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1

Quiescent X-ray emission from an evolved brown dwarf ?  

E-print Network

I report on the X-ray detection of Gl569Bab. During a 25ksec Chandra observation the binary brown dwarf is for the first time spatially separated in X-rays from the flare star primary Gl569A. Companionship to Gl569A constrains the age of the brown dwarf pair to ~300-800 Myr. The observation presented here is only the second X-ray detection of an evolved brown dwarf. About half of the observing time is dominated by a large flare on Gl569Bab, the remainder is characterized by weak and non-variable emission just above the detection limit. This emission -- if not related to the afterglow of the flare -- represents the first detection of a quiescent corona on a brown dwarf, representing an important piece in the puzzle of dynamos in the sub-stellar regime.

B. Stelzer

2004-09-27

2

A Thermal Bremsstrahlung Model For the Quiescent X-ray Emission from Sagittarius A*  

E-print Network

I consider the thermal bremsstrahlung emission from hot accretion flows (Bondi/ADAFs), taking into account the finite size of the observing telescope's beam (R_beam) relative to the Bondