respect to solar values. I compare the observed elemental abundances and abundance ratios to theoretical calculations and find that our data are consistent with a progenitor mass of approximately 15 20 M⊙ if the heavy element ejecta are radially mixed out to a high velocity. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617-253-5668; Fax 617-253-1690.) (Abstract shortened by UMI.)

Measuring the Mass Distribution in Z is Approximately 0.2 Cluster Lenses with XMM, HST and CFHT

NASA Technical Reports Server (NTRS)

2004-01-01

Being the most massive gravitationally bound objects in the Universe, clusters of galaxies are prime targets for studies of structure formation and evolution. Specifically the comoving space density of virialized clusters of a given mass (or X-ray temperature), but also the frequency and degree of substructure, as well as the shape of the cluster mass profile are quantities whose current values and evolution as a function of lookback time can provide important constraints on the cosmological and physical parameters of structure formation theories. The project funded by NASA grant NAG 5-10041 intended to take such studies to a new level by combining observations of a well-selected cluster sample by three state-of-the-art telescopes: HST, to accurately measure the mass distribution in the cluster core (approx. 0.5 h(sup -1)(sub 50) Mpc) via strong gravitational lensing; CFHT, to measure the large scale mass distribution out to approx. 3 Mpc via weak lensing; and XMM, to measure the gas density and temperature distribution accurately on intermediate scales < 1.5 Mpc. XMM plays a pivotal role in this context as the calibration of X-ray mass measurements through accurate, spatially resolved X-ray temperature measurements (particularly in the cosmologically most sensitive range of kT> 5 keV) is central to the questions outlined above. This set of observations promised to yield the best cluster mass measurements obtained so far for a representative sample, thus allowing us to: 1) Measure the high-mass end of the local cluster mass function; 2) Test predictions of a universal cluster mass profile; 3) calibrate the mass-temperature and temperature-luminosity relations for clusters and the scatter around these relations, which is vital for studies of cluster evolution using the X-ray temperature and X-ray luminosity functions.

X-ray clusters from a high-resolution hydrodynamic PPM simulation of the cold dark matter universe

NASA Technical Reports Server (NTRS)

Bryan, Greg L.; Cen, Renyue; Norman, Michael L.; Ostriker, Jermemiah P.; Stone, James M.

1994-01-01

A new three-dimensional hydrodynamic code based on the piecewise parabolic method (PPM) is utilized to compute the distribution of hot gas in the standard Cosmic Background Explorer (COBE)-normalized cold dark matter (CDM) universe. Utilizing periodic boundary conditions, a box with size 85 h(exp-1) Mpc, having cell size 0.31 h(exp-1) Mpc, is followed in a simulation with 270(exp 3)=10(exp 7.3) cells. Adopting standard parameters determined from COBE and light-element nucleosynthesis, Sigma(sub 8)=1.05, Omega(sub b)=0.06, we find the X-ray-emitting clusters, compute the luminosity function at several wavelengths, the temperature distribution, and estimated sizes, as well as the evolution of these quantities with redshift. The results, which are compared with those obtained in the preceding paper (Kang et al. 1994a), may be used in conjuction with ROSAT and other observational data sets. Overall, the results of the two computations are qualitatively very similar with regard to the trends of cluster properties, i.e., how the number density, radius, and temeprature depend on luminosity and redshift. The total luminosity from clusters is approximately a factor of 2 higher using the PPM code (as compared to the 'total variation diminishing' (TVD) code used in the previous paper) with the number of bright clusters higher by a similar factor. The primary conclusions of the prior paper, with regard to the power spectrum of the primeval density perturbations, are strengthened: the standard CDM model, normalized to the COBE microwave detection, predicts too many bright X-ray emitting clusters, by a factor probably in excess of 5. The comparison between observations and theoretical predictions for the evolution of cluster properties, luminosity functions, and size and temperature distributions should provide an important discriminator among competing scenarios for the development of structure in the universe.

The space density of Compton-thick AGN at z ≈ 0.8 in the zCOSMOS-Bright Survey

NASA Astrophysics Data System (ADS)

Vignali, C.; Mignoli, M.; Gilli, R.; Comastri, A.; Iwasawa, K.; Zamorani, G.; Mainieri, V.; Bongiorno, A.

2014-11-01

Context. The obscured accretion phase in black hole growth is a crucial ingredient in many models linking the active galactic nuclei (AGN) activity with the evolution of their host galaxy. At present, a complete census of obscured AGN is still missing, although several attempts in this direction have been carried out recently, mostly in the hard X-rays and at mid-infrared wavelengths. Aims: The purpose of this work is to assess whether the [Ne v] emission line at 3426 Å can reliably pick up obscured AGN up to z ≈ 1 by assuming that it is a reliable proxy of the intrinsic AGN luminosity and using moderately deep X-ray data to characterize the amount of obscuration. Methods: A sample of 69 narrow-line (Type 2) AGN at z ≈ 0.65-1.20 were selected from the 20k-zCOSMOS Bright galaxy sample on the basis of the presence of the [Ne v]3426 Å emission. The X-ray properties of these galaxies were then derived using the Chandra-COSMOS coverage of the field; the X-ray-to-[Ne v] flux ratio, coupled with X-ray spectral and stacking analyses, was then used to infer whether Compton-thin or Compton-thick absorption is present in these sources. Then the [Ne v] luminosity function was computed to estimate the space density of Compton-thick AGN at z ≈ 0.8. Results: Twenty-three sources were detected by Chandra, and their properties are consistent with moderate obscuration (on average, ≈a few × 1022 cm-2). The X-ray properties of the remaining 46 X-ray undetected Type 2 AGN (among which we expect to find the most heavily obscured objects) were derived using X-ray stacking analysis. Current data, supported by Monte Carlo simulations, indicate that a fraction as high as ≈40% of the present sample is likely to be Compton thick. The space density of Compton-thick AGN with logL2-10 keV> 43.5 at z = 0.83 is ΦThick = (9.1 ± 2.1) × 10-6 Mpc-3, in good agreement with both X-ray background model expectations and the previously measured space density for objects in a similar redshift and luminosity range. We regard our selection technique for Compton-thick AGN as clean but not complete, since even a mild extinction in the narrow-line region can suppress [Ne v] emission. Therefore, our estimate of their space density should be considered as a lower limit.

The Geometry of the Infrared and X-Ray Obscurer in a Dusty Hyperluminous Quasar

NASA Astrophysics Data System (ADS)

Farrah, Duncan; Baloković, Mislav; Stern, Daniel; Harris, Kathryn; Kunimoto, Michelle; Walton, Dominic J.; Alexander, David M.; Arévalo, Patricia; Ballantyne, David R.; Bauer, Franz E.; Boggs, Steven; Brandt, William N.; Brightman, Murray; Christensen, Finn; Clements, David L.; Craig, William; Fabian, Andrew; Hailey, Charles; Harrison, Fiona; Koss, Michael; Lansbury, George B.; Luo, Bin; Paine, Jennie; Petty, Sara; Pitchford, Kate; Ricci, Claudio; Zhang, William

2016-11-01

We study the geometry of the active galactic nucleus (AGN) obscurer in IRAS 09104+4109, an IR-luminous, radio-intermediate FR-I source at z = 0.442, using infrared data from Spitzer and Herschel, X-ray data from NuSTAR, Swift, Suzaku, and Chandra, and an optical spectrum from Palomar. The infrared data imply a total rest-frame 1-1000 μm luminosity of 5.5 × 1046 erg s-1 and require both an AGN torus and a starburst model. The AGN torus has an anisotropy-corrected IR luminosity of 4.9 × 1046 erg s-1 and a viewing angle and half-opening angle both of approximately 36° from pole-on. The starburst has a star formation rate of (110 ± 34) M ⊙ yr-1 and an age of <50 Myr. These results are consistent with two epochs of luminous activity in IRAS 09104+4109: one approximately 150 Myr ago, and one ongoing. The X-ray data suggest a photon index of Γ ≃ 1.8 and a line-of-sight column density of N H ≃ 5 × 1023 cm-2. This argues against a reflection-dominated hard X-ray spectrum, which would have implied a much higher N H and luminosity. The X-ray and infrared data are consistent with a bolometric AGN luminosity of L bol ˜ (0.5-2.5) × 1047 erg s-1. The X-ray and infrared data are further consistent with coaligned AGN obscurers in which the line of sight “skims” the torus. This is also consistent with the optical spectra, which show both coronal iron lines and broad lines in polarized but not direct light. Combining constraints from the X-ray, optical, and infrared data suggest that the AGN obscurer is within a vertical height of 20 pc, and a radius of 125 pc, of the nucleus.

The Geometry of the Infrared and X-Ray Obscurer in a Dusty Hyperluminous Quasar

NASA Technical Reports Server (NTRS)

Farrah, Duncan; Balokovic, Mislav; Stern, Daniel; Harris, Kathryn; Kunimoto, Michelle; Walton, Dominc J.; Alexander, David M.; Arevalo, Patricia; Ballantyne, David R.; Bauer, Franz E.;

X-ray studies of quasars with the Einstein Observatory

NASA Technical Reports Server (NTRS)

Tananbaum, H.; Branduardi, G.; Fabbiano, G.; Feigelson, E.; Giacconi, R.; Henry, J. P.; Avni, Y.; Elvis, M.; Pye, J. P.; Soltan, A.

1979-01-01

Results of an investigation of the X-ray properties of quasars conducted using the Einstein Observatory (HEAO 2) are reported. The positions, fluxes and luminosities of 35 known quasars were observed by the Einstein high-resolution imaging detector and the imaging proportional counter. Assuming optical redshifts as valid distance indicators, 0.5-4.5 keV X-ray luminosities ranging from 10 to the 43rd to 10 to the 47 ergs/sec are obtained, with evidence of very little cold gas absorption. Flux variability on a time scale of less than 10,000 sec is observed for the quasar OX 169, which implies a mass between 8 x 10 to the 5th and 2 x 10 to the 8th solar masses for the black hole assumed to be responsible for the emission. Preliminary results of the quasar survey also indicate that quasars contribute significantly to the diffuse X-ray background.

Spatial clustering and halo occupation distribution modelling of local AGN via cross-correlation measurements with 2MASS galaxies

NASA Astrophysics Data System (ADS)

Krumpe, Mirko; Miyaji, Takamitsu; Coil, Alison L.; Aceves, Hector

2018-02-01

We present the clustering properties and halo occupation distribution (HOD) modelling of very low redshift, hard X-ray-detected active galactic nuclei (AGN) using cross-correlation function measurements with Two-Micron All Sky Survey galaxies. Spanning a redshift range of 0.007 < z < 0.037, with a median z = 0.024, we present a precise AGN clustering study of the most local AGN in the Universe. The AGN sample is drawn from the SWIFT/BAT 70-month and INTEGRAL/IBIS eight year all-sky X-ray surveys and contains both type I and type II AGN. We find a large-scale bias for the full AGN sample of b=1.04^{+0.10}_{-0.11}, which corresponds to a typical host dark matter halo mass of M_h^typ=12.84^{+0.22}_{-0.30} h^{-1} M_{⊙}. When split into low and high X-ray luminosity and type I and type II AGN subsamples, we detect no statistically significant differences in the large-scale bias parameters. However, there are differences in the small-scale clustering, which are reflected in the full HOD model results. We find that low and high X-ray luminosity AGN, as well as type I and type II AGN, occupy dark matter haloes differently, with 3.4σ and 4.0σ differences in their mean halo masses, respectively, when split by luminosity and type. The latter finding contradicts a simple orientation-based AGN unification model. As a by-product of our cross-correlation approach, we also present the first HOD model of 2MASS galaxies.

THE CHANDRA COSMOS LEGACY SURVEY: OPTICAL/IR IDENTIFICATIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marchesi, S.; Civano, F.; Urry, C. M.

2016-01-20

We present the catalog of optical and infrared counterparts of the Chandra  COSMOS-Legacy  Survey, a 4.6 Ms Chandra  program on the 2.2 deg{sup 2} of the COSMOS field, combination of 56 new overlapping observations obtained in Cycle 14 with the previous C-COSMOS survey. In this Paper we report the i, K, and 3.6 μm identifications of the 2273 X-ray point sources detected in the new Cycle 14 observations. We use the likelihood ratio technique to derive the association of optical/infrared (IR) counterparts for 97% of the X-ray sources. We also update the information for the 1743 sources detected in C-COSMOS,more » using new K and 3.6 μm information not available when the C-COSMOS analysis was performed. The final catalog contains 4016 X-ray sources, 97% of which have an optical/IR counterpart and a photometric redshift, while ≃54% of the sources have a spectroscopic redshift. The full catalog, including spectroscopic and photometric redshifts and optical and X-ray properties described here in detail, is available online. We study several X-ray to optical (X/O) properties: with our large statistics we put better constraints on the X/O flux ratio locus, finding a shift toward faint optical magnitudes in both soft and hard X-ray band. We confirm the existence of a correlation between X/O and the the 2–10 keV luminosity for Type 2 sources. We extend to low luminosities the analysis of the correlation between the fraction of obscured AGNs and the hard band luminosity, finding a different behavior between the optically and X-ray classified obscured fraction.« less

Nustar Reveals an Intrinsically X-ray Weak Broad Absorption Line Quasar in the Ultraluminous Infrared Galaxy Markarian 231

NASA Technical Reports Server (NTRS)

Teng, Stacy H.; Brandt. W. N.; Harrison, F. A.; Luo, B.; Alexander, D. M.; Bauer, F. E.; Boggs, S. E.; Christensen, F. E.; Comastri, A.; Craig, W. W.;

Supermassive Black Holes in Late-type Spiral Galaxies: Constraining High Mass X-ray Binary Contamination

NASA Astrophysics Data System (ADS)

Dittenber, Benjamin; Hodges-Kluck, Edmund J.; Gallo, Elena

2018-06-01

Supermassive black holes (SMBHs) are known to commonly reside in the centers of large galaxies, but it is unclear whether they reside in smaller galaxies (M_* < M_sun x 10^10). X-rays are the most efficient way to detect low-level accretion, and provide the best measurement of the occupation fraction. X-ray binaries can be nearly as bright as SMBHs that have sub-Eddington accretion rates. High-mass XRBs (HMXBs) are especially problematic because they can get brighter than low-mass XRBs. However, previous estimates of HMXB contamination (based on the optical continuum to get the fraction of HMXBs expected in the nucleus) may be too high. A better approach is to use FUV or H-alpha, which directly trace ongoing star formation. We did this in a sample of 30 late-type galaxies with Chandra data. We calculate the total Expected X-ray Luminosity from XRBs (L_x) for each sample galaxy using existing relationships between X-ray luminosity and SFR. We estimate the fraction of the stellar formation in the nucleus by measuring the fraction of nuclear UV or H-alpha light there (total SFR is from the far infrared). Our Galex data is scaled with a sample of 6 Swift UVOT galaxies to measure with the same aperture size that previous works have used in the B-band. We found that the mean L_x,c for Swift scaled FUV ratios is ~2.025 x 10^36 and the mean L_x,c for H-alpha ratios is 7.693 x 10^35. These luminosities are 1.9 and 5 times smaller than B-band measured luminosities respectively. These results suggest that HMXBs do not contribute as much contamination in these galaxies as previously thought. Therefore, with a lower contamination, estimates of the occupation fraction from late-type galaxies are more reliable.

Tracing black hole accretion with SED decomposition and IR lines: from local galaxies to the high-z Universe

NASA Astrophysics Data System (ADS)

Gruppioni, C.; Berta, S.; Spinoglio, L.; Pereira-Santaella, M.; Pozzi, F.; Andreani, P.; Bonato, M.; De Zotti, G.; Malkan, M.; Negrello, M.; Vallini, L.; Vignali, C.

2016-06-01

We present new estimates of AGN accretion and star formation (SF) luminosity in galaxies obtained for the local 12 μm sample of Seyfert galaxies (12MGS), by performing a detailed broad-band spectral energy distribution (SED) decomposition including the emission of stars, dust heated by SF and a possible AGN dusty torus. Thanks to the availability of data from the X-rays to the sub-millimetre, we constrain and test the contribution of the stellar, AGN and SF components to the SEDs. The availability of Spitzer-InfraRed Spectrograph (IRS) low-resolution mid-infrared (mid-IR) spectra is crucial to constrain the dusty torus component at its peak wavelengths. The results of SED fitting are also tested against the available information in other bands: the reconstructed AGN bolometric luminosity is compared to those derived from X-rays and from the high excitation IR lines tracing AGN activity like [Ne V] and [O IV]. The IR luminosity due to SF and the intrinsic AGN bolometric luminosity are shown to be strongly related to the IR line luminosity. Variations of these relations with different AGN fractions are investigated, showing that the relation dispersions are mainly due to different AGN relative contribution within the galaxy. Extrapolating these local relations between line and SF or AGN luminosities to higher redshifts, by means of recent Herschel galaxy evolution results, we then obtain mid- and far-IR line luminosity functions useful to estimate how many star-forming galaxies and AGN we expect to detect in the different lines at different redshifts and luminosities with future IR facilities (e.g. JWST, SPICA).

Galactic star formation rates gauged by stellar end-products

NASA Astrophysics Data System (ADS)

Persic, M.; Rephaeli, Y.

2007-02-01

Young galactic X-ray point sources (XPs) closely trace the ongoing star formation in galaxies. From measured XP number counts we extract the collective 2-10 keV luminosity of young XPs, L_x^yXP, which we use to gauge the current star formation rate (SFR) in galaxies. We find that, for a sample of local star-forming galaxies (i.e., normal spirals and mild starbursts), L_x^yXP correlates linearly with the SFR over three decades in luminosity. A separate, high-SFR sample of starburst ULIRGs can be used to check the calibration of the relation. Using their (presumably SF-related) total 2-10 keV luminosities we find that these sources satisfy the SFR-L_x^yXP relation, as defined by the weaker sample, and extend it to span ˜5 decades in luminosity. The SFR-L_x^yXP relation is also likely to hold for distant (z ˜ 1) Hubble Deep Field North galaxies, especially so if these high-SFR objects are similar to the (more nearby) ULIRGs. It is argued that the SFR-L_x^yXP relation provides the most adequate X-ray estimator of instantaneous SFR by the phenomena characterizing massive stars from their birth (FIR emission from placental dust clouds) through their death as compact remnants (emitting X-rays by accreting from a close donor). For local, low/intermediate-SFR galaxies, the simultaneous existence of a correlation of the instantaneous SFR with the total 2-10 keV luminosity, L_x, which traces the SFR integrated over the last ˜109 yr, suggests that during such epoch the SF in these galaxies has been proceeding at a relatively constant rate.

Suzaku Observation of Two Ultraluminous X-ray Sources in NGC 1313

NASA Technical Reports Server (NTRS)

Mizuno, T.; Miyawaki, R.; Ebisawa, K.; Kubota, A.; Miyamoto, M.; Winter, L.; Ueda, Y.; Isobe, N.; Dewangan, G.; Mushotzky, R.F.;

X-Ray Temperatures, Luminosities, and Masses from XMM-Newton Follow-up of the First Shear-selected Galaxy Cluster Sample

DOE Office of Scientific and Technical Information (OSTI.GOV)

Deshpande, Amruta J.; Hughes, John P.; Wittman, David, E-mail: amrejd@physics.rutgers.edu, E-mail: jph@physics.rutgers.edu, E-mail: dwittman@physics.ucdavis.edu

We continue the study of the first sample of shear-selected clusters from the initial 8.6 square degrees of the Deep Lens Survey (DLS); a sample with well-defined selection criteria corresponding to the highest ranked shear peaks in the survey area. We aim to characterize the weak lensing selection by examining the sample’s X-ray properties. There are multiple X-ray clusters associated with nearly all the shear peaks: 14 X-ray clusters corresponding to seven DLS shear peaks. An additional three X-ray clusters cannot be definitively associated with shear peaks, mainly due to large positional offsets between the X-ray centroid and the shearmore » peak. Here we report on the XMM-Newton properties of the 17 X-ray clusters. The X-ray clusters display a wide range of luminosities and temperatures; the L {sub X} − T {sub X} relation we determine for the shear-associated X-ray clusters is consistent with X-ray cluster samples selected without regard to dynamical state, while it is inconsistent with self-similarity. For a subset of the sample, we measure X-ray masses using temperature as a proxy, and compare to weak lensing masses determined by the DLS team. The resulting mass comparison is consistent with equality. The X-ray and weak lensing masses show considerable intrinsic scatter (∼48%), which is consistent with X-ray selected samples when their X-ray and weak lensing masses are independently determined.« less

Searching for hidden AGN in nearby star-forming galaxies with Chandra

NASA Astrophysics Data System (ADS)

Tzanavaris, P.; Georgantopoulos, I.

2007-06-01

Aims: We searched for X-ray signatures of AGN in a sample of star-forming, relatively early-type, nearby spiral galaxies, from the optical spectroscopic sample of Ho et al. The tight correlations between the masses of central supermassive black holes and bulge mass or velocity dispersion suggest that such galaxies are likely to host black holes in their centres. The aim is to look for X-ray signs of activity in these gas-rich environments. Methods: We identified chandra ACIS-S images of the X-ray counterparts of 9 sources from the optical sample. We isolated 10 individual X-ray sources closest to the optical position and calculated their X-ray luminosity, L_X, and X-ray colours. Using Hα luminosities, we also calculated star formation rates. For four sources with a high number of net counts in the X-ray band, we extracted X-ray spectra to which we fitted standard spectral models. We modelled Fe Kα emission by Gaussians, and assessed the significance of adding such a component to a fit by means of a calibration of the standard F-test. For the rest of the sources, we estimated values for the intrinsic hydrogen column density, N_H^int, and the power-law photon index, Γ, which can reproduce the observed soft and hard X-ray colours. Results: All spectral fits include a power law, a diffuse hot gas, a Galactic absorption and an intrinsic absorption component. For the nuclear sources of NGC 2782 and NGC 3310, a Fe Kα emission-line component is included with high significance. At the same time the power-law component is flat (index Γ ˜ 0 and 1.3). Both sources have high star-formation rates, with the rate for NGC 2782 being the highest in our sample. Conclusions: The detection of Fe Kα emission coming from a central, isolated source in NGC 2782 and NGC 3310, points towards a hidden AGN in two out of nine relatively early-type, star-forming spirals observed both with Palomar and Chandra. Larger samples need to be explored, but this evidence suggests that the presence of an AGN is likely in massive, disturbed starbursts. The contribution of X-ray emission from these AGN is small: For the central source, the bolometric luminosity is a fraction of a few ×10-5 of the Eddington luminosity. The X-ray flux of the central source is between 10 and 20% of the total galactic flux in the 0.2-10 keV band.

X ray emission from Wolf-Rayet stars with recurrent dust formation

NASA Technical Reports Server (NTRS)

Rawley, Gayle L.

1993-01-01

We were granted a ROSAT observation of the Wolf-Rayet star WR 137 (equals HD 192641) to test a proposed mechanism for producing the infrared variability reported by Williams et al. (1987). These studies showed one clear infrared outburst preceded by what may be the dimming of a previous outburst. The recurrent dust formation model was put forward by Williams et al. (1990) to account for similar variability seen in WR 140, which varies in both the infrared and X-ray bands. The detected X-ray flux from WR 140 was observed to decrease from its normally high (for Wolf-Rayet stars) level as the infrared flux increased. Observation of two apparently-periodic infrared outbursts led to the hypothesis that WR 140 had an O star companion in an eccentric orbit, and that the increase in infrared flux came from a dust formation episode triggered by the compression of the O star and Wolf-Rayet star winds. The absorption of the X-rays by the increased material explained the decrease in flux at those wavelengths. If the infrared variability in WR 137 were caused by a similar interaction of the Wolf-Rayet star with a companion, we might expect that WR 137 would show corresponding X-ray variability and an X-ray luminosity somewhat higher than typical WC stars, as well as a phase-dependent non-thermal X-ray spectrum. Our goals in this study were to obtain luminosity estimates from our counting rates for comparison with previous observations of WR 137 and other WC class stars, especially WR 140; to compare the luminosity with the IR lightcurve; and to characterize the spectral shape of the X-ray emission, including the column density.

X-ray and Ultraviolet Properties of AGNs in Nearby Dwarf Galaxies

NASA Astrophysics Data System (ADS)

Baldassare, Vivienne F.; Reines, Amy E.; Gallo, Elena; Greene, Jenny E.

2017-02-01

We present new Chandra X-ray Observatory and Hubble Space Telescope observations of eight optically selected broad-line active galactic nucleus (AGN) candidates in nearby dwarf galaxies (z < 0.055). Including archival Chandra observations of three additional sources, our sample contains all 10 galaxies from Reines et al. (2013) with both broad Hα emission and narrow-line AGN ratios (six AGNs, four composites), as well as one low-metallicity dwarf galaxy with broad Hα and narrow-line ratios characteristic of star formation. All 11 galaxies are detected in X-rays. Nuclear X-ray luminosities range from L 0.5-7keV ≈ 5 × 1039 to 1 × 1042 ergs-1. In all cases except for the star-forming galaxy, the nuclear X-ray luminosities are significantly higher than would be expected from X-ray binaries, providing strong confirmation that AGNs and composite dwarf galaxies do indeed host actively accreting black holes (BHs). Using our estimated BH masses (which range from ˜7 × 104 to 1 × 106 M ⊙), we find inferred Eddington fractions ranging from ˜0.1% to 50%, I.e., comparable to massive broad-line quasars at higher redshift. We use the HST imaging to determine the ratio of UV to X-ray emission for these AGNs, finding that they appear to be less X-ray luminous with respect to their UV emission than more massive quasars (I.e., α OX values an average of 0.36 lower than expected based on the relation between α OX and 2500 Å luminosity). Finally, we discuss our results in the context of different accretion models onto nuclear BHs.

X-Ray and Ultraviolet Properties of AGNs in Nearby Dwarf Galaxies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baldassare, Vivienne F.; Gallo, Elena; Reines, Amy E.

2017-02-10

We present new Chandra X-ray Observatory and Hubble Space Telescope observations of eight optically selected broad-line active galactic nucleus (AGN) candidates in nearby dwarf galaxies ( z < 0.055). Including archival Chandra observations of three additional sources, our sample contains all 10 galaxies from Reines et al. (2013) with both broad H α emission and narrow-line AGN ratios (six AGNs, four composites), as well as one low-metallicity dwarf galaxy with broad H α and narrow-line ratios characteristic of star formation. All 11 galaxies are detected in X-rays. Nuclear X-ray luminosities range from L {sub 0.5–7keV} ≈ 5 × 10{sup 39}more » to 1 × 10{sup 42} ergs{sup −1}. In all cases except for the star-forming galaxy, the nuclear X-ray luminosities are significantly higher than would be expected from X-ray binaries, providing strong confirmation that AGNs and composite dwarf galaxies do indeed host actively accreting black holes (BHs). Using our estimated BH masses (which range from ∼7 × 10{sup 4} to 1 × 10{sup 6} M {sub ⊙}), we find inferred Eddington fractions ranging from ∼0.1% to 50%, i.e., comparable to massive broad-line quasars at higher redshift. We use the HST imaging to determine the ratio of UV to X-ray emission for these AGNs, finding that they appear to be less X-ray luminous with respect to their UV emission than more massive quasars (i.e., α {sub OX} values an average of 0.36 lower than expected based on the relation between α {sub OX} and 2500 Å luminosity). Finally, we discuss our results in the context of different accretion models onto nuclear BHs.« less

Ultraluminous X-ray bursts in two ultracompact companions to nearby elliptical galaxies.

PubMed

Irwin, Jimmy A; Maksym, W Peter; Sivakoff, Gregory R; Romanowsky, Aaron J; Lin, Dacheng; Speegle, Tyler; Prado, Ian; Mildebrath, David; Strader, Jay; Liu, Jifeng; Miller, Jon M

2016-10-20

A flaring X-ray source was found near the galaxy NGC 4697 (ref. 1). Two brief flares were seen, separated by four years. During each flare, the flux increased by a factor of 90 on a timescale of about one minute. There is no associated optical source at the position of the flares, but if the source was at the distance of NGC 4697, then the luminosities of the flares were greater than 10 39 erg per second. Here we report the results of a search of archival X-ray data for 70 nearby galaxies looking for similar flares. We found two ultraluminous flaring sources in globular clusters or ultracompact dwarf companions of parent elliptical galaxies. One source flared once to a peak luminosity of 9 × 10 40 erg per second; the other flared five times to 10 40 erg per second. The rise times of all of the flares were less than one minute, and the flares then decayed over about an hour. When not flaring, the sources appear to be normal accreting neutron-star or black-hole X-ray binaries, but they are located in old stellar populations, unlike the magnetars, anomalous X-ray pulsars or soft γ repeaters that have repetitive flares of similar luminosities.

New cataclysmic variables and other exotic binaries in the globular cluster 47 Tucanae*

NASA Astrophysics Data System (ADS)

Rivera Sandoval, L. E.; van den Berg, M.; Heinke, C. O.; Cohn, H. N.; Lugger, P. M.; Anderson, J.; Cool, A. M.; Edmonds, P. D.; Wijnands, R.; Ivanova, N.; Grindlay, J. E.

2018-04-01

We present 22 new (+3 confirmed) cataclysmic variables (CVs) in the non-core-collapsed globular cluster 47 Tucanae (47 Tuc). The total number of CVs in the cluster is now 43, the largest sample in any globular cluster so far. For the identifications we used near-ultraviolet (NUV) and optical images from the Hubble Space Telescope, in combination with X-ray results from the Chandra X-ray Observatory. This allowed us to build the deepest NUV CV luminosity function of the cluster to date. We found that the CVs in 47 Tuc are more concentrated towards the cluster centre than the main-sequence turn-off stars. We compared our results to the CV populations of the core-collapsed globular clusters NGC 6397 and NGC 6752. We found that 47 Tuc has fewer bright CVs per unit mass than those two other clusters. That suggests that dynamical interactions in core-collapsed clusters play a major role creating new CVs. In 47 Tuc, the CV population is probably dominated by primordial and old dynamically formed systems. We estimated that the CVs in 47 Tuc have total masses of ˜1.4 M⊙. We also found that the X-ray luminosity function of the CVs in the three clusters is bimodal. Additionally, we discuss a possible double degenerate system and an intriguing/unclassified object. Finally, we present four systems that could be millisecond pulsar companions given their X-ray and NUV/optical colours. For one of them we present very strong evidence for being an ablated companion. The other three could be CO or He white dwarfs.

Discovery of a 105 ms X-Ray Pulsar in Kesteven 79: On the Nature of Compact Central Objects in Supernova Remnants

NASA Astrophysics Data System (ADS)

Gotthelf, E. V.; Halpern, J. P.; Seward, F. D.

2005-07-01

We report the discovery of 105 ms X-ray pulsations from the compact central object (CCO) in the supernova remnant Kes 79 using data acquired with the Newton X-Ray Multi-Mirror Mission (XMM-Newton). Two observations of the pulsar taken 6 days apart yield an upper limit on its spin-down rate of P˙<7×10-14 s s-1 and no evidence for binary orbital motion. The implied energy loss rate is E˙<2×1036 ergs s-1, the surface magnetic field strength is Bp<3×1012 G, and the spin-down age is τ>24 kyr. The latter exceeds the remnant's estimated age, suggesting that the pulsar was born spinning near its current period. The X-ray spectrum of PSR J1852+0040 is best characterized by a blackbody model of temperature kTBB=0.44+/-0.03 keV, radius RBB~0.9 km, and Lbol=3.7×1033 ergs s-1 at d=7.1 kpc. The sinusoidal light curve is modulated with a pulsed fraction of >45%, suggestive of a small hot spot on the surface of the rotating neutron star. The lack of a discernible pulsar wind nebula is consistent with an interpretation of PSR J1852+0040 as a rotation-powered pulsar whose spin-down luminosity falls below the empirical threshold for generating bright wind nebulae, E˙c~4×1036 ergs s-1. The age discrepancy implies that its E˙ has always been below E˙c, perhaps a distinguishing property of the CCOs. Alternatively, the X-ray spectrum of PSR J1852+0040 suggests a low-luminosity anomalous X-ray pulsar (AXP), but the weak inferred Bp field is incompatible with a magnetar theory of its X-ray luminosity. We cannot exclude accretion from a fallback disk. The ordinary spin parameters discovered from PSR J1852+0040 highlight the difficulty that existing theories of isolated neutron stars have in explaining the high luminosities and temperatures of CCO thermal X-ray spectra.

Evolution of X-ray activity of 1-3 Msun late-type stars in early post-main-sequence phases

NASA Astrophysics Data System (ADS)

Pizzolato, N.; Maggio, A.; Sciortino, S.

2000-09-01

We have investigated the variation of coronal X-ray emission during early post-main-sequence phases for a sample of 120 late-type stars within 100 pc, and with estimated masses in the range 1-3 Msun, based on Hipparcos parallaxes and recent evolutionary models. These stars were observed with the ROSAT/PSPC, and the data processed with the Palermo-CfA pipeline, including detection and evaluation of X-ray fluxes (or upper limits) by means of a wavelet transform algorithm. We have studied the evolutionary history of X-ray luminosity and surface flux for stars in selected mass ranges, including stars with inactive A-type progenitors on the main sequence and lower mass solar-type stars. Our stellar sample suggests a trend of increasing X-ray emission level with age for stars with masses M > 1.5 Msun, and a decline for lower-mass stars. A similar behavior holds for the average coronal temperature, which follows a power-law correlation with the X-ray luminosity, independently of their mass and evolutionary state. We have also studied the relationship between X-ray luminosity and surface rotation rate for stars in the same mass ranges, and how this relationships departs from the Lx ~ vrot2 law followed by main-sequence stars. Our results are interpreted in terms of a magnetic dynamo whose efficiency depends on the stellar evolutionary state through the mass-dependent changes of the stellar internal structure, including the properties of envelope convection and the internal rotation profile.

X-ray emission from galaxies - The distribution of low-luminosity X-ray sources in the Galactic Centre region

NASA Astrophysics Data System (ADS)

Heard, Victoria; Warwick, Robert

2012-09-01

We report a study of the extended X-ray emission observed in the Galactic Centre (GC) region based on archival XMM-Newton data. The GC diffuse emission can be decomposed into three distinct components: the emission from low-luminosity point sources; the fluorescence of (and reflection from) dense molecular material; and soft (kT ~1 keV), diffuse thermal plasma emission most likely energised by supernova explosions. Here, we examine the emission due to unresolved point sources. We show that this source component accounts for the bulk of the 6.7-keV and 6.9-keV line emission. We fit the surface brightness distribution evident in these lines with an empirical 2-d model, which we then compare with a prediction derived from a 3-d mass model for the old stellar population in the GC region. We find that the X-ray surface brightness declines more rapidly with angular offset from Sgr A* than the mass-model prediction. One interpretation is that the X-ray luminosity per solar mass characterising the GC source population is increasing towards the GC. Alternatively, some refinement of the mass-distribution within the nuclear stellar disc may be required. The unresolved X-ray source population is most likely dominated by magnetic CVs. We use the X-ray observations to set constraints on the number density of such sources in the GC region. Our analysis does not support the premise that the GC is pervaded by very hot (~ 7.5 keV) thermal plasma, which is truly diffuse in nature.

X-Ray Scaling Relations of Early-type Galaxies

NASA Astrophysics Data System (ADS)

Babyk, Iu. V.; McNamara, B. R.; Nulsen, P. E. J.; Hogan, M. T.; Vantyghem, A. N.; Russell, H. R.; Pulido, F. A.; Edge, A. C.

2018-04-01

X-ray luminosity, temperature, gas mass, total mass, and their scaling relations are derived for 94 early-type galaxies (ETGs) using archival Chandra X-ray Observatory observations. Consistent with earlier studies, the scaling relations, L X ∝ T 4.5±0.2, M ∝ T 2.4±0.2, and L X ∝ M 2.8±0.3, are significantly steeper than expected from self-similarity. This steepening indicates that their atmospheres are heated above the level expected from gravitational infall alone. Energetic feedback from nuclear black holes and supernova explosions are likely heating agents. The tight L X –T correlation for low-luminosity systems (i.e., below 1040 erg s‑1) are at variance with hydrodynamical simulations, which generally predict higher temperatures for low-luminosity galaxies. We also investigate the relationship between total mass and pressure, Y X = M g × T, finding M\\propto {Y}X0.45+/- 0.04. We explore the gas mass to total mass fraction in ETGs and find a range of 0.1%–1.0%. We find no correlation between the gas-to-total mass fraction with temperature or total mass. Higher stellar velocity dispersions and higher metallicities are found in hotter, brighter, and more massive atmospheres. X-ray core radii derived from β-model fitting are used to characterize the degree of core and cuspiness of hot atmospheres.

X-ray detections of submillimetre galaxies: active galactic nuclei versus starburst contribution

NASA Astrophysics Data System (ADS)

Johnson, S. P.; Wilson, G. W.; Wang, Q. D.; Williams, C. C.; Scott, K. S.; Yun, M. S.; Pope, A.; Lowenthal, J.; Aretxaga, I.; Hughes, D.; Kim, M. J.; Kim, S.; Tamura, Y.; Kohno, K.; Ezawa, H.; Kawabe, R.; Oshima, T.

2013-05-01

We present a large-scale study of the X-ray properties and near-IR-to-radio spectral energy distributions (SEDs) of submillimetre galaxies (SMGs) detected at 1.1 mm with the AzTEC instrument across a ˜1.2 square degree area of the sky. Combining deep 2-4 Ms Chandra data with Spitzer IRAC/MIPS and Very Large Array data within the Great Observatories Origins Deep Survey North (GOODS-N), GOODS-S and COSMOS fields, we find evidence for active galactic nucleus (AGN) activity in ˜14 per cent of 271 AzTEC SMGs, ˜28 per cent considering only the two GOODS fields. Through X-ray spectral modelling and multiwavelength SED fitting using Monte Carlo Markov chain techniques to Siebenmorgen et al. (AGN) and Efstathiou, Rowan-Robinson & Siebenmorgen (starburst) templates, we find that while star formation dominates the IR emission, with star formation rates (SFRs) ˜100-1000 M⊙ yr-1, the X-ray emission for most sources is almost exclusively from obscured AGNs, with column densities in excess of 1023 cm-2. Only for ˜6 per cent of our sources do we find an X-ray-derived SFR consistent with NIR-to-radio SED derived SFRs. Inclusion of the X-ray luminosities as a prior to the NIR-to-radio SED effectively sets the AGN luminosity and SFR, preventing significant contribution from the AGN template. Our SED modelling further shows that the AGN and starburst templates typically lack the required 1.1 mm emission necessary to match observations, arguing for an extended, cool dust component. The cross-correlation function between the full samples of X-ray sources and SMGs in these fields does not indicate a strong correlation between the two populations at large scales, suggesting that SMGs and AGNs do not necessarily trace the same underlying large-scale structure. Combined with the remaining X-ray-dim SMGs, this suggests that sub-mm-bright sources may evolve along multiple tracks, with X-ray-detected SMGs representing transitionary objects between periods of high star formation and AGN activity, while X-ray-faint SMGs represent a brief starburst phase of more normal galaxies.

The X-Ray Luminosity-Mass Relation for Local Clusters of Galaxies

NASA Astrophysics Data System (ADS)

Stanek, Rebecca; Evrard, A.; Boehringer, H.; Schuecker, P.; Nord, B.

2006-12-01

My thesis is centered on investigating scaling relations of galaxy clusters. Focusing on the relationship between soft X-ray luminosity and mass (L-M) for low-redshift clusters of galaxies, I have determined the mean parameters to 5%, and calculated a formal measure of the scatter in the L-M relation. I model the L-M relation with a conditional probability function including a mean power-law scaling relation, L Mpρsc(z), and log-normal scatter in mass at fixed luminosity, σlnM. Convolving with the halo mass function, I compute expected counts in redshift and flux that, after appropriate survey effects are included, are compared to REFLEX survey data. Combining the likelihood analysis with the measured variance in L-T relation from HIFLUGCS, I obtain fit parameters p=1.59+/-0.05, lnL15,0=1.34+/-0.09, and σlnM=0.37+/-0.05 for self-similar redshift evolution (s = 7/6) in a concordance (Ωm=0.3, ΩΛ=0.7, σ8=0.9) universe. I find a substantially (factor 2) dimmer intercept and slightly steeper slope than the values published using hydrostatic mass estimates of the HIFLUGCS sample and show that a Malmquist bias of the X-ray flux-limited sample accounts for this effect. I accommodate the new WMAP constraints with a compromise model with Ωm=0.24, σ8=0.85, and somewhat lower scatter σlnM=0.25. I will also present work in progress from galaxy cluster population statistics in the Millennium Simulation with Gas (MSG), specifically focusing on the scatter and covariance between cluster properties at a fixed epoch.

Large-Scale Structure Studies with the REFLEX Cluster Survey

NASA Astrophysics Data System (ADS)

Schuecker, P.; Bohringer, H.; Guzzo, L.; Collins, C.; Neumann, D. M.; Schindler, S.; Voges, W.

1998-12-01

First preliminary results of the ROSAT ESO Flux-Limited X-Ray (REFLEX) Cluster Survey are described. The survey covers 13,924 square degrees of the southern hemisphere. The present sample consists of about 470 rich clusters (1/3 non Abell/ACO clusters) with X-ray fluxes S >= 3.0 times 10^{-12} erg s^{-1} cm^{-2} (0.1-2.4 keV) and redshifts z <= 0.3. In contrast to other low-redshift surveys, the cumulative flux-number counts have an almost Euclidean slope. Comoving cluster number densities are found to be almost redshift-independent throughout the total survey volume. The X-ray luminosity function is well described by a Schechter function. The power spectrum of the number density fluctuations could be measured on scales up to 400 h^{-1} Mpc. A deeper survey with about 800 galaxy clusters in the same area is in progress.

A NuSTAR SURVEY OF NEARBY ULTRALUMINOUS INFRARED GALAXIES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Teng, Stacy H.; Rigby, Jane R.; Ptak, Andrew

We present a Nuclear Spectroscopic Telescope Array (NuSTAR), Chandra, and XMM-Newton survey of nine of the nearest ultraluminous infrared galaxies (ULIRGs). The unprecedented sensitivity of NuSTAR at energies above 10 keV enables spectral modeling with far better precision than was previously possible. Six of the nine sources observed were detected sufficiently well by NuSTAR to model in detail their broadband X-ray spectra, and recover the levels of obscuration and intrinsic X-ray luminosities. Only one source (IRAS 13120–5453) has a spectrum consistent with a Compton-thick active galactic nucleus (AGN), but we cannot rule out that a second source (Arp 220) harborsmore » an extremely highly obscured AGN as well. Variability in column density (reduction by a factor of a few compared to older observations) is seen in IRAS 05189–2524 and Mrk 273, altering the classification of these borderline sources from Compton-thick to Compton-thin. The ULIRGs in our sample have surprisingly low observed fluxes in high-energy (>10 keV) X-rays, especially compared to their bolometric luminosities. They have lower ratios of unabsorbed 2–10 keV to bolometric luminosity, and unabsorbed 2–10 keV to mid-IR [O iv] line luminosity than do Seyfert 1 galaxies. We identify IRAS 08572+3915 as another candidate intrinsically X-ray weak source, similar to Mrk 231. We speculate that the X-ray weakness of IRAS 08572+3915 is related to its powerful outflow observed at other wavelengths.« less

Towards A Complete Census of Compton-thick AGN and N_H Distribution in the Local Universe

NASA Astrophysics Data System (ADS)

Annuar, A.; Gandhi, P.; Alexander, D.; Asmus, D.; Goulding, A.; Harrison, C.; Lansbury, G.

2014-07-01

Many studies have shown that Compton-thick AGNs (CTAGNs) provide important contribution to the cosmic X-ray background spectrum (˜25% at 20keV). They are expected to dominate the Seyfert 2 population in the local universe, yet only ˜20 bona fide CTAGNs are known. We present an updated census of CTAGN population in the local universe using a volume-limited AGN sample complete to D=15Mpc. Intrinsic relations between 2-10keV X-ray luminosity and mid-IR emission at 12μm, [OIV]λ25.68μm and [NeV]λ14.32μm are investigated, and it is found that the emission at 12μm has the tightest correlation with the X-ray luminosity.Candidates for CTAGN are then selected using this relation and by comparing their 12μm luminosity with the observed X-ray luminosity.We also investigate the Compton-thick nature of these sources using the optical [OIII]λ5007{A}:X-ray diagnostic for comparison, and find that 35-50% of the sample are Compton-thick,of which 10-20% would be missed with the optical approach.Finally, we estimate the intrinsic N_{H} distribution of AGN population in the local universe from this analysis, and show that up to 70% of the sources are heavily obscured (N_{H}>10^{23} cm^{-2}), with ≥50% lying in the Compton-thick regime (N_{H}>10^{24} cm^{-2}).This work provides a well-defined local benchmark for AGN obscuration studies.

Centre-excised X-ray luminosity as an efficient mass proxy for future galaxy cluster surveys

DOE PAGES

Mantz, Adam B.; Allen, Steven W.; Morris, R. Glenn; ...

2017-10-02

The cosmological constraining power of modern galaxy cluster catalogues can be improved by obtaining low-scatter mass proxy measurements for even a small fraction of sources. In the context of large upcoming surveys that will reveal the cluster population down to the group scale and out to high redshifts, efficient strategies for obtaining such mass proxies will be valuable. Here in this work, we use high-quality weak-lensing and X-ray mass estimates for massive clusters in current X-ray-selected catalogues to revisit the scaling relations of the projected, centre-excised X-ray luminosity (L ce), which previous work suggests correlates tightly with total mass. Ourmore » data confirm that this is the case with Lce having an intrinsic scatter at fixed mass comparable to that of gas mass, temperature or YX. Compared to the other proxies, however, Lce is less susceptible to systematic uncertainties due to background modelling, and can be measured precisely with shorter exposures. This opens up the possibility of using L ce to estimate masses for large numbers of clusters discovered by new X-ray surveys (e.g. eROSITA) directly from the survey data, as well as for clusters discovered at other wavelengths with relatively short follow-up observations. We describe a simple procedure for making such estimates from X-ray surface brightness data, and comment on the spatial resolution required to apply this method as a function of cluster mass and redshift. Lastly, we also explore the potential impact of Chandra and XMM–Newton follow-up observations over the next decade on dark energy constraints from new cluster surveys.« less

High-redshift Galaxies and Black Holes Detectable with the JWST: A Population Synthesis Model from Infrared to X-Rays

NASA Astrophysics Data System (ADS)

Volonteri, Marta; Reines, Amy E.; Atek, Hakim; Stark, Daniel P.; Trebitsch, Maxime

2017-11-01

The first billion years of the Universe has been a pivotal time: stars, black holes (BHs), and galaxies formed and assembled, sowing the seeds of galaxies as we know them today. Detecting, identifying, and understanding the first galaxies and BHs is one of the current observational and theoretical challenges in galaxy formation. In this paper we present a population synthesis model aimed at galaxies, BHs, and active galactic nuclei (AGNs) at high redshift. The model builds a population based on empirical relations. The spectral energy distribution of galaxies is determined by age and metallicity, and that of AGNs by BH mass and accretion rate. We validate the model against observations, and predict properties of galaxies and AGN in other wavelength and/or luminosity ranges, estimating the contamination of stellar populations (normal stars and high-mass X-ray binaries) for AGN searches from the infrared to X-rays, and vice versa for galaxy searches. For high-redshift galaxies with stellar ages < 1 {Gyr}, we find that disentangling stellar and AGN emission is challenging at restframe UV/optical wavelengths, while high-mass X-ray binaries become more important sources of confusion in X-rays. We propose a color-color selection in the James Webb Space Telescope bands to separate AGN versus star-dominated galaxies in photometric observations. We also estimate the AGN contribution, with respect to massive, hot, and metal-poor stars, at driving high-ionization lines, such as C IV and He II. Finally, we test the influence of the minimum BH mass and occupation fraction of BHs in low-mass galaxies on the restframe UV/near-IR and X-ray AGN luminosity function.

Centre-excised X-ray luminosity as an efficient mass proxy for future galaxy cluster surveys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mantz, Adam B.; Allen, Steven W.; Morris, R. Glenn

The cosmological constraining power of modern galaxy cluster catalogues can be improved by obtaining low-scatter mass proxy measurements for even a small fraction of sources. In the context of large upcoming surveys that will reveal the cluster population down to the group scale and out to high redshifts, efficient strategies for obtaining such mass proxies will be valuable. Here in this work, we use high-quality weak-lensing and X-ray mass estimates for massive clusters in current X-ray-selected catalogues to revisit the scaling relations of the projected, centre-excised X-ray luminosity (L ce), which previous work suggests correlates tightly with total mass. Ourmore » data confirm that this is the case with Lce having an intrinsic scatter at fixed mass comparable to that of gas mass, temperature or YX. Compared to the other proxies, however, Lce is less susceptible to systematic uncertainties due to background modelling, and can be measured precisely with shorter exposures. This opens up the possibility of using L ce to estimate masses for large numbers of clusters discovered by new X-ray surveys (e.g. eROSITA) directly from the survey data, as well as for clusters discovered at other wavelengths with relatively short follow-up observations. We describe a simple procedure for making such estimates from X-ray surface brightness data, and comment on the spatial resolution required to apply this method as a function of cluster mass and redshift. Lastly, we also explore the potential impact of Chandra and XMM–Newton follow-up observations over the next decade on dark energy constraints from new cluster surveys.« less

A Chandra observation of the interacting pair of galaxies NGC 4485/4490

NASA Astrophysics Data System (ADS)

Roberts, T. P.; Warwick, R. S.; Ward, M. J.; Murray, S. S.

2002-12-01

We report the results of a 20-ks Chandra ACIS-S observation of the galaxy pair NGC 4485/4490. This is an interacting system containing a late-type spiral with an enhanced star formation rate (NGC 4490), and an irregular companion that possesses a disturbed morphology. A total of 29 discrete X-ray sources are found coincident with NGC 4490, but only one is found within NGC 4485. The sources range in observed X-ray luminosity from ~2 × 1037 to 4 × 1039 erg s-1. The more luminous sources appear, on average, to be spectrally harder than the fainter sources, an effect that is attributable to increased absorption in their spectra. Extensive diffuse X-ray emission is detected coincident with the disc of NGC 4490, and in the tidal tail of NGC 4485, which appears to be thermal in nature and hence the signature of a hot interstellar medium in both galaxies. However, the diffuse component accounts for only ~10 per cent of the total X-ray luminosity of the system (2 × 1040 erg s-1, 0.5-8 keV), which arises predominantly in a handful of the brightest discrete sources. This diffuse emission fraction is unusually low for a galaxy pair which has many characteristics that would lead it to be classified as a starburst system, possibly as a consequence of the small gravitational potential well of the system. The discrete source population, on the other hand, is similar to that observed in other starburst systems, possessing a flat luminosity function slope of ~-0.6 and a total of six ultraluminous X-ray sources (ULX). Five of the ULX are identified as probable black hole X-ray binary systems, and the sixth (which is coincident with a radio continuum source) is identified as an X-ray luminous supernova remnant. The ULX all lie in star formation regions, providing further evidence of the link between the ULX phenomenon and active star formation. Importantly, this shows that even in star-forming regions, the ULX population is dominated by accreting systems. We discuss the implications of this work for physical models of the nature of ULX, and in particular how it argues against the intermediate-mass black hole hypothesis.

Resolving the Puzzle of MS1248-7+5706

NASA Technical Reports Server (NTRS)

Aldcroft, Thomas

1999-01-01

The X-ray source MS1248.7+5706 has been identified as a radio-quiet quasar at z=1.84, making it an ideal object for investigating the X-ray spectral evolution of radio-quiet quasars. However. spectral modeling of our ASCA observation of this X-ray source indicated that it might be confused by or misidentified with, a nearby K5V star. A high-resolution X-ray image has been obtained with the ROSAT HRI to enable us to interpret our ASCA spectra. An analysis of the new HRI observation shows that the X-ray source in the ASCA error circle most closely coincides with the position of the K5V star. It therefore appears that the identification of MS1248.7+5706 with a z=1.84 quasar is incorrect. Since MS1248.7+5706 is the second most luminous quasar in the Einstein Medium Sensitivity Survey, the bright end of the EMSS luminosity function will be impacted.

Cosmological evolution of supermassive black holes in galactic centers unveiled by hard X-ray observations

PubMed Central

UEDA, Yoshihiro

2015-01-01

We review the current understanding of the cosmological evolution of supermassive black holes in galactic centers elucidated by X-ray surveys of active galactic nuclei (AGNs). Hard X-ray observations at energies above 2 keV are the most efficient and complete tools to find “obscured” AGNs, which are dominant populations among all AGNs. Combinations of surveys with various flux limits and survey area have enabled us to determine the space number density and obscuration properties of AGNs as a function of luminosity and redshift. The results have essentially solved the origin of the X-ray background in the energy band below ∼10 keV. The downsizing (or anti-hierarchical) evolution that more luminous AGNs have the space-density peak at higher redshifts has been discovered, challenging theories of galaxy and black hole formation. Finally, we summarize unresolved issues on AGN evolution and prospects for future X-ray missions. PMID:25971656

An X-ray Investigation of the NGC 346 Field in the SMC (2): The Field Population

NASA Technical Reports Server (NTRS)

Naze, Y.; Hartwell, J. M.; Stevens, I. R.; Manfroid, J.; Marchenko. S.; Corcoran, M. F.; Moffat, A. F. J.; Skalkowski, G.; White, Nicholas E. (Technical Monitor)

2002-01-01

We present results from a Chandra observation of the NGC 346 cluster, the ionizing source of N66, the most luminous H II region and the largest star formation region in the SMC. In the first part of this investigation, we have analysed the X-ray properties of the cluster itself and the remarkable star HD 5980. But the field contains additional objects of interest. In total, 79 X-ray point sources were detected in the Chandra observation and we investigate here their characteristics in details. The sources possess rather high HRs, and their cumulative luminosity function is steeper than the SMC's trend. Their absorption columns suggest that most of the sources belong to NGC 346. Using new UBVRI imaging with the ESO 2.2m telescope, we also discovered possible counterparts for 36 of these X-ray sources. Finally, some objects show X-ray and/or optical variability, and thus need further monitoring.

Rosat Observations of Nine Globular Clusters

NASA Technical Reports Server (NTRS)

Rappaport, S.; Dewey, D.; Levine, A.; Macri, L.

1994-01-01

The ROSAT HRI was used to image fields around nine Galactic globular clusters that have central densities in the range of 10(exp 4) - 10(exp 5) solar mass pc(exp -3) and that had not previously been observed with the Einstein Observatory. We detected X-ray sources associated with Pal 2 and NGC 6304 with luminosities of 1.1 x 10(exp 34) ergs/s and 1.2 x 10(exp 33) ergs/s, respectively. No X-ray emission was detected from the source in Ter 6, thus confirming its transient nature. In all, there were 23 serendipitous sources found in the nine fields; none was apparently associated with any of the other seven clusters. The results are discussed in the context of low-luminosity cluster X-ray sources, in general.

Black Hole Event Horizons and Advection-Dominated Accretion

NASA Technical Reports Server (NTRS)

McClintock, Jeffrey; Mushotzky, Richard F. (Technical Monitor)

2001-01-01

The XMM data on black-hole X-ray novae are only now becoming available and they have so far not been included in any publications. This work is part of a larger project that makes use of both XMM and Chandra data. Our first publication on the Chandra results is the following: "New Evidence for Black Hole Event Horizons from Chandra" by M.R. Garcia, J.E. McClintock, R. Narayan, P. Callanan, D. Barret and S. Murray (2001, ApJ, 553, L47). Therein we present the luminosities of the two black-hole X-ray novae, GRO J0422+22 and 4U1 543-47, which were observed by Chandra. These results are combined with the luminosities of four additional black-hole X-ray novae, which were observed as part of a Chandra GTO program (PI: S. Murray). The very low, but nonzero, quiescent X-ray luminosities of these black hole binaries is very difficult to understand in the context of standard viscous accretion disk theory. The principal result of this work is that X-ray novae that contain black hole primaries are about 100 times fainter that X-ray novae that contain neutron star primaries. This result had been suggested in earlier work, but the present work very firmly establishes this large luminosity difference. The result is remarkable because the black-hole and the neutron-star systems are believed to be similar in many respects. Most importantly, the mass transfer rate from the secondary star is believed to be very comparable for the two kinds of systems for similar orbital periods. The advection-dominated accretion flow (ADAF) model provides a natural framework for understanding the extraordinarily low luminosities of the black hole systems and the hundred-fold greater luminosities of the neutron star systems. The chief feature of an ADAF is that the heat energy in the accreting gas is trapped in the gas and travels with it, rather than being radiated promptly. Thus the accreting gas reaches the central object with a huge amount of thermal energy. If the accretor is a black hole, the thermal energy will disappear through the event horizon, and the object will be very dim. On the other hand, if the central object is a neutron star or any other object with a surface, then the energy will be radiated from the surface, and the object will be bright.

An X-ray Investigation of the NGC 346 Field. 1; The LBV HD 5980 and the NGC 346 Cluster

NASA Technical Reports Server (NTRS)

Naze, Y.; Hartwell, J. M.; Stevens, I. R.; Corcoran, M. F.; Chu, Y.-H.; Koenigsberger, G.; Moffat, A. F. J.; Niemela, V. S.

2002-01-01

We present results from a Chandra observation of the NGC 346 star formation region, which contains numerous massive stars, and is related to N66, the largest H(II) region of the SMC (Small Magellanic Cloud). In this first paper, we will focus on the characteristics of the main objects of the field. The NGC 346 cluster itself shows only relatively faint X-ray emission (with L((sub X)(sup unabs)) is approximately 1.5 x 10(exp 34) erg s(exp -1), tightly correlated with the core of the cluster. In the field also lies HD 5980, a LBV (Luminous Blue Variable) star in a binary (or triple system) that is detected for the first time at X-ray energies. The star is X-ray bright, with an unabsorbed luminosity of L((sub X)(sup unabs)) is approximately 1.7 x 10(exp 34) erg s(exp -1), but needs to be monitored further to investigate its X-ray variability over a complete orbital cycle. The high X-ray luminosity may be associated either with colliding winds in the binary system or with the 1994 eruption. HD 5980 is surrounded by a region of diffuse X-ray emission, which may be a superimposed supernova remnant.

Cosmological constraints from Chandra observations of galaxy clusters.

PubMed

Allen, Steven W

2002-09-15

Chandra observations of rich, relaxed galaxy clusters allow the properties of the X-ray gas and the total gravitating mass to be determined precisely. Here, we present results for a sample of the most X-ray luminous, dynamically relaxed clusters known. We show that the Chandra data and independent gravitational lensing studies provide consistent answers on the mass distributions in the clusters. The mass profiles exhibit a form in good agreement with the predictions from numerical simulations. Combining Chandra results on the X-ray gas mass fractions in the clusters with independent measurements of the Hubble constant and the mean baryonic matter density in the Universe, we obtain a tight constraint on the mean total matter density of the Universe, Omega(m), and an interesting constraint on the cosmological constant, Omega(Lambda). We also describe the 'virial relations' linking the masses, X-ray temperatures and luminosities of galaxy clusters. These relations provide a key step in linking the observed number density and spatial distribution of clusters to the predictions from cosmological models. The Chandra data confirm the presence of a systematic offset of ca. 40% between the normalization of the observed mass-temperature relation and the predictions from standard simulations. This finding leads to a significant revision of the best-fit value of sigma(8) inferred from the observed temperature and luminosity functions of clusters.

New Constraints for X-ray Reprocessing Around Supermassive Black Holes: Near and Far with State-of-the-Art Multi-Mission Modeling

NASA Astrophysics Data System (ADS)

Tzanavaris, Panayiotis

Fluorescent Fe K emission from neutral matter in AGN spectracan arise in the accretion disk around the centralsupermassive black hole [SMBH] ("broad" line) and/or in distant matter ("narrow"line). If it is broad, it provides a unique windowto the strong gravity SMBH regime, including information on SMBH spin;if it is narrow, it probesthe distant reprocessor, likely a clumpy torus. We will use broadband X-ray data from four NASA X-ray missionsfor 45 nearby AGNs, and 1. Assess whether any known "broad" relativistic lines can be modeledas "narrow"instead, by means of self-consistent modeling of fluorescence,direct, and scattered continua; 2. Measure absorbing column densities both in and out of the line of sight; 3. Bootstrap measures of intrinsic bolometric AGN luminosity, with X-ray and optical data. This work will provide updated results on a) black hole spin, with implications on AGN jet power and accretion history; b) the census of highly-obscured (Compton thick) vs. Compton thin AGNs, with implications on models of the Cosmic X-ray Background; c) calibrations of Fe K line, X-ray intrinsic continuum, [OIII] and [OIV] luminosities as measures of intrinsc bolometric AGN luminosity, with implications on AGN feedback and galaxy evolution. Key in our approach is a physically based, self-consistent modeling of the narrow line, with finite column density in and out of the line of sight, and the latest relativistic modeling of the broad line.

Mini-Survey of SDSS OIII AGN with Swift

NASA Technical Reports Server (NTRS)

Angelina, Lorella; George, Ian

2007-01-01

There is a common wisdom that every massive galaxy has a massive block hole. However, most of these objects either are not radiating or until recently have been very difficult to detect. The Sloan Digital Sky Survey (SDSS) data, based on the [OIII] line indicate that perhaps up to 20% of all galaxies may be classified as AGN a surprising result that must be checked with independent data. X-ray surveys have revealed that hard X-ray selected AGN show a strong luminosity dependent evolution and their luminosity function (LF) shows a dramatic break towards low Lx (at all z). This is seen for all types of AGN, but is stronger for the broad-line objects. In sharp contrast, the local LF of (optically-selected samples) shows no such break and no differences between narrow and broad-line objects. Assuming both hard X-ray and [OIII] emission are fair indicators of AGN activity, it is important to understand this discrepancy. We present here the results of a mini-survey done with Swift on a selected sample of SDSS selected AGN. The objects have been sampled at different L([OIII]) to check the relation with the Lx observed with Swift.

Effect of non-stationary accretion on spectral state transitions: An example of a persistent neutron star LMXB 4U1636–536

NASA Astrophysics Data System (ADS)

Zhang, Hui; Yu, Wen-Fei

2018-03-01

Observations of black hole and neutron star X-ray binaries show that the luminosity of the hard-to-soft state transition is usually higher than that of the soft-to-hard state transition, indicating additional parameters other than mass accretion rate are required to interpret spectral state transitions. It has been found in some individual black hole or neutron star soft X-ray transients that the luminosity corresponding to the hard-to-soft state transition is positively correlated with the peak luminosity of the following soft state. In this work, we report the discovery of the same correlation in the single persistent neutron star low mass X-ray binary (LMXB) 4U 1636–536 based on data from the All Sky Monitor (ASM) on board RXTE, the Gas Slit Camera (GSC) on board MAXI and the Burst Alert Telescope (BAT) on board Swift. We also found such a positive correlation holds in this persistent neutron star LMXB in a luminosity range spanning about a factor of four. Our results indicate that non-stationary accretion also plays an important role in driving X-ray spectral state transitions in persistent accreting systems with small accretion flares, which is much less dramatic compared with the bright outbursts seen in many Galactic LMXB transients.

Final Technical Report

NASA Technical Reports Server (NTRS)

Heckman, Timothy M.

1997-01-01

We have analysed ROSAT X-ray data for a small sample of starburst galaxies in order to understand the physical origin of the X-ray emission and probe the physics and phenomenology of galactic-scale outflows of hot gas ('superwinds') that are driven by tile mechanical energy supplied by the ensemble of supernovae in the starbursts. We have found that the X-ray emission in the ROSAT energy band comes from a population of compact hard sources (most likely X-ray binaries) and hot diffuse gas with a temperature ranging from a few to ten million K. This gas is spatially-extended on galactic scales and its properties are entirely consistent with theoretical expectations for a starburst-driven superwind. The starbursts studied span a range of roughly 1000 in bolometric luminosity and are hosted by galaxies ranging from dwarfs through L* spirals through ma,ior galactic mergers. The X-ray properties of these o@jecls scale in a natural way with the luminosity of tile starburst: more powerful starbursts are more X-ray luminous and create hot outflowing gas whose energy content is likewise larger.

CAN THE SUBSONIC ACCRETION MODEL EXPLAIN THE SPIN PERIOD DISTRIBUTION OF WIND-FED X-RAY PULSARS?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Tao; Shao, Yong; Li, Xiang-Dong, E-mail: lixd@nju.edu.cn

Neutron stars in high-mass X-ray binaries (HMXBs) generally accrete from the wind matter of their massive companion stars. Recently, Shakura et al. suggested a subsonic accretion model for low-luminosity (<4 × 10{sup 36} erg s{sup −1}), wind-fed X-ray pulsars. To test the feasibility of this model, we investigate the spin period distribution of wind-fed X-ray pulsars with a supergiant companion star, using a population synthesis method. We find that the modeled distribution of supergiant HMXBs in the spin period–orbital period diagram is consistent with observations, provided that the winds from the donor stars have relatively low terminal velocities (≲1000 kmmore » s{sup −1}). The measured wind velocities in several supergiant HMXBs seem to favor this viewpoint. The predicted number ratio of wind-fed X-ray pulsars with persistent X-ray luminosities that are higher and lower than 4 × 10{sup 36} erg s{sup −1} is about 1:10.« less

Discovery of radio emission from the brown dwarf LP944-20.

PubMed

Berger, E; Ball, S; Becker, K M; Clarke, M; Frail, D A; Fukuda, T A; Hoffman, I M; Mellon, R; Momjian, E; Murphy, N W; Teng, S H; Woodruff, T; Zauderer, B A; Zavala, R T

2001-03-15

Brown dwarfs are not massive enough to sustain thermonuclear fusion of hydrogen at their centres, but are distinguished from gas-giant planets by their ability to burn deuterium. Brown dwarfs older than approximately 10 Myr are expected to possess short-lived magnetic fields and to emit radio and X-rays only very weakly from their coronae. An X-ray flare was recently detected on the brown dwarf LP944-20, whereas previous searches for optical activity (and one X-ray search) yielded negative results. Here we report the discovery of quiescent and flaring radio emission from LP944-20, with luminosities several orders of magnitude larger than predicted by the empirical relation between the X-ray and radio luminosities that has been found for many types of stars. Interpreting the radio data within the context of synchrotron emission, we show that LP944-20 has an unusually weak magnetic field in comparison to active M-dwarf stars, which might explain the previous null optical and X-ray results, as well as the strength of the radio emissions compared to those at X-ray wavelengths.

ASCA Observations

NASA Technical Reports Server (NTRS)

Helfand, David J.

1998-01-01

This recently expired grant has supported the work of the PI, his students, and his collaborators on a variety of ASCA projects over the past four years. Annual reports have summarized much of the work accomplished; here we provide a brief review of the work resulting from this effort, and a summary of the personnel who have benefited from the grant's support. Starburst Galaxies with Extreme X-ray Luminosities This project began as a careful examination of the claims of Boller et al. (1992) that there were dozens of "normal" galaxies in the ROSAT All-Sky Survey that had X-ray luminosities in excess of 1042 erg sec, higher than that seen in the hundreds of non-AGN galaxies observed with Einstein. If true, this suggested that X-ray emission associated with star formation activity might have a significant contribution to make to the still unexplained cosmic X-ray background (XRB). Since some of our earlier work with the Einstein Observatory Deep Surveys had suggested a similar possibility and several sets of authors over the years had modelled the starburst XRB contribution, these claims were worth pursuing. Our work expanded the examination beyond the RASS to include earlier claims of high-luminosity galaxies powered by starburst emission (selected in this case on the basis of the far-IR luminosities). The result of extensive followup observations under several programs using ROSAT, ASCA, and ground-based facilities was to show that nearly all of these objects in fact have hidden AGN at their cores, and that their luminosities are not in any way extraordinary.

The X-Ray Light Curve of the Very Luminous Supernova SN 1978K in NGC 1313

NASA Astrophysics Data System (ADS)

Schlegel, Eric M.; Petre, R.; Colbert, E. J. M.

1996-01-01

We present the 0.5-2.0 keV light curve of the X-ray luminous supernova SN 1978K in NGC 1313, based on six ROSAT observations spanning 1990 July to t994 July. SN 1978K is one of a few supernovae or supernova remnants that are very luminous (˜1039-1040 ergs s-1) in the X-ray, optical, and radio bands, and the first, at a supernova age of 10-20 yr, for which sufficient data exist to create an X-ray light curve. The X-ray flux is approximately constant over the 4 yr sampled by our observations, which were obtained 12-16 yr after the initial explosion. Three models exist to explain the large X-ray luminosity: pulsar input, a reverse shock running back into the expanding debris of the supernova, and the outgoing shock crushing of cloudlets in the debris field. Based upon calculations of Chevalier & Fransson, a pulsar cannot provide sufficient energy to produce the soft X-ray luminosity. Based upon the models and the light curve to date, it is not possible to discern the evolutionary phase of the supernova.

Systematic study of magnetar outbursts

NASA Astrophysics Data System (ADS)

Coti Zelati, F.; Rea, N.; Pons, J. A.; Campana, S.; Esposito, P.

2017-12-01

We present the results of the systematic study of all magnetar outbursts observed to date through a reanalysis of data acquired in about 1100 X-ray observations. We track the temporal evolution of the luminosity for all these events, model empirically their decays, and estimate the characteristic decay time-scales and the energy involved. We study the link between different parameters (maximum luminosity increase, outburst peak luminosities, quiescent X-ray and bolometric luminosities, energetics, decay time-scales, magnetic field, spin-down luminosity and age), and reveal several correlations between different quantities. We discuss our results in the framework of the models proposed to explain the triggering mechanism and evolution of magnetar outbursts. The study is complemented by the Magnetar Outburst Online Catalog (http://www.magnetars.ice.csic.es), an interactive database where the user can plot any combination of the parameters derived in this work and download all reduced data.

A Correlation Between the Intrinsic Brightness and Average Decay Rate of Gamma-Ray Burst X-Ray Afterglow Light Curves

NASA Technical Reports Server (NTRS)

Racusin, J. L.; Oates, S. R.; De Pasquale, M.; Kocevski, D.

2016-01-01

We present a correlation between the average temporal decay (alpha X,avg, greater than 200 s) and early-time luminosity (LX,200 s) of X-ray afterglows of gamma-ray bursts as observed by the Swift X-ray Telescope. Both quantities are measured relative to a rest-frame time of 200 s after the gamma-ray trigger. The luminosity â€" average decay correlation does not depend on specific temporal behavior and contains one scale-independent quantity minimizing the role of selection effects. This is a complementary correlation to that discovered by Oates et al. in the optical light curves observed by the Swift Ultraviolet Optical Telescope. The correlation indicates that, on average, more luminous X-ray afterglows decay faster than less luminous ones, indicating some relative mechanism for energy dissipation. The X-ray and optical correlations are entirely consistent once corrections are applied and contamination is removed. We explore the possible biases introduced by different light-curve morphologies and observational selection effects, and how either geometrical effects or intrinsic properties of the central engine and jet could explain the observed correlation.

A Large X-Ray Outburst in Mira A

NASA Astrophysics Data System (ADS)

Karovska, Margarita; Schlegel, Eric; Hack, Warren; Raymond, John C.; Wood, Brian E.

2005-04-01

We report the Chandra ACIS-S detection of a bright soft X-ray transient in the Mira AB interacting symbiotic-like binary. We have resolved the system for the first time in X-rays. Using Chandra and Hubble Space Telescope images, we determine that the unprecedented outburst is likely associated with the cool asymptotic giant branch (AGB) star, Mira A, the prototype of the Mira class of variables. X-rays have never before been detected from an AGB star, and the recent activity signals that the system is undergoing dramatic changes. The total X-ray luminosity of the system is several times higher than the luminosity estimated using previous XMM-Newton and ROSAT observations. The outburst may be caused by a giant flare in Mira A associated with a mass ejection or a jet and may have long-term consequences on the system. We dedicate this paper to the memory of Janet A. Mattei, who inspired this work and made these observations possible for many years.

Predictions of a population of cataclysmic variables in globular clusters

NASA Technical Reports Server (NTRS)

Di Stefano, R.; Rappaport, S.

1994-01-01

We have studied the number of cataclysmic variables (CVs) that should be active in globular clusters during the present epoch as a result of binary formation via two-body tidal capture. We predict the orbital period and luminosity distributions of CVs in globular clusters. The results arebased on Monte Carlo simulations combined with evolution calculations appropriate to each system formed during the lifetime of two specific globular clusters, omega Cen and 47 Tuc. From our study of these two clusters, which represent the range of core densities and states of mass segregation that are likely to be interesting, we extrapolate our results to the Galactic globlular cluster system. Although there is at present little direct observational evidence of CVs in globular clusters, we find that there should be a large number of active systems. We predict that there should be more than approximately 100 CVs in both 47 Tuc and omega Cen and several thousand in the Galactic globular cluster system. These numbers are based on two-body processes alone and represent a lower bound on the number of systems that may have been formed as a result of stellar interaction within globular clusters. The relation between these calculations and the paucity of optically detected CVs in globular clusters is discussed. Should future observations fail to find convincing evidence of a substantial population of cluster CVs, then the two-body tidal capture scenario is likely to be seriously constrained. Of the CVs we espect in 47 Tuc and omega Cen, approximately 45 and 20, respectively, should have accretion luminosities above 10(exp 33) ergs/s. If one utilizes a relation for converting accretion luminosity to hard X-ray luminosity that is based on observations of Galactic plane CVs, even these sources will not exhibit X-ray luminosities above 10(exp 33) ergs/s. While we cannot account directly for the most luminous subset of the low-luminosity globular cluster X-ray sources without assuming an evolutionary pattern that is different from that of the majority of CVs in the disk, we are able to account for all of the observed lower luminosity subset of these sources, many of which have been recently discovered through ROSAT observations. In order for our predicted integrated cluster X-ray luminosities to be consistent with observational upper limits, the relation between accretion and X-ray luminosities should be something like that inferred from the Galactic plane population of CVs. Our calculations predict a large number of systems with L(sub acc) is less than 10(exp 32) ergs/s. Although our calculations imply that globular clusters should have an enhancement of CVs relative to the number thought to be present in the Galactic disk, this enhancement is at most roughly an order of magnitude, not comparable to the factor of approximately 100 for low-mass X-ray binaries (LMXBs).

A study of excess H-alpha emission in chromospherically active M dwarf

NASA Technical Reports Server (NTRS)

Young, Arthur; Skumanich, Andrew; Stauffer, John R.; Harlan, Eugene; Bopp, Bernard W.

1989-01-01

Spectroscopic observations from three observatories are combined to study the properties of the excess H-alpha emission which characterizes the most chromospherically active subset of the M dwarf stars, known as the dMe stars. It is demonstrated that the excess H-alpha luminosity from these stars is a monotonically decreasing function of their (R-I) color, and evidence is presented which suggests that the product of the mean surface brightness and the mean filling factor of the emissive regions is essentially constant with color. Another significant result of the study is a linear correlation between the excess luminosity in H-alpha and the coronal X-ray luminosity.

The KONA Survey: A Near-IR Perspective of the Circumnuclear Environment of local Seyfert Galaxies

NASA Astrophysics Data System (ADS)

Hicks, Erin K. S.; Mueller Sanchez, Francisco; Malkan, Matthew Arnold

2018-06-01

With the Keck OSIRIS Nearby AGN, KONA, survey we simultaneously probe the stellar, molecular gas, and ionized gas kinematics within the central 400 pc of a sample of 40 local representative AGN. KONA's spatially resolved spectra enable an unprecedented study of the feeding and feedback processes in bona- fide AGN. We present a study the nuclear K-band properties of these local Seyferts, as well as the integrated molecular hydrogen and stellar distribution and kinematic at radii varying from 25 to 200 pc. We find that the luminosities of the unresolved Seyfert 1 sources at 2.1 microns are correlated with the hard X-ray luminosities over 3 orders of magnitude in both K-band and X-ray luminosities, implying that the majority of the emission is non-stellar. No correlation is found between the 2.1 microns luminosity and hard X-ray luminosity for the Seyfert 2 galaxies. The spatial extent and spectral slope of the Seyfert 2 galaxies indicates the presence of nuclear star formation and attenuating material (gas and dust), which is found to be compact in some galaxies and in others extended. A comparison of the circumnuclear stellar and molecular hydrogen properties (flux distribution, surface brightness, and velocity dispersion) in Seyfert 1 and 2 sources will also be presented.

The black hole candidate XTE J1752-223 towards and in quiescence: optical and simultaneous X-ray-radio observations

NASA Astrophysics Data System (ADS)

Ratti, E. M.; Jonker, P. G.; Miller-Jones, J. C. A.; Torres, M. A. P.; Homan, J.; Markoff, S.; Tomsick, J. A.; Kaaret, P.; Wijnands, R.; Gallo, E.; Özel, F.; Steeghs, D. T. H.; Fender, R. P.

2012-07-01

We present optical, X-ray and radio observations of the black hole transient (BHT) XTE J1752-223 towards and in quiescence. Optical photometry shows that the quiescent magnitude of XTE J1752-223 is fainter than 24.4 mag in the i' band. A comparison with measurements of the source during its 2009-2010 outburst shows that the outburst amplitude is more than 8 mag in the i' band. Known X-ray properties of the source combined with the faintness of the quiescence optical counterpart and the large outburst optical amplitude point towards a short orbital-period system (Porb≲ 6.8 h) with an M type (or later) mass donor, at a distance of 3.5 ≲d≲ 8 kpc. Simultaneous X-ray and radio data were collected with Chandra and the Expanded Very Large Array (EVLA), allowing constraints to be placed on the quiescent X-ray and radio flux of XTE J1752-223. Furthermore, using data covering the final stage of the outburst decay, we investigated the low-luminosity end of the X-ray-radio correlation for this source and compared it with other BHTs. We found that XTE J1752-223 adds to the number of outliers with respect to the 'standard' X-ray-radio luminosity relation. Furthermore, XTE J1752-223 is the second source, after the BHT H1743-322, that shows a transition from the region of the outliers towards the 'standard' correlation at low luminosity. Finally, we report on a faint, variable X-ray source we discovered with Chandra at an angular distance of ˜2.9 arcsec to XTE J1752-223 and at a position angle consistent with that of the radio jets previously observed from the BHT. We discuss the possibility that we detected X-ray emission associated with a jet from XTE J1752-223.

X-Ray Temperatures, Luminosities, and Masses from XMM-Newton Follow-upof the First Shear-selected Galaxy Cluster Sample

NASA Astrophysics Data System (ADS)

Deshpande, Amruta J.; Hughes, John P.; Wittman, David

2017-04-01

We continue the study of the first sample of shear-selected clusters from the initial 8.6 square degrees of the Deep Lens Survey (DLS); a sample with well-defined selection criteria corresponding to the highest ranked shear peaks in the survey area. We aim to characterize the weak lensing selection by examining the sample’s X-ray properties. There are multiple X-ray clusters associated with nearly all the shear peaks: 14 X-ray clusters corresponding to seven DLS shear peaks. An additional three X-ray clusters cannot be definitively associated with shear peaks, mainly due to large positional offsets between the X-ray centroid and the shear peak. Here we report on the XMM-Newton properties of the 17 X-ray clusters. The X-ray clusters display a wide range of luminosities and temperatures; the L X -T X relation we determine for the shear-associated X-ray clusters is consistent with X-ray cluster samples selected without regard to dynamical state, while it is inconsistent with self-similarity. For a subset of the sample, we measure X-ray masses using temperature as a proxy, and compare to weak lensing masses determined by the DLS team. The resulting mass comparison is consistent with equality. The X-ray and weak lensing masses show considerable intrinsic scatter (˜48%), which is consistent with X-ray selected samples when their X-ray and weak lensing masses are independently determined. Some of the data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.

Characterising large-scale structure with the REFLEX II cluster survey

NASA Astrophysics Data System (ADS)

Chon, Gayoung

2016-10-01

We study the large-scale structure with superclusters from the REFLEX X-ray cluster survey together with cosmological N-body simulations. It is important to construct superclusters with criteria such that they are homogeneous in their properties. We lay out our theoretical concept considering future evolution of superclusters in their definition, and show that the X-ray luminosity and halo mass functions of clusters in superclusters are found to be top-heavy, different from those of clusters in the field. We also show a promising aspect of using superclusters to study the local cluster bias and mass scaling relation with simulations.

A HARD X-RAY POWER-LAW SPECTRAL CUTOFF IN CENTAURUS X-4

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chakrabarty, Deepto; Nowak, Michael A.; Tomsick, John A.

2014-12-20

The low-mass X-ray binary (LMXB) Cen X-4 is the brightest and closest (<1.2 kpc) quiescent neutron star transient. Previous 0.5-10 keV X-ray observations of Cen X-4 in quiescence identified two spectral components: soft thermal emission from the neutron star atmosphere and a hard power-law tail of unknown origin. We report here on a simultaneous observation of Cen X-4 with NuSTAR (3-79 keV) and XMM-Newton (0.3-10 keV) in 2013 January, providing the first sensitive hard X-ray spectrum of a quiescent neutron star transient. The 0.3-79 keV luminosity was 1.1×10{sup 33} D{sub kpc}{sup 2} erg s{sup –1}, with ≅60% in the thermalmore » component. We clearly detect a cutoff of the hard spectral tail above 10 keV, the first time such a feature has been detected in this source class. We show that thermal Comptonization and synchrotron shock origins for the hard X-ray emission are ruled out on physical grounds. However, the hard X-ray spectrum is well fit by a thermal bremsstrahlung model with kT{sub e} = 18 keV, which can be understood as arising either in a hot layer above the neutron star atmosphere or in a radiatively inefficient accretion flow. The power-law cutoff energy may be set by the degree of Compton cooling of the bremsstrahlung electrons by thermal seed photons from the neutron star surface. Lower thermal luminosities should lead to higher (possibly undetectable) cutoff energies. We compare Cen X-4's behavior with PSR J1023+0038, IGR J18245–2452, and XSS J12270–4859, which have shown transitions between LMXB and radio pulsar modes at a similar X-ray luminosity.« less

The X-Ray Luminosity-Mass Relation for Local Clusters of Galaxies

NASA Astrophysics Data System (ADS)

Stanek, R.; Evrard, A. E.; Böhringer, H.; Schuecker, P.; Nord, B.

2006-09-01

We investigate the relationship between soft X-ray luminosity and mass for low-redshift clusters of galaxies by comparing observed number counts and scaling laws to halo-based expectations of ΛCDM cosmologies. We model the conditional likelihood of halo luminosity as a lognormal distribution of fixed width, centered on a scaling relation, L~Mpρsc(z), and consider two values for s, appropriate for self-similar evolution or no evolution. Convolving with the halo mass function, we compute expected counts in redshift and flux that, after appropriate survey effects are included, we compare to REFLEX survey data. Counts alone provide only an upper limit on the scatter in mass at fixed luminosity, σlnM<0.4. We argue that the observed, intrinsic variance in the temperature-luminosity relation is directly indicative of mass-luminosity variance and derive σlnM=0.43+/-0.06 from HIFLUGCS data. When added to the likelihood analysis, we derive values p=1.59+/-0.05, lnL15,0=1.34+/-0.09, and σlnM=0.37+/-0.05 for self-similar redshift evolution in a concordance (Ωm=0.3, ΩΛ=0.7, σ8=0.9) universe. The present-epoch intercept is sensitive to power spectrum normalization, L15,0~σ-48, and the slope is weakly sensitive to the matter density, p~Ω1/2m. We find a substantially (factor 2) dimmer intercept and slightly steeper slope than the values published using hydrostatic mass estimates of the HIFLUGCS sample and show that a Malmquist bias of the X-ray flux-limited sample accounts for this effect. In light of new WMAP constraints, we discuss the interplay between parameters and sources of systematic error and offer a compromise model with Ωm=0.24, σ8=0.85, and somewhat lower scatter σlnM=0.25, in which hydrostatic mass estimates remain accurate to ~15%. We stress the need for independent calibration of the L-M relation via weak gravitational lensing.

An Unlikely Radio Halo in the Low X-Ray Luminosity Galaxy Cluster RXCJ1514.9-1523

NASA Technical Reports Server (NTRS)

Marketvitch, M.; ZuHone, J. A.; Lee, D.; Giacintucci, S.; Dallacasa, D.; Venturi, T.; Brunetti, G.; Cassano, R.; Markevitch, M.; Athreya, R. M.

2011-01-01

Aims: We report the discovery of a giant radio halo in the galaxy cluster RXCJ1514,9-1523 at z=0.22 with a relatively low X-ray luminosity, L(sub X) (0.1-2.4kev) approx. 7 x 10(exp 44) ergs/s. Methods: This faint, diffuse radio source is detected with the Giant Meterwave Radio Telescope at 327 MHz. The source is barely detected at 1.4 GHz in a NVSS pointing that we have reanalyzed. Results: The integrated radio spectrum of the halo is quite steep, with a slope alpha = 1.6 between 327 MHz and 1.4 GHz. While giant radio halos are common in more X-ray luminous cluster mergers, there is a less than 10% probability to detect a halo in systems with L(sub X) < 8 x 10(exp 44) ergs/s. The detection of a new giant halo in this borderline luminosity regime can be particularly useful for discriminating between the competing theories for the origin of ultrarelativistic electrons in clusters. Furthermore, if our steep radio spectral index is confirmed by future deeper radio observations, this cluster would provide another example of the very rare, new class of ultra-steep spectrum radio halos, predicted by the model in which the cluster cosmic ray electrons are produced by turbulent reacceleration.

Probing high-redshift clusters with HST/ACS gravitational weak-lensing and Chandra x-ray observations

NASA Astrophysics Data System (ADS)

Jee, Myungkook James

2006-06-01

Clusters of galaxies, the largest gravitationally bound objects in the Universe, are useful tracers of cosmic evolution, and particularly detailed studies of still-forming clusters at high-redshifts can considerably enhance our understanding of the structure formation. We use two powerful methods that have become recently available for the study of these distant clusters: spaced- based gravitational weak-lensing and high-resolution X-ray observations. Detailed analyses of five high-redshift (0.8 < z < 1.3) clusters are presented based on the deep Advanced Camera for Surveys (ACS) and Chandra X-ray images. We show that, when the instrumental characteristics are properly understood, the newly installed ACS on the Hubble Space Telescope (HST) can detect subtle shape distortions of background galaxies down to the limiting magnitudes of the observations, which enables the mapping of the cluster dark matter in unprecedented high-resolution. The cluster masses derived from this HST /ACS weak-lensing study have been compared with those from the re-analyses of the archival Chandra X-ray data. We find that there are interesting offsets between the cluster galaxy, intracluster medium (ICM), and dark matter centroids, and possible scenarios are discussed. If the offset is confirmed to be uniquitous in other clusters, the explanation may necessitate major refinements in our current understanding of the nature of dark matter, as well as the cluster galaxy dynamics. CL0848+4452, the highest-redshift ( z = 1.27) cluster yet detected in weak-lensing, has a significant discrepancy between the weak- lensing and X-ray masses. If this trend is found to be severe and common also for other X-ray weak clusters at redshifts beyond the unity, the conventional X-ray determination of cluster mass functions, often inferred from their immediate X-ray properties such as the X-ray luminosity and temperature via the so-called mass-luminosity (M-L) and mass-temperature (M-T) relations, will become highly unstable in this redshift regime. Therefore, the relatively unbiased weak-lensing measurements of the cluster mass properties can be used to adequately calibrate the scaling relations in future high-redshift cluster investigations.

A Search for Millisecond-pulsar Radio Emission from the Faint Quiescent Soft X-Ray Transient 1H 1905+000

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mikhailov, K.; Van Leeuwen, J.; Jonker, P. G., E-mail: K.Mikhailov@uva.nl

Transitional millisecond pulsars (tMSPs) switch between an accretion-powered state without radio pulsations and a rotation-powered state with radio pulsations. In the former state, tMSPs are X-ray bright, while in the latter state, they are X-ray dim. Soft X-ray transients (SXTs) undergo similar switches in X-ray, between “high” states with bright X-ray outbursts and “low” states of quiescence. The upper limit on the quiescent X-ray luminosity of SXT 1H 1905+000 suggests that its luminosity might be similar to that of the known tMSPs. A detection of radio pulsations would link SXTs more strongly with tMSPs; and thus, e.g., put stricter constraintsmore » on tMSP transitional timescales through the connection with the well-known SXT periods of quiescence. A nondetection allows us, based on the telescope sensitivity, to estimate how likely these sources are to pulsate in radio. Over a 10-year span, 2006–2015, we carried out targeted radio observations at 400/800 MHz with Arecibo, and searched for radio pulsations from the quiescent SXT 1H 1905+000. None of the observations have revealed radio pulsations from the targeted SXT. For a 1 ms pulsar, our flux density upper limit is 10.3 μ Jy. At an assumed distance of 10 kpc this translates to a pseudo-luminosity upper limit of 1.0 mJy kpc{sup 2}, which makes our search complete to ∼85% of the known MSP population. Given the high sensitivity, and the generally large beaming fraction of millisecond pulsars, we conclude that SXT 1H 1905+000 is unlikely to emit in radio as a tMSP.« less

An X-Ray/SDSS Sample: Observational Characterization of The Outflowing Gas

NASA Astrophysics Data System (ADS)

Perna, Michele; Brusa, M.; Lanzuisi, G.; Mignoli, M.

2016-10-01

Powerful ionised AGN-driven outflows, commonly detected both locally and at high redshift, are invoked to contribute to the co-evolution of SMBH and galaxies through feedback phenomena. Our recent works (Brusa+2015; 2016; Perna+2015a,b) have shown that the XMM-COSMOS targets with evidence of outflows collected so far ( 10 sources) appear to be associated with low X-ray kbol corrections (Lbol /LX ˜ 18), in spite of their spread in obscuration, in the locations on the SFR-Mstar diagram, in their radio emission. A higher statistical significance is required to validate a connection between outflow phenomena and a X-ray loudness. Moreover, in order to validate their binding nature to the galaxy fate, it is crucial to correctly determine the outflow energetics. This requires time consuming integral field spectroscopic (IFS) observations, which are, at present, mostly limited to high luminosity objectsThe study of SDSS data offers a complementary strategy to IFS efforts. I will present physical and demographic characterization of the AGN-galaxy system during the feedback phase obtained studying a sample of 500 X-ray/SDSS AGNs, at z<0.8. Outflow velocity inferred from [OIII]5007 emission line profile has been related to optical (e.g., [OIII] and bolometric luminosities, Eddington ratio, stellar velocity dispersion) and X-ray properties (intrinsic X-ray luminosity, obscuration and X-ray kbol correction), to determine what drives ionised winds. Several diagnostic line ratios have been used to infer the physical properties of the ionised outflowing gas. The knowledge of these properties can reduce the actual uncertainties in the outflow energetics by a factor of ten, pointing to improve our understanding of the AGN outflow phenomenon and its impact on galaxy evolution.

Storm in a Teacup: X-Ray View of an Obscured Quasar and Superbubble

NASA Astrophysics Data System (ADS)

Lansbury, George B.; Jarvis, Miranda E.; Harrison, Chris M.; Alexander, David M.; Del Moro, Agnese; Edge, Alastair C.; Mullaney, James R.; Thomson, Alasdair P.

2018-03-01

We present the X-ray properties of the “Teacup AGN” (SDSS J1430+1339), a z = 0.085 type 2 quasar that is interacting dramatically with its host galaxy. Spectral modeling of the central quasar reveals a powerful, highly obscured active galactic nucleus (AGN) with a column density of N H = (4.2–6.5) × 1023 cm‑2 and an intrinsic luminosity of L 2–10 keV = (0.8–1.4) × 1044 erg s‑1. The current high bolometric luminosity inferred (L bol ≈1045–1046 erg s‑1) has ramifications for previous interpretations of the Teacup as a fading/dying quasar. High-resolution Chandra imaging data reveal a ≈10 kpc loop of X-ray emission, cospatial with the “eastern bubble” previously identified in luminous radio and ionized gas (e.g., [O III] line) emission. The X-ray emission from this structure is in good agreement with a shocked thermal gas, with T = (4–8) × 106 K, and there is evidence for an additional hot component with T ≳ 3 × 107 K. Although the Teacup is a radiatively dominated AGN, the estimated ratio between the bubble power and the X-ray luminosity is in remarkable agreement with observations of ellipticals, groups, and clusters of galaxies undergoing AGN feedback.

Stellar wind measurements for Colliding Wind Binaries using X-ray observations

NASA Astrophysics Data System (ADS)

Sugawara, Yasuharu; Maeda, Yoshitomo; Tsuboi, Yohko

2017-11-01

We report the results of the stellar wind measurement for two colliding wind binaries. The X-ray spectrum is the best measurement tool for the hot postshock gas. By monitoring the changing of the the X-ray luminosity and column density along with the orbital phases, we derive the mass-loss rates of these stars.

Discovery of the correlation between peak episodic jet power and X-ray peak luminosity of the soft state in black hole transients

NASA Astrophysics Data System (ADS)

Zhang, H.; Yu, W.

2015-08-01

Episodic jets are usually observed in the intermediate state of black hole transients during their X-ray outbursts. Here we report the discovery of a strong positive correlation between the peak radio power of the episodic jet Pjet and the corresponding peak X-ray luminosity Lx of the soft state (in Eddington units) in a complete sample of the outbursts of black hole transients observed during the RXTE era of which data are available, which follows the relation log Pjet = (2.2 ± 0.3) + (1.6 ± 0.2) × log Lx. The transient ultraluminous X-ray source in M31 and HLX-1 in EXO 243-49 fall on the relation if they contain stellar-mass black hole and either stellar-mass black hole or intermediate-mass black hole, respectively. Besides, a significant correlation between the peak power of the episodic jet and the rate of increase of the X-ray luminosity dLx/dt during the rising phase of those outbursts is also found, following log Pjet = (2.0 ± 0.4) + (0.7 ± 0.2) × log dLx/dt. In GX 339-4 and H 1743-322 in which data for two outbursts are available, measurements of the peak radio power of the episodic jet and the X-ray peak luminosity (and its rate of change) shows similar positive correlations between outbursts, which demonstrate the dominant role of accretion over black hole spin in generating episodic jet power. On the other hand, no significant difference is seen among the systems with different measured black hole spin in current sample. This implies that the power of the episodic jet is strongly affected by non-stationary accretion instead of black hole spin characterized primarily by the rate of change of the mass accretion rate.

The Einstein database of IPC x-ray observations of optically selected and radio-selected quasars, 1.

NASA Technical Reports Server (NTRS)

Wilkes, Belinda J.; Tananbaum, Harvey; Worrall, D. M.; Avni, Yoram; Oey, M. S.; Flanagan, Joan

1994-01-01

We present the first volume of the Einstein quasar database. The database includes estimates of the X-ray count rates, fluxes, and luminosities for 514 quasars and Seyfert 1 galaxies observed with the Imaging Proportional Counter (IPC) aboard the Einstein Observatory. All were previously known optically selected or radio-selected objects, and most were the targets of the X-ray observations. The X-ray properties of the Active Galactic Nuclei (AGNs) have been derived by reanalyzing the IPC data in a systematic manner to provide a uniform database for general use by the astronomical community. We use the database to extend earlier quasar luminosity studies which were made using only a subset of the currently available data. The database can be accessed on internet via the SAO Einstein on-line system ('Einline') and is available in ASCII format on magnetic tape and DOS diskette.

Einstein observations of EF Eridani (2A 0311-227) - The textbook example of AM Herculis-type systems

NASA Technical Reports Server (NTRS)

Beuermann, K.; Stella, L.; Patterson, J.

1987-01-01

Hard and soft X-ray spectra of the AM Herculis star EF Eridani obtained with the Einstein Observatory are found to be fitted by a thermal bremsstrahlung spectrum with kT of about 20 keV, and a blackbody spectrum with kT of between 16 and about 33 eV, respectively. EF Eri is shown to behave almost exactly as predicted by simple theory, with its soft X-ray luminosity not exceeding the hard X-ray luminosity by more than a factor of three, and both spectra originating from the same active pole of the accreting white dwarf. The data are consistent with a model involving an accretion stream penetrating deep into the magnetosphere of the white dwarf, such that accretion occurs along nonpolar field lines, and an 'X-ray auroral oval' emission is formed on the surface of the white dwarf.

Obscured Black Hole Growth at High Redshift and High Luminosity

NASA Astrophysics Data System (ADS)

Urry, C. Megan

We propose to complete the census of cosmic black hole growth by measuring luminous and/or distant quasars using Spitzer, Herschel, Chandra and XMM-Newton imaging in Stripe 82 the deepest Sloan Digital Sky Survey field, and now the premier legacy field among 100 deg2 survey areas. These extensive ancillary data offer unsurpassed sensitivity to accreting supermassive black holes in luminous quasars out to z 6, including obscured objects missed by optical/UV surveys. We address six science goals centered on the growth of supermassive black holes: 1) We will constrain the mass accreted in luminous quasars by determining the evolving luminosity function of high-luminosity X-ray-selected AGN, including obscured quasars, especially at high redshift, where previous surveys have limited statistics. 2) We will build a comprehensive multi-wavelength population synthesis model that describes cosmic black hole accretion across most of the history of the Universe, constrained by the wealth of data now available. This will be the first population synthesis model that is constrained at high luminosity and high redshift (courtesy of Stripe 82X). 3) We will characterize the spectral energy distributions (SEDs) of luminous X-ray selected quasars, including obscured ones. We will assess the dust content in the host galaxies and diagnose the relative contributions of black hole fueling and star formation, using Herschel data to probe the cold molecular gas from which stars form and comparing X-rays from accretion onto the central black hole. We will also use high-quality optical imaging to disentangle nuclear from host galaxy emission in a representative sub-sample of quasars. 4) Using Spitzer, Herschel, Chandra, XMM-Newton, and optical data, we will identify candidates for the most heavily obscured black holes, which we will follow up with ground-based IR spectroscopy using Keck and Palomar (to which Yale has guaranteed access). In this way we will recover obscured AGN missed by optical surveys, mitigating optical biases in quasar demography. 5) We will investigate the large-scale environments of quasars, in which black holes appear to acquire at least half of their mass, by studying the clustering of AGN in Stripe 82. Specifically, we will measure the halo occupation distribution, which is the probability of a dark matter halo of a given mass to host central and satellite AGN above a given luminosity. We will assess whether rapid black hole growth depends on halo mass, and how the average halo mass in which AGN occur might depend on AGN or galaxy properties. For this analysis, the hundreds of luminous quasars at z>2 in Stripe 82X and its high redshift completeness (92%) are particularly important. 6) We will investigate early black hole growth at z>6 by analyzing fluctuations in the infrared and X-ray backgrounds (i.e., below source detection levels). Specifically, we will directly correlate the Spitzer-measured cosmic infrared background (CIB) and the cosmic X-ray background (CXB) measured with XMM-Newton, on roughly 20 times larger scales than previous studies. This offers the best probe of early BH growth until high-sensitivity X-ray observatories like Athena and Lynx. These studies will determine how much mass is accreted in the most luminous and/or obscured quasars, and how the energy released into galaxies depends on key variables such as redshift, AGN luminosity, Eddington ratio and wavelength. This accurate, data validated estimate of the radiation deposited into host galaxies is essential for incorporating feedback into models of galaxy evolution. The Stripe 82X survey, as the richest multiwavelength survey covering >30 deg2 of the sky, deep enough in X-rays to see luminous quasars out to z 10, will yield many important discoveries, ideally including unexpected ones found by others in the community.

SPECTRAL PROPERTIES OF X-RAY BINARIES IN CENTAURUS A

DOE Office of Scientific and Technical Information (OSTI.GOV)

Burke, Mark J.; Raychaudhury, Somak; Kraft, Ralph P.

2013-04-01

We present a spectral investigation of X-ray binaries (XBs) in NGC 5128 (Cen A), using six 100 ks Chandra observations taken over two months in 2007. We divide our sample into thermally and non-thermally dominated states based on the behavior of the fitted absorption column N{sub H}, and present the spectral parameters of sources with L{sub x} {approx}> 2 Multiplication-Sign 10{sup 37} erg s{sup -1}. The majority of sources are consistent with being neutron star low-mass X-ray binaries (NS LMXBs) and we identify three transient black hole (BH) LMXB candidates coincident with the dust lane, which is the remnant ofmore » a small late-type galaxy. Our results also provide tentative support for the apparent 'gap' in the mass distribution of compact objects between {approx}2-5 M{sub Sun }. We propose that BH LMXBs are preferentially found in the dust lane, and suggest this is because of the younger stellar population. The majority ({approx}70%-80%) of potential Roche lobe filling donors in the Cen A halo are {approx}> 12 Gyr old, while BH LMXBs require donors {approx}> 1 M{sub Sun} to produce the observed peak luminosities. This requirement for more massive donors may also explain recent results that claim a steepening of the X-ray luminosity function with age at L{sub x} {>=} 5 Multiplication-Sign 10{sup 38} erg s{sup -1} for the XB population of early-type galaxies; for older stellar populations, there are fewer stars {approx}> 1 M{sub Sun }, which are required to form the more luminous sources.« less

ROSAT observations of NGC 2146: Evidence for a starburst-driven superwind

NASA Technical Reports Server (NTRS)

Armus, L.; Heckman, T. M.; Weaver, K. A.; Lehnert, M. D.

1995-01-01

We have imaged the edge-on starburst galaxy NGC 2146 with the Position Sensitive Proportional Counter (PSPC) and the High Resolution Imager (HRI) on board ROSAT and have compared these data to optical images and long-slit spectra. NGC 2146 possesses a very large X-ray nebula with a half-light radius of 1 min (4 kpc) and a maximum diameter of approximately 4 min, or 17 kpc. The X-ray emission is resolved by the PSPC and preferentially oriented along the minor axis, with a total flux of 1.1 x 10(exp -12) ergs/sq cm/s over 0.2 - 2.4 keV and a luminosity of approximately 3 x 10(exp 40) ergs/s. The inner X-ray nebula is resolved by the HRI into at least four bright knots together with strong diffuse emission responsible for at least 50% of the flux within a radius of 0.5 min (approximately 2 kpc). The brightest knot has a luminosity of (2 - 3) x 10(exp 39) ergs/s. The X-ray nebula has a spatial extent much larger than the starburst ridge seen at centimeter wavelengths by Kronberg & Biermann (1981) and is oriented in a `X-like' pattern along the galaxy minor axis at a position angle of approximately 30 degrees. This minor-axis X-ray emission is associated with a region of H alpha and dust filaments seen in optical images. Optical spectra show that the emission-line gas along the minor axis is characterized by relatively broad lines (approximately 250 km/s full width half-maximum (FWHM)) and by `shocklike' emission-line flux ratios. Together with the blue-asymmetric nuclear emission-line and NaD interstellar absorption-line profiles, these optical data strongly suggest the presence of a starburst-driven superwind. The X-ray spectrum extracted from the central 5 min contains a strong Fe L emission-line complex at 0.6 - 1.0 keV and a hard excess above 1.0 keV. The spectrum is best described with a two-component model, containing a soft (kT approximately 400 - 500 eV) Raymond-Smith thermal plasma together with either a Gamma = 1.7 power-law or a kT greater than 2.2 keV bremsstrahlung component. The soft thermal component provides approximately 30% of the total luminosity over 0.2 - 2.4 keV, or approximately 10(exp 40) ergs/s. The pressure derived from the soft component of the X-ray spectrum is consistent with that predicted from a starburst-driven superwind if the filling factor of the warm gas is approximately 1% - 10 %. If the hard X-ray component is thermal gas associated with the galactic outflow, the filling factor must be close to unity. Predictions of the luminosity, temperature, and size of an adiabatic starburst-generated windblown bubble are consistent with those measured for the soft thermal X-ray emission in NGC 2146. The hard X-ray component, however, has a luminosity much larger than predicted by the superwind model if this component is thermal emission from gas heated by an internal shock in the expanding bubble. We briefly review various possibilities as to the nature of the hard X-ray component in NGC 2146.

THE GEOMETRY OF THE INFRARED AND X-RAY OBSCURER IN A DUSTY HYPERLUMINOUS QUASAR

DOE Office of Scientific and Technical Information (OSTI.GOV)

Farrah, Duncan; Harris, Kathryn; Baloković, Mislav

2016-11-01

We study the geometry of the active galactic nucleus (AGN) obscurer in IRAS 09104+4109, an IR-luminous, radio-intermediate FR-I source at z = 0.442, using infrared data from Spitzer and Herschel , X-ray data from NuSTAR , Swift , Suzaku , and Chandra , and an optical spectrum from Palomar. The infrared data imply a total rest-frame 1–1000 μ m luminosity of 5.5 × 10{sup 46} erg s{sup −1} and require both an AGN torus and a starburst model. The AGN torus has an anisotropy-corrected IR luminosity of 4.9 × 10{sup 46} erg s{sup −1} and a viewing angle and half-openingmore » angle both of approximately 36° from pole-on. The starburst has a star formation rate of (110 ± 34) M {sub ⊙} yr{sup −1} and an age of <50 Myr. These results are consistent with two epochs of luminous activity in IRAS 09104+4109: one approximately 150 Myr ago, and one ongoing. The X-ray data suggest a photon index of Γ ≃ 1.8 and a line-of-sight column density of N {sub H} ≃ 5 × 10{sup 23} cm{sup −2}. This argues against a reflection-dominated hard X-ray spectrum, which would have implied a much higher N {sub H} and luminosity. The X-ray and infrared data are consistent with a bolometric AGN luminosity of L {sub bol} ∼ (0.5–2.5) × 10{sup 47} erg s{sup −1}. The X-ray and infrared data are further consistent with coaligned AGN obscurers in which the line of sight “skims” the torus. This is also consistent with the optical spectra, which show both coronal iron lines and broad lines in polarized but not direct light. Combining constraints from the X-ray, optical, and infrared data suggest that the AGN obscurer is within a vertical height of 20 pc, and a radius of 125 pc, of the nucleus.« less

Discovery of a 105-ms X-ray Pulsar in Kesteven-79: On the Nature of Compact Central Objects in Supernova Remnants

NASA Technical Reports Server (NTRS)

Gotthelf, E. V.; Halpern, J. P.; Seward, F. D.

2005-01-01

We report the discovery of 105-ms X-ray pulsations from the compact central object (CCO) in the supernova remnant \\snr\\ using data acquired with the {\\it Newton X-Ray Multi-Mirror Mission). Using two observations of the pulsar taken 6-days apart we derive an upper limit on its spin-down rate of $\\dot P < 9 \\times 10"{-14}$-s-${-l)$,a nd find no evidence for binary orbital motion. The implied energy loss rate is $\\dot E < 3 \\times 10A{36)$-ergs-s$A{-1)$, polar magnetic field strength is $B-{\\rm p) < 3 \\times 10A{12)$-G, and spin-down age is $\\tau > 18.5$-kyr. The latter exceeds the remnant's estimated age, suggesting that the pulsar was born spinning near its current period. The X-ray spectrum of \\psr\\ is best characterized as a blackbody of temperature $kT {BB) =, 0.43\\pm0.02$ keV, radius $R-{BB) \\approx 1.3$-km, and $I{\\rm bol) = 5.2 \\times 10A{33)$ ergs-sSA{-1)$ at $d = 7.1$-kpc. The sinusoidal light curve is modulated with a pulsed fraction of $>45\\%$, suggestive of a small hot spot on the surface of the rotating neutron star. The lack of a discernible pulsar wind nebula is consistent with an interpretation of \\psr\\ as a rotation-powered pulsar whose spin-down luminosity falls below the empirical threshold for generating bright wind nebulae, $\\dot E-{\\rm c) = 4 \\times 10A{36)$-ergs-sSA{-I)$. The age discrepancy suggests that its $\\dot E$ has always been below $\\dot E c$, perhaps a distinguishing property of the CCOs. Alternatively, the X-ray spectrum of \\psr\\ suggests a low-luminosity AXP, but the weak inferred $B-{\\rm p)$ field is incompatible with a magnetar theory of its X-ray luminosity. The ordinary spin parameters discovered from \\psr\\ highlight the inability of existing theories to explain the high luminosities and temperatures of CCO thermal X-ray spectra.

Discovery of an Energetic Pulsar Associated with SNR G76.9+1.0

NASA Technical Reports Server (NTRS)

Arzoumanian, Zaven; Gotthelf, E. V.; Ransom, S. M.; Safi-Harb, S.; Kothes, R.; Landecker, T. L.

2012-01-01

We report the discovery of PSR J2022-<-3842, a 24 ms radio and X-ray pulsar in the supernova remnant G76.9+i.0, in observations with the Chandra X-ray telescope, the Robert C. Byrd Green Bank Radio Telescope, and the Rossi X-ray Timing Explorer (RXTE). The pulsar's spin-down rate implies a rotation-powered luminosity E = 1.2 X 10(exp 38) erg/s, a surface dipole magnetic field strength B(sub S), = 1.0 X 10(exp 12) G, and a characteristic age of 8.9 kyr. PSR J2022+3842 is thus the second-most energetic Galactic pulsar known, after the Crab, as well as the most rapidly-rotating young, radio-bright pulsar known. The radio pulsations are highly dispersed and broadened by interstellar scattering, and we find that a large (delta f/f approximates 1.9 x 10(exp -6)) spin glitch must have occurred between our discovery and confirmation observations. The X-ray pulses are narrow (0.06 cycles FWHM) and visible up to 20 keV, consistent with magnetospheric emission from a rotation-powered pulsar. The Chandra X-ray image identifies the pulsar with a hard, unresolved source at the midpoint of the double-lobed radio morphology of G76.9+ 1.0 and embedded within faint, compact X-ray nebulosity. The spatial relationship of the X-ray and radio emissions is remarkably similar to extended structure seen around the Vela pulsar. The combined Chandra and RXTE pulsar spectrum is well-fitted by an absorbed power-law model with column density N(sub H) = (1.7 +/- 0.3) x 10(exp 22) / sq cm and photon index Gamma = 1.0 +/- 0.2; it implies that the Chandra point-source flux is virtually 100% pulsed. For a distance of 10 kpc, the X-ray luminosity of PSR J2022+3842 is L(sub x){2-1O keV) = 7.0 x 10(exp 33) erg/s. Despite being extraordinarily energetic, PSR J2022+3842 lacks a bright X-ray wind nebula and has an unusually low conversion efficiency of spin-down power to X-ray luminosity, Lx/E = 5.9 X 10(exp-5).

Big Data in the SHELA Field: Investigating Galaxy Quenching at High Redshifts

NASA Astrophysics Data System (ADS)

Stevans, Matthew L.; Finkelstein, Steven L.; Wold, Isak; Kawinwanichakij, Lalitwadee; Sherman, Sydney; Gebhardt, Karl; Jogee, Shardha; Papovich, Casey J.; Ciardullo, Robin; Gronwall, Caryl; Gawiser, Eric J.; Acquaviva, Viviana; Casey, Caitlin; Florez, Jonathan; HETDEX Team

2017-06-01

We present a measurement of the z ~ 4 Lyman break galaxy (LBG) rest-frame UV luminosity function to investigate the onset of quenching in the early universe. The bright-end of the galaxy luminosity function typically shows an exponential decline far steeper than that of the underlying halo mass function. This is typically attributed to negative feedback from past active galactic nuclei (AGN) activity as well as dust attenuation. Constraining the abundance of bright galaxies at early times (z > 3) can provide a key insight into the mechanisms regulating star formation in galaxies. However, existing studies suffer from low number statistics and/or the inability to robustly remove stellar and AGN contaminants. In this study we take advantage of the unprecedentedly large (24 deg^2) Spitzer/HETDEX Exploratory Large Area (SHELA) field and its deep multi-wavelength photometry, which includes DECam ugriz, NEWFIRM K-band, Spitzer/IRAC, Herschel/SPIRE, and X-ray from XMM-Newton and Chandra. With SHELA’s deep imaging over a large area we are uniquely positioned to study statistically significant samples of massive galaxies at high redshifts (z > 3) when the first massive galaxies began quenching. We select our sample using photometric redshifts from the EAZY software package (Brammer et al. 2008) based on the optical and far-infrared imaging. We directly identify and remove stellar contaminants and AGN with IRAC colors and X-ray detections, respectively. By pinning down the exact shape of the bright-end of the z ~ 4 LBG luminosity function, we provide the deepest probe yet into the baryonic physics dominating star formation and quenching in the early universe.

The global 21-cm signal in the context of the high- z galaxy luminosity function

NASA Astrophysics Data System (ADS)

Mirocha, Jordan; Furlanetto, Steven R.; Sun, Guochao

2017-01-01

We build a new model for the global 21-cm signal that is calibrated to measurements of the high-z galaxy luminosity function (LF) and further tuned to match the Thomson scattering optical depth of the cosmic microwave background, τe. Assuming that the z ≲ 8 galaxy population can be smoothly extrapolated to higher redshifts, the recent decline in best-fitting values of τe and the inefficient heating induced by X-ray binaries (the presumptive sources of the high-z X-ray background) imply that the entirety of cosmic reionization and reheating occurs at z ≲ 12. In contrast to past global 21-cm models, whose z ˜ 20 (ν ˜ 70 MHz) absorption features and strong ˜25 mK emission features were driven largely by the assumption of efficient early star formation and X-ray heating, our new models peak in absorption at ν ˜ 110 MHz at depths ˜-160 mK and have negligible emission components. Current uncertainties in the faint-end of the LF, binary populations in star-forming galaxies, and UV and X-ray escape fractions introduce ˜20 MHz (˜50 mK) deviations in the trough's frequency (amplitude), while emission signals remain weak (≲10 mK) and are confined to ν ≳ 140 MHz. These predictions, which are intentionally conservative, suggest that the detection of a 21-cm absorption minimum at frequencies below ˜90 MHz and/or emission signals stronger than ˜10mK at ν ≲ 140 MHz would provide strong evidence for `new' sources at high redshifts, such as Population III stars and their remnants.

A Study of Low-mass X-Ray Binaries in the Low-luminosity Regime

NASA Astrophysics Data System (ADS)

Sonbas, E.; Dhuga, K. S.; Göğüş, E.

2018-02-01

A recent study of a small sample of X-ray binaries (XRBs) suggests a significant softening of spectra of neutron star (NS) binaries as compared to black hole (BH) binaries in the luminosity range 1034–1037 erg s‑1. This softening is quantified as an anticorrelation between the spectral index and the 0.5–10 keV X-ray luminosity. We extend the study to significantly lower luminosities (i.e., ∼a few × 1030 erg s‑1) for a larger sample of XRBs. We find evidence for a significant anticorrelation between the spectral index and the luminosity for a group of NS binaries in the luminosity range 1032–1033 erg s‑1. Our analysis suggests a steep slope for the correlation i.e., ‑2.12 ± 0.63. In contrast, BH binaries do not exhibit the same behavior. We examine the possible dichotomy between NS and BH binaries in terms of a Comptonization model that assumes a feedback mechanism between an optically thin hot corona and an optically thick cool source of soft photons. We gauge the NS–BH dichotomy by comparing the extracted corona temperatures, Compton-y parameters, and the Comptonization amplification factors: the mean temperature of the NS group is found to be significantly lower than the equivalent temperature for the BH group. The extracted Compton-y parameters and the amplification factors follow the theoretically predicted relation with the spectral index.

The XMM-Newton Extended Survey of the Taurus Molecular Cloud (XEST)

NASA Technical Reports Server (NTRS)

Guedel, M.; Briggs, K. R.; Arzner, K.; Audard, M.; Bouvier, J.; Feigelson, E. D.; Franciosini, E.; Glauser, A.; Grosso, N.; Micela, G.;

The average 0.5-200 keV spectrum of local active galactic nuclei and a new determination of the 2-10 keV luminosity function at z ≈ 0

NASA Astrophysics Data System (ADS)

Ballantyne, D. R.

2014-01-01

The broad-band X-ray spectra of active galactic nuclei (AGNs) contains information about the nuclear environment from Schwarzschild radii scales (where the primary power law is generated in a corona) to distances of ˜1 pc (where the distant reflector may be located). In addition, the average shape of the X-ray spectrum is an important input into X-ray background synthesis models. Here, local (z ≈ 0) AGN luminosity functions (LFs) in five energy bands are used as a low-resolution, luminosity-dependent X-ray spectrometer in order to constrain the average AGN X-ray spectrum between 0.5 and 200 keV. The 15-55 keV LF measured by Swift-BAT is assumed to be the best determination of the local LF, and then a spectral model is varied to determine the best fit to the 0.5-2 keV, 2-10 keV, 3-20 keV and 14-195 keV LFs. The spectral model consists of a Gaussian distribution of power laws with a mean photon-index <Γ> and cutoff energy Ecut, as well as contributions from distant and disc reflection. The reflection strength is parametrized by varying the Fe abundance relative to solar, AFe, and requiring a specific Fe Kα equivalent width (EW). In this way, the presence of the X-ray Baldwin effect can be tested. The spectral model that best fits the four LFs has <Γ> = 1.85 ± 0.15, E_{cut}=270^{+170}_{-80} keV, A_{Fe}=0.3^{+0.3}_{-0.15}. The sub-solar AFe is unlikely to be a true measure of the gas-phase metallicity, but indicates the presence of strong reflection given the assumed Fe Kα EW. Indeed, parametrizing the reflection strength with the R parameter gives R=1.7^{+1.7}_{-0.85}. There is moderate evidence for no X-ray Baldwin effect. Accretion disc reflection is included in the best-fitting model, but it is relatively weak (broad iron Kα EW < 100 eV) and does not significantly affect any of the conclusions. A critical result of our procedure is that the shape of the local 2-10 keV LF measured by HEAO-1 and MAXI is incompatible with the LFs measured in the hard X-rays by Swift-BAT and RXTE. We therefore present a new determination of the local 2-10 keV LF that is consistent with all other energy bands, as well as the de-evolved 2-10 keV LF estimated from the XMM-Newton Hard Bright Survey. This new LF should be used to revise current measurements of the evolving AGN LF in the 2-10 keV band. Finally, the suggested absence of the X-ray Baldwin effect points to a possible origin for the distant reflector in dusty gas not associated with the AGN obscuring medium. This may be the same material that produces the compact 12 μm source in local AGNs.

SMC X-3: the closest ultraluminous X-ray source powered by a neutron star with non-dipole magnetic field

NASA Astrophysics Data System (ADS)

Tsygankov, S. S.; Doroshenko, V.; Lutovinov, A. A.; Mushtukov, A. A.; Poutanen, J.

2017-09-01

Aims: The magnetic field of accreting neutron stars determines their overall behavior including the maximum possible luminosity. Some models require an above-average magnetic field strength (≳1013 G) in order to explain super-Eddington mass accretion rate in the recently discovered class of pulsating ultraluminous X-ray sources (ULX). The peak luminosity of SMC X-3 during its major outburst in 2016-2017 reached 2.5 × 1039 erg s-1 comparable to that in ULXs thus making this source the nearest ULX-pulsar. Determination of the magnetic field of SMC X-3 is the main goal of this paper. Methods: SMC X-3 belongs to the class of transient X-ray pulsars with Be optical companions, and exhibited a giant outburst in July 2016-March 2017. The source has been observed over the entire outburst with the Swift/XRT and Fermi/GBM telescopes, as well as the NuSTAR observatory. Collected data allowed us to estimate the magnetic field strength of the neutron star in SMC X-3 using several independent methods. Results: Spin evolution of the source during and between the outbursts, and the luminosity of the transition to the so-called propeller regime in the range of (0.3-7) × 1035 erg s-1 imply a relatively weak dipole field of (1-5) × 1012 G. On the other hand, there is also evidence for a much stronger field in the immediate vicinity of the neutron star surface. In particular, transition from super- to sub-critical accretion regime associated with the cease of the accretion column and very high peak luminosity favor a field that is an order of magnitude stronger. This discrepancy makes SMC X-3 a good candidate for possessing significant non-dipolar components of the field, and an intermediate source between classical X-ray pulsars and accreting magnetars which may constitute an appreciable fraction of ULX population.

Swift Observations of SMC X-3 during Its 2016-2017 Super-Eddington Outburst

NASA Astrophysics Data System (ADS)

Weng, Shan-Shan; Ge, Ming-Yu; Zhao, Hai-Hui; Wang, Wei; Zhang, Shuang-Nan; Bian, Wei-Hao; Yuan, Qi-Rong

2017-07-01

The Be X-ray pulsar SMC X-3 underwent a giant outburst from 2016 August to 2017 March, which was monitored with the Swift satellite. During the outburst, its broadband flux increased dramatically, and the unabsorbed X-ray luminosity reached an extreme value of ˜ {10}39 erg s-1 around August 24. Using the Swift/XRT data, we measured the observed pulse frequency of the neutron star to compute the orbital parameters of the binary system. After applying the orbital corrections to Swift observations, we found that the spin frequency increased steadily from 128.02 mHz on August 10 and approached the spin equilibrium of ˜128.74 mHz in 2017 January with an unabsorbed luminosity of {L}{{X}}˜ 2× {10}37 erg s-1, indicating a strong dipolar magnetic field of B˜ 6.8× {10}12 G at the neutron star surface. The spin-up rate is tightly correlated with its X-ray luminosity during the super-Eddington outburst. The pulse profile in the Swift/XRT data is variable, showing double peaks at the early stage of outburst and then merging into a single peak at low luminosity. Additionally, we report that a low-temperature ({kT}˜ 0.2 keV) thermal component emerges in the phase-averaged spectra as the flux decays, and it may be produced from the outer truncated disk or the boundary layer between the exterior flow and the magnetosphere.

X-rays from accretion of red giant winds

NASA Technical Reports Server (NTRS)

Jura, M.; Helfand, D. J.

1984-01-01

X-ray observations of the late-type red giants Mira and R Aqr obtained with the Einstein Observatory are presented, and the general problems of white dwarf accretion from late-type giant winds is considered. The extremely low measured luminosities obtained for the two systems leads to the conclusion that the companions of Mira and R Aqr are most likely low-mass main sequence objects rather than white dwarfs as is usually assumed. The expected X-ray luminosities of true red giant/white dwarf systems are considered, and it is concluded that far too few have been detected if the canonical accretion scenario is adopted. A possible explanation of this situation in terms of grain-dominated Eddington-limited accretion is proposed.

Prospects for AGN Science using the ART-XC on the SRG Mission

NASA Technical Reports Server (NTRS)

Swartz, Douglas A.; Elsner, Ronald F.; Gubarev, Mikhail V.; O'Dell, Stephen L.; Ramsey, Brian D.; Bonamente, Massimiliano

2012-01-01

The enhanced hard X-ray sensitivity provided by the Astronomical Roentgen Telescope to the Spectrum Roentgen Gamma mission facilitates the detection of heavily obscured and other hard-spectrum cosmic X-ray sources. The SRG all-sky survey will obtain large, statistically-well-defined samples of active galactic nuclei (AGN) including a significant population of local heavily-obscured AGN. In anticipation of the SRG all-sky survey, we investigate the prospects for refining the bright end of the AGN luminosity function and determination of the local black hole mass function and comparing the spatial distribution of AGN with large-scale structure defined by galaxy clusters and groups. Particular emphasis is placed on studies of the deep survey Ecliptic Pole regions.

A decade of Rossi X-ray Timing Explorer Seyfert observations: An RXTE Seyfert spectral database

NASA Astrophysics Data System (ADS)

Mattson, Barbara Jo

2008-10-01

With over forty years of X-ray observations, we should have a grasp on the X- ray nature of active galactic nuclei (AGN). The unification model of Antonucci and Miller (1985) offered a context for understanding observations by defining a "typical" AGN geometry, with observed spectral differences explained by line- of-sight effects. However, the emerging picture is that the central AGN is more complex than unification alone can describe. We explore the unified model with a systematic X-ray spectral study of bright Seyfert galaxies observed by the Rossi X-Ray Timing Explorer (RXTE) over its first 10 years. We develop a spectral-fit database of 821 time-resolved spectra from 39 Seyfert galaxies fitted to a model describing the effects of an X-ray power-law spectrum reprocessed and absorbed by material in the central AGN region. We observe a relationship between radio and X-ray properties for Seyfert 1s, with the spectral parameters differing between radio-loud and radio-quiet Seyfert 1s. We also find a complex relationship between the Fe K equivalent width ( EW ) and the power-law photon index (Gamma) for the Seyfert 1s, with a correlation for the radio-loud sources and an anti-correlation for the radio- quiet sources. These results can be explained if X-rays from the relativistic jet in radio-loud sources contribute significantly to the observed spectrum. We observe scatter in the EW-Gamma relationship for the Seyfert 2s, suggesting complex environments that unification alone cannot explain. We see a strong correlation between Gamma and the reflection fraction ( R ) in the Seyfert 1 and 2 samples, but modeling degeneracies are present, so this relationship cannot be trusted as instructive of the AGN physics. For the Seyfert 1 sample, we find an anticorrelation between EW and the 2 to 10 keV luminosity ( L x ), also known as the X-ray Baldwin effect. This may suggest that higher luminosity sources contain less material or may be due to a time-lag effect. We do not observe the previously reported relationship between Gamma and the ratio of L x to the Eddington luminosity.

A catalogue of optical to X-ray spectral energy distributions of z ≈ 2 quasars observed with Swift - I. First results

NASA Astrophysics Data System (ADS)

Lawther, D.; Vestergaard, M.; Raimundo, S.; Grupe, D.

2017-06-01

We present the Swift optical to X-ray spectral energy distributions (SEDs) of 44 quasars at redshifts z ≈ 2 observed by Swift, part of a larger program to establish and characterize the optical through X-ray SEDs of moderate-redshift quasars. Here, we outline our analysis approach and present preliminary analysis and results for the first third of the full quasar sample. Not all quasars in the sample are detected in X-rays; all of the X-ray-detected objects so far are radio loud. As expected for radio-loud objects, they are X-ray bright relative to radio-quiet quasars of comparable optical luminosities, with an average αox =1.39 ± 0.03 (where αox is the power-law slope connecting the monochromatic flux at 2500 Å and at 2 keV), and display hard X-ray spectra. We find integrated 3000 Å-25 keV accretion luminosities of between 0.7 × 1046 erg s-1 and 5.2 × 1047 erg s-1. Based on single-epoch spectroscopic virial black hole mass estimates, we find that these quasars are accreting at substantial Eddington fractions, 0.1 ≲ L/LEdd ≲ 1.

The 4U 0115+63: Another energetic gamma ray binary pulsar

NASA Technical Reports Server (NTRS)

Chadwick, P. M.; Dipper, N. A.; Dowthwaite, J. C.; Kirkman, I. W.; Mccomb, T. J. L.; Orford, K. J.; Turver, K. E.

1985-01-01

Following the discovery of Her X-1 as a source of pulsed 1000 Gev X-rays, a search for emission from an X-ray binary containing a pulsar with similar values of period, period derivative and luminosity was successful. The sporadic X-ray binary 4U 0115-63 has been observed, with probability 2.5 x 10 to the minus 6 power ergs/s to emit 1000 GeV gamma-rays with a time averaged energy flux of 6 to 10 to the 35th power.

A ROTSE-I/ROSAT Survey of X-ray Emission from Contact Binary Stars

NASA Astrophysics Data System (ADS)

Geske, M.; McKay, T.

2005-05-01

Using public data from the ROSAT All Sky Survey (RASS) and the ROTSE-I Sky Patrols, the incidence of strong x-ray emissions from contact binary systems was examined. The RASS data was matched to an expanded catalog of contact binary systems from the ROTSE-I data, using a 35 arc second radius. X-ray luminosities for matching objects were then determined. This information was then used to evaluate the total x-ray emissions from all such objects, in order to determine their contribution to the galactic x-ray background.

X-ray spectral hardening and radio non-detection of MAXI J1535-571

NASA Astrophysics Data System (ADS)

Russell, T. D.; Altamirano, S. Rapisarda. D.; Miller-Jones, J. C. A.; Plotkin, R.; Tetarenko, A. J.; Sivakoff, G. R.; JACPOT XRB Collaboration

2018-05-01

MAXI J1535-571 (ATels #10699, #10700, #10702, #10704, #10708, #10711, #10716) has been in a soft X-ray spectral state since late November (ATel #11020). The source has remained in this soft state down to X-ray luminosities much lower than typically seen (ATel #11568), and is currently below MAXI and BAT sensitivity limits.

X-Ray Probes of Cosmic Star Formation History

NASA Technical Reports Server (NTRS)

Ghosh, Pranab; White, Nicholas E.

2001-01-01

We discuss the imprints left by a cosmological evolution of the star formation rate (SFR) on the evolution of X-ray luminosities Lx of normal galaxies, using the scheme earlier proposed by us, wherein the evolution of LX of a galaxy is driven by the evolution of its X-ray binary population. As indicated in our earlier work, the profile of Lx with redshift can both serve as a diagnostic probe of the SFR profile and constrain evolutionary models for X-ray binaries. We report here the first calculation of the expected evolution of X-ray luminosities of galaxies, updating our work by using a suite of more recently developed SFR profiles that span the currently plausible range. The first Chandra deep imaging results on Lx evolution are beginning to probe the SFR profile of bright spiral galaxies; the early results are consistent with predictions based on current SFR models. Using these new SFR profiles, the resolution of the "birthrate problem" of low-mass X-ray binaries and recycled, millisecond pulsars in terms of an evolving global SFR is more complete. We discuss the possible impact of the variations in the SFR profile of individual galaxies and galaxy types.

A First Estimate of the X-Ray Binary Frequency as a Function of Star Cluster Mass in a Single Galactic System

NASA Astrophysics Data System (ADS)

Clark, D. M.; Eikenberry, S. S.; Brandl, B. R.; Wilson, J. C.; Carson, J. C.; Henderson, C. P.; Hayward, T. L.; Barry, D. J.; Ptak, A. F.; Colbert, E. J. M.

2008-05-01

We use the previously identified 15 infrared star cluster counterparts to X-ray point sources in the interacting galaxies NGC 4038/4039 (the Antennae) to study the relationship between total cluster mass and X-ray binary number. This significant population of X-Ray/IR associations allows us to perform, for the first time, a statistical study of X-ray point sources and their environments. We define a quantity, η, relating the fraction of X-ray sources per unit mass as a function of cluster mass in the Antennae. We compute cluster mass by fitting spectral evolutionary models to Ks luminosity. Considering that this method depends on cluster age, we use four different age distributions to explore the effects of cluster age on the value of η and find it varies by less than a factor of 4. We find a mean value of η for these different distributions of η = 1.7 × 10-8 M-1⊙ with ση = 1.2 × 10-8 M-1⊙. Performing a χ2 test, we demonstrate η could exhibit a positive slope, but that it depends on the assumed distribution in cluster ages. While the estimated uncertainties in η are factors of a few, we believe this is the first estimate made of this quantity to "order of magnitude" accuracy. We also compare our findings to theoretical models of open and globular cluster evolution, incorporating the X-ray binary fraction per cluster.

THE LONGEST TIMESCALE X-RAY VARIABILITY REVEALS EVIDENCE FOR ACTIVE GALACTIC NUCLEI IN THE HIGH ACCRETION STATE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang Youhong, E-mail: youhong.zhang@mail.tsinghua.edu.cn

2011-01-01

The All Sky Monitor (ASM) on board the Rossi X-ray Timing Explorer has continuously monitored a number of active galactic nuclei (AGNs) with similar sampling rates for 14 years, from 1996 January to 2009 December. Utilizing the archival ASM data of 27 AGNs, we calculate the normalized excess variances of the 300-day binned X-ray light curves on the longest timescale (between 300 days and 14 years) explored so far. The observed variance appears to be independent of AGN black-hole mass and bolometric luminosity. According to the scaling relation of black-hole mass (and bolometric luminosity) from galactic black hole X-ray binariesmore » (GBHs) to AGNs, the break timescales that correspond to the break frequencies detected in the power spectral density (PSD) of our AGNs are larger than the binsize (300 days) of the ASM light curves. As a result, the singly broken power-law (soft-state) PSD predicts the variance to be independent of mass and luminosity. Nevertheless, the doubly broken power-law (hard-state) PSD predicts, with the widely accepted ratio of the two break frequencies, that the variance increases with increasing mass and decreases with increasing luminosity. Therefore, the independence of the observed variance on mass and luminosity suggests that AGNs should have soft-state PSDs. Taking into account the scaling of the break timescale with mass and luminosity synchronously, the observed variances are also more consistent with the soft-state than the hard-state PSD predictions. With the averaged variance of AGNs and the soft-state PSD assumption, we obtain a universal PSD amplitude of 0.030 {+-} 0.022. By analogy with the GBH PSDs in the high/soft state, the longest timescale variability supports the standpoint that AGNs are scaled-up GBHs in the high accretion state, as already implied by the direct PSD analysis.« less

A multiwavelength study of SXP 1062, the long-period X-ray pulsar associated with a supernova remnant

NASA Astrophysics Data System (ADS)

González-Galán, A.; Oskinova, L. M.; Popov, S. B.; Haberl, F.; Kühnel, M.; Gallagher, J.; Schurch, M. P. E.; Guerrero, M. A.

2018-04-01

SXP 1062 is a Be X-ray binary (BeXB) located in the Small Magellanic Cloud. It hosts a long-period X-ray pulsar and is likely associated with the supernova remnant MCSNR J0127-7332. In this work we present a multiwavelength view on SXP 1062 in different luminosity regimes. We consider monitoring campaigns in optical (OGLE survey) and X-ray (Swift telescope). During these campaigns a tight coincidence of X-ray and optical outbursts is observed. We interpret this as typical Type I outbursts as often detected in BeXBs at periastron passage of the neutron star (NS). To study different X-ray luminosity regimes in depth, during the source quiescence we observed it with XMM-Newton while Chandra observations followed an X-ray outburst. Nearly simultaneously with Chandra observations in X-rays, in optical the RSS/SALT telescope obtained spectra of SXP 1062. On the basis of our multiwavelength campaign we propose a simple scenario where the disc of the Be star is observed face-on, while the orbit of the NS is inclined with respect to the disc. According to the model of quasi-spherical settling accretion our estimation of the magnetic field of the pulsar in SXP 1062 does not require an extremely strong magnetic field at the present time.

Searching for X-ray emission from AGB stars

NASA Astrophysics Data System (ADS)

Ramstedt, S.; Montez, R.; Kastner, J.; Vlemmings, W. H. T.

2012-07-01

Context. Magnetic fields have been measured around asymptotic giant branch (AGB) stars of all chemical types using maser polarization observations. If present, a large-scale magnetic field would lead to X-ray emission, which should be observable using current X-ray observatories. Aims: The aim is to search the archival data for AGB stars that are intrinsic X-ray emitters. Methods: We have searched the ROSAT, CXO, and XMM-Newton archives for serendipitous X-ray observations of a sample of ~500 AGB stars. We specifically searched for the AGB stars detected with GALEX. The data is calibrated, analyzed and the X-ray luminosities and temperatures are estimated as functions of the circumstellar absorption. Results: We identify 13 AGB stars as having either serendipitous or targeted observations in the X-ray data archives, however for a majority of the sources the detailed analysis show that the detections are questionable. Two new sources are detected by ROSAT: T Dra and R UMa. The spectral analysis suggests that the emission associated with these sources could be due to coronal activity or interaction across a binary system. Conclusions: Further observations of the detected sources are necessary to clearly determine the origin of the X-ray emission. Moreover, additional objects should be subject to targeted X-ray observations in order to achieve better constraints for the magnetic fields around AGB stars. Appendices are available in electronic form at http://www.aanda.org

THE CHANDRA PLANETARY NEBULA SURVEY (ChanPlaNS). III. X-RAY EMISSION FROM THE CENTRAL STARS OF PLANETARY NEBULAE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Montez, R. Jr.; Kastner, J. H.; Freeman, M.

2015-02-10

We present X-ray spectral analysis of 20 point-like X-ray sources detected in Chandra Planetary Nebula Survey observations of 59 planetary nebulae (PNe) in the solar neighborhood. Most of these 20 detections are associated with luminous central stars within relatively young, compact nebulae. The vast majority of these point-like X-ray-emitting sources at PN cores display relatively ''hard'' (≥0.5 keV) X-ray emission components that are unlikely to be due to photospheric emission from the hot central stars (CSPN). Instead, we demonstrate that these sources are well modeled by optically thin thermal plasmas. From the plasma properties, we identify two classes of CSPN X-raymore » emission: (1) high-temperature plasmas with X-ray luminosities, L {sub X}, that appear uncorrelated with the CSPN bolometric luminosity, L {sub bol} and (2) lower-temperature plasmas with L {sub X}/L {sub bol} ∼ 10{sup –7}. We suggest these two classes correspond to the physical processes of magnetically active binary companions and self-shocking stellar winds, respectively. In many cases this conclusion is supported by corroborative multiwavelength evidence for the wind and binary properties of the PN central stars. By thus honing in on the origins of X-ray emission from PN central stars, we enhance the ability of CSPN X-ray sources to constrain models of PN shaping that invoke wind interactions and binarity.« less

The Short Bursts in SGR 1806-20, 1E 1048-5937, and SGR 0501+4516

NASA Astrophysics Data System (ADS)

Qu, Zhijie; Li, Zhaosheng; Chen, Yupeng; Dai, Shi; Ji, Long; Xu, Renxin; Zhang, Shu

2015-03-01

We analyzed temporal and spectral properties, focusing on the short bursts, for three anomalous X-ray pulsars (AXPs) and soft gamma repeaters (SGRs), including SGR 1806-20, 1E 1048-5937 and SGR 0501+4516. Using the data from XMM-Newton, we located the short bursts by Bayesian blocks algorithm. The short bursts' duration distributions for three sources were fitted by two lognormal functions. The spectra of shorter bursts ($< 0.2~\\rm s$) and longer bursts ($\\geq 0.2~\\rm s$) can be well fitted in two blackbody components model or optically thin thermal bremsstrahlung model for SGR 0501+4516. We also found that there is a positive correlation between the burst luminosity and the persistent luminosity with a power law index $\\gamma = 1.23 \\pm 0.18 $. The energy ratio of this persistent emission to the time averaged short bursts is in the range of $10 - 10^3$, being comparable to the case in Type I X-ray burst.

X-ray Emission from Early Universe Analog Galaxies

NASA Astrophysics Data System (ADS)

Brorby, Matthew; Kaaret, Philip; Prestwich, Andrea H.; Mirabel, I. Felix; Feng, Hua

2016-01-01

Around 300,000 years after the Big Bang, the Universe had cooled enough to combine and form neutral atoms. This signified the beginning of a time known as the Dark Ages. Neutral matter began to fall into the dark matter gravitational wells that were seeded after the initial moments of the Big Bang. As the first stars and galaxies formed within these gravitational wells, the surrounding baryonic matter was heated and started to ionize. The source of energetic photons that heated and reionized the early Universe remains uncertain. Early galaxies had low metallicity and recent population synthesis calculations suggest that the number and luminosity of high-mass X-ray binaries are enhanced in star-forming galaxies with low metallicity, offering a potentially important and previously overlooked source of heating and reionization. Here we examine two types of local galaxies that have been shown to be good analogs to the early galaxies in the Universe: Blue compact dwarf galaxies (BCDs) and Lyman Break Analogs (LBAs).A BCD is defined by its blue optical colors, low metallicities, and physically small size. This makes BCDs the best available local analogs for early star formation. We analyzed data from a sample of 25 metal-poor BCDs and compared our results with those of near-solar metallicity galaxies. Using a Bayesian approach, we showed that the X-ray luminosity function for the low-metallicity BCDs is significantly elevated relative to the XLF for near-solar metallicity galaxies.Larger, gas-rich galaxies may have formed shortly after these first galaxies. These larger galaxies would be similar in their properties to the high-redshift Lyman break galaxies (LBGs). LBAs provide the best local comparison to the LBGs. We studied a sample of 10 LBAs in order to measure the relation between star formation rate and X-ray luminosity for these galaxies. We found that for LBAs with intermediate sub-solar metallicities, there is enhanced X-ray emission relative to the expected value from near-solar metallicity galaxies.By incorporating our results into simulations used to predict the redshifted 21cm signal from the early Universe, unique and observable predictions could be made for future 21cm observations.

A dark jet dominates the power output of the stellar black hole Cygnus X-1.

PubMed

Gallo, Elena; Fender, Rob; Kaiser, Christian; Russell, David; Morganti, Raffaella; Oosterloo, Tom; Heinz, Sebastian

2005-08-11

Black holes undergoing accretion are thought to emit the bulk of their power in the X-ray band by releasing the gravitational potential energy of the infalling matter. At the same time, they are capable of producing highly collimated jets of energy and particles flowing out of the system with relativistic velocities. Here we show that the 10-solar-mass (10M(o)) black hole in the X-ray binary Cygnus X-1 (refs 3-5) is surrounded by a large-scale (approximately 5 pc in diameter) ring-like structure that appears to be inflated by the inner radio jet. We estimate that in order to sustain the observed emission of the ring, the jet of Cygnus X-1 has to carry a kinetic power that can be as high as the bolometric X-ray luminosity of the binary system. This result may imply that low-luminosity stellar-mass black holes as a whole dissipate the bulk of the liberated accretion power in the form of 'dark', radiatively inefficient relativistic outflows, rather than locally in the X-ray-emitting inflow.

X-Ray Flare Candidates in Short Gamma-Ray Bursts

NASA Technical Reports Server (NTRS)

Margutti, R.; Chincarini, G.; Granot, J.; Guidorzi, C.; Berger, E.; Bernardini, M. G.; Geherls, N.; Soderberg, A. M.; Stamatikos, M.; Zaninoni, E.

2012-01-01

We present the first systematic study of X-ray flare candidates in short gamma-ray bursts (SGRBs) exploiting the large 6-year Swift database with the aim to constrain the physical nature of such fluctuations. We find that flare candidates appear in different types of SGRB host galaxy environments and show no clear correlation with the X-ray afterglow lifetime; flare candidates are detected both in SGRBs with a bright extended emission in the soft gamma-rays and in SGRBs which do not show such component. We furthermore show that SGRB X-ray flare candidates only partially share the set of observational properties of long GRB (LGRB) flares. In particular, the main parameter driving the duration evolution of X-ray variability episodes in both classes is found to be the elapsed time from the explosion, with very limited dependence on the different progenitors, environments, central engine life-times, prompt variability time-scales and energy budgets. On the contrary, SGRB flare candidates significantly differ from LGRB flares in terms of peak luminosity, isotropic energy, flare-to-prompt luminosity ratio and relative variability flux. However, these differences disappear when the central engine time-scales and energy budget are accounted for, suggesting that (i) flare candidates and prompt pulses in SGRBs likely have a common origin; (ii) similar dissipation and/or emission mechanisms are responsible for the prompt and flare emission in long and short GRBs, with SGRBs being less energetic albeit faster evolving versions of the long class. Finally, we show that in strict analogy to the SGRB prompt emission, flares candidates fall off the lag-luminosity relation defined by LGRBs, thus strengthening the SGRB flare-prompt pulse connection.

Spectroscopic follow-up of variability-selected active galactic nuclei in the Chandra Deep Field South

NASA Astrophysics Data System (ADS)

Boutsia, K.; Leibundgut, B.; Trevese, D.; Vagnetti, F.

2009-04-01

Context: Supermassive black holes with masses of 10^5-109 M⊙ are believed to inhabit most, if not all, nuclear regions of galaxies, and both observational evidence and theoretical models suggest a scenario where galaxy and black hole evolution are tightly related. Luminous AGNs are usually selected by their non-stellar colours or their X-ray emission. Colour selection cannot be used to select low-luminosity AGNs, since their emission is dominated by the host galaxy. Objects with low X-ray to optical ratio escape even the deepest X-ray surveys performed so far. In a previous study we presented a sample of candidates selected through optical variability in the Chandra Deep Field South, where repeated optical observations were performed in the framework of the STRESS supernova survey. Aims: The analysis is devoted to breaking down the sample in AGNs, starburst galaxies, and low-ionisation narrow-emission line objects, to providing new information about the possible dependence of the emission mechanisms on nuclear luminosity and black-hole mass, and eventually studying the evolution in cosmic time of the different populations. Methods: We obtained new optical spectroscopy for a sample of variability selected candidates with the ESO NTT telescope. We analysed the new spectra, together with those existing in the literature and studied the distribution of the objects in U-B and B-V colours, optical and X-ray luminosity, and variability amplitude. Results: A large fraction (17/27) of the observed candidates are broad-line luminous AGNs, confirming the efficiency of variability in detecting quasars. We detect: i) extended objects which would have escaped the colour selection and ii) objects of very low X-ray to optical ratio, in a few cases without any X-ray detection at all. Several objects resulted to be narrow-emission line galaxies where variability indicates nuclear activity, while no emission lines were detected in others. Some of these galaxies have variability and X-ray to optical ratio close to active galactic nuclei, while others have much lower variability and X-ray to optical ratio. This result can be explained by the dilution of the nuclear light due to the host galaxy. Conclusions: Our results demonstrate the effectiveness of supernova search programmes to detect large samples of low-luminosity AGNs. A sizable fraction of the AGN in our variability sample had escaped X-ray detection (5/47) and/or colour selection (9/48). Spectroscopic follow-up to fainter flux limits is strongly encouraged. Based on observations collected at the European Southern Observatory, Chile, 080.B-0187(A).

Disc-jet quenching of the galactic black hole Swift J1753.5-0127

NASA Astrophysics Data System (ADS)

Rushton, A. P.; Shaw, A. W.; Fender, R. P.; Altamirano, D.; Gandhi, P.; Uttley, P.; Charles, P. A.; Kolehmainen, M.; Anderson, G. E.; Rumsey, C.; Titterington, D. J.

2016-11-01

We report on radio and X-ray monitoring observations of the BHC Swift J1753.5-0127 taken over a ˜10 yr period. Presented are daily radio observations at 15 GHz with the Arcminute Microkelvin Imager Large Array (AMI-LA) and X-ray data from Swift X-ray Telescope and Burst Alert Telescope. Also presented is a deep 2 h JVLA observation taken in an unusually low-luminosity soft-state (with a low disc temperature). We show that although the source has remained relatively radio-quiet compared to XRBs with a similar X-ray luminosity in the hard-state, the power-law relationship scales as ζ = 0.96 ± 0.06, I.e. slightly closer to what has been considered for radiatively inefficient accretion discs. We also place the most stringent limit to date on the radio-jet quenching in an XRB soft-state, showing the connection of the jet quenching to the X-ray power-law component; the radio flux in the soft-state was found to be < 21 μJy, which is a quenching factor of ≳ 25.

Probing black hole accretion in quasar pairs at high redshift

NASA Astrophysics Data System (ADS)

Vignali, C.; Piconcelli, E.; Perna, M.; Hennawi, J.; Gilli, R.; Comastri, A.; Zamorani, G.; Dotti, M.; Mathur, S.

2018-06-01

Models and observations suggest that luminous quasar activity is triggered by mergers, so it should preferentially occur in the most massive primordial dark matter haloes, where the frequency of mergers is expected to be the highest. Since the importance of galaxy mergers increases with redshift, we identify the high-redshift Universe as the ideal laboratory for studying dual AGN. Here, we present the X-ray properties of two systems of dual quasars at z = 3.0-3.3 selected from the SDSS DR6 at separations of 6-8 arcsec (43-65 kpc) and observed by Chandra for ≈65 ks each. Both members of each pair are detected with good photon statistics to allow us to constrain the column density, spectral slope and intrinsic X-ray luminosity. We also include a recently discovered dual quasar at z = 5 (separation of 21 arcsec, 136 kpc) for which XMM-Newton archival data allow us to detect the two components separately. Using optical spectra we derived bolometric luminosities, BH masses and Eddington ratios that were compared to those of luminous SDSS quasars in the same redshift ranges. We find that the brighter component of both quasar pairs at z ≈ 3.0-3.3 has high luminosities compared to the distribution of SDSS quasars at similar redshift, with J1622A having an order magnitude higher luminosity than the median. This source lies at the luminous end of the z ≈ 3.3 quasar luminosity function. While we cannot conclusively state that the unusually high luminosities of our sources are related to their having a close companion, for J1622A there is only a 3 per cent probability that it is by chance.

An X-ray Observation of the L1251 Dark Cloud

NASA Technical Reports Server (NTRS)

Simon, Theodore

2006-01-01

An X-ray image of the L1251 dark cloud in Cepheus was obtained with the XMM-Newton telescope. More than three dozen sources were detected above a 3 delta limit in X-ray luminosity of L(sub X = 10(exp 29) ergs/s. Among the detections are eight optically visible T Tauri stars, which had been identified in earlier work from their emission at H(alpha). The two strongest X-ray sources have steady luminosities of L(sub X) approx. 10(exp 31) ergs/s and are at the saturation limit for X-ray activity in late-type stars, L(sub X)/L(sub bol) approx. 10(exp -3). X-ray emission was also observed from two CO emission cores in L1251, core C (L1251A) and core E (L1251B). Both regions contain high-velocity molecular gas, bright IRAS sources (Class I protostars), thermal radio sources, and Herbig-Haro (HH) jets. In L1251A strong X-ray emission was discovered in close proximity to the near-inbred and radio source IRSA/VLA 7 and to IRAS 22343+7501. IRSA/VLA 7 thus appears to be the most likely source of the molecular and HH outflows in L1251A. In L1251B X-ray emission was observed from a visible T Tauri star, KP2-44, which is thought to be the driving source for HH 189. Also reported is the tentative detection of X-ray emission from VLA 3, a thermal radio continuum source in L1251B that is closely associated with the extreme Class I protostar IRAS 22376+7455.

Hot gas in the cold dark matter scenario: X-ray clusters from a high-resolution numerical simulation

NASA Technical Reports Server (NTRS)

Kang, Hyesung; Cen, Renyue; Ostriker, Jeremiah P.; Ryu, Dongsu

1994-01-01

A new, three-dimensional, shock-capturing hydrodynamic code is utilized to determine the distribution of hot gas in a standard cold dark matter (CDM) model of the universe. Periodic boundary conditions are assumed: a box with size 85 h(exp -1) Mpc having cell size 0.31 h(exp -1) Mpc is followed in a simulation with 270(exp 3) = 10(exp 7.3) cells. Adopting standard parameters determined from COBE and light-element nucleosynthesis, sigma(sub 8) = 1.05, omega(sub b) = 0.06, and assuming h = 0.5, we find the X-ray-emitting clusters and compute the luminosity function at several wavelengths, the temperature distribution, and estimated sizes, as well as the evolution of these quantities with redshift. We find that most of the total X-ray emissivity in our box originates in a relatively small number of identifiable clusters which occupy approximately 10(exp -3) of the box volume. This standard CDM model, normalized to COBE, produces approximately 5 times too much emission from clusters having L(sub x) is greater than 10(exp 43) ergs/s, a not-unexpected result. If all other parameters were unchanged, we would expect adequate agreement for sigma(sub 8) = 0.6. This provides a new and independent argument for lower small-scale power than standard CDM at the 8 h(exp -1) Mpc scale. The background radiation field at 1 keV due to clusters in this model is approximately one-third of the observed background, which, after correction for numerical effects, again indicates approximately 5 times too much emission and the appropriateness of sigma(sub 8) = 0.6. If we have used the observed ratio of gas to total mass in clusters, rather than basing the mean density on light-element nucleosynthesis, then the computed luminosity of each cluster would have increased still further, by a factor of approximately 10. The number density of clusters increases to z approximately 1, but the luminosity per typical cluster decreases, with the result that evolution in the number density of bright clusters is moderate in this redshift range, showing a broad peak near z = 0.7, and then a rapid decline above redshift z = 3. Detailed computations of the luminosity functions in the range L(sub x) = 10(exp 40) - 10(exp 44) ergs/s in various energy bands are presented for both cluster central regions and total luminosities to be used in comparison with ROSAT and other observational data sets. The quantitative results found disagree significantly with those found by other investigators using semianalytic techniques. We find little dependence of core radius on cluster luminosity and a dependence of temperature on luminosity given by log kT(sub x) = A + B log L(sub x), which is slightly steeper (B = 0.38) than is indicated by observations. Computed temperatures are somewhat higher than observed, as expected, in that COBE-normalized CDM has too much power on the relevant scales. A modest average temperature gradient is found, with temperatures dropping to 90% of central values at 0.4 h(exp -1) Mpc and 70% of central values at 0.9 h(exp -1) Mpc. Examining the ratio of gas to total mass in the clusters normalized to Omega(sub B) h(exp 2) = 0.015, and comparing with observations, we conclude, in agreement with White (1991), that the cluster observations argue for an open universe.

The Great Pretenders Among the ULX Class

NASA Technical Reports Server (NTRS)

Christodoulou, Dimitris M.; Laycock, Silas G. T.; Kazanas, Demosthenes; Cappallo, Rigel; Contopoulos, Ioannis

2017-01-01

The recent discoveries of pulsed X-ray emission from three ultraluminous X-ray (ULX) sources have finally enabled us to recognize a subclass within the ULX class: the great pretenders, neutron stars (NSs) that appear to emit X-ray radiation at isotropic luminosities Lx = 7 x 10(exp 39) erg/s - 1 x 10(exp 41) erg/s only because their emissions are strongly beamed toward our direction and our sight lines are offset by only a few degrees from their magnetic-dipole axes. The three known pretenders appear to be stronger emitters than the presumed black holes of the ULX class, such as Holmberg II & IX X-1, IC10 X-1 and NGC 300 X-1. For these three NSs, we have adopted a single reasonable assumption, that their brightest observed outbursts unfold at the Eddington rate, and we have calculated both their propeller states and their surface magnetic-field magnitudes. We find that the results are not at all different from those recently obtained for the Magellanic Be/X-ray pulsars: the three NSs reveal modest magnetic fields of about 0.3 - 0.4 TG and beamed propeller-line X-ray luminosities of approx. 10(exp 36) - 10(exp 37) erg/s, substantially below the Eddington limit.

AN OPTICAL AND X-RAY STUDY OF THE FOSSIL GROUP RX J1340.6+4018

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mendes de Oliveira, Claudia L.; Cypriano, Eduardo S.; Sodre, Laerte

2009-08-15

Fossil groups are systems with one single central elliptical galaxy and an unusual lack of luminous galaxies in the inner regions. The standard explanation for the formation of these systems suggests that the lack of bright galaxies is due to galactic cannibalism. In this study, we show the results of an optical and X-ray analysis of RX J1340.6+4018, the prototype fossil group. The data indicate that RX J1340.6+4018 is similar to clusters in almost every sense (dynamical mass, X-ray luminosity, M/L, and luminosity function) except for the lack of L* galaxies. There are claims in the literature that fossil systemsmore » have a lack of small mass halos, compared to predictions based on the lambda cold dark matter scenario. The observational data gathered on this and other fossil groups so far offer no support for this idea. Analysis of the SN Ia/SN II ejecta ratio in the inner and outer regions shows a marginally significant central dominance of SN Ia material. This suggests that either the merger which originated in the central galaxy was dry or the group has been formed at early epochs, although better data are needed to confirm this result.« less

The HELLAS2XMM survey. IV. Optical identifications and the evolution of the accretion luminosity in the Universe

NASA Astrophysics Data System (ADS)

Fiore, F.; Brusa, M.; Cocchia, F.; Baldi, A.; Carangelo, N.; Ciliegi, P.; Comastri, A.; La Franca, F.; Maiolino, R.; Matt, G.; Molendi, S.; Mignoli, M.; Perola, G. C.; Severgnini, P.; Vignali, C.

2003-10-01

We present results from the photometric and spectroscopic identification of 122 X-ray sources recently discovered by XMM-Newton in the 2-10 keV band (the HELLAS2XMM 1dF sample). Their flux cover the range 8*E-15-4*E-13 erg cm-2 s-1 and the total area surveyed is 0.9 square degrees. One of the most interesting results (which is found also in deeper sourveys) is that about 20% of the hard X-ray selected sources have an X-ray to optical flux ratio (X/O) ten times or more higher than that of optically selected AGN. Unlike the faint sources found in the ultra-deep Chandra and XMM-Newton surveys, which reach X-ray (and optical) fluxes more than one order of magnitude lower than the HELLAS2XMM survey sources, many of the extreme X/O sources in our sample have Rprotect la25 and are therefore accessible to optical spectroscopy. We report the identification of 13 sources with X/Oprotect ga10 (to be compared with 9 sources known from the deeper, pencil-beam surveys). Eight of them are narrow line QSO (seemingly the extension to very high luminosity of the type 2 Seyfert galaxies), four are broad line QSO. The results from our survey are also used to make reliable predictions about the luminosity of the sources not yet spectroscopically identified, both in our sample and in deeper Chandra and XMM-Newton samples. We then use a combined sample of 317 hard X-ray selected sources (HELLAS2XMM 1dF, Chandra Deep Field North 1Msec, Chandra SSA13 and XMM-Newton Lockman Hole flux limited samples), 221 with measured redshifts, to evaluate the cosmological evolution of the hard X-ray source's number and luminosity densities. Looking backward in time, the low luminosity sources (log L2-10 keV=43-44 erg s-1) increase in number at a much slower rate than the very high luminosity sources (log L2-10 keV >44.5 erg s-1), reaching a maximum around z=1 and then levelling off beyond z=2. This translates into an accretion driven luminosity density which is dominated by sources with log L2-10 keV <44.5 erg s-1 up to at least z=1, while the contribution of the same sources and of those with log L2-10 keV >44.5 erg s-1 appear, with yet rather large uncertainties, to be comparable between z=2 and 4. Based on observations collected at the European Southern Observatory, La Silla and Paranal, Chile, and at the Telescopio Nazionale Galileo, Roque de Los Muchachos, La Palma, TF, Spain. Based also on observations made with XMM-Newton, an ESA science mission. Table 1 is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/409/79

X-RAYS FROM A RADIO-LOUD COMPACT BROAD ABSORPTION LINE QUASAR 1045+352 AND THE NATURE OF OUTFLOWS IN RADIO-LOUD BROAD ABSORPTION LINE QUASARS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kunert-Bajraszewska, Magdalena; Katarzynski, Krzysztof; Siemiginowska, Aneta

2009-11-10

We present new results on X-ray properties of radio-loud broad absorption line (BAL) quasars and focus on broadband spectral properties of a high-ionization BAL (HiBAL) compact steep spectrum (CSS) radio-loud quasar 1045+352. This HiBAL quasar has a very complex radio morphology indicating either strong interactions between a radio jet and the surrounding interstellar medium or a possible re-start of the jet activity. We detected 1045+352 quasar in a short 5 ksec Chandra ACIS-S observation. We applied theoretical models to explain spectral energy distribution of 1045+352 and argue that non-thermal, inverse-Compton (IC) emission from the innermost parts of the radio jetmore » can account for a large fraction of the observed X-ray emission. In our analysis, we also consider a scenario in which the observed X-ray emission from radio-loud BAL quasars can be a sum of IC jet X-ray emission and optically thin corona X-ray emission. We compiled a sample of radio-loud BAL quasars that were observed in X-rays to date and report no correlation between their X-ray and radio luminosity. However, the radio-loud BAL quasars show a large range of X-ray luminosities and absorption columns. This is consistent with the results obtained earlier for radio-quiet BAL quasars and may indicate an orientation effect in BAL quasars or more complex dependence between X-ray emission, radio emission, and an orientation based on the radio morphology.« less

Free Magnetic Energy and Coronal Heating

NASA Technical Reports Server (NTRS)

Winebarger, Amy; Moore, Ron; Falconer, David

2012-01-01

Previous work has shown that the coronal X-ray luminosity of an active region increases roughly in direct proportion to the total photospheric flux of the active region's magnetic field (Fisher et al. 1998). It is also observed, however, that the coronal luminosity of active regions of nearly the same flux content can differ by an order of magnitude. In this presentation, we analyze 10 active regions with roughly the same total magnetic flux. We first determine several coronal properties, such as X-ray luminosity (calculated using Hinode XRT), peak temperature (calculated using Hinode EIS), and total Fe XVIII emission (calculated using SDO AIA). We present the dependence of these properties on a proxy of the free magnetic energy of the active region

A luminous X-ray outburst from an intermediate-mass black hole in an off-centre star cluster

NASA Astrophysics Data System (ADS)

Lin, Dacheng; Strader, Jay; Carrasco, Eleazar R.; Page, Dany; Romanowsky, Aaron J.; Homan, Jeroen; Irwin, Jimmy A.; Remillard, Ronald A.; Godet, Olivier; Webb, Natalie A.; Baumgardt, Holger; Wijnands, Rudy; Barret, Didier; Duc, Pierre-Alain; Brodie, Jean P.; Gwyn, Stephen D. J.

2018-06-01

A unique signature for the presence of massive black holes in very dense stellar regions is occasional giant-amplitude outbursts of multi-wavelength radiation from tidal disruption and subsequent accretion of stars that make a close approach to the black holes1. Previous strong tidal disruption event (TDE) candidates were all associated with the centres of largely isolated galaxies2-6. Here, we report the discovery of a luminous X-ray outburst from a massive star cluster at a projected distance of 12.5 kpc from the centre of a large lenticular galaxy. The luminosity peaked at 1043 erg s-1 and decayed systematically over 10 years, approximately following a trend that supports the identification of the event as a TDE. The X-ray spectra were all very soft, with emission confined to be ≲3.0 keV, and could be described with a standard thermal disk. The disk cooled significantly as the luminosity decreased—a key thermal-state signature often observed in accreting stellar-mass black holes. This thermal-state signature, coupled with very high luminosities, ultrasoft X-ray spectra and the characteristic power-law evolution of the light curve, provides strong evidence that the source contains an intermediate-mass black hole with a mass tens of thousand times that of the solar mass. This event demonstrates that one of the most effective means of detecting intermediate-mass black holes is through X-ray flares from TDEs in star clusters.

Chandra Survey of Nearby Galaxies: Testing the Accretion Model for Low-luminosity AGNs

NASA Astrophysics Data System (ADS)

She, Rui; Ho, Luis C.; Feng, Hua; Cui, Can

2018-06-01

From a Chandra sample of active galactic nuclei (AGNs) in nearby galaxies, we find that for low-luminosity AGNs, either the intrinsic absorption column density, or the fraction of absorbed AGNs, positively scales with the Eddington ratio for L bol/L Edd ≲ 10‑2. Such a behavior, along with the softness of the X-ray spectrum at low luminosities, is in good agreement with the picture that they are powered by hot accretion flows surrounding supermassive black holes. Numerical simulations find that outflows are inevitable with hot accretion flows, and the outflow rate is correlated with the innermost accretion rate in the low-luminosity regime. This agrees well with our results, suggesting that the X-ray absorption originates from, or is associated with, the outflow material. Gas and dust on larger scales may also produce the observed correlation. Future correlation analyses may help differentiate the two scenarios.

Observations of galactic X-ray sources by OSO-7

NASA Technical Reports Server (NTRS)

Markert, T. H.; Canizares, C. R.; Clark, G. W.; Hearn, D. R.; Li, F. K.; Sprott, G. F.; Winkler, P. F.

1977-01-01

We present the MIT data from the OSO-7 satellite for observations of the galactic plane between 1971 and 1974. A number of sources discovered in the MIT all-sky survey are described in detail: MX 0049 + 59, MX 0836 - 42, MX 1353 - 64, MX 1406 - 61, MX 1418 - 61, MX 1709 - 40, and MX 1608 - 52 (the persistent source suggested to be associated with the X-ray burst source XB 1608 - 52). Upper limits to the X-ray emission from a number of interesting objects are also derived. General results describing all of our observations of galactic sources are presented. Specifically, we display the number-intensity diagrams, luminosity functions, and color-color diagrams for all of the sources we detected. The data are divided between disk and bulge populations, and the characteristics of the two groups are contrasted. Finally, the concept of X-ray source populations and the relationship of globular cluster sources and burst sources to the disk and bulge populations are discussed.

ASCA Observations of "Type 2" LINERs Evidence for a Stellar Source of Ionization

NASA Technical Reports Server (NTRS)

Terashima, Yuichi; Ho, Luis C.; Ptak, Andrew F.; Mushotzky, Richard F.; Serlemitsos, Peter J.; Yaqoob, Tahir; Kunieda, Hideyo

1999-01-01

We present ASCA observations of LINERs without broad H.alpha emission in their optical spectra. The sample of "type 2" LINERs consists of NGC 404, 4111, 4192, 4457, and 4569. We have detected X-ray emission from all the objects except for NGC 404; among the detected objects are two so-called transition objects (NGC 4192 and NGC 4569), which have been postulated to be composite nuclei having both an H II region and a LINER component. The images of NGC 4111 and NGC 4569 in the soft (0.5-2 keV) and hard (2-7 keV) X-ray bands are extended on scales of several kpc. The X-ray spectra of NGC 4111, NGC 4457 and NGC 4569 are well fitted by a two-component model that consists of soft thermal emission with kT approximately 0.65 keV and a hard component represented by a power law (photon index approximately 2) or by thermal bremsstrahlung emission (kT approximately several keV). The extended hard X-rays probably come from discrete sources, while the soft emission most likely originates from hot gas produced by active star formation in the host galaxy. We have found no clear evidence for the presence of active galactic nuclei (AGNs) in the sample. Using black hole masses estimated from host galaxy bulge luminosities, we obtain an upper limit on the implied Eddington ratios less than 5 x 10(exp -5). If an AGN component is the primary ionization source of the optical emission lines, then it must be heavily obscured with a column density significantly larger than 10(exp 23)/sq cm, since the observed X-ray luminosity is insufficient to drive the luminosities of the optical emission lines. Alternatively, the optical emission could be ionized by a population of exceptionally hot stars. This interpretation is consistent with the small [O I] lambda6300/H.alpha ratios observed in these sources, the ultraviolet spectral characteristics in the cases where such information exists, and the X-ray results reported here. We also analyze the X-ray properties of NGC 4117, a low-luminosity Seyfert 2 galaxy serendipitously observed in the field of NGC 4111.

The Intermediate Luminosity Optical Transient SN 2010da: The Progenitor, Eruption, and Aftermath of a Peculiar Supergiant High-mass X-Ray Binary

NASA Astrophysics Data System (ADS)

Villar, V. A.; Berger, E.; Chornock, R.; Margutti, R.; Laskar, T.; Brown, P. J.; Blanchard, P. K.; Czekala, I.; Lunnan, R.; Reynolds, M. T.

2016-10-01

We present optical spectroscopy, ultraviolet-to-infrared imaging, and X-ray observations of the intermediate luminosity optical transient (ILOT) SN 2010da in NGC 300 (d = 1.86 Mpc) spanning from -6 to +6 years relative to the time of outburst in 2010. Based on the light-curve and multi-epoch spectral energy distributions of SN 2010da, we conclude that the progenitor of SN 2010da is a ≈10-12 M ⊙ yellow supergiant possibly transitioning into a blue-loop phase. During outburst, SN 2010da had a peak absolute magnitude of M bol ≲ -10.4 mag, dimmer than other ILOTs and supernova impostors. We detect multi-component hydrogen Balmer, Paschen, and Ca II emission lines in our high-resolution spectra, which indicate a dusty and complex circumstellar environment. Since the 2010 eruption, the star has brightened by a factor of ≈5 and remains highly variable in the optical. Furthermore, we detect SN 2010da in archival Swift and Chandra observations as an ultraluminous X-ray source (L X ≈ 6 × 1039 erg s-1). We additionally attribute He II 4686 Å and coronal Fe emission lines in addition to a steady X-ray luminosity of ≈1037 erg s-1 to the presence of a compact companion.

Mass constraints to Sco X-1 from Bowen fluorescence and deep near-infrared spectroscopy

NASA Astrophysics Data System (ADS)

Mata Sánchez, D.; Muñoz-Darias, T.; Casares, J.; Steeghs, D.; Ramos Almeida, C.; Acosta Pulido, J. A.

2015-04-01

More than 50 years after the dawn of X-ray astronomy, the dynamical parameters of the prototypical X-ray binary Sco X-1 are still unknown. We combine a Monte Carlo analysis, which includes all the previously known orbital parameters of the system, along with the K-correction to set dynamical constraints to the masses of the compact object (M1 < 1.73 M⊙) and the companion star (0.28 M⊙ < M2 < 0.70 M⊙). For the case of a canonical neutron star mass of M1 ˜ 1.4 M⊙, the orbital inclination is found to be lower than 40°. We also present the best near-infrared spectrum of the source to date. There is no evidence of donor star features on it, but we are able to constrain the veiling factor as a function of the spectral type of the secondary star. The combination of both techniques restricts the spectral type of the donor to be later than K4 and luminosity class IV. It also constrains the contribution of the companion light to the infrared emission of Sco X-1 to be lower than 33 per cent. This implies that the accretion related luminosity of the system in the K band is larger than ˜4 × 1035 erg s-1.

The Great Pretenders Among the ULX Class

NASA Astrophysics Data System (ADS)

Christodoulou, Dimitris M.; Laycock, Silas G. T.; Kazanas, Demosthenes; Cappallo, Rigel; Contopoulos, Ioannis

2017-05-01

The recent discoveries of pulsed X-ray emission from three ultraluminous X-ray (ULX) sources have finally enabled us to recognize a subclass within the ULX class: the great pretenders, neutron stars (NSs) that appear to emit X-ray radiation at isotropic luminosities {L}{{X}}=7× {10}39 {erg} {{{s}}}-1-1× {10}41 {erg} {{{s}}}-1 only because their emissions are strongly beamed toward our direction and our sight lines are offset by only a few degrees from their magnetic-dipole axes. The three known pretenders appear to be stronger emitters than the presumed black holes of the ULX class, such as Holmberg II & IX X-1, IC10 X-1 and NGC 300 X-1. For these three NSs, we have adopted a single reasonable assumption, that their brightest observed outbursts unfold at the Eddington rate, and we have calculated both their propeller states and their surface magnetic-field magnitudes. We find that the results are not at all different from those recently obtained for the Magellanic Be/X-ray pulsars: the three NSs reveal modest magnetic fields of about 0.3-0.4 TG and beamed propeller-line X-ray luminosities of ˜ {10}36-{10}37 {erg} {{{s}}}-1, substantially below the Eddington limit.

The XMM-Newton Extended Survey of the Taurus Molecular Cloud (XEST)

NASA Astrophysics Data System (ADS)

Feigelson, Eric; Guedel, M.

2007-12-01

The XMM-Newton Extended Survey of the Taurus Molecular Cloud is an exceptionally large and growing X-ray survey of the Taurus Molecular Cloud (TMC). Now comprising 31 1/2-degree diameter fields, observed with the three XMM-Newton EPIC cameras. High-resolution spectroscopy has been obtained for about ten T Tauri stars (TTS) with the RGS instruments, and the Optical Monitor secured an optical/UV survey. XEST detects essentially the entire surveyed TTS population of the TMC in X-rays including about half of the observed (8/16) brown dwarfs and Class I protostars (8/20). Several new candidate members are identified. The X-ray luminosity (LX) of TTS shows related correlations with both stellar bolometric luminosity and mass. Classical TTS show suppressed X-ray output in the CCD band by a factor of about 2. These statistical results confirm results from other star formation regions. Different from previous reports on TMC, XEST identifies no activity-rotation relation. Brown dwarfs are found to follow trends set by TTS, both for accreting and non-accreting objects. But a decrease of the fractional luminosity, LX/Lbol, is seen with decreasing mass indicating weakened heating efficiency in the substellar domain. XEST reports five members of the class of "Two-Absorber X-Ray" (TAX) sources which reveal a double-peaked spectrum originating from two unrelated sources with different absorption column densities. The softer emission is thought to be related to jets, as explicitly seen in DG Tau. RGS spectroscopy shows a systematic "X-ray soft excess" in classical TTS, suggesting excessive cool (1-2 MK) plasma due to accretion, although the excess seems to correlate with magnetic activity as well. XEST has been supported by the Space Science Institute (Bern/Switz.).

Fossil Groups as Cosmological Labs

NASA Astrophysics Data System (ADS)

D'Onghia, Elena

Optical and X-ray measurements of fossil groups (FGs) suggest that they are old and relaxed systems. If FGs are assembled at higher redshift, there is enough time for intermediate-luminosity galaxies to merge, resulting in the formation of the brightest group galaxy (BGG). We carry out the first, systematic study of a large sample of FGs, the "FOssil Group Origins'' (FOGO) based on an International Time Project at the Roque de los Muchachos Observatory. For ten FOGO FGs we have been awarded time at SUZAKU Telescope to measure the temperature of the hot intragroup gas (IGM). For these systems we plan to evaluate and correlate their X-ray luminosity and X-ray temperature, Lx-Tx, optical luminosity and X-ray temperature, Lopt-Tx, and group velocity dispersion with their X-ray temperature, sigma V-Tx, as compared to the non fossil systems. By combining these observations with state-of-art cosmological hydrodynamical simulations we will open a new window into the study of the IGM and the nature of fossil systems. Our proposed work will be of direct relevance for the understanding and interpretation of data from several NASA science missions. Specifically, the scaling relations obtained from these data combined with our predictions obtained using state-of-the-art hydrodynamical simulation numerical adopting a new hydrodynamical scheme will motivate new proposal on CHANDRA X-ray telescope for fossil groups and clusters. We will additionally create a public Online Planetarium Show. This will be an educational site, containing an interactive program called: "A Voyage to our Universe''. In the show we will provide observed images of fossil groups and similar images and movies obtained from the numerical simulations showing their evolution. The online planetarium show will be a useful reference and an interactive educational tool for both students and the public.

Accretion Properties of a Sample of Hard X-Ray (<60 keV) Selected Seyfert 1 Galaxies

NASA Astrophysics Data System (ADS)

Wang, J.; Mao, Y. F.; Wei, J. Y.

2009-02-01

We examine the accretion properties in a sample of 42 hard (3-60 keV) X-ray selected nearby broad-line active galactic nuclei (AGNs). The energy range in the sample is harder than that usually used in similar previous studies. These AGNs are mainly complied from the RXTE All Sky Survey, and complemented by the released INTEGRAL AGN catalog. The black hole masses, bolometric luminosities of AGN, and Eddington ratios are derived from their optical spectra in terms of the broad Hβ emission line. The tight correlation between the hard X-ray (3-20 keV) and bolometric/line luminosity is well identified in our sample. Also identified is a strong inverse Baldwin relationship of the Hβ emission line. In addition, all of these hard X-ray AGNs are biased toward luminous objects with a high Eddington ratio (mostly between 0.01 and 0.1) and a low column density (<1022 cm-2), which is most likely due to the selection effect of the surveys. The hard X-ray luminosity is consequently found to be strongly correlated with the black hole mass. We believe the sample completeness will be improved in the next few years by the ongoing Swift and the International Gamma-Ray Astrophysics Laboratory missions, and by the next advanced missions, such as NuSTAR, Simbol-X, and NeXT. Finally, the correlation between RFe (= optical Fe II/Hβ) and disk temperature as assessed by T vprop (L/L Edd)M -1 BH leads us to suggest that the strength of the Fe II emission is mainly determined by the shape of the ionizing spectrum.

Heavy X-ray obscuration in the most luminous galaxies discovered by WISE

NASA Astrophysics Data System (ADS)

Vito, F.; Brandt, W. N.; Stern, D.; Assef, R. J.; Chen, C.-T. J.; Brightman, M.; Comastri, A.; Eisenhardt, P.; Garmire, G. P.; Hickox, R.; Lansbury, G.; Tsai, C.-W.; Walton, D. J.; Wu, J. W.

2018-03-01

Hot dust-obscured galaxies (DOGs) are hyperluminous (L8-1000 μm > 1013 L⊙) infrared galaxies with extremely high (up to hundreds of K) dust temperatures. The sources powering both their extremely high luminosities and dust temperatures are thought to be deeply buried and rapidly accreting supermassive black holes (SMBHs). Hot DOGs could therefore represent a key evolutionary phase in which the SMBH growth peaks. X-ray observations can be used to study their obscuration levels and luminosities. In this work, we present the X-ray properties of the 20 most luminous (Lbol ≳ 1014 L⊙) known hot DOGs at z = 2-4.6. Five of them are covered by long-exposure (10-70 ks) Chandra and XMM-Newton observations, with three being X-ray detected, and we study their individual properties. One of these sources (W0116-0505) is a Compton-thick candidate, with column density NH = (1.0-1.5) × 1024 cm-2 derived from X-ray spectral fitting. The remaining 15 hot DOGs have been targeted by a Chandra snapshot (3.1 ks) survey. None of these 15 are individually detected; therefore, we applied a stacking analysis to investigate their average emission. From hardness ratio analysis, we constrained the average obscuring column density and intrinsic luminosity to be log NH (cm-2) > 23.5 and LX ≳ 1044 erg s-1, which are consistent with results for individually detected sources. We also investigated the LX-L6 μm and LX-Lbol relations, finding hints that hot DOGs are typically X-ray weaker than expected, although larger samples of luminous obscured quasi-stellar objects are needed to derive solid conclusions.

HRI observations of the Pleiades

NASA Technical Reports Server (NTRS)

Harnden, F. R., Jr.; Caillault, J.-P.; Damiani, F.; Kashyap, V.; Micela, G.; Prosser, C.; Rosner, R.; Sciortino, S.; Stauffer, J.

1996-01-01

The preliminary analysis of the data from the first four Rosat high resolution imager (HRI) pointings provided many new faint Pleiades detections. The completion of the high resolution survey of the most source-confused regions of this open cluster will lead to the construction of proper X-ray luminosity functions and will yield a definitive assessment of the coronal emission of the Pleiades members.

CHANDRA CHARACTERIZATION OF X-RAY EMISSION IN THE YOUNG F-STAR BINARY SYSTEM HD 113766

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lisse, C. M.; Christian, D. J.; Wolk, S. J.

Using Chandra , we have obtained imaging X-ray spectroscopy of the 10–16 Myr old F-star binary HD 113766. We individually resolve the 1.″4 separation binary components for the first time in the X-ray and find a total 0.3–2.0 keV luminosity of 2.2 × 10{sup 29} erg s{sup −1}, consistent with previous RASS estimates. We find emission from the easternmost, infrared-bright, dusty member HD 113766A to be only ∼10% that of the western, infrared-faint member HD 113766B. There is no evidence for a 3rd late-type stellar or substellar member of HD 113766 with L {sub x} > 6 × 10{sup 25} erg s{sup −1} within 2′ ofmore » the binary pair. The ratio of the two stars’ X-ray luminosity is consistent with their assignments as F2V and F6V by Pecaut et al. The emission is soft for both stars, kT {sub Apec} = 0.30–0.50 keV, suggesting X-rays produced by stellar rotation and/or convection in young dynamos, but not accretion or outflow shocks, which we rule out. A possible 2.8 ± 0.15 (2 σ ) hr modulation in the HD 113766B X-ray emission is seen, but at very low confidence and of unknown provenance. Stellar wind drag models corresponding to L {sub x} ∼ 2 × 10{sup 29} erg s{sup −1} argue for a 1 mm dust particle lifetime around HD 113766B of only ∼90,0000 years, suggesting that dust around HD 113766B is quickly removed, whereas 1 mm sized dust around HD 113766A can survive for >1.5 × 10{sup 6} years. At 10{sup 28}–10{sup 29} erg s{sup −1} X-ray luminosity, astrobiologically important effects, like dust warming and X-ray photolytic organic synthesis, are likely for any circumstellar material in the HD 113766 systems.« less

Multiwavelength Properties of the X-Ray Sources in the Groth-Westphal Strip Field

NASA Astrophysics Data System (ADS)

Miyaji, Takamitsu; Sarajedini, Vicki; Griffiths, Richard E.; Yamada, Toru; Schurch, Matthew; Cristóbal-Hornillos, David; Motohara, Kentaro

2004-06-01

We summarize the multiwavelength properties of X-ray sources detected in the 80 ks XMM-Newton observation of the Groth-Westphal strip, a contiguous strip of 28 Hubble Space Telescope Wide Field Planetary Camera 2 (WFPC2) images. Among the ~150 X-ray sources detected in the XMM-Newton field of view, 23 are within the WFPC2 fields. Ten spectroscopic redshifts are available from the Deep Extragalactic Evolutionary Probe and Canada-France Redshift Survey projects. Four of these show broad Mg II emission and can be classified as type 1 active galactic nuclei (AGNs). Two of those without any broad lines, nevertheless, have [Ne V] emission, which is an unambiguous signature of AGN activity. One is a narrow-line Seyfert 1 and the other a type 2 AGN. As a follow-up, we have made near-infrared spectroscopic observations using the OHS/CISCO spectrometer for five of the X-ray sources for which we found no indication of AGN activity in the optical spectrum. We have detected Hα+[N II] emission in four of them. A broad Hα component and/or a large [N II]/Hα ratio is seen, suggestive of AGN activity. Nineteen sources have been detected in the Ks band, and four of these are extremely red objects (EROs) (I814-Ks>4). The optical counterparts for the majority of the X-ray sources are bulge-dominated. The I814-Ks color of these bulge-dominated hosts are indeed consistent with evolving elliptical galaxies, while contaminations from star formation/AGNs seems to be present in their V606-I814 color. Assuming that the known local relations among the bulge luminosity, central velocity dispersion, and the mass of the central blackhole still hold at z~1, we compare the AGN luminosity with the Eddington luminosity of the central blackhole mass. The AGN bolometric luminosity to Eddington luminosity ratio ranges from 0.3% to 10%. Based on observations from the XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA member states and NASA. Also based on data collected at Subaru Telescope, which is operated by the National Astronomical Observatory of Japan.

Galactic Sources Detected in the NuSTAR Serendipitous Survey

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tomsick, John A.; Clavel, Maïca; Chiu, Jeng-Lun

The Nuclear Spectroscopic Telescope Array (NuSTAR) provides an improvement in sensitivity at energies above 10 keV by two orders of magnitude over non-focusing satellites, making it possible to probe deeper into the Galaxy and universe. Lansbury and collaborators recently completed a catalog of 497 sources serendipitously detected in the 3–24 keV band using 13 deg{sup 2} of NuSTAR coverage. Here, we report on an optical and X-ray study of 16 Galactic sources in the catalog. We identify 8 of them as stars (but some or all could have binary companions), and use information from Gaia to report distances and X-ray luminositiesmore » for 3 of them. There are 4 CVs or CV candidates, and we argue that NuSTAR J233426–2343.9 is a relatively strong CV candidate based partly on an X-ray spectrum from XMM-Newton . NuSTAR J092418–3142.2, which is the brightest serendipitous source in the Lansbury catalog, and NuSTAR J073959–3147.8 are low-mass X-ray binary candidates, but it is also possible that these 2 sources are CVs. One of the sources is a known high-mass X-ray binary (HMXB), and NuSTAR J105008–5958.8 is a new HMXB candidate that has strong Balmer emission lines in its optical spectrum and a hard X-ray spectrum. We discuss the implications of finding these HMXBs for the surface density (log N –log S ) and luminosity function of Galactic HMXBs. We conclude that with the large fraction of unclassified sources in the Galactic plane detected by NuSTAR in the 8–24 keV band, there could be a significant population of low-luminosity HMXBs.« less

A low-luminosity soft state in the short-period black hole X-ray binary Swift J1753.5-0127

NASA Astrophysics Data System (ADS)

Shaw, A. W.; Gandhi, P.; Altamirano, D.; Uttley, P.; Tomsick, J. A.; Charles, P. A.; Fürst, F.; Rahoui, F.; Walton, D. J.

2016-05-01

We present results from the spectral fitting of the candidate black hole X-ray binary Swift J1753.5-0127 in an accretion state previously unseen in this source. We fit the 0.7-78 keV spectrum with a number of models, however the preferred model is one of a multitemperature disc with an inner disc temperature kTin = 0.252 ± 0.003 keV scattered into a steep power-law with photon index Γ =6.39^{+0.08}_{-0.02} and an additional hard power-law tail (Γ = 1.79 ± 0.02). We report on the emergence of a strong disc-dominated component in the X-ray spectrum and we conclude that the source has entered the soft state for the first time in its ˜10 yr prolonged outburst. Using reasonable estimates for the distance to the source (3 kpc) and black hole mass (5 M⊙), we find the unabsorbed luminosity (0.1-100 keV) to be ≈0.60 per cent of the Eddington luminosity, making this one of the lowest luminosity soft states recorded in X-ray binaries. We also find that the accretion disc extended towards the compact object during its transition from hard to soft, with the inner radius estimated to be R_{in}=28.0^{+0.7}_{-0.4} R_g or ˜12Rg, dependent on the boundary condition chosen, assuming the above distance and mass, a spectral hardening factor f = 1.7 and a binary inclination I = 55°.

Colliding winds from early-type stars in binary systems

NASA Technical Reports Server (NTRS)

Stevens, Ian R.; Blondin, John M.; Pollock, A. M. T.

1992-01-01

The dynamics of the wind and shock structure formed by the wind collision in early-type binary systems is examined by means of a 2D hydrodynamics code, which self-consistently accounts for radiative cooling, and represents a significant improvement over previous attempts to model these systems. The X-ray luminosity and spectra of the shock-heated region, accounting for wind attenuation and the influence of different abundances on the resultant level and spectra of X-ray emission are calculated. A variety of dynamical instabilities that are found to dominate the intershock region is examined. These instabilities are found to be particularly important when postshock material is able to cool. These instabilities disrupt the postshock flow and add a time variability of order 10 percent to the X-ray luminosity. The X-ray spectrum of these systems is found to vary with the nuclear abundances of winds. These theoretical models are used to study several massive binary systems, in particular V444 Cyg and HD 193793.

X-ray View of Four High-Luminosity Swift-BAT AGN: Unveiling Obscuration and Reflection with Suzaku

NASA Technical Reports Server (NTRS)

Fiorettil, V.; Angelini, L.; Mushotzky, R. F.; Koss, M.; Malaguti, G.

2013-01-01

Aims. A complete census of obscured Active Galactic Nuclei (AGN) is necessary to reveal the history of the super massive black hole (SMBH) growth and galaxy evolution in the Universe given the complex feedback processes and the fact that much of this growth occurs in an obscured phase. In this context, hard X-ray surveys and dedicated follow-up observations represent a unique tool for selecting highly absorbed AGN and for characterizing the obscuring matter surrounding the SMBH. Here we focus on the absorption and reflection occurring in highly luminous, quasar-like AGN, to study the relation between the geometry of the absorbing matter and the AGN nature (e.g. X-ray, optical, and radio properties), and to help to determine the column density dependency on the AGN luminosity. Methods. The Swift/BAT nine-month survey observed 153 AGN, all with ultra-hard X-ray BAT fluxes in excess of 10(exp -11) erg per square centimeter and an average redshift of 0.03. Among them, four of the most luminous BAT AGN (44.73 less than LogLBAT less than 45.31) were selected as targets of Suzaku follow-up observations: J2246.0+3941 (3C 452), J0407.4+0339 (3C 105), J0318.7+6828, and J0918.5+0425. The column density, scattered/reflected emission, the properties of the Fe K line, and a possible variability are fully analyzed. For the latter, the spectral properties from Chandra, XMM-Newton and Swift/XRT public observations were compared with the present Suzaku analysis, adding an original spectral analysis when non was available from the literature. Results. Of our sample, 3C 452 is the only certain Compton-thick AGN candidate because of i) the high absorption (N(sub H) approximately 4 × 10(exp 23) per square centimeter) and strong Compton reflection; ii) the lack of variability; iii) the "buried" nature, i.e. the low scattering fraction (less than 0.5%) and the extremely low relative [OIII] luminosity. In contrast 3C 105 is not reflection-dominated, despite the comparable column density, X-ray luminosity and radio morphology, but shows a strong long-term variability in flux and scattering fraction, consistent with the soft emission being scattered from a distant region (e.g., the narrow emission line region). The sample presents high (greater than 100) X-to- [OIII] luminosity ratios, with an extreme value of R(sup X)(sub [OIII]) approximately 800 for 3C 452, confirming the [OIII] luminosity to be affected by residual extinction in presence of mild absorption, especially for "buried" AGN such as 3C 452. Three of our targets are powerful FRII radio galaxies, which is shown by their high luminosity and absorption; this makes them the most luminous and absorbed AGN of the BAT Seyfert survey despite the inversely proportional N(sub H) - L(sub X) relation.

An X-ray image of the violent interstellar medium in 30 Doradus

NASA Technical Reports Server (NTRS)

Wang, Q.; Helfand, D. J.

1991-01-01

A detailed analysis of the X-ray emission from the largest H II region complex in the Local Group, 30 Dor, is presented. Applying a new maximum entropy deconvolution algorithm to the Einstein Observatory data, reveals striking correlations among the X-ray, radio, and optical morphologies of the region, with X-ray-emitting bubbles filling cavities surrounded by H-alpha shells and coextensive diffuse X-ray and radio continuum emission from throughout the region. The total X-ray luminosity in the 0.16-3.5 keV band from an area within 160 pc of the central cluster R136 is about 2 x 10 to the 37th ergs/sec.

Impact of ultraluminous X-ray sources on photoabsorption in the first galaxies

NASA Astrophysics Data System (ADS)

Sazonov, S.; Khabibullin, I.

2018-05-01

In the local Universe, integrated X-ray emission from high-mass X-ray binaries (HMXBs) is dominated by the brightest ultraluminous X-ray sources (ULXs) with luminosity ≳1040 erg s-1. Such rare objects probably also dominated the production of X-rays in the early Universe. We demonstrate that a ULX with LX ˜ 1040-1041 erg s-1 (isotropic-equivalent luminosity in the 0.1-10 keV energy band) shining for ˜105 yr (the expected duration of a supercritically accreting phase in HMXBs) can significantly ionize the ISM in its host dwarf galaxy of total mass M ˜ 107-108 M⊙ and thereby reduce its opacity to soft X-rays. As a result, the fraction of the soft X-ray (below 1 keV) radiation from the ULX escaping into the intergalactic medium (IGM) can increase from ˜20-50 per cent to ˜30-80 per cent over its lifetime. This implies that HMXBs can induce a stronger heating of the IGM at z ≳ 10 compared to estimates neglecting the ULX feedback on the ISM. However, larger galaxies with M ≳ 3 × 108 M⊙ could not be significantly ionized even by the brightest ULXs in the early Universe. Since such galaxies probably started to dominate the global star formation rate at z ≲ 10, the overall escape fraction of soft X-rays from the HMXB population probably remained low, ≲30 per cent, at these epochs.

X-ray Follow-ups of XSS J12270-4859: A Low-mass X-ray Binary with Gamma-ray Fermi-LAT Association

NASA Technical Reports Server (NTRS)

deMartino, D.; Belloni, T.; Falanga, M.; Papitto, A.; Motta, S.; Pellizzoni, A.; Evangelista, Y.; Piano, G.; Masetti, N.; Mouchet, M.;

ACTIVE GALACTIC NUCLEUS OBSCURATION FROM WINDS: FROM DUSTY INFRARED-DRIVEN TO WARM AND X-RAY PHOTOIONIZED

PubMed Central

Dorodnitsyn, A.; Kallman, T.

2016-01-01

We present calculations of AGN winds at ~parsec scales, along with the associated obscuration. We take into account the pressure of infrared radiation on dust grains and the interaction of X-rays from a central black hole with hot and cold plasma. Infrared radiation (IR) is incorporated in radiation-hydrodynamic simulations adopting the flux-limited diffusion approximation. We find that in the range of X-ray luminosities L=0.05 – 0.6Ledd, the Compton-thick part of the flow (aka torus) has an opening angle of approximately 72° – 75° regardless of the luminosity. At L ≳ 0.1 the outflowing dusty wind provides the obscuration with IR pressure playing a major role. The global flow consists of two phases: the cold flow at inclinations θ ≳ 70° and a hot, ionized wind of lower density at lower inclinations. The dynamical pressure of the hot wind is important in shaping the denser IR supported flow. At luminosities ≤0.1Ledd episodes of outflow are followed by extended periods when the wind switches to slow accretion. PMID:27642184

NuSTARUnveils a Compton-Thick Type 2 Quasar in MrK 34

DOE PAGES

Gandhi, P.; Lansbury, G. B.; Alexander, D. M.; ...

2014-08-22

We present Nuclear Spectroscopic Telescope Array ( NuSTAR) 3-40 keV observations of the optically selected Type 2 quasar (QSO2) SDSS J1034+6001 or Mrk 34. The high-quality hard X-ray spectrum and archival XMM- Newton data can be fitted self-consistently with a reflection-dominated continuum and a strong Fe Kα fluorescence line with equivalent width >1 keV. Prior X-ray spectral fitting below 10 keV showed the source to be consistent with being obscured by Compton-thin column densities of gas along the line of sight, despite evidence for much higher columns from multiwavelength data. NuSTAR now enables a direct measurement of this column andmore » shows that N H lies in the Compton-thick (CT) regime. The new data also show a high intrinsic 2-10 keV luminosity of L 2-10 ~ 10 44 erg s –1, in contrast to previous low-energy X-ray measurements where L 2-10 ≲ 10 43 erg s –1 (i.e., X-ray selection below 10 keV does not pick up this source as an intrinsically luminous obscured quasar). Both the obscuring column and the intrinsic power are about an order of magnitude (or more) larger than inferred from pre- NuSTAR X-ray spectral fitting. Mrk 34 is thus a "gold standard" CT QSO2 and is the nearest non-merging system in this class, in contrast to the other local CT quasar NGC 6240, which is currently undergoing a major merger coupled with strong star formation. For typical X-ray bolometric correction factors, the accretion luminosity of Mrk 34 is high enough to potentially power the total infrared luminosity. In conclusion, X-ray spectral fitting also shows that thermal emission related to star formation is unlikely to drive the observed bright soft component below ~3 keV, favoring photoionization instead.« less

SN 2005ip: A Luminous Type IIn Supernova Emerging from a Dense Circumstellar Medium as Revealed by X-Ray Observations

NASA Astrophysics Data System (ADS)

Katsuda, Satoru; Maeda, Keiichi; Nozawa, Takaya; Pooley, David; Immler, Stefan

2014-01-01

We report on the X-ray spectral evolution of the nearby Type IIn supernova (SN) 2005ip based on Chandra and Swift observations covering ~1-6 yr after explosion. X-ray spectra in all epochs are well fitted by a thermal emission model with kT >~ 7 keV. The somewhat high temperature suggests that the X-ray emission mainly arises from the circumstellar medium (CSM) heated by the forward shock. We find that the spectra taken two to three years after the explosion are heavily absorbed (N H ~ 5 × 1022 cm-2), but the absorption gradually decreases to the level of the Galactic absorption (N H ~ 4 × 1020 cm-2) at the final epoch. This indicates that the SN went off in a dense CSM and that the forward shock has overtaken it. The intrinsic X-ray luminosity stays constant until the final epoch, when it drops by a factor of ~2. The intrinsic 0.2-10 keV luminosity during the plateau phase is measured to be ~1.5 × 1041 erg s-1, ranking SN 2005ip as one of the brightest X-ray SNe. Based on the column density, we derive a lower limit of a mass-loss rate to be \\dot{M}˜ 1.5× 10-2 (Vw /100 km s-1) M ⊙ yr-1, which roughly agrees with that inferred from the X-ray luminosity, \\dot{M}˜ 2× 10-2 (Vw /100 km s-1) M ⊙ yr-1, where Vw is the circumstellar wind speed. Such a high mass-loss rate suggests that the progenitor star had eruptive mass ejections similar to a luminous blue variable star. The total mass ejected in the eruptive period is estimated to be ~15 M ⊙, indicating that the progenitor mass is >~ 25 M ⊙.

Cosmic evolution of AGN with moderate-to-high radiative luminosity in the COSMOS field

NASA Astrophysics Data System (ADS)

Ceraj, L.; Smolčić, V.; Delvecchio, I.; Delhaize, J.; Novak, M.

2018-05-01

We study the moderate-to-high radiative luminosity active galactic nuclei (HLAGN) within the VLA-COSMOS 3 GHz Large Project. The survey covers 2.6 square degrees centered on the COSMOS field with a 1σ sensitivity of 2.3 μJy/beam across the field. This provides the simultaneously largest and deepest radio continuum survey available to date with exquisite multi-wavelength coverage. The survey yields 10,830 radio sources with signal-to-noise ratios >=5. A subsample of 1,604 HLAGN is analyzed here. These were selected via a combination of X-ray luminosity and mid-infrared colors. We derive luminosity functions for these AGN and constrain their cosmic evolution out to a redshift of z ~ 6, for the first time decomposing the star formation and AGN contributions to the radio continuum emission in the AGN. We study the evolution of number density and luminosity density finding a peak at z ~ 1.5 followed by a decrease out to a redshift z ~ 6.

On the Weak-Wind Problem in Massive Stars: X-Ray Spectra Reveal a Massive Hot Wind in mu Columbae

NASA Technical Reports Server (NTRS)

Huenemoerder, David P.; Oskinova, Lidia M.; Ignace, Richard; Waldron, Wayne L.; Todt, Helge; Hamaguchi, Kenji; Kitamoto, Shunji

2012-01-01

Mu Columbae is a prototypical weak-wind O star for which we have obtained a high-resolution X-ray spectrum with the Chandra LETG/ACIS instrument and a low-resolution spectrum with Suzaku. This allows us, for the first time, to investigate the role of X-rays on the wind structure in a bona fide weak-wind system and to determine whether there actually is a massive hot wind. The X-ray emission measure indicates that the outflow is an order of magnitude greater than that derived from UV lines and is commensurate with the nominal wind-luminosity relationship for O stars. Therefore, the "weak-wind problem"--identified from cool wind UV/optical spectra--is largely resolved by accounting for the hot wind seen in X-rays. From X-ray line profiles, Doppler shifts, and relative strengths, we find that this weak-wind star is typical of other late O dwarfs. The X-ray spectra do not suggest a magnetically confined plasma-the spectrum is soft and lines are broadened; Suzaku spectra confirm the lack of emission above 2 keV. Nor do the relative line shifts and widths suggest any wind decoupling by ions. The He-like triplets indicate that the bulk of the X-ray emission is formed rather close to the star, within five stellar radii. Our results challenge the idea that some OB stars are "weak-wind" stars that deviate from the standard wind-luminosity relationship. The wind is not weak, but it is hot and its bulk is only detectable in X-rays.

Snapshots in X-ray binary evolution: Using Hα Emitters and post-starburst galaxies to study the age-dependence of XRB populations

NASA Astrophysics Data System (ADS)

Basu-Zych, Antara; Hornschemeier, Ann; Fragkos, Anastasios; Lehmer, Bret; Zezas, Andreas; Yukita, Mihoko; Tzanavaris, Panayiotis

2018-01-01

The X-ray emission in galaxies, due to X-ray binaries (XRBs), appears to depend on global galaxy properties such as stellar mass (M*), star formation rate (SFR), metallicity, and stellar age. This poster will present unique galaxy populations with well-defined stellar ages to test current relations and models. Specifically, Hα emitters (HAEs), which are nearby analogs of galaxies in the early universe, trace how XRBs form and evolve in young, metal-poor environments. We find that HAEs have lower X-ray luminosities per SFR and metallicity compared to other normal galaxies. At such young ages (<10Myr), XRBs may not have fully formed. Therefore, these observations provide constraints for the expected X-ray emission from XRBs in the early Universe. Post-starburst galaxies, selected by the strength of the Hδ equivalent width (> 500 Å), probe the XRB population related to stellar ages of 0.1-1 Gyr. At these ages, the donor star is expected to be an A-star whose mass is ~2 M⊙ and similar to that of the compact object, which may potentially lead to high mass transfer rates and high X-ray luminosities. Together, these samples offer important constraints for the evolution of XRBs with stellar age.

The faint X-ray sources in and out of omega Centauri: X-ray observations and optical identifications

NASA Technical Reports Server (NTRS)

Cool, Adrienne M.; Grindlay, Jonathan E.; Bailyn, Charles D.; Callanan, Paul J.; Hertz, Paul

1995-01-01

We present the results of an observation of the globular cluster omega Cen (NGC 5139) with the Einstein high-resolution imager (HRI). Of the five low-luminosity X-ray sources toward omega Cen which were first identified with the Einstein imaging proportional counter (IPC) (Hertz and Grindlay 1983a, b), two are detected in the Einstein HRI observation: IPC sources A and D. These detections provide source positions accurate to 3 sec-4 sec; the positions are confirmed in a ROSAT HRI observation reported here. Using CCD photometry and spectroscopy, we have identified both sources as foreground dwarf M stars with emission lines (dMe). The chance projection of two Mde stars within approximately 13 min of the center of omega Cen is not extraordinary, given the space density of these stellar coronal X-ray sources. We discuss the possible nature of the three as yet unidentified IPC sources toward omega Cen, and consider the constraints that the Einstein observations place on the total population of X-ray sources in this cluster. The integrated luminosity from faint X-ray sources in omega Cen appears to be low relative to both the old open cluster M67 and the post-core-collapse globular, NGC 6397.

Origin of the X-ray Spectral Variation and Seemingly Broad Iron Line Strucuture in the Seyfert Galaxies

NASA Astrophysics Data System (ADS)

Ebisawa, Ken; Naoki, Iso

2012-07-01

X-ray intensities and spectra of the Seyfert galaxies are known to be variable. Some of the sources have characteristic seemingly broad iron line structure, and their spectral variations are small in the iron line energy band. MCG-6-30-15 is such an archetypal source, and Miyakawa (2011) proposed a "Variable Partial Covering (VPC)" model to explain its continuum spectral variation, seemingly broad iron line structure, and small spectral variation in the iron energy band simultaneously, only due to variation of a single parameter. That single parameter is the "partial covering fraction" to describe the geometrical fraction of the X-ray emitting area covered by the ionized absorbers in the line of sight. The intrinsic X-ray luminosity is hardly variable in this model. We have applied the VPC model to the 27 Seyfert galaxies observed with Suzaku, and found that spectral variations of the 22 sources are successfully explained by this model only varying the partial covering fraction. Intrinsic X-ray luminosities of Seyfert galaxies are not variable, as opposed to what they apparently seem, and gravitationally red-shifted iron line is not necessary. Those ionized absorbing clouds are most likely to be Broad Line Region (BLR) clouds, and we will be able to constrain the BLR structure from X-ray observations.

Swift and SALT observations of the multiple outbursts of MAXI J1957+032

NASA Astrophysics Data System (ADS)

Mata Sánchez, D.; Charles, P. A.; Armas Padilla, M.; Buckley, D. A. H.; Israel, G. L.; Linares, M.; Muñoz-Darias, T.

2017-06-01

The new recurrent X-ray transient MAXI J1957+032 has had four X-ray outbursts within 16 months, all very briefly detected (lasting <5 d). During the most recent event (2016 September/October), we obtained with the Southern African Large Telescope the first optical spectrum of the transient counterpart, showing the classic blue continuum of an X-ray irradiated disc in an LMXB and no other features. At high Galactic latitude below the plane (-13°) reddening is low but there is no quiescent counterpart visible on any of the existing sky surveys, nor any other known X-ray source in the region. Swift monitoring of three of the four events is presented, showing rapidly fading X-ray outbursts together with significant UVOT detections in the UV (W1,M2,W2), U and B bands. The optical properties are most like those of the short-period LMXBs, which, combined with the softening witnessed during the decay to quiescence would place the system at d < 13 kpc. The short duration and short recurrence time of the outbursts are reminiscent of the accreting millisecond X-ray pulsars, which exhibit peak luminosities of ˜ 1 per cent LEdd. Assuming this peak luminosity would place MAXI J1957+032 at a distance of d ˜ 5-6 kpc.

Truncation of the Inner Accretion Disk Around a Black Hole at Low Luminosity

NASA Technical Reports Server (NTRS)

Tomsick, John A.; Yamoka, Kazutaka; Corbel, Stephane; Kaaret, Philip; Kalemci, Emrah; Migliari, Simone

2011-01-01

Most black hole binaries show large changes in X-ray luminosity caused primarily by variations in mass accretion rate. An important question for understanding black hole accretion and jet production is whether the inner edge of the accretion disk recedes at low accretion rate. Measurements of the location of the inner edge (R(sub in)) can be made using iron emission lines that arise due to fluorescence of iron in the disk, and these indicate that R(sub in) is very close to the black hole at high and moderate luminosities (greater than or equal to 1% of the Eddington luminosity, L(sub Edd). Here, we report on X-ray observations of the black hole GX 339-4 in the hard state by Suzaku and the Rossi X-ray Timing Explorer that extend iron line studies to 0.14% L(sub Edd) and show that R(sub in) increases by a factor of greater than 27 over the value found when GX 339-4 was bright. The exact value of R(sub in) depends on the inclination of the inner disk (i), and we derive 90% confidence limits of R(sub in) greater than 35 R(sub g) at i = 0 degrees and R(sub in) greater than 175 R(sub g) at i = 30 degrees. This provides direct evidence that the inner portion of the disk is not present at low luminosity, allowing for the possibility that the inner disk is replaced by advection- or magnetically dominated accretion flows.

Deep Extragalactic X-Ray Surveys

NASA Astrophysics Data System (ADS)

Brandt, W. N.; Hasinger, G.

2005-09-01

Deep surveys of the cosmic X-ray background are reviewed in the context of observational progress enabled by the Chandra X-Ray Observatory and the X-Ray Multi-Mirror Mission-Newton. The sources found by deep surveys are described along with their redshift and luminosity distributions, and the effectiveness of such surveys at selecting active galactic nuclei (AGN) is assessed. Some key results from deep surveys are highlighted, including (a) measurements of AGN evolution and the growth of supermassive black holes, (b) constraints on the demography and physics of high-redshift AGN, (c) the X-ray AGN content of infrared and submillimeter galaxies, and (d) X-ray emission from distant starburst and normal galaxies. We also describe some outstanding problems and future prospects for deep extragalactic X-ray surveys.

Accretion and Outflows in X-ray Binaries: What's Really Going on During X-ray Quiescence

NASA Astrophysics Data System (ADS)

MacDonald, Rachel K. D.; Bailyn, Charles D.; Buxton, Michelle

2015-01-01

X-ray binaries, consisting of a star and a stellar-mass black hole, are wonderful laboratories for studying accretion and outflows. They evolve on timescales quite accessible to us, unlike their supermassive cousins, and allow the possibility of gaining a deeper understanding of these two common astrophysical processes. Different wavelength regimes reveal different aspects of the systems: radio emission is largely generated by outflows and jets, X-ray emission by inner accretion flows, and optical/infrared (OIR) emission by the outer disk and companion star. The search for relationships between these different wavelengths is thus an area of active research, aiming to reveal deeper connections between accretion and outflows.Initial evidence for a strong, tight correlation between radio and X-ray emission has weakened as further observations and newly-discovered sources have been obtained. This has led to discussions of multiple tracks or clusters, or the possibility that no overall relation exists for the currently-known population of X-ray binaries. Our ability to distinguish among these options is hampered by a relative lack of observations at lower luminosities, and especially of truly X-ray quiescent (non-outbursting) systems. Although X-ray binaries spend the bulk of their existence in quiescence, few quiescent sources have been observed and multiple observations of individual sources are largely nonexistent. Here we discuss new observations of the lowest-luminosity quiescent X-ray binary, A0620-00, and the place this object occupies in investigations of the radio/X-ray plane. For the first time, we also incorporate simultaneous OIR data with the radio and X-ray data.In December 2013 we took simultaneous observations of A0620-00 in the X-ray (Chandra), the radio (EVLA), and the OIR (SMARTS 1.3m). These X-ray and radio data allowed us to investigate similarities among quiescent X-ray binaries, and changes over time for this individual object, in the radio/X-ray plane. In addition, our OIR observations allowed us to examine the radio and X-ray information in relation to the different OIR states of behavior (passive and active) known to exist during X-ray quiescence.

A Comparison of the X-Ray Emission from Tidal Disruption Events with those of Active Galactic Nuclei

NASA Astrophysics Data System (ADS)

Auchettl, Katie; Ramirez-Ruiz, Enrico; Guillochon, James

2018-01-01

One of the main challenges of current tidal disruption events (TDEs) studies is that emission arising from active galactic nucleus (AGN) activity may potentially mimic the expected X-ray emission of a TDE. Here we compare the X-ray properties of TDEs and AGNs to determine a set of characteristics that would allow us to discriminate between flares arising from these two objects. We find that at peak, TDEs are brighter than AGNs found at similar redshifts. However, compared to pre-flare upper limits, highly variable AGNs can produce flares of a similar order of magnitude as those seen from X-ray TDEs. Nevertheless, TDEs decay significantly more monotonically, and their emission exhibits little variation in spectral hardness as a function of time. We also find that X-ray TDEs are less absorbed, and their emission is much softer than the emission detected from AGNs found at similar redshifts. We derive the X-ray luminosity function (LF) for X-ray TDEs using the events from Auchettl et al. Interestingly, our X-ray LF closely matches the theoretically derived LF by Milosavljević et al., which assumes a higher TDE rate currently estimated from observations. Using our results and the results of Stone & Metzger, we estimate a TDE rate of (0.7–4.7) × 10‑4 year‑1 per galaxy, higher than current observational estimates. We find that TDEs can contribute significantly to the LF of AGNs for z ≲ 0.4, while there is no evidence that TDEs influence the growth of 106–7 M ⊙ BHs. However, BHs < 106 M ⊙ can grow from TDEs arising from super-Eddington accretion without contributing significantly to the observed AGN LF at z = 0.

Activity from the Be/X-ray binary system V0332+53 during its intermediate-luminosity outburst in 2008

NASA Astrophysics Data System (ADS)

Caballero-García, M. D.; Camero-Arranz, A.; Özbey Arabacı, M.; Zurita, C.; Suso, J.; Gutiérrez-Soto, J.; Beklen, E.; Kiaeerad, F.; Garrido, R.; Hudec, R.

2016-05-01

Aims: We present a study of the Be/X-ray binary system V 0332+53 with the main goal of characterizing its behaviour mainly during the intermediate-luminosity X-ray event in 2008. In addition, we aim to contribute to the understanding of the behaviour of the donor companion by including optical data from our dedicated campaign starting in 2006. Methods: V 0332+53 was observed by RXTE and Swift during the decay of the intermediate-luminosity X-ray outburst of 2008, and with Suzaku before the rising of the third normal outburst of the 2010 series. In addition, we present recent data from the Spanish ground-based astronomical observatories of El Teide (Tenerife), Roque de los Muchachos (La Palma), and Sierra Nevada (Granada), and since 2006 from the Turkish TÜBİTAK National Observatory (Antalya). We have performed temporal analyses to investigate the transient behaviour of this system during several outbursts. Results: Our optical study revealed that continuous mass ejection episodes from the Be star have been taking place since 2006 and another is currently ongoing. The broad-band 1-60 keV X-ray spectrum of the neutron star during the decay of the 2008 outburst was well fitted with standard phenomenological models that were enhanced by an absorption feature of unknown origin at about 10 keV and a narrow iron K-alpha fluorescence line at 6.4 keV. For the first time in V 0332+53 we tentatively see an increase in the cyclotron line energy with increasing flux (although further and more sensitive observations are needed to confirm this). The fast aperiodic variability shows a quasi-periodic oscillation (QPO) at 227 ± 9 mHz only during the lowest luminosities, which might indicate that the inner regions surrounding the magnetosphere are more visible during the lowest flux states.

Evidence for Black Hole Growth in Local Analogs to Lyman Break Galaxies

NASA Technical Reports Server (NTRS)

Jia, Jianjun; Ptak, Andrew; Heckman, Timothy M.; Overzier, Roderik A.; Hornschemeier, Ann; LaMassa, Stephanie M.

2011-01-01

We have used XMM-Newton to observe six Lyman break analogs (LBAs): members of the rare population of local galaxies that have properties that are very similar to distant Lyman break galaxies. Our six targets were specifically selected because they have optical emission-line properties that are intermediate between starbursts and Type 2 (obscured) active galactic nuclei (AGNs). Our new X-ray data provide an important diagnostic of the presence of an AGN. We find X-ray luminosities of order 10(sup 42) erg per second and ratios of X-ray to far-IR lummositles that are higher than values in pure starburst galaxies by factors ranging from approximately 3 to 30. This strongly suggests the presence of an AGN in at least some of the galaxies. The ratios of the luminosities of the hard (2-10 keV) X-ray to [O III] emission line are low by about an order of magnitude compared with Type 1 AGN, but are consistent with the broad range seen in Type 2 AGN. Either the AGN hard X-rays are significantly obscured or the [O III] emission is dominated by the starburst. We searched for an iron emission line at approximately 6.4 ke V, which is a key feature of obscured AGNs, but only detected emission at the approximately 2sigma level. Finally, we find that the ratios of the mid-infrared (24 micrometer) continuum to [O III]lambda 5007 luminosities in these LBAs are higher than the values for Type 2 AGN by an average of 0.8 dex. Combining all these clues, we conclude that an AGN is likely to be present, but that the bolometric luminosity is produced primarily by an intense starburst. If these black holes are radiating at the Eddington limit, their masses would lie in the range of 10(sup 5) - 10(sup 6) solar mass. These objects may offer ideal local laboratories to investigate the processes by which black holes grew in the early universe.

The 155-day X-ray cycle of the very massive Wolf-Rayet star Melnick 34 in the Large Magellanic Cloud

NASA Astrophysics Data System (ADS)

Pollock, A. M. T.; Crowther, P. A.; Tehrani, K.; Broos, Patrick S.; Townsley, Leisa K.

2018-03-01

The Wolf-Rayet star Mk 34 was observed more than 50 times as part of the deep T-ReX Chandra ACIS-I X-ray imaging survey of the Tarantula Nebula in the Large Magellanic Cloud conducted between 2014 May and 2016 January. Its brightness showed one bright maximum and repeated faint minima which help define an X-ray recurrence time of 155.1 ± 0.1 d that is probably the orbital period of an eccentric binary system. The maximum immediately precedes the minimum in the folded X-ray light curve as confirmed by new Swift XRT observations. Notwithstanding its extreme median luminosity of 1.2 × 1035 erg s-1, which makes it over an order of magnitude brighter than comparable stars in the Milky Way, Mk 34 is almost certainly a colliding-wind binary system. Its spectrum shows phase-related changes of luminosity and absorption that are probably related to the orbital dynamics of two of the most massive stars known.

Collapsar γ-ray bursts: how the luminosity function dictates the duration distribution

NASA Astrophysics Data System (ADS)

Petropoulou, Maria; Barniol Duran, Rodolfo; Giannios, Dimitrios

2017-12-01

Jets in long-duration γ-ray bursts (GRBs) have to drill through the collapsing star in order to break out of it and produce the γ-ray signal while the central engine is still active. If the breakout time is shorter for more powerful engines, then the jet-collapsar interaction acts as a filter of less luminous jets. We show that the observed broken power-law GRB luminosity function is a natural outcome of this process. For a theoretically motivated breakout time that scales with jet luminosity as L-χ with χ ∼ 1/3-1/2, we show that the shape of the γ-ray duration distribution can be uniquely determined by the GRB luminosity function and matches the observed one. This analysis has also interesting implications about the supernova-central engine connection. We show that not only successful jets can deposit sufficient energy in the stellar envelope to power the GRB-associated supernovae, but also failed jets may operate in all Type Ib/c supernovae.

The fraction of AGNs in major merger galaxies and its luminosity dependence

NASA Astrophysics Data System (ADS)

Weigel, Anna K.; Schawinski, Kevin; Treister, Ezequiel; Trakhtenbrot, Benny; Sanders, David B.

2018-05-01

We use a phenomenological model which connects the galaxy and active galactic nucleus (AGN) populations to investigate the process of AGNs triggering through major galaxy mergers at z ˜ 0. The model uses stellar mass functions as input and allows the prediction of AGN luminosity functions based on assumed Eddington ratio distribution functions (ERDFs). We show that the number of AGNs hosted by merger galaxies relative to the total number of AGNs increases as a function of AGN luminosity. This is due to more massive galaxies being more likely to undergo a merger and does not require the assumption that mergers lead to higher Eddington ratios than secular processes. Our qualitative analysis also shows that to match the observations, the probability of a merger galaxy hosting an AGN and accreting at a given Eddington value has to be increased by a factor ˜10 relative to the general AGN population. An additional significant increase of the fraction of high Eddington ratio AGNs among merger host galaxies leads to inconsistency with the observed X-ray luminosity function. Physically our results imply that, compared to the general galaxy population, the AGN fraction among merger galaxies is ˜10 times higher. On average, merger triggering does however not lead to significantly higher Eddington ratios.

A Chandra Survey of Milky Way Globular Clusters. I. Emissivity and Abundance of Weak X-Ray Sources

NASA Astrophysics Data System (ADS)

Cheng, Zhongqun; Li, Zhiyuan; Xu, Xiaojie; Li, Xiangdong

2018-05-01

Based on archival Chandra data, we have carried out an X-ray survey of 69, or nearly half the known population of, Milky Way globular clusters (GCs), focusing on weak X-ray sources, mainly cataclysmic variables (CVs) and coronally active binaries (ABs). Using the cumulative X-ray luminosity per unit stellar mass (i.e., X-ray emissivity) as a proxy of the source abundance, we demonstrate a paucity (lower by 41% ± 27% on average) of weak X-ray sources in most GCs relative to the field, which is represented by the Solar Neighborhood and Local Group dwarf elliptical galaxies. We also revisit the mutual correlations among the cumulative X-ray luminosity (L X), cluster mass (M), and stellar encounter rate (Γ), finding {L}{{X}}\\propto {M}0.74+/- 0.13, {L}{{X}}\\propto {{{Γ }}}0.67+/- 0.07 and {{Γ }}\\propto {M}1.28+/- 0.17. The three quantities can further be expressed as {L}{{X}}\\propto {M}0.64+/- 0.12 {{{Γ }}}0.19+/- 0.07, which indicates that the dynamical formation of CVs and ABs through stellar encounters in GCs is less dominant than previously suggested, and that the primordial formation channel has a substantial contribution. Taking these aspects together, we suggest that a large fraction of primordial, soft binaries have been disrupted in binary–single or binary–binary stellar interactions before they could otherwise evolve into X-ray-emitting close binaries, whereas the same interactions also have led to the formation of new close binaries. No significant correlations between {L}{{X}}/{L}K and cluster properties, including dynamical age, metallicity, and structural parameters, are found.

No evidence for a significant AGN contribution to cosmic hydrogen reionization

NASA Astrophysics Data System (ADS)

Parsa, Shaghayegh; Dunlop, James S.; McLure, Ross J.

2018-03-01

We reinvestigate a claimed sample of 22 X-ray detected active galactic nuclei (AGN) at redshifts z > 4, which has reignited the debate as to whether young galaxies or AGN reionized the Universe. These sources lie within the Great Observatories Origins Deep Survey-South (GOODS-S)/Cosmic Assembly Near-Infrared Deep Extragalactic Legacy Survey (CANDELS) field, and we examine both the robustness of the claimed X-ray detections (within the Chandra 4Ms imaging) and perform an independent analysis of the photometric redshifts of the optical/infrared counterparts. We confirm the reality of only 15 of the 22 reported X-ray detections, and moreover find that only 12 of the 22 optical/infrared counterpart galaxies actually lie robustly at z > 4. Combining these results we find convincing evidence for only seven X-ray AGN at z > 4 in the GOODS-S field, of which only one lies at z > 5. We recalculate the evolving far-ultraviolet (1500 Å) luminosity density produced by AGN at high redshift, and find that it declines rapidly from z ≃ 4 to z ≃ 6, in agreement with several other recent studies of the evolving AGN luminosity function. The associated rapid decline in inferred hydrogen ionizing emissivity contributed by AGN falls an order-of-magnitude short of the level required to maintain hydrogen ionization at z ≃ 6. We conclude that all available evidence continues to favour a scenario in which young galaxies reionized the Universe, with AGN making, at most, a very minor contribution to cosmic hydrogen reionization.

Spectra of black hole accretion models of ultraluminous X-ray sources

NASA Astrophysics Data System (ADS)

Narayan, Ramesh; Sa̧dowski, Aleksander; Soria, Roberto

2017-08-01

We present general relativistic radiation magnetohydrodynamics simulations of super-Eddington accretion on a 10 M⊙ black hole. We consider a range of mass accretion rates, black hole spins and magnetic field configurations. We compute the spectra and images of the models as a function of viewing angle and compare them with the observed properties of ultraluminous X-ray sources (ULXs). The models easily produce apparent luminosities in excess of 1040 erg s-1 for pole-on observers. However, the angle-integrated radiative luminosities rarely exceed 2.5 × 1039 erg s-1 even for mass accretion rates of tens of Eddington. The systems are thus radiatively inefficient, though they are energetically efficient when the energy output in winds and jets is also counted. The simulated models reproduce the main empirical types of spectra - disc-like, supersoft, soft, hard - observed in ultraluminous X-ray sources (ULXs). The magnetic field configuration, whether 'standard and normal evolution' (SANE) or 'magnetically arrested disc' (MAD), has a strong effect on the results. In SANE models, the X-ray spectral hardness is almost independent of accretion rate, but decreases steeply with increasing inclination. MAD models with non-spinning black holes produce significantly softer spectra at higher values of \\dot{M}, even at low inclinations. MAD models with rapidly spinning black holes are unique. They are radiatively efficient (efficiency factor ˜10-20 per cent), superefficient when the mechanical energy output is also included (70 per cent) and produce hard blazar-like spectra. In all models, the emission shows strong geometrical beaming, which disagrees with the more isotropic illumination favoured by observations of ULX bubbles.

The NuSTAR Serendipitous Survey: The 40-month Catalog and the Properties of the Distant High-energy X-Ray Source Population

NASA Astrophysics Data System (ADS)

Lansbury, G. B.; Stern, D.; Aird, J.; Alexander, D. M.; Fuentes, C.; Harrison, F. A.; Treister, E.; Bauer, F. E.; Tomsick, J. A.; Baloković, M.; Del Moro, A.; Gandhi, P.; Ajello, M.; Annuar, A.; Ballantyne, D. R.; Boggs, S. E.; Brandt, W. N.; Brightman, M.; Chen, C.-T. J.; Christensen, F. E.; Civano, F.; Comastri, A.; Craig, W. W.; Forster, K.; Grefenstette, B. W.; Hailey, C. J.; Hickox, R. C.; Jiang, B.; Jun, H. D.; Koss, M.; Marchesi, S.; Melo, A. D.; Mullaney, J. R.; Noirot, G.; Schulze, S.; Walton, D. J.; Zappacosta, L.; Zhang, W. W.

2017-02-01

We present the first full catalog and science results for the Nuclear Spectroscopic Telescope Array (NuSTAR) serendipitous survey. The catalog incorporates data taken during the first 40 months of NuSTAR operation, which provide ≈20 Ms of effective exposure time over 331 fields, with an areal coverage of 13 deg2, and 497 sources detected in total over the 3-24 keV energy range. There are 276 sources with spectroscopic redshifts and classifications, largely resulting from our extensive campaign of ground-based spectroscopic follow-up. We characterize the overall sample in terms of the X-ray, optical, and infrared source properties. The sample is primarily composed of active galactic nuclei (AGNs), detected over a large range in redshift from z = 0.002 to 3.4 (median of < z> =0.56), but also includes 16 spectroscopically confirmed Galactic sources. There is a large range in X-ray flux, from {log}({f}3-24{keV}/{erg} {{{s}}}-1 {{cm}}-2)≈ -14 to -11, and in rest-frame 10-40 keV luminosity, from {log}({L}10-40{keV}/{erg} {{{s}}}-1)≈ 39 to 46, with a median of 44.1. Approximately 79% of the NuSTAR sources have lower-energy (<10 keV) X-ray counterparts from XMM-Newton, Chandra, and Swift XRT. The mid-infrared (MIR) analysis, using WISE all-sky survey data, shows that MIR AGN color selections miss a large fraction of the NuSTAR-selected AGN population, from ≈15% at the highest luminosities ({L}{{X}}> {10}44 erg s-1) to ≈80% at the lowest luminosities ({L}{{X}}< {10}43 erg s-1). Our optical spectroscopic analysis finds that the observed fraction of optically obscured AGNs (I.e., the type 2 fraction) is {F}{Type2}={53}-15+14 % , for a well-defined subset of the 8-24 keV selected sample. This is higher, albeit at a low significance level, than the type 2 fraction measured for redshift- and luminosity-matched AGNs selected by <10 keV X-ray missions.

The Electromagnetic Counterpart of the Binary Neutron Star Merger LIGO/Virgo GW170817. VIII. A Comparison to Cosmological Short-duration Gamma-Ray Bursts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fong, W.; Berger, E.; Blanchard, P. K.

Here, we present a comprehensive comparison of the properties of the radio through X-ray counterpart of GW170817 and the properties of short-duration gamma-ray bursts (GRBs). For this effort, we utilize a sample of 36 short GRBs spanning a redshift range ofmore » $$z \\approx 0.12-2.6$$ discovered over 2004-2017. We find that the counterpart to GW170817 has an isotropic-equivalent luminosity that is $$\\approx 3000$$ times less than the median value of on-axis short GRB X-ray afterglows, and $$\\gtrsim10^{4}$$ times less than that for detected short GRB radio afterglows. Moreover, the allowed jet energies and particle densities inferred from the radio and X-ray counterparts to GW170817 and on-axis short GRB afterglows are remarkably similar, suggesting that viewing angle effects are the dominant, and perhaps only, difference in their observed radio and X-ray behavior. From comparison to previous claimed kilonovae following short GRBs, we find that the optical and near-IR counterpart to GW170817 is comparatively under-luminous by a factor of $$\\approx 3-5$$, indicating a range of kilonova luminosities and timescales. A comparison of the optical limits following short GRBs on $$\\lesssim 1$$ day timescales also rules out a "blue" kilonova of comparable optical isotropic-equivalent luminosity in one previous short GRB. Finally, we investigate the host galaxy of GW170817, NGC4993, in the context of short GRB host galaxy stellar population properties. We find that NGC4993 is superlative in terms of its large luminosity, old stellar population age, and low star formation rate compared to previous short GRB hosts. Additional events within the Advanced LIGO/VIRGO volume will be crucial in delineating the properties of the host galaxies of NS-NS mergers, and connecting them to their cosmological counterparts.« less

The Electromagnetic Counterpart of the Binary Neutron Star Merger LIGO/Virgo GW170817. VIII. A Comparison to Cosmological Short-duration Gamma-Ray Bursts

DOE PAGES

Fong, W.; Berger, E.; Blanchard, P. K.; ...

2017-10-16

Here, we present a comprehensive comparison of the properties of the radio through X-ray counterpart of GW170817 and the properties of short-duration gamma-ray bursts (GRBs). For this effort, we utilize a sample of 36 short GRBs spanning a redshift range ofmore » $$z \\approx 0.12-2.6$$ discovered over 2004-2017. We find that the counterpart to GW170817 has an isotropic-equivalent luminosity that is $$\\approx 3000$$ times less than the median value of on-axis short GRB X-ray afterglows, and $$\\gtrsim10^{4}$$ times less than that for detected short GRB radio afterglows. Moreover, the allowed jet energies and particle densities inferred from the radio and X-ray counterparts to GW170817 and on-axis short GRB afterglows are remarkably similar, suggesting that viewing angle effects are the dominant, and perhaps only, difference in their observed radio and X-ray behavior. From comparison to previous claimed kilonovae following short GRBs, we find that the optical and near-IR counterpart to GW170817 is comparatively under-luminous by a factor of $$\\approx 3-5$$, indicating a range of kilonova luminosities and timescales. A comparison of the optical limits following short GRBs on $$\\lesssim 1$$ day timescales also rules out a "blue" kilonova of comparable optical isotropic-equivalent luminosity in one previous short GRB. Finally, we investigate the host galaxy of GW170817, NGC4993, in the context of short GRB host galaxy stellar population properties. We find that NGC4993 is superlative in terms of its large luminosity, old stellar population age, and low star formation rate compared to previous short GRB hosts. Additional events within the Advanced LIGO/VIRGO volume will be crucial in delineating the properties of the host galaxies of NS-NS mergers, and connecting them to their cosmological counterparts.« less

Outburst of GX304-1 Monitored with INTEGRAL: Positive Correlation Between the Cyclotron Line Energy and Flux

NASA Technical Reports Server (NTRS)

Klochkov, D.; Doroshenko, V.; Santangelo, A.; Staubert, R.; Ferrigno, C.; Kretschmar, P.; Caballero, I.; Wilms, J.; Kreykenbohm, I.; Pottschmidt, I.;

Science from a glimpse: Hubble SNAPshot observations of massive galaxy clusters

NASA Astrophysics Data System (ADS)

Repp, A.; Ebeling, H.

2018-06-01

Hubble Space Telescope SNAPshot surveys of 86 X-ray selected galaxy clusters at 0.3 < z < 0.5 from the MACS sample have proven invaluable for the exploration of a wide range of astronomical research topics. We here present an overview of the four MACS SNAPshot surveys conducted from Cycle 14 to Cycle 20 as part of a long-term effort aimed at identifying exceptional cluster targets for in-depth follow up by the extragalactic community. We also release redshifts and X-ray luminosities of all clusters observed as part of this initiative. To illustrate the power of SNAPshot observations of MACS clusters, we explore several aspects of galaxy evolution illuminated by the images obtained for these programmes. We confirm the high lensing efficiency of X-ray selected clusters at z > 0.3. Examining the evolution of the slope of the cluster red sequence, we observe at best a slight decrease with redshift, indicating minimal age contribution since z ˜ 1. Congruent to previous studies' findings, we note that the two BCGs which are significantly bluer (≥5σ) than their clusters' red sequences reside in relaxed clusters and exhibit pronounced internal structure. Thanks to our targets' high X-ray luminosity, the subset of our sample observed with Chandra adds valuable leverage to the X-ray luminosity-optical richness relation, which, albeit with substantial scatter, is now clearly established from groups to extremely massive clusters of galaxies. We conclude that SNAPshot observations of MACS clusters stand to continue to play a vital pathfinder role for astrophysical investigations across the entire electromagnetic spectrum.

Suzaku observations of low surface brightness cluster Abell 1631

NASA Astrophysics Data System (ADS)

Babazaki, Yasunori; Mitsuishi, Ikuyuki; Ota, Naomi; Sasaki, Shin; Böhringer, Hans; Chon, Gayoung; Pratt, Gabriel W.; Matsumoto, Hironori

2018-04-01

We present analysis results for a nearby galaxy cluster Abell 1631 at z = 0.046 using the X-ray observatory Suzaku. This cluster is categorized as a low X-ray surface brightness cluster. To study the dynamical state of the cluster, we conduct four-pointed Suzaku observations and investigate physical properties of the Mpc-scale hot gas associated with the A 1631 cluster for the first time. Unlike relaxed clusters, the X-ray image shows no strong peak at the center and an irregular morphology. We perform spectral analysis and investigate the radial profiles of the gas temperature, density, and entropy out to approximately 1.5 Mpc in the east, north, west, and south directions by combining with the XMM-Newton data archive. The measured gas density in the central region is relatively low (a few ×10-4 cm-3) at the given temperature (˜2.9 keV) compared with X-ray-selected clusters. The entropy profile and value within the central region (r < 0.1 r200) are found to be flatter and higher (≳400 keV cm2). The observed bolometric luminosity is approximately three times lower than that expected from the luminosity-temperature relation in previous studies of relaxed clusters. These features are also observed in another low surface brightness cluster, Abell 76. The spatial distributions of galaxies and the hot gas appear to be different. The X-ray luminosity is relatively lower than that expected from the velocity dispersion. A post-merger scenario may explain the observed results.

Suzaku observations of low surface brightness cluster Abell 1631

NASA Astrophysics Data System (ADS)

Babazaki, Yasunori; Mitsuishi, Ikuyuki; Ota, Naomi; Sasaki, Shin; Böhringer, Hans; Chon, Gayoung; Pratt, Gabriel W.; Matsumoto, Hironori

2018-06-01

We present analysis results for a nearby galaxy cluster Abell 1631 at z = 0.046 using the X-ray observatory Suzaku. This cluster is categorized as a low X-ray surface brightness cluster. To study the dynamical state of the cluster, we conduct four-pointed Suzaku observations and investigate physical properties of the Mpc-scale hot gas associated with the A 1631 cluster for the first time. Unlike relaxed clusters, the X-ray image shows no strong peak at the center and an irregular morphology. We perform spectral analysis and investigate the radial profiles of the gas temperature, density, and entropy out to approximately 1.5 Mpc in the east, north, west, and south directions by combining with the XMM-Newton data archive. The measured gas density in the central region is relatively low (a few ×10-4 cm-3) at the given temperature (˜2.9 keV) compared with X-ray-selected clusters. The entropy profile and value within the central region (r < 0.1 r200) are found to be flatter and higher (≳400 keV cm2). The observed bolometric luminosity is approximately three times lower than that expected from the luminosity-temperature relation in previous studies of relaxed clusters. These features are also observed in another low surface brightness cluster, Abell 76. The spatial distributions of galaxies and the hot gas appear to be different. The X-ray luminosity is relatively lower than that expected from the velocity dispersion. A post-merger scenario may explain the observed results.

X-Ray Properties of Lensing-Selected Clusters

NASA Astrophysics Data System (ADS)

Paterno-Mahler, Rachel; Sharon, Keren; Bayliss, Matthew; McDonald, Michael; Gladders, Michael; Johnson, Traci; Dahle, Hakon; Rigby, Jane R.; Whitaker, Katherine E.; Florian, Michael; Wuyts, Eva

2017-08-01

I will present preliminary results from the Michigan Swift X-ray observations of clusters from the Sloan Giant Arcs Survey (SGAS). These clusters were lensing selected based on the presence of a giant arc visible from SDSS. I will characterize the morphology of the intracluster medium (ICM) of the clusters in the sample, and discuss the offset between the X-ray centroid, the mass centroid as determined by strong lensing analysis, and the BCG position. I will also present early-stage work on the scaling relation between the lensing mass and the X-ray luminosity.

Investigation relative to the Roentgen Satellite (ROSAT)

NASA Technical Reports Server (NTRS)

Elvis, Martin S.; Primini, Francis A.; Fabbiano, Guiseppina; Harris, Daniel E.; Jones-Foreman, Christine; Trinchieri, Ginevra; Golub, Leon; Bookbinder, Jay; Seward, Frederick D.; Zombeck, Martin V.

1994-01-01

Reports include: High Resolution Observations of the Central Region of M31; The X-ray Emission of Low-X-ray-Luminosity Early-Type Galaxies: Gas Versus Compact Sources; Interaction Between Cluster Gas and Radio Features of Cygnus A; Hot Gas and Dark Halos in Early-Type Galaxies; A Gravitational Lens in X-rays - 0957+461; How Massive are Early-Type Galaxies?; Three Crab-Like SNR in the Large Magellanic Cloud; and Soft X-ray Emission from Boundary Layers in Cataclysmic Variables. Papers submitted to the Astrophysical Journal are attached.

Is NeII a Tracer for X-Rays in Disks around Tauri Stars?

NASA Astrophysics Data System (ADS)

Guedel, Manuel

2007-10-01

Although dust grains dominate the appearance of protoplanetary disks because of their high opacity, the key processes for disk evolution and planetesimal formation are driven through the dynamical state of the gas. In contrast to the dust component, we do not have a similar knowledge of the gas component. One of the Spitzer breakthroughs was the detection of the [Ne II] 12.8um line. Glassgold et al. (2007) proposed that this line provides diagnostics for a warm disk surface layer that is heated and ionized by stellar X-rays. A correlation of the [Ne II] luminosity with the X-ray luminosity is expected. The statistical sample so far available is insufficient to test this hypothesis. We aim at significantly enlarging the sample, with the goal of confirming or refuting this model.

Twenty-two emission-line AGNs from the HEAO-1 X-ray survey

NASA Technical Reports Server (NTRS)

Remillard, R. A.; Bradt, H. V. D.; Brissenden, R. J. V.; Buckley, D. A. H.; Roberts, W.; Schwartz, D. A.; Stroozas, B. A.; Tuohy, I. R.

1993-01-01

We report 22 emission-line AGN as bright, hard X-ray sources. All of them appear to be new classifications with the exception of one peculiar IRAS source which is a known quasar and has no published spectrum. This sample exhibits a rich diversity in optical spectral properties and luminosities, ranging from a powerful broad-absorption-line quasar to a weak nucleus embedded in a nearby NGC galaxy. Two cases confer X-ray luminosities in excess of 10 exp 47 erg/s. However, there is a degree of uncertainty in the X-ray identification for the AGN fainter than V about 16.5. Optically, several AGN exhibit very strong Fe II emission. One Seyfert galaxy with substantial radio flux is an exception to the common association of strong Fe II emission and radio-quiet AGN. The previously recognized IRAS quasar shows extreme velocities in the profiles of the forbidden lines; the 0 III pair is broadened to the point that the lines are blended. Several of these AGN show evidence of intrinsic obscuration, illustrating the effectiveness of hard X-ray surveys in locating AGN through high column density.

HICOSMO - cosmology with a complete sample of galaxy clusters - I. Data analysis, sample selection and luminosity-mass scaling relation

NASA Astrophysics Data System (ADS)

Schellenberger, G.; Reiprich, T. H.

2017-08-01

The X-ray regime, where the most massive visible component of galaxy clusters, the intracluster medium, is visible, offers directly measured quantities, like the luminosity, and derived quantities, like the total mass, to characterize these objects. The aim of this project is to analyse a complete sample of galaxy clusters in detail and constrain cosmological parameters, like the matter density, Ωm, or the amplitude of initial density fluctuations, σ8. The purely X-ray flux-limited sample (HIFLUGCS) consists of the 64 X-ray brightest galaxy clusters, which are excellent targets to study the systematic effects, that can bias results. We analysed in total 196 Chandra observations of the 64 HIFLUGCS clusters, with a total exposure time of 7.7 Ms. Here, we present our data analysis procedure (including an automated substructure detection and an energy band optimization for surface brightness profile analysis) that gives individually determined, robust total mass estimates. These masses are tested against dynamical and Planck Sunyaev-Zeldovich (SZ) derived masses of the same clusters, where good overall agreement is found with the dynamical masses. The Planck SZ masses seem to show a mass-dependent bias to our hydrostatic masses; possible biases in this mass-mass comparison are discussed including the Planck selection function. Furthermore, we show the results for the (0.1-2.4) keV luminosity versus mass scaling relation. The overall slope of the sample (1.34) is in agreement with expectations and values from literature. Splitting the sample into galaxy groups and clusters reveals, even after a selection bias correction, that galaxy groups exhibit a significantly steeper slope (1.88) compared to clusters (1.06).

The properties of cross-correlation and spectra of the low-mass X-ray binary 4U 1608-52

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lei, Ya-Juan; Yuan, Hai-Long; Dong, Yi-Qiao

With RXTE data, we analyzed the cross-correlation function between the soft and hard X-rays of the transient atoll source 4U 1608-52. We found anti-correlations in three outbursts occurred in 1998, 2002, and 2010, and we found significant time lags of several hundreds of seconds in the latter two outbursts. Our results show no correlation between the soft and hard X-rays in the extreme island state and a dominated positive correlation in the lower banana state. Anti-correlations are presented at the upper banana state for the outburst of 2010 and at the island and the lower left banana states for themore » other two outbursts. So far for atoll sources, the cross-correlation has been studied statistically only for 4U 1735-44, where anti-correlations showed up in the upper banana state. Here our investigation on 4U 1608-52 provides a similar result in its 2010 outburst. In addition, we notice that the luminosities in the upper banana of the 1998 and 2002 outbursts are about 1.5 times that of the 2010 outburst whose luminosity in the upper banana is close to that of 4U 1735-44. The results suggest that the states in the color-color diagram of a source could be correlated with the luminosity of the source. A further spectral analysis during the 2010 outburst is also shown, which suggests that the disk can be a little truncated in the upper banana. The feature on the upper banana is similar to the previous results of the flaring branch in Z sources.« less

The Discovery of Lensed Radio and X-ray Sources Behind the Frontier Fields Cluster MACS J0717.5+3745 with the JVLA and Chandra

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weeren, R. J. van; Ogrean, G. A.; Jones, C.

We report on high-resolution JVLA and Chandra observations of the Hubble Space Telescope (HST) Frontier Cluster MACS J0717.5+3745. MACS J0717.5+3745 offers the largest contiguous magnified area of any known cluster, making it a promising target to search for lensed radio and X-ray sources. With the high-resolution 1.0–6.5 GHz JVLA imaging in A and B configuration, we detect a total of 51 compact radio sources within the area covered by the HST imaging. Within this sample, we find seven lensed sources with amplification factors larger than two. None of these sources are identified as multiply lensed. Based on the radio luminosities,more » the majority of these sources are likely star-forming galaxies with star-formation rates (SFRs) of 10–50 M ⊙ yr -1 located at 1≲ z ≲ 2. Two of the lensed radio sources are also detected in the Chandra image of the cluster. These two sources are likely active galactic nuclei, given their 2–10 keV X-ray luminosities of ~ 10 43-44 erg s -1. From the derived radio luminosity function, we find evidence for an increase in the number density of radio sources at 0.6 < z < 2.0, compared to a z < 0.3 sample. Lastly, our observations indicate that deep radio imaging of lensing clusters can be used to study star-forming galaxies, with SFRs as low as ~10M ⊙ yr -1, at the peak of cosmic star formation history.« less

The Discovery of Lensed Radio and X-ray Sources Behind the Frontier Fields Cluster MACS J0717.5+3745 with the JVLA and Chandra

DOE PAGES

Weeren, R. J. van; Ogrean, G. A.; Jones, C.; ...

2016-01-27

We report on high-resolution JVLA and Chandra observations of the Hubble Space Telescope (HST) Frontier Cluster MACS J0717.5+3745. MACS J0717.5+3745 offers the largest contiguous magnified area of any known cluster, making it a promising target to search for lensed radio and X-ray sources. With the high-resolution 1.0–6.5 GHz JVLA imaging in A and B configuration, we detect a total of 51 compact radio sources within the area covered by the HST imaging. Within this sample, we find seven lensed sources with amplification factors larger than two. None of these sources are identified as multiply lensed. Based on the radio luminosities,more » the majority of these sources are likely star-forming galaxies with star-formation rates (SFRs) of 10–50 M ⊙ yr -1 located at 1≲ z ≲ 2. Two of the lensed radio sources are also detected in the Chandra image of the cluster. These two sources are likely active galactic nuclei, given their 2–10 keV X-ray luminosities of ~ 10 43-44 erg s -1. From the derived radio luminosity function, we find evidence for an increase in the number density of radio sources at 0.6 < z < 2.0, compared to a z < 0.3 sample. Lastly, our observations indicate that deep radio imaging of lensing clusters can be used to study star-forming galaxies, with SFRs as low as ~10M ⊙ yr -1, at the peak of cosmic star formation history.« less

The radio-X-ray relation as a star formation indicator: results from the Very Large Array-Extended Chandra Deep Field-South

NASA Astrophysics Data System (ADS)

Vattakunnel, S.; Tozzi, P.; Matteucci, F.; Padovani, P.; Miller, N.; Bonzini, M.; Mainieri, V.; Paolillo, M.; Vincoletto, L.; Brandt, W. N.; Luo, B.; Kellermann, K. I.; Xue, Y. Q.

2012-03-01

In order to trace the instantaneous star formation rate (SFR) at high redshift, and thus help in understanding the relation between the different emission mechanisms related to star formation, we combine the recent 4-Ms Chandra X-ray data and the deep Very Large Array radio data in the Extended Chandra Deep Field-South region. We find 268 sources detected both in the X-ray and radio bands. The availability of redshifts for ˜95 per cent of the sources in our sample allows us to derive reliable luminosity estimates and the intrinsic properties from X-ray analysis for the majority of the objects. With the aim of selecting sources powered by star formation in both bands, we adopt classification criteria based on X-ray and radio data, exploiting the X-ray spectral features and time variability, taking advantage of observations scattered across more than 10 years. We identify 43 objects consistent with being powered by star formation. We also add another 111 and 70 star-forming candidates detected only in the radio and X-ray bands, respectively. We find a clear linear correlation between radio and X-ray luminosity in star-forming galaxies over three orders of magnitude and up to z˜ 1.5. We also measure a significant scatter of the order of 0.4 dex, higher than that observed at low redshift, implying an intrinsic scatter component. The correlation is consistent with that measured locally, and no evolution with redshift is observed. Using a locally calibrated relation between the SFR and the radio luminosity, we investigate the LX(2-10 keV)-SFR relation at high redshift. The comparison of the SFR measured in our sample with some theoretical models for the Milky Way and M31, two typical spiral galaxies, indicates that, with current data, we can trace typical spirals only at z≤ 0.2, and strong starburst galaxies with SFRs as high as ˜100 M⊙ yr-1, up to z˜ 1.5.

Orbital Parameters and Spectroscopy of the Transient X-Ray Pulsar 4U 0115+63

NASA Technical Reports Server (NTRS)

Mueller, Sebastian; Obst,Maria; Kreykenbohm, Ingo; Fuerst, Felix; Kuehnel, Matthias; Wilms, Joern; Klochkov, Dmitry; Staubert, Ruediger; Santangelo, Andrea; Pottschmidt, Katja;

Analysis of the Einstein sample of early-type galaxies

NASA Technical Reports Server (NTRS)

Eskridge, Paul B.; Fabbiano, Giuseppina

1993-01-01

The EINSTEIN galaxy catalog contains x-ray data for 148 early-type (E and SO) galaxies. A detailed analysis of the global properties of this sample are studied. By comparing the x-ray properties with other tracers of the ISM, as well as with observables related to the stellar dynamics and populations of the sample, we expect to determine more clearly the physical relationships that determine the evolution of early-type galaxies. Previous studies with smaller samples have explored the relationships between x-ray luminosity (L(sub x)) and luminosities in other bands. Using our larger sample and the statistical techniques of survival analysis, a number of these earlier analyses were repeated. For our full sample, a strong statistical correlation is found between L(sub X) and L(sub B) (the probability that the null hypothesis is upheld is P less than 10(exp -4) from a variety of rank correlation tests. Regressions with several algorithms yield consistent results.

Spin period evolution of the newly identified ULX pulsar (NGC 300 ULX1) associated with the supernova impostor SN2010da

NASA Astrophysics Data System (ADS)

Vasilopoulos, G.; Haberl, F.; Carpano, S.; Maitra, C.

2018-01-01

Following the discovery of the newly discovered ULX pulsar in NGC 300 (ATel #11158) we searched the available X-ray data for the evolution of the spin period of the neutron star and the X-ray luminosity.

The Nature and Evolutionary History of GRO J1744-28

NASA Technical Reports Server (NTRS)

Rappaport, S.

1997-01-01

GRO J1744-28 is the first known X-ray source to display bursts, periodic pulsations, and quasi-periodic oscillations. This source may thus provide crucial clues that will lead to an understanding of the differences in the nature of the X-ray variability from various accreting neutron stars. The orbital period is 11.8 days, and the measured mass function of 1.31 x 10(exp -4) solar mass is one of the smallest among all known binaries. If we assume that the donor star is a low-mass giant transferring matter through the inner Lagrange point, then we can show that its mass is lower than approximately 0.7 solar mass and probably closer to 0.25 solar mass. Higher mass, but unevolved, donor stars are shown to be implausible. We also demonstrate that the current He core mass of the donor star lies in the range of 0.20-0.25 solar mass. Thus, this system is most likely in the final stages of losing its hydrogen-rich envelope, with only a small amount of mass remaining in the envelope. If this picture is correct, then GRO J1744-28 may well represent the closest observational link that we have between the low-mass X-ray binaries and recycled binary pulsars in wide orbits. We have carried out a series of binary evolution calculations and explored, both systematically and via a novel Monte Carlo approach, the range of initial system parameters and input physics that can lead to the binary parameters of the present-day GRO J1744-28 system. The input parameters include both the initial total mass and the core mass of the donor star, the neutron-star mass, the strength of the magnetic braking, the mass-capture fraction, and the specifics of the core mass/radius relation for giants. Through these evolution calculations, we compute probability distributions for the current binary system parameters (i.e., the total mass, core mass, radius, luminosity, and K-band magnitude of the donor star, the neutron star mass, the orbital inclination angle, and the semimajor axis of the binary). Our calculations yield the following values for the GRO J1744-28 system parameters (with 95% confidence limits in parentheses): donor star mass: 0.24 solar mass (0.2-0.7 solar mass); He core mass of the donor star: 0.22 solar mass (0.20-0.25 solar mass); neutron-star mass: 1.7 solar mass (1.39-1.96 solar mass); orbital inclination angle: 18deg (7deg-22deg); semi- major axis: 64 lt-s (60-67 lt-s); radius of the donor star: 6.2 solar radius(6-9 solar radius); luminosity of donor star: 23 solar luminosity (15-49 solar luminosity), and long-term mass transfer rate at the current epoch: 5 x 10(exp -10)solar mass/yr (2 x 10(exp -10) to 5 x 10(exp -9)solar mass/yr). We deduce that the magnetic field of the underlying neutron star lies in the range of approximately 1.8 x 10(exp 11)G to approximately 7 x 10(exp 11)G, with a most probable value of 2.7 x 10(exp 11)G. This is evidently sufficiently strong to funnel the accretion flow onto the magnetic polar caps and suppress the thermonuclear flashes that would otherwise give rise to the type 1 X-ray bursts observed in most X-ray bursters. We present a simple paradigm for magnetic accreting neutron stars where X-ray pulsars, GRO J1744-28, the Rapid Burster, and the type 1 X-ray bursters may form a continuum of possible behaviors among accreting neutron stars, with the strength of the neutron-star magnetic field serving as a crucial parameter that determines the mode of X-ray variability from a given object.

Low-mass Active Galactic Nuclei on the Fundamental Plane of Black Hole Activity

NASA Astrophysics Data System (ADS)

Qian, Lei; Dong, Xiao-Bo; Xie, Fu-Guo; Liu, Wenjuan; Li, Di

2018-06-01

It is widely known that in active galactic nuclei (AGNs) and black hole X-ray binaries (BHXBs), there is a tight correlation among their radio luminosity (L R ), X-ray luminosity (L X), and BH mass ({M}BH}), the so-called “fundamental plane” (FP) of BH activity. Yet the supporting data are very limited in the {M}BH} regime between stellar mass (i.e., BHXBs) and 106.5 {M}ȯ (namely, the lower bound of supermassive BHs in common AGNs). In this work, we developed a new method to measure the 1.4 GHz flux directly from the images of the VLA FIRST survey, and apply it to the type-1 low-mass AGNs in the Dong et al. sample. As a result, we obtained 19 new low-mass AGNs for FP research with both {M}BH} estimates ({M}BH} ≈ 105.5–6.5 {M}ȯ ), reliable X-ray measurements, and (candidate) radio detections, tripling the number of such candidate sources in the literature. Most (if not all) of the low-mass AGNs follow the standard radio/X-ray correlation and the universal FP relation fitted with the combined data set of BHXBs and supermassive AGNs by Gültekin et al.; the consistency in the radio/X-ray correlation slope among those accretion systems supports the picture that the accretion and ejection (jet) processes are quite similar in all accretion systems of different {M}BH}. In view of the FP relation, we speculate that the radio loudness { \\mathcal R } (i.e., the luminosity ratio of the jet to the accretion disk) of AGNs depends not only on Eddington ratio, but probably also on {M}BH}.

Constraining Accreting Binary Populations in Normal Galaxies

NASA Astrophysics Data System (ADS)

Lehmer, Bret; Hornschemeier, A.; Basu-Zych, A.; Fragos, T.; Jenkins, L.; Kalogera, V.; Ptak, A.; Tzanavaris, P.; Zezas, A.

2011-01-01

X-ray emission from accreting binary systems (X-ray binaries) uniquely probe the binary phase of stellar evolution and the formation of compact objects such as neutron stars and black holes. A detailed understanding of X-ray binary systems is needed to provide physical insight into the formation and evolution of the stars involved, as well as the demographics of interesting binary remnants, such as millisecond pulsars and gravitational wave sources. Our program makes wide use of Chandra observations and complementary multiwavelength data sets (through, e.g., the Spitzer Infrared Nearby Galaxies Survey [SINGS] and the Great Observatories Origins Deep Survey [GOODS]), as well as super-computing facilities, to provide: (1) improved calibrations for correlations between X-ray binary emission and physical properties (e.g., star-formation rate and stellar mass) for galaxies in the local Universe; (2) new physical constraints on accreting binary processes (e.g., common-envelope phase and mass transfer) through the fitting of X-ray binary synthesis models to observed local galaxy X-ray binary luminosity functions; (3) observational and model constraints on the X-ray evolution of normal galaxies over the last 90% of cosmic history (since z 4) from the Chandra Deep Field surveys and accreting binary synthesis models; and (4) predictions for deeper observations from forthcoming generations of X-ray telesopes (e.g., IXO, WFXT, and Gen-X) to provide a science driver for these missions. In this talk, we highlight the details of our program and discuss recent results.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nyland, Kristina; Marvil, Josh; Young, Lisa M.

We present the results of deep, high-resolution, 5 GHz Expanded Very Large Array (EVLA) observations of the nearby, dwarf lenticular galaxy and intermediate-mass black hole candidate (M{sub BH} {approx} 4.5 Multiplication-Sign 10{sup 5} M{sub Sun }), NGC 404. For the first time, radio emission at frequencies above 1.4 GHz has been detected in this galaxy. We found a modestly resolved source in the NGC 404 nucleus with a total radio luminosity of 7.6 {+-} 0.7 Multiplication-Sign 10{sup 17} W Hz{sup -1} at 5 GHz and a spectral index from 5 to 7.45 GHz of {alpha} = -0.88 {+-} 0.30. NGCmore » 404 is only the third central intermediate-mass black hole candidate detected in the radio regime with subarcsecond resolution. The position of the radio source is consistent with the optical center of the galaxy and the location of a known, hard X-ray point source (L{sub X} {approx} 1.2 Multiplication-Sign 10{sup 37} erg s{sup -1}). The faint radio and X-ray emission could conceivably be produced by an X-ray binary, star formation, a supernova remnant, or a low-luminosity active galactic nucleus powered by an intermediate-mass black hole. In light of our new EVLA observations, we find that the most likely scenario is an accreting intermediate-mass black hole, with other explanations being either incompatible with the observed X-ray and/or radio luminosities or statistically unlikely.« less

THE INTERMEDIATE LUMINOSITY OPTICAL TRANSIENT SN 2010DA: THE PROGENITOR, ERUPTION, AND AFTERMATH OF A PECULIAR SUPERGIANT HIGH-MASS X-RAY BINARY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Villar, V. A.; Berger, E.; Blanchard, P. K.

We present optical spectroscopy, ultraviolet-to-infrared imaging, and X-ray observations of the intermediate luminosity optical transient (ILOT) SN 2010da in NGC 300 ( d = 1.86 Mpc) spanning from −6 to +6 years relative to the time of outburst in 2010. Based on the light-curve and multi-epoch spectral energy distributions of SN 2010da, we conclude that the progenitor of SN 2010da is a ≈10–12 M {sub ⊙} yellow supergiant possibly transitioning into a blue-loop phase. During outburst, SN 2010da had a peak absolute magnitude of M {sub bol} ≲ −10.4 mag, dimmer than other ILOTs and supernova impostors. We detect multi-componentmore » hydrogen Balmer, Paschen, and Ca ii emission lines in our high-resolution spectra, which indicate a dusty and complex circumstellar environment. Since the 2010 eruption, the star has brightened by a factor of ≈5 and remains highly variable in the optical. Furthermore, we detect SN 2010da in archival Swift and Chandra observations as an ultraluminous X-ray source ( L {sub X} ≈ 6 × 10{sup 39} erg s{sup −1}). We additionally attribute He ii 4686 Å and coronal Fe emission lines in addition to a steady X-ray luminosity of ≈10{sup 37} erg s{sup −1} to the presence of a compact companion.« less

Small Pixel Hybrid CMOS X-ray Detectors

NASA Astrophysics Data System (ADS)

Hull, Samuel; Bray, Evan; Burrows, David N.; Chattopadhyay, Tanmoy; Falcone, Abraham; Kern, Matthew; McQuaide, Maria; Wages, Mitchell

2018-01-01

Concepts for future space-based X-ray observatories call for a large effective area and high angular resolution instrument to enable precision X-ray astronomy at high redshift and low luminosity. Hybrid CMOS detectors are well suited for such high throughput instruments, and the Penn State X-ray detector lab, in collaboration with Teledyne Imaging Sensors, has recently developed new small pixel hybrid CMOS X-ray detectors. These prototype 128x128 pixel devices have 12.5 micron pixel pitch, 200 micron fully depleted depth, and include crosstalk eliminating CTIA amplifiers and in-pixel correlated double sampling (CDS) capability. We report on characteristics of these new detectors, including the best read noise ever measured for an X-ray hybrid CMOS detector, 5.67 e- (RMS).

A New Compton-Thick AGN in Our Cosmic Backyard: Unveiling the Buried Nucleus in NGC 1448 with NuSTAR

NASA Technical Reports Server (NTRS)

Annuar, A.; Alexander, D. M.; Ghandi, P.; Lansbury, G. B.; Asmus, D.; Ballantyne, D. R.; Bauer, F. E.; Boggs, S. E.; Boorman, P. G.; Brandt, W. N.;

M Stars in the TW Hydra Association: A Chandra Large Program Survey

NASA Astrophysics Data System (ADS)

Punzi, Kristina; Kastner, Joel; Principe, David; Stelzer, Beate; Gorti, Uma; Pascucci, Illaria; Argiroffi, Costanza

2018-01-01

We have conducted a Cycle 18 Chandra Large Program survey of very cool members of the $\\sim$ 8 Myr-old TW Hydra Association (TWA) to extend our previous study of the potential connections between M star disks and X-rays (Kastner et al. 2016, AJ, 152, 3) to the extreme low-mass end of the stellar initial mass function. The spectral types of our targets extend down to the M/L borderline. Thus we can further investigate the potential connection between the intense X-ray emission from young, low-mass stars and the lifetimes of their circumstellar planet-forming discs, as well as better constrain the age at which coronal activity declines for stellar masses approaching the H-burning limit of $\\sim$ 0.08 M$_{\\odot}$. We present preliminary results from the Cycle 18 survey, including X-ray detection statistics and measurements of relative X-ray luminosities and coronal (X-ray) temperatures for those TWA stars detected by Chandra. This research is supported by SAO/CXC grant GO7-18002A and NASA Astrophysics Data Analysis program grants NNX12AH37G and NNX16AG13G to RIT.

High-Mass X-ray Binaries in hard X- rays

NASA Astrophysics Data System (ADS)

Lutovinov, Alexander

We present a review of the latest results of the all-sky survey, performed with the INTEGRAL observatory. The deep exposure spent by INTEGRAL in the Galactic plane region, as well as for nearby galaxies allowed us to obtain a flux limited sample for High Mass X-ray Binaries in the Local Galactic Group and measure their physical properties, like a luminosity function, spatial density distribution, etc. Particularly, it was determined the most accurate up to date spatial density distribution of HMXBs in the Galaxy and its correlation with the star formation rate distribution. Based on the measured value of the vertical distribution of HMXBs (a scale-height h~85 pc) we also estimated a kinematical age of HMXBs. Properties of the population of HMXBs are explained in the framework of the population synthesis model. Based on this model we argue that a flaring activity of so-called supergiant fast X-ray transients (SFXTs), the recently recognized sub-sample of HMXBs, is likely related with the magnetic arrest of their accretion. The resulted global characteristics of the HMXB population are used for predictions of sources number counts in sky surveys of future X-ray missions.

Evidence for Intermediate Polars as the Origin of the Galactic Center Hard X-Ray Emission

NASA Technical Reports Server (NTRS)

Hailey, Charles J.; Mori, Kaya; Perez, Kerstin; Canipe, Alicia M.; Hong, Jaesub; Tomsick, John A.; Boggs, Steven E.; Christensen, Finn E.; Craig, William W.; Fornasini, Francesa;

VizieR Online Data Catalog: Chandra ACIS survey in nearby galaxies. II (Wang+, 2016)

NASA Astrophysics Data System (ADS)

Wang, S.; Qiu, Y.; Liu, J.; Bregman, J. N.

2018-03-01

Based on the recently completed Chandra/ACIS survey of X-ray point sources in nearby galaxies, we study the X-ray luminosity functions (XLFs) for X-ray point sources in different types of galaxies and the statistical properties of ultraluminous X-ray sources (ULXs). Uniform procedures are developed to compute the detection threshold, to estimate the foreground/background contamination, and to calculate the XLFs for individual galaxies and groups of galaxies, resulting in an XLF library of 343 galaxies of different types. With the large number of surveyed galaxies, we have studied the XLFs and ULX properties across different host galaxy types, and confirm with good statistics that the XLF slope flattens from lenticular (α{\\sim}1.50{\\pm}0.07) to elliptical ({\\sim}1.21{\\pm}0.02), to spirals ({\\sim}0.80{\\pm}0.02), to peculiars ({\\sim}0.55{\\pm}0.30), and to irregulars ({\\sim}0.26{\\pm}0.10). The XLF break dividing the neutron star and black hole binaries is also confirmed, albeit at quite different break luminosities for different types of galaxies. A radial dependency is found for ellipticals, with a flatter XLF slope for sources located between D25 and 2D25, suggesting the XLF slopes in the outer region of early-type galaxies are dominated by low-mass X-ray binaries in globular clusters. This study shows that the ULX rate in early-type galaxies is 0.24{\\pm}0.05 ULXs per surveyed galaxy, on a 5σ confidence level. The XLF for ULXs in late-type galaxies extends smoothly until it drops abruptly around 4x1040erg/s, and this break may suggest a mild boundary between the stellar black hole population possibly including 30M{\\sun} black holes with super-Eddington radiation and intermediate mass black holes. (1 data file).

X-ray radiative transfer in protoplanetary disks. The role of dust and X-ray background fields

NASA Astrophysics Data System (ADS)

Rab, Ch.; Güdel, M.; Woitke, P.; Kamp, I.; Thi, W.-F.; Min, M.; Aresu, G.; Meijerink, R.

2018-01-01

Context. The X-ray luminosities of T Tauri stars are about two to four orders of magnitude higher than the luminosity of the contemporary Sun. As these stars are born in clusters, their disks are not only irradiated by their parent star but also by an X-ray background field produced by the cluster members. Aims: We aim to quantify the impact of X-ray background fields produced by young embedded clusters on the chemical structure of disks. Further, we want to investigate the importance of the dust for X-ray radiative transfer in disks. Methods: We present a new X-ray radiative transfer module for the radiation thermo-chemical disk code PRODIMO (PROtoplanetary DIsk MOdel), which includes X-ray scattering and absorption by both the gas and dust component. The X-ray dust opacities can be calculated for various dust compositions and dust-size distributions. For the X-ray radiative transfer we consider irradiation by the star and by X-ray background fields. To study the impact of X-rays on the chemical structure of disks we use the well established disk ionization tracers N2H+ and HCO+. Results: For evolved dust populations (e.g. grain growth), X-ray opacities are mostly dominated by the gas; only for photon energies E ≳ 5-10 keV do dust opacities become relevant. Consequently the local disk X-ray radiation field is only affected in dense regions close to the disk midplane. X-ray background fields can dominate the local X-ray disk ionization rate for disk radii r ≳ 20 au. However, the N2H+ and HCO+ column densities are only significantly affected in cases of low cosmic-ray ionization rates (≲10-19 s-1), or if the background flux is at least a factor of ten higher than the flux level of ≈10-5 erg cm-2 s-1 expected for clusters typical for the solar vicinity. Conclusions: Observable signatures of X-ray background fields in low-mass star-formation regions, like Taurus, are only expected for cluster members experiencing a strong X-ray background field (e.g. due to their location within the cluster). For the majority of the cluster members, the X-ray background field has relatively little impact on the disk chemical structure.

Consequences of narrow cyclotron emission from Hercules X-1

NASA Technical Reports Server (NTRS)

Weaver, R. P.

1978-01-01

The implications of the recent observations of a narrow cyclotron line in the hard X-ray spectrum of Hercules X-1 are studied. A Monte Carlo code is used to simulate the X-ray transfer of an intrinsically narrow feature at approximately 56 keV through an opaque, cold magnetospheric shell. The results of this study indicate that if a narrow line can be emitted by the source region, then only about 10% of the photons remain in a narrow feature after scattering through the shell. The remaining photons are scattered into a broad feature (FWHM approximately 30 keV) that peaks near 20 keV. Thus, these calculations indicate that the intrinsic source luminosity of the cyclotron line is at least an order of magnitude greater than the observed luminosity.

X-Ray Emission from the Wolf-Rayet Bubble S 308

NASA Technical Reports Server (NTRS)

Toala, J. A.; Guerrero, M. A.; Chu, Y.-H.; Gruendl, R. A.; Arthur, S. J.; Smith, R. C.; Snowden, S. L.

2012-01-01

The Wolf-Rayet (WR) bubble S 308 around the WR star HD 50896 is one of the only two WR bubbles known to possess X-ray emission. We present XMM-Newton observations of three fields of this WR bubble that, in conjunction with an existing observation of its Northwest quadrant (Chu et al. 2003), map most of the nebula. The X-ray emission from S 308 displays a limb-brightened morphology, with a 22' in size central cavity and a shell thickness of approx. 8'. This X-ray shell is confined by the optical shell of ionized material. The spectrum is dominated by the He-like triplets of N VI at approx.0.43 keV and O VII at approx.0.5 keV, and declines towards high energies, with a faint tail up to 1 keV. This spectrum can be described by a two-temperature optically thin plasma emission model (T1 approx.1.1 x 10(exp 6) K, T2 approx.13 x 10(exp 6) K), with a total X-ray luminosity approx.3 x 10(exp 33) erg/s at the assumed distance of 1.8 kpc. Qualitative comparison of the X-ray morphology of S 308 with the results of numerical simulations of wind-blown WR bubbles suggests a progenitor mass of 40 Stellar mass and an age in the WR phase approx.20,000 yrs. The X-ray luminosity predicted by simulatioms including the effects of heat conduction is in agreement with the observations, however, the simulated X-ray spectrum indicates generally hotter gas than is derived from the observations. We suggest that non-equilibrium ionization (NEI) may provide an explanation for this discrepancy.

FRESH ACTIVITY IN OLD SYSTEMS: RADIO AGNs IN FOSSIL GROUPS OF GALAXIES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hess, Kelley M.; Wilcots, Eric M.; Hartwick, Victoria L., E-mail: hess@ast.uct.ac.za, E-mail: ewilcots@astro.wisc.edu, E-mail: vhartwick@wisc.edu

2012-08-15

We present the first systematic 1.4 GHz Very Large Array radio continuum survey of fossil galaxy group candidates. These are virialized systems believed to have assembled over a gigayear in the past through the merging of galaxy group members into a single, isolated, massive elliptical galaxy and featuring an extended hot X-ray halo. We use new photometric and spectroscopic data from Sloan Digital Sky Survey Data Release 7 to determine that three of the candidates are clearly not fossil groups. Of the remaining 30 candidates, 67% contain a radio-loud (L{sub 1.4GHz} > 10{sup 23} W Hz{sup -1}) active galactic nucleusmore » (AGN) at the center of their dominant elliptical galaxy. We find a weak correlation between the radio luminosity of the AGN and the X-ray luminosity of the halo suggesting that the AGN contributes to energy deposition into the intragroup medium. We only find a correlation between the radio and optical luminosity of the central elliptical galaxy when we include X-ray-selected, elliptically dominated non-fossil groups, indicating a weak relationship between AGN strength and the mass assembly history of the groups. The dominant elliptical galaxy of fossil groups is on average roughly an order of magnitude more luminous than normal group elliptical galaxies in optical, X-ray, and radio luminosities and our findings are consistent with previous results that the radio-loud fraction in elliptical galaxies is linked to the stellar mass of a population. The current level of activity in fossil groups suggests that AGN fueling continues long after the last major merger. We discuss several possibilities for fueling the AGN at the present epoch.« less

Late Time Multi-wavelength Observations of Swift J1644+5734: A Luminous Optical/IR Bump and Quiescent X-Ray Emission

NASA Astrophysics Data System (ADS)

Levan, A. J.; Tanvir, N. R.; Brown, G. C.; Metzger, B. D.; Page, K. L.; Cenko, S. B.; O'Brien, P. T.; Lyman, J. D.; Wiersema, K.; Stanway, E. R.; Fruchter, A. S.; Perley, D. A.; Bloom, J. S.

2016-03-01

We present late time multi-wavelength observations of Swift J1644+57, suggested to be a relativistic tidal disruption flare (TDF). Our observations extend to >4 years from discovery and show that 1.4 years after outburst the relativistic jet switched off on a timescale less than tens of days, corresponding to a power-law decay faster than t-70. Beyond this point weak X-rays continue to be detected at an approximately constant luminosity of LX ˜ 5 × 1042 erg s-1 and are marginally inconsistent with a continuing decay of t-5/3, similar to that seen prior to the switch-off. Host photometry enables us to infer a black hole mass of MBH = 3 × 106 M⊙, consistent with the late time X-ray luminosity arising from sub-Eddington accretion onto the black hole in the form of either an unusually optically faint active galactic nucleus or a slowly varying phase of the transient. Optical/IR observations show a clear bump in the light curve at timescales of 30-50 days, with a peak magnitude (corrected for host galaxy extinction) of MR ˜ -22 to -23. The luminosity of the bump is significantly higher than seen in other, non-relativistic TDFs and does not match any re-brightening seen at X-ray or radio wavelengths. Its luminosity, light curve shape, and spectrum are broadly similar to those seen in superluminous supervnovae, although subject to large uncertainties in the correction of the significant host extinction. We discuss these observations in the context of both TDF and massive star origins for Swift J1644+5734 and other candidate relativistic tidal flares.

Understanding The Time Evolution Of Luminosity And Associated Accretion Structures In X-Ray Pulsars

NASA Astrophysics Data System (ADS)

Laycock, Silas

We propose to analyze the large archive of RXTE, XMM-Newton and Chandra observations of X-ray Binary Pulsars in the Magellanic Clouds and Milky Way. There are some 2000 individual RXTE PCA pointings on the SMC spanning 15 years, and a smaller number on the LMC. Each PCA observation covers a large fraction of the whole SMC (or LMC) population, and we are able to deconvolve the sometimes simultaneous signals to create an unrivaled record of pulsar temporal behavior. More than 200 XMM- Newton and Chandra observations of the SMC/LMC and individual Galactic pulsars provide information at lower luminosity levels. Together, these datasets cover the entire range of variability timescales and accretion regimes in High Mass X-ray Binaries. We will produce a comprehensive library of energy- resolved pulse profiles covering the entire luminosity and spin-period parameter space, and make this available to the community. We will then model these pulse profiles using state of the art techniques to parameterize the morphology, and publish the resulting data-cube. This result will include for example the distribution of offsets between magnetic and spin axes. These products are needed for the next generation of advances in neutron star theory and modeling. The unique dataset will also enable us to determine the upper and lower limits of accretion powered luminosity in a large statistically complete sample of neutron stars, and hence make several direct tests of fundamental NS parameters and accretion physics. In addition the long-duration of the dataset and "whole-galaxy" nature of the SMC sample make possible a new statistical approach to uncover the duty-cycle distribution and hence population demographics of transient High Mass X-ray Binary (HMXB) populations.

NuSTAR Observations of the Compton-thick Active Galactic Nucleus and Ultraluminous X-Ray Source Candidate in NGC 5643

NASA Astrophysics Data System (ADS)

Annuar, A.; Gandhi, P.; Alexander, D. M.; Lansbury, G. B.; Arévalo, P.; Ballantyne, D. R.; Baloković, M.; Bauer, F. E.; Boggs, S. E.; Brandt, W. N.; Brightman, M.; Christensen, F. E.; Craig, W. W.; Del Moro, A.; Hailey, C. J.; Harrison, F. A.; Hickox, R. C.; Matt, G.; Puccetti, S.; Ricci, C.; Rigby, J. R.; Stern, D.; Walton, D. J.; Zappacosta, L.; Zhang, W.

2015-12-01

We present two Nuclear Spectroscopic Telescope Array (NuSTAR) observations of the local Seyfert 2 active galactic nucleus (AGN) and an ultraluminous X-ray source (ULX) candidate in NGC 5643. Together with archival data from Chandra, XMM-Newton, and Swift-BAT, we perform a high-quality broadband spectral analysis of the AGN over two decades in energy (˜0.5-100 keV). Previous X-ray observations suggested that the AGN is obscured by a Compton-thick (CT) column of obscuring gas along our line of sight. However, the lack of high-quality ≳10 keV observations, together with the presence of a nearby X-ray luminous source, NGC 5643 X-1, have left significant uncertainties in the characterization of the nuclear spectrum. NuSTAR now enables the AGN and NGC 5643 X-1 to be separately resolved above 10 keV for the first time and allows a direct measurement of the absorbing column density toward the nucleus. The new data show that the nucleus is indeed obscured by a CT column of NH ≳ 5 × 1024 cm-2. The range of 2-10 keV absorption-corrected luminosity inferred from the best-fitting models is L2-10,int = (0.8-1.7) × 1042 erg s-1, consistent with that predicted from multiwavelength intrinsic luminosity indicators. In addition, we also study the NuSTAR data for NGC 5643 X-1 and show that it exhibits evidence of a spectral cutoff at energy E ˜ 10 keV, similar to that seen in other ULXs observed by NuSTAR. Along with the evidence for significant X-ray luminosity variations in the 3-8 keV band from 2003 to 2014, our results further strengthen the ULX classification of NGC 5643 X-1.

Soft X-Ray Observations of a Complete Sample of X-Ray--selected BL Lacertae Objects

NASA Astrophysics Data System (ADS)

Perlman, Eric S.; Stocke, John T.; Wang, Q. Daniel; Morris, Simon L.

1996-01-01

We present the results of ROSAT PSPC observations of the X-ray selected BL Lacertae objects (XBLs) in the complete Einstein Extended Medium Sensitivity Survey (EM MS) sample. None of the objects is resolved in their respective PSPC images, but all are easily detected. All BL Lac objects in this sample are well-fitted by single power laws. Their X-ray spectra exhibit a variety of spectral slopes, with best-fit energy power-law spectral indices between α = 0.5-2.3. The PSPC spectra of this sample are slightly steeper than those typical of flat ratio-spectrum quasars. Because almost all of the individual PSPC spectral indices are equal to or slightly steeper than the overall optical to X-ray spectral indices for these same objects, we infer that BL Lac soft X-ray continua are dominated by steep-spectrum synchrotron radiation from a broad X-ray jet, rather than flat-spectrum inverse Compton radiation linked to the narrower radio/millimeter jet. The softness of the X-ray spectra of these XBLs revives the possibility proposed by Guilbert, Fabian, & McCray (1983) that BL Lac objects are lineless because the circumnuclear gas cannot be heated sufficiently to permit two stable gas phases, the cooler of which would comprise the broad emission-line clouds. Because unified schemes predict that hard self-Compton radiation is beamed only into a small solid angle in BL Lac objects, the steep-spectrum synchrotron tail controls the temperature of the circumnuclear gas at r ≤ 1018 cm and prevents broad-line cloud formation. We use these new ROSAT data to recalculate the X-ray luminosity function and cosmological evolution of the complete EMSS sample by determining accurate K-corrections for the sample and estimating the effects of variability and the possibility of incompleteness in the sample. Our analysis confirms that XBLs are evolving "negatively," opposite in sense to quasars, with Ve/Va = 0.331±0.060. The statistically significant difference between the values for X-ray and radio-selected BL Lac objects remains a difficulty for models which unify these two types of objects. We have identified one addition to the sample, so that the sample now has 23 objects. We find no evidence for a substantial number of unidentified low-luminosity BL Lac objects hidden in our sample, as had been suggested by Browne & Marcha (1993) although a few such objects may be present.

Exploring X-Ray Binary Populations in Compact Group Galaxies With Chandra

NASA Technical Reports Server (NTRS)

Tzanavaris, P.; Hornschemeier, A. E..; Gallagher, S. C.; Lenkic, L.; Desjardins, T. D.; Walker, L. M.; Johnson, K. E.; Mulchaey, J. S.

2016-01-01

We obtain total galaxy X-ray luminosities, LX, originating from individually detected point sources in a sample of 47 galaxies in 15 compact groups of galaxies (CGs). For the great majority of our galaxies, we find that the detected point sources most likely are local to their associated galaxy, and are thus extragalactic X-ray binaries (XRBs) or nuclear active galactic nuclei (AGNs). For spiral and irregular galaxies, we find that, after accounting for AGNs and nuclear sources, most CG galaxies are either within the +/-1s scatter of the Mineo et al. LX-star formation rate (SFR) correlation or have higher LX than predicted by this correlation for their SFR. We discuss how these "excesses" may be due to low metallicities and high interaction levels. For elliptical and S0 galaxies, after accounting for AGNs and nuclear sources, most CG galaxies are consistent with the Boroson et al. LX-stellar mass correlation for low-mass XRBs, with larger scatter, likely due to residual effects such as AGN activity or hot gas. Assuming non-nuclear sources are low- or high-mass XRBs, we use appropriate XRB luminosity functions to estimate the probability that stochastic effects can lead to such extreme LX values. We find that, although stochastic effects do not in general appear to be important, for some galaxies there is a significant probability that high LX values can be observed due to strong XRB variability.

Dust Grains and the Luminosity of Circumnuclear Water Masers in Active Galaxies

NASA Technical Reports Server (NTRS)

Collison, Alan J.; Watson, William D.

1995-01-01

In previous calculations for the luminosities of 22 GHz water masers, the pumping is reduced and ultimately quenched with increasing depth into the gas because of trapping of the infrared (approximately equals 30-150 micrometers), spectral line radiation of the water molecule. When the absorption (and reemission) of infrared radiation by dust grains is included, we demonstrate that the pumping is no longer quenched but remains constant with increasing optical depth. A temperature difference between the grains and the gas is required. Such conditions are expected to occur, for example, in the circumnuclear masing environments created by X-rays in active galaxies. Here, the calculated 22 GHz maser luminosities are increased by more than an order of magnitude. Application to the well-studied, circumnuclear masing disk in the galaxy NGC 4258 yields a maser luminosity near that inferred from observations if the observed X-ray flux is assumed to be incident onto only the inner surface of the disk.

A Chandra X-Ray Study of NGC 1068 IL the Luminous X-Ray Source Population

NASA Technical Reports Server (NTRS)

Smith, David A.; Wilson, Andrew S.

2003-01-01

We present an analysis of the compact X-ray source population in the Seyfert 2 galaxy NGC 1068, imaged with a approx. 50 ks Chandra observation. We find a total of 84 compact sources on the S3 chip, of which 66 are located within the 25.0 B-mag/arcsec isophote of the galactic disk of NGC 1068. Spectra have been obtained for the 21 sources with at least 50 counts and modeled with both multicolor disk blackbody and power-law models. The power-law model provides the better description of the spectrum for 18 of these sources. For fainter sources, the spectral index has been estimated from the hardness ratio. Five sources have 0.4 - 8 keV intrinsic luminosities greater than 10(exp 39)ergs/ s, assuming that their emission is isotropic and that they are associated with NGC 1068. We refer to these sources as intermediate-luminosity X-ray objects (ISOs). If these five sources are X-ray binaries accreting with luminosities that are both sub-Eddington and isotropic, then the implied source masses are approx greater than 7 solar mass, and so they are inferred to be black holes. Most of the spectrally modeled sources have spectral shapes similar to Galactic black hole candidates. However, the brightest compact source in NGC 1068 has a spectrum that is much harder than that found in Galactic black hole candidates and other ISOs. The brightest source also shows large amplitude variability on both short-term and long-term timescales, with the count rate possibly decreasing by a factor of 2 in approx. 2 ks during our Chundra observation, and the source flux decreasing by a factor of 5 between our observation and the grating observations taken just over 9 months later. The ratio of the number of sources with luminosities greater than 2.1 x 10(exp 38) ergs/s in the 0.4 - 8 keV band to the rate of massive (greater than 5 solar mass) star formation is the same, to within a factor of 2, for NGC 1068, the Antennae, NGC 5194 (the main galaxy in M51), and the Circinus galaxy. This suggests that the rate of production of X-ray binaries per massive star is approximately the same for galaxies with currently active star formation, including "starbursts."

Tracing the Mass-Dependent Star Formation History of Late-Type Galaxies using X-ray Emission: Results from the CHANDRA Deep Fields

NASA Technical Reports Server (NTRS)

Lehmer, B.D; Brandt, W.N.; Schneider, D.P.; Steffen, A.T.; Alexander, D.M.; Bell, E.F.; Hornschemeier, A.E.; McIntosh, D.H.; Bauer, F.E.; Gilli, R.;

Spectral formation in a radiative shock: application to anomalous X-ray pulsars and soft gamma-ray repeaters

NASA Astrophysics Data System (ADS)

Kylafis, N. D.; Trümper, J. E.; Ertan, Ü.

2014-02-01

Context. In the fallback disk model for the persistent emission of anomalous X-ray pulsars (AXPs) and soft gamma-ray repeaters (SGRs), the hard X-ray emission arises from bulk- and thermal Comptonization of bremsstrahlung photons, which are generated in the accretion column. The relatively low X-ray luminosity of these sources implies a moderate transverse optical depth to electron scattering, with photons executing a small number of shock crossings before escaping sideways. Aims: We explore the range of spectral shapes that can be obtained with this model and characterize the most important parameter dependencies. Methods: We use a Monte Carlo code to study the crisscrossing of photons in a radiative shock in an accretion column and compute the resulting spectrum. Results: As expected, high-energy power-law X-ray spectra are produced in radiative shocks with photon-number spectral index Γ ≳ 0.5. We find that the required transverse optical depth is 1 ≲ τ⊥ ≲ 7. Such spectra are observed in low-luminosity X-ray pulsars. Conclusions: We demonstrate here with a simple model that Compton upscattering in the radiative shock in the accretion column can produce hard X-ray spectra similar to those seen in the persistent and transient emission of AXPs and SGRs. In particular, one can obtain a high-energy power-law spectrum, with photon-number spectral-index Γ ~ 1 and a cutoff at 100 - 200 keV, with a transverse Thomson optical depth of ~5, which is shown to be typical in AXPs/SGRs.

PSR J2022 plus 3842: An Energetic Radio and X-Ray Pulsar Associated with SNR G76.9 plus 1.0

NASA Technical Reports Server (NTRS)

Arzoumanian, Z.; Gotthelf, E. V.; Ransom, S. M.; Kothes, R.; Landecker, T. L.

2010-01-01

We present Chandra X-ray Observatory, Robert C. Byrd Green Bank Radio Telescope (GBT), and Rossi X-ray Timing Explorer (RXTE) observations directed toward the radio supernova remnant (SNR) G76.9+1.0. The Chandra investigation reveals a hard, unresolved X-ray source coincident with the midpoint of the double-lobed radio morphology and surrounded by faint, compact X-ray nebulosity. These features suggest that an energetic neutron star is powering a pulsar wind nebula (PWN) seen in synchrotron emission. Indeed, the spatial relationship of the X-ray and radio emissions is remarkably similar to the extended emission around the Vela pulsar. A follow-up pulsation search with the GBT uncovered a highly-dispersed (DM = 427 +/- 1 pc/cu cm) and highly-scattered pulsar with a period of 24 ms. Its subsequently measured spin-down rate implies a characteristic age T(sub c) = 8.9 kyr, making PSR J2022+3842 the most rapidly rotating young radio pulsar known. With a spin-down luminosity E = 1.2 x 10(exp 38) erg/s, it is the second-most energetic Galactic pulsar known, after the Crab pulsar. The 24-ms pulsations have also been detected in the RXTE observation; the combined Chandra and RXTE spectral fit suggests that the Chandra point-source emission is virtually 100% pulsed. The 2-16 keV spectrum of the narrow (0.06 cycles FWHM) pulse is well-fitted by an absorbed power-law model with column density N(sub H) = (1.7 +/- 0.5) x 10(exp 22)/sq cm and photon index Gamma = 1.0 +/- 0.2, strongly suggestive of magnetospheric emission. For an assumed distance of 10 kpc, the 2-10 keV luminosity of L(sub X) = 6.9 x 10(exp 33) erg/s suggests one of the lowest known X-ray conversion efficiencies L(sub X)/ E = 5.8 x 10(exp -5), similar to that of the Vela pulsar. Finally, the PWN around PSR J2022+3842 revealed by Chandra is also underluminous, with F(sub PWN)/ F(sub PSR) < or approx.1 in the 2-10 keV band, a further surprise given the pulsar's high spin-down luminosity.

ON THE WEAK-WIND PROBLEM IN MASSIVE STARS: X-RAY SPECTRA REVEAL A MASSIVE HOT WIND IN {mu} COLUMBAE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huenemoerder, David P.; Oskinova, Lidia M.; Todt, Helge

2012-09-10

{mu} Columbae is a prototypical weak-wind O star for which we have obtained a high-resolution X-ray spectrum with the Chandra LETG/ACIS instrument and a low-resolution spectrum with Suzaku. This allows us, for the first time, to investigate the role of X-rays on the wind structure in a bona fide weak-wind system and to determine whether there actually is a massive hot wind. The X-ray emission measure indicates that the outflow is an order of magnitude greater than that derived from UV lines and is commensurate with the nominal wind-luminosity relationship for O stars. Therefore, the {sup w}eak-wind problem{sup -}identified frommore » cool wind UV/optical spectra-is largely resolved by accounting for the hot wind seen in X-rays. From X-ray line profiles, Doppler shifts, and relative strengths, we find that this weak-wind star is typical of other late O dwarfs. The X-ray spectra do not suggest a magnetically confined plasma-the spectrum is soft and lines are broadened; Suzaku spectra confirm the lack of emission above 2 keV. Nor do the relative line shifts and widths suggest any wind decoupling by ions. The He-like triplets indicate that the bulk of the X-ray emission is formed rather close to the star, within five stellar radii. Our results challenge the idea that some OB stars are 'weak-wind' stars that deviate from the standard wind-luminosity relationship. The wind is not weak, but it is hot and its bulk is only detectable in X-rays.« less

The broad-band SEDs of four `hypervariable' AGN

NASA Astrophysics Data System (ADS)

Collinson, James S.; Ward, Martin J.; Lawrence, Andy; Bruce, Alastair; MacLeod, Chelsea L.; Elvis, Martin; Gezari, Suvi; Marshall, Philip J.; Done, Chris

2018-03-01

We present an optical-to-X-ray spectral analysis of four `hypervariable' AGN (HVAs) discovered by comparing Pan-STARRS data to that from the Sloan Digital Sky Survey over a 10 yr baseline (Lawrence et al.). There is some evidence that these objects are X-ray loud for their corresponding UV luminosities, but given that we measured them in a historic high state, it is not clear whether to take the high state or low state as typical of the properties of these HVAs. We estimate black hole masses based on Mg II and H α emission line profiles, and either the high- or low-state luminosities, finding mass ranges log (MBH/M⊙) = 8.2-8.8 and log (MBH/M⊙) = 7.9-8.3, respectively. We then fit energy-conserving models to the spectral energy distributions (SEDs), obtaining strong constraints on the bolometric luminosity and αOX. We compare the SED properties with a larger, X-ray selected AGN sample for both of these scenarios, and observe distinct groupings in spectral shape versus luminosity parameter space. In general, the SED properties are closer to normal if we assume that the low state is representative. This supports the idea that the large slow outbursts may be due to extrinsic effects (for example microlensing) as opposed to accretion rate changes, but a larger sample of HVAs is needed to be confident of this conclusion.

Quasar spectral variability from the XMM-Newton serendipitous source catalogue

NASA Astrophysics Data System (ADS)

Serafinelli, R.; Vagnetti, F.; Middei, R.

2017-04-01

Context. X-ray spectral variability analyses of active galactic nuclei (AGN) with moderate luminosities and redshifts typically show a "softer when brighter" behaviour. Such a trend has rarely been investigated for high-luminosity AGNs (Lbol ≳ 1044 erg/s), nor for a wider redshift range (e.g. 0 ≲ z ≲ 5). Aims: We present an analysis of spectral variability based on a large sample of 2700 quasars, measured at several different epochs, extracted from the fifth release of the XMM-Newton Serendipitous Source Catalogue. Methods: We quantified the spectral variability through the parameter β defined as the ratio between the change in the photon index Γ and the corresponding logarithmic flux variation, β = -ΔΓ/Δlog FX. Results: Our analysis confirms a softer when brighter behaviour for our sample, extending the previously found general trend to high luminosity and redshift. We estimate an ensemble value of the spectral variability parameter β = -0.69 ± 0.03. We do not find dependence of β on redshift, X-ray luminosity, black hole mass or Eddington ratio. A subsample of radio-loud sources shows a smaller spectral variability parameter. There is also some change with the X-ray flux, with smaller β (in absolute value) for brighter sources. We also find significant correlations for a small number of individual sources, indicating more negative values for some sources.

A decades-long fast-rise-exponential-decay flare in low-luminosity AGN NGC 7213

NASA Astrophysics Data System (ADS)

Yan, Zhen; Xie, Fu-Guo

2018-03-01

We analysed the four-decades-long X-ray light curve of the low-luminosity active galactic nucleus (LLAGN) NGC 7213 and discovered a fast-rise-exponential-decay (FRED) pattern, i.e. the X-ray luminosity increased by a factor of ≈4 within 200 d, and then decreased exponentially with an e-folding time ≈8116 d (≈22.2 yr). For the theoretical understanding of the observations, we examined three variability models proposed in the literature: the thermal-viscous disc instability model, the radiation pressure instability model, and the TDE model. We find that a delayed tidal disruption of a main-sequence star is most favourable; either the thermal-viscous disc instability model or radiation pressure instability model fails to explain some key properties observed, thus we argue them unlikely.

Relativistic Particle Population and Magnetic Fields in Clusters of Galaxies

NASA Astrophysics Data System (ADS)

Kushnir, Doron

2011-08-01

We derive constrains on the cosmic ray (CR) population and magnetic fields (MF) in clusters of galaxies, based on: 1. The correlation between the radio and the X-ray luminosities: the former emitted by synchrotron of secondary electrons in a strong MF, >˜3 muG; In the core, the CR energy is ˜10^{-3} of the thermal energy; The source of CR is the accretion shock (AS), which accelerate CR with efficiency >˜1%. 2. The HXR luminosity: emitted by IC of CMB photons by electrons accelerated in AS with efficiency >˜1%. The constrains imply that gamma-ray emission from secondaries will be difficult to detect with existing/planned instruments. However, the extended emission from primary electrons might be detected by future HXR (NuStar, Simbol-X) and gamma-ray observations (Fermi, HESS, VERITAS).

X-ray Spectroscopy of a TDE

NASA Astrophysics Data System (ADS)

Kochanek, Christopher

2017-09-01

Tidal disruption events (TDE), where supermassive black holes destroy stars to produce accretion flares, are of great current observational and theoretical interest. Here we propose a four epoch HRC/LETG X-ray spectroscopic ``movie'' of a TDE spread over the first 40 days of an X-ray bright TDE, including any discovered by our ASAS-SN survey, supported and extended by higher cadence Swift XRT/UVOT observations over the first 100 days. For this next X-ray bright TDE, we will measure the evolution of the X-ray emission (luminosity/temperature) from the hot accretion disk, the emission reprocessed by the debris into UV/optical, and use X-ray absorption (or emission) features to look at the abundances and the evolution of the kinematics and ionization parameter.

The TESIS Project: Are Type 2 QSO Hidden in X-Ray Emitting EROs?

NASA Astrophysics Data System (ADS)

Severgnini, P.; Della Ceca, R.; Braito, V.; Saracco, P.; Longhetti, M.; Bender, R.; Drory, N.; Feulner, G.; Hopp, U.; Mannucci, F.; Maraston, C.

X-ray selected EROs are, on average, the hardest X-ray sources in medium and deep X-ray fields. This coupled with their extremely red colors (R-K > 5) suggest that they represent one of the most promising population where looking for high-luminosity (LX > 1044 erg s-1) and X-ray obscured (NH > 1022 cm-2) type2 AGNs, the so called QSO2 (e.g., [5]; [4]; Mignoli et al. submitted to A&A). These latter are predicted in large density by the synthesis model of the Cosmic X-ray background [9] even if only few observational evidences have been found so far (e.g., [1] and references therein; Caccianiga et al. A&A accepted).

Luminosity function and jet structure of Gamma-Ray Burst

NASA Astrophysics Data System (ADS)

Pescalli, A.; Ghirlanda, G.; Salafia, O. S.; Ghisellini, G.; Nappo, F.; Salvaterra, R.

2015-02-01

The structure of gamma-ray burst (GRB) jets impacts on their prompt and afterglow emission properties. The jet of GRBs could be uniform, with constant energy per unit solid angle within the jet aperture, or it could be structured, namely with energy and velocity that depend on the angular distance from the axis of the jet. We try to get some insight about the still unknown structure of GRBs by studying their luminosity function. We show that low (1046-48 erg s-1) and high (i.e. with L ≥ 1050 erg s-1) luminosity GRBs can be described by a unique luminosity function, which is also consistent with current lower limits in the intermediate luminosity range (1048-50 erg s-1). We derive analytical expressions for the luminosity function of GRBs in uniform and structured jet models and compare them with the data. Uniform jets can reproduce the entire luminosity function with reasonable values of the free parameters. A structured jet can also fit adequately the current data, provided that the energy within the jet is relatively strongly structured, i.e. E ∝ θ-k with k ≥ 4. The classical E ∝ θ-2 structured jet model is excluded by the current data.

Discovery of Diffuse Hard X-ray Emission associated with Jupiter

NASA Astrophysics Data System (ADS)

Ezoe, Y.; Miyoshi, Y.; Ishikawa, K.; Ohashi, T.; Terada, N.; Uchiyama, Y.; Negoro, H.

2009-12-01

Our discovery of diffuse hard (1-5 keV) X-ray emission around Jupiter is reported. Recent Chandra and XMM-Newton observations revealed several types of X-rays in the vicinity of Jupiter such as auroral and disk emission from Jupiter and faint diffuse X-rays from the Io Plasma Torus (see Bhardwaj et al. 2007 for review). To investigate possible diffuse hard X-ray emission around Jupiter with the highest sensitivity, we conducted data analysis of Suzaku XIS observations of Jupiter on Feb 2006. After removing satellite and planetary orbital motions, we detected a significant diffuse X-ray emission extending to ~6 x 3 arcmin with the 1-5 keV X-ray luminosity of ~3e15 erg/s. The emitting region very well coincided with the Jupiter's radiation belts. The 1-5 keV X-ray spectrum was represented by a simple power law model with a photon index of 1.4. Such a flat continuum strongly suggests non-thermal origin. Although such an emission can be originated from multiple background point sources, its possibility is quite low. We hence examined three mechanisms, assuming that the emission is truly diffuse: bremsstrahlung by keV electrons, synchrotron emission by TeV electrons, and inverse Compton scattering of solar photons by MeV electrons. The former two can be rejected because of the X-ray spectral shape and implausible existence of TeV electrons around Jupiter, respectively. The last possibility was found to be possible because tens MeV electrons, which have been confirmed in inner radiation belts (Bolton et al. 2002), can kick solar photons to the keV energy range and provide a simple power-law continuum. We estimated an average electron density from the X-ray luminosity assuming the oblate spheroid shaped emitting region with 8 x 8 x 4 Jovian radii. The necessary density was 0.02 1/cm3 for 50 MeV electrons. Hence, our results may suggest a new particle acceleration phenomenon around Jupiter.

Renewed Activity from the X-Ray Transient SAXJ 1810.8-2609 with Integral

NASA Astrophysics Data System (ADS)

Fiocchi, M.; Natalucci, L.; Chenevez, J.; Bazzano, A.; Tarana, A.; Ubertini, P.; Brandt, S.; Beckmann, V.; Federici, M.; Galis, R.; Hudec, R.

2009-03-01

We report on the results of International Gamma-Ray Astrophysics Laboratory (INTEGRAL) observations of the neutron star low-mass X-ray binary SAX J1810.8-2609 during its latest active phase in 2007 August. The current outburst is the first one since 1998 and the derived luminosity is 1.1-2.6 ×1036 erg s-1 in the 20-100 keV energy range. This low outburst luminosity and the long-term time-average accretion rate of ~5 × 10-12 M sun yr-1 suggest that SAX J1810.8-2609 is a faint soft X-ray transient. During the flux increase, spectra are consistent with a thermal Comptonization model with a temperature plasma of kT e~ 23-30 keV and an optical depth of τ~ 1.2-1.5, independent of the luminosity of the system. This is a typical low hard spectral state for which the X-ray emission is attributed to the upscattering of soft seed photons by a hot, optically thin electron plasma. During the decay, spectra have a different shape, the high energy tail being compatible with a single power law. This confirm similar behavior observed by BeppoSAX during the previous outburst, with the absence of visible cutoff in the hard X-ray spectrum. INTEGRAL/JEM-X instrument observed four X-ray bursts in Fall 2007. The first one has the highest peak flux (≈3.5 crab in 3-25 keV) giving an upper limit to the distance of the source of about 5.7 kpc, for a L Edd ≈ 3.8 × 1038 erg s-1. The observed recurrence time of ~ 1.2 days and the ratio of the total energy emitted in the persistent flux to that emitted in the bursts (α~ 73) allow us to conclude that the burst fuel was composed by mixed hydrogen and helium with X >= 0.4. INTEGRAL is an ESA project with Instruments and Science Data Center funded by ESA member states, especially the PI countries: Denmark, France, Germany, Italy, Switzerland, Spain; Czech Republic and Poland; and with the participation of Russia and USA.

A NuSTAR OBSERVATION OF THE GAMMA-RAY-EMITTING X-RAY BINARY AND TRANSITIONAL MILLISECOND PULSAR CANDIDATE 1RXS J154439.4–112820

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bogdanov, Slavko

I present a 40 ks Nuclear Spectroscopic Telescope Array observation of the recently identified low-luminosity X-ray binary and transitional millisecond pulsar (tMSP) candidate 1RXS J154439.4 112820, which is associated with the high-energy γ -ray source 3FGL J1544.6 1125. The system is detected up to ∼30 keV with an extension of the same power-law spectrum and rapid large-amplitude variability between two flux levels observed in soft X-rays. These findings provide further evidence that 1RXS J154439.4 112820 belongs to the same class of objects as the nearby bona fide tMSPs PSR J1023+0038 and XSS J12270 4859 and therefore almost certainly hosts amore » millisecond pulsar accreting at low luminosity. I also examine the long-term accretion history of 1RXS J154439.4 112820 based on archival optical, ultraviolet, X-ray, and γ -ray light curves covering approximately the past decade. Throughout this period, the source has maintained similar flux levels at all wavelengths, which is an indication that it has not experienced prolonged episodes of a non-accreting radio pulsar state but may spontaneously undergo such events in the future.« less

Truncation of the Inner Accretion Disk Around a Black Hole at Low Luminosity

NASA Technical Reports Server (NTRS)

Tomsick, John A.; Yamaoka, Kazutaka; Corbel, Stephane; Kaaret, Philip; Kalemci, Emrah; Migliari, Simone

2009-01-01

Most black hole binaries show large changes in X-ray luminosity caused primarily by variations in mass accretion rate. An important question for understanding black hole accretion and jet production is whether the inner edge of the accretion disk recedes at low accretion rate. Measurements of the location of the inner edge (R(sub in)) can be made using iron emission lines that arise due to fluorescence of iron in the disk, and these indicate that R(sub in) is very close to the black hole at high and moderate luminosities (greater than approximately equal to 1% of the Eddington luminosity, L(sub Edd). Here, we report on X-ray observation of the black hole GX 339-4 in the hard state by Suzaku and the Rossi X-ray Timing Explorer (RXTE) that extend iron line studies to 0.14% L(sub Edd) and show that R(sub in) increases by a factor of greater than 27 over the value found when GX 339-4 was bright. The exact value of R(sub in) depends on the inclination of the inner disk (i), and we derive 90% confidence limits of R(sub in) greater than 35R(sub g) at i = 0 degrees and R(sub in) greater than 175R(sub g) at i = 30 degrees. This provides direct evidence that the inner portion of the disk is not present at low luminosity, allowing for the possibility that the inner disk is replaced by advection- or magnetically-dominated accretion flows.

iPTF16fnl: A Faint and Fast Tidal Disruption Event in an E+A Galaxy

DOE PAGES

Blagorodnova, N.; Gezari, S.; Hung, T.; ...

2017-07-20

Here, we present ground-based and Swift observations of iPTF16fnl, a likely tidal disruption event (TDE) discovered by the intermediate Palomar Transient Factory (iPTF) survey at 66.6 Mpc. The light curve of the object peaked at an absolute magmore » $${M}_{g}=-17.2$$. The maximum bolometric luminosity (from optical and UV) was $${L}_{p}\\simeq (1.0\\pm 0.15)\\times {10}^{43}$$ erg s -1, an order of magnitude fainter than any other optical TDE discovered so far. The luminosity in the first 60 days is consistent with an exponential decay, with $$L\\propto {e}^{-(t-{t}_{0})/\\tau }$$, where t 0 = 57631.0 (MJD) and $$\\tau \\simeq 15$$ days. The X-ray shows a marginal detection at $${L}_{X}={2.4}_{-1.1}^{1.9}\\times {10}^{39}$$ erg s -1 (Swift X-ray Telescope). No radio counterpart was detected down to 3σ, providing upper limits for monochromatic radio luminosities of $${\

iPTF16fnl: A Faint and Fast Tidal Disruption Event in an E+A Galaxy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Blagorodnova, N.; Gezari, S.; Hung, T.

Here, we present ground-based and Swift observations of iPTF16fnl, a likely tidal disruption event (TDE) discovered by the intermediate Palomar Transient Factory (iPTF) survey at 66.6 Mpc. The light curve of the object peaked at an absolute magmore » $${M}_{g}=-17.2$$. The maximum bolometric luminosity (from optical and UV) was $${L}_{p}\\simeq (1.0\\pm 0.15)\\times {10}^{43}$$ erg s -1, an order of magnitude fainter than any other optical TDE discovered so far. The luminosity in the first 60 days is consistent with an exponential decay, with $$L\\propto {e}^{-(t-{t}_{0})/\\tau }$$, where t 0 = 57631.0 (MJD) and $$\\tau \\simeq 15$$ days. The X-ray shows a marginal detection at $${L}_{X}={2.4}_{-1.1}^{1.9}\\times {10}^{39}$$ erg s -1 (Swift X-ray Telescope). No radio counterpart was detected down to 3σ, providing upper limits for monochromatic radio luminosities of $${\

Hybrid accretion disks in active galactic nuclei. I - Structure and spectra

NASA Technical Reports Server (NTRS)

Wandel, Amri; Liang, Edison P.

1991-01-01

A unified treatment is presented of the two distinct states of vertically thin AGN accretion disks: a cool (about 10 to the 6th K) optically thick solution, and a hot (about 10 to the 9th K) optically thin solution. A generalized formalism and a new radiative cooling equation valid in both regimes are introduced. A new luminosity limit is found at which the hot and cool alpha solutions merge into a single solution of intermediate optical depth. Analytic solutions for the disk structure are given, and output spectra are computed numerically. This is used to demonstrate the prospect of fitting AGN broadband spectra containing both the UV bump as well as the hard X-ray and gamma-ray tail, using a single accretion disk model. Such models are found to make definite predictions about the observed spectrum, such as the relation between the hard X-ray spectral index, the UV-to-X-ray luminosity ratio, and a feature of about 1 MeV.

Fast transient X-rays from flare stars and RS CVn binaries

NASA Astrophysics Data System (ADS)

Rao, A. R.; Vahia, M. N.

1987-12-01

The authors have studied the fast transient X-ray (FTX) observations of the Ariel V satellite. They find that the FTX have characteristics very similar to the stellar flares detected in flare stars and RS CVn binaries by other satellites. It is found that, of the possible candidate objects, only the flare stars and RS CVn binaries can be associated with the Ariel V observations. 11 new flare stars and RS CVn binaries are associated with the FTX. This brings the total number of identifications with the flare stars and RS CVn binaries to 17. The authors further study the flare properties and correlate the peak X-ray luminosity of these Ariel V sources with the bolometric luminosity of the candidate stars. They discuss a solar flare model and show that the observed correlation can be explained under the assumption of constant temperature loops of binary sizes.

A new catalogue of ultraluminous X-ray sources (and more!)

NASA Astrophysics Data System (ADS)

Roberts, T.; Earnshaw, H.; Walton, D.; Middleton, M.; Mateos, S.

2017-10-01

Many of the critical issues of ultraluminous X-ray source (ULX) science - for example the prevalence of IMBH and/or ULX pulsar candidates within the wider ULX population - can only be addressed by studying statistical samples of ULXs. Similarly, characterising the range of properties displayed by ULXs, and so understanding their accretion physics, requires large samples of objects. To this end, we introduce a new catalogue of 376 ultraluminous X-ray sources and 1092 less luminous point X-ray sources associated with nearby galaxies, derived from the 3XMM-DR4 catalogue. We highlight applications of this catalogue, for example the identification of new IMBH candidates from the most luminous ULXs; and examining the physics of objects at the Eddington threshold, where their luminosities of ˜ 10^{39} erg s^{-1} indicate their accretion rates are ˜ Eddington. We also show how the catalogue can be used to start to examine a wider range of lower luminosity (sub-ULX) point sources in star forming galaxies than previously accessible through spectral stacking, and argue why this is important for galaxy formation in the high redshift Universe.

NuSTAR Observations of Heavily Obscured Quasars Selected by WISE

NASA Astrophysics Data System (ADS)

Yan, Wei

2017-08-01

A key goal of the Nuclear Spectroscopic Telescope Array (NuSTAR) program is to find and characterize heavily obscured quasars, luminous accreting supermassive black holes hidden by gas and dust. Based on mid-infrared (IR) photometry from Wide-Field Infrared Survey Explorer (WISE) and optical photometry from the Sloan Digital Sky Surveys, we have selected a large population of obscured quasars; here we report the NuSTAR observations of four WISE-selected heavily obscured quasars for which we have optical spectroscopy from the Southern African Large Telescope and KECK Telescope. Three of four objects are undetected with NuSTAR, while the fourth has only a marginal detection. We confirm our objects have observed hard X-ray (10-40 keV) luminosities at or below ~1043 erg s-1. We compare IR and X-ray luminosities to obtain estimates of hydrogen column NH based on the suppression of the hard X-ray emission. We estimate NH to be at or greater than 1025 cm-2, confirming that WISE and optical selection can identify very heavily obscured quasars that may be missed in X-ray surveys.

Simulating Electron Cyclotron Maser Emission for Low Mass Stars

NASA Astrophysics Data System (ADS)

Llama, Joe; Jardine, Moira

2018-01-01

Zeeman-Doppler Imaging (ZDI) is a powerful technique that enables us to map the large-scale magnetic fields of stars spanning the pre- and main-sequence. Coupling these magnetic maps with field extrapolation methods allow us to investigate the topology of the closed, X-ray bright corona, and the cooler, open stellar wind.Using ZDI maps of young M dwarfs with simultaneous radio light curves obtained from the VLA, we present the results of modeling the Electron-Cyclotron Maser (ECM) emission from these systems. We determine the X-ray luminosity and ECM emission that is produced using the ZDI maps and our field extrapolation model. We compare these findings with the observed radio light curves of these stars. This allows us to predict the relative phasing and amplitude of the stellar X-ray and radio light curves.This benchmarking of our model using these systems allows us to predict the ECM emission for all stars that have a ZDI map and an observed X-ray luminosity. Our model allows us to understand the origin of transient radio emission observations and is crucial for disentangling stellar and exoplanetary radio signals.

High-energy Emission from Nonrelativistic Radiative Shocks: Application to Gamma-Ray Novae

NASA Astrophysics Data System (ADS)

Vurm, Indrek; Metzger, Brian D.

2018-01-01

The observation of GeV gamma-rays from novae by Fermi/LAT demonstrates that the nonrelativistic radiative shocks in these systems can accelerate particles to energies of at least ∼10 GeV. The low-energy extension of the same nonthermal particle distribution inevitably gives rise to emission in the hard X-ray band. Above ≳ 10 {keV}, this radiation can escape the system without significant absorption/attenuation, and can potentially be detected by NuSTAR. We present theoretical models for hard X-ray and gamma-ray emission from radiative shocks in both leptonic and hadronic scenarios, accounting for the rapid evolution of the downstream properties due to the fast cooling of thermal plasma. We find that due to strong Coulomb losses, only a fraction of {10}-4{--}{10}-3 of the gamma-ray luminosity is radiated in the NuSTAR band; nevertheless, this emission could be detectable simultaneously with the LAT emission in bright gamma-ray novae with a ∼50 ks exposure. The spectral slope in hard X-rays is α ≈ 0 for typical nova parameters, thus serving as a testable prediction of the model. Our work demonstrates how combined hard X-ray and gamma-ray observations can be used to constrain properties of the nova outflow (velocity, density, and mass outflow rate) and particle acceleration at the shock. A very low X-ray to gamma-ray luminosity ratio ({L}{{X}}/{L}γ ≲ 5× {10}-4) would disfavor leptonic models for the gamma-ray emission. Our model can also be applied to other astrophysical environments with radiative shocks, including SNe IIn and colliding winds in massive star binaries.

On the X-ray temperature of hot gas in diffuse nebulae

NASA Astrophysics Data System (ADS)

Toalá, J. A.; Arthur, S. J.

2018-05-01

X-ray emitting diffuse nebulae around hot stars are observed to have soft-band temperatures in the narrow range [1-3]× 106 K, independent of the stellar wind parameters and the evolutionary stage of the central star. We discuss the origin of this X-ray temperature for planetary nebulae (PNe), Wolf-Rayet nebulae (WR) and interstellar wind bubbles around hot young stars in our Galaxy and the Magellanic Clouds. We calculate the differential emission measure (DEM) distributions as a function of temperature from previously published simulations and combine these with the X-ray emission coefficient for the 0.3-2.0 keV band to estimate the X-ray temperatures. We find that all simulated nebulae have DEM distributions with steep negative slopes, which is due to turbulent mixing at the interface between the hot shocked stellar wind and the warm photoionized gas. Sharply peaked emission coefficients act as temperature filters and emphasize the contribution of gas with temperatures close to the peak position, which coincides with the observed X-ray temperatures for the chemical abundance sets we consider. Higher metallicity nebulae have lower temperature and higher luminosity X-ray emission. We show that the second temperature component found from spectral fitting to X-ray observations of WR nebulae is due to a significant contribution from the hot shocked stellar wind, while the lower temperature principal component is dominated by nebular gas. We suggest that turbulent mixing layers are the origin of the soft X-ray emission in the majority of diffuse nebulae.

On the X-ray temperature of hot gas in diffuse nebulae

NASA Astrophysics Data System (ADS)

Toalá, J. A.; Arthur, S. J.

2018-07-01

X-ray-emitting diffuse nebulae around hot stars are observed to have soft-band temperatures in the narrow range [1-3] × 106K, independent of the stellar wind parameters and the evolutionary stage of the central star. We discuss the origin of this X-ray temperature for planetary nebulae, Wolf-Rayet (WR) nebulae, and interstellar wind bubbles around hot young stars in our Galaxy and the Magellanic Clouds. We calculate the differential emission measure (DEM) distributions as a function of temperature from previously published simulations and combine these with the X-ray emission coefficient for the 0.3-2.0 keV band to estimate the X-ray temperatures. We find that all simulated nebulae have DEM distributions with steep negative slopes, which is due to turbulent mixing at the interface between the hot shocked stellar wind and the warm photoionized gas. Sharply peaked emission coefficients act as temperature filters and emphasize the contribution of gas with temperatures close to the peak position, which coincides with the observed X-ray temperatures for the chemical abundance sets we consider. Higher metallicity nebulae have lower temperature and higher luminosity X-ray emission. We show that the second temperature component found from spectral fitting to X-ray observations of WR nebulae is due to a significant contribution from the hot shocked stellar wind, while the lower temperature principal component is dominated by nebular gas. We suggest that turbulent mixing layers are the origin of the soft X-ray emission in the majority of diffuse nebulae.

Metallicity Effects on Stellar Magnetic Activity: Blanco 1 as a Test Case

NASA Technical Reports Server (NTRS)

Harnden, F. R., Jr.; Mushotzky, Richard F. (Technical Monitor)

2003-01-01

We present X-ray Luminosity Distributions (XLDs) of late-type members (dF, dG, dK, dM) of the Blanco 1 cluster, based on ROSAT-HRI data and new astrometric-photometric membership obtained from the GSC-II project. For the first time we present the XLD of dM stars of this cluster. The high metallicity of Blanco 1 allows us to investigate the role of chemical composition on the coronal emission of late-type stars. Comparison between X-ray Luminosity Distributions of Blanco 1 and Pleiades, NGC2516 and alpha Per suggests a possible metallicity effect in dM stars.

X-Ray Iron Line Constraints on the Inner Accretion Disk and Black Hole Spin

NASA Technical Reports Server (NTRS)

Reynolds, C. S.

2000-01-01

The broad iron line, seen in the X-ray spectra of many AGN, is thought to originate from the inner regions of the black hole accretion disk. I will summarize recent developments in using this line to probe the accretion disk structure, as well as the mass and spin of black holes n Seyfert galaxies. In particular, I will present observational evidence suggesting that the inner regions of the accretion disks in low-luminosity AGN (LLAGN) are distinctly different from those in higher-luminosity AGN. This tentative result lends support models of LLAGN based upon advective accretion disks.

A study of accretion discs around rapidly rotating neutron stars in general relativity and its applications to four low mass X-ray binaries

NASA Astrophysics Data System (ADS)

Bhattacharyya, Sudip

2002-02-01

We calculate the accretion disc temperature profiles, disc luminosities and boundary layer luminosities for rapidly rotating neutron stars considering the full effect of general relativity. We compare the theoretical values of these quantities with their values inferred from EXOSAT data for four low mass X-ray binary sources: XB 1820-30, GX 17+2, GX 9+1 and GX 349+2 and constrain the values of several properties of these sources. According to our calculations, the neutron stars in GX 9+1 and GX 349+2 are rapidly rotating and stiffer equations of state are unfavoured.

AGN Obscuration from Winds: From Dusty Infrared-Driven to Warm and X-Ray Photoionized

NASA Technical Reports Server (NTRS)

Dorodnitsyn, A.; Kallman, T.

2012-01-01

We present calculations of AGN winds at approximate parsec scales, along with the associated obscuration. We take into account the pressure of infrared radiation on dust grains and the interaction of X-rays from a central black hole with hot and cold plasma. Infrared radiation (IR) is incorporated in radiation-hydrodynamic simulations adopting the flux-limited diffusion approximation. We find that in the range of X-ray luminosities L=0.05 - 0.6L(sub Edd) the Compton-thick part of the flow (aka torus) has an opening angle of approximately 72? -75? regardless of the luminosity. At L 0.1 the outflowing dusty wind provides the obscuration with IR pressure playing a major role. The global flow consists of two phases: the cold flow at inclinations (theta) greater than or approximately 70? and a hot, ionized wind of lower density at lower inclinations. The dynamical pressure of the hot wind is important in shaping the denser IR supported flow. At luminosities less than or equal to 0.1L(sub Edd) episodes of outflow are followed by extended periods when the wind switches to slow accretion.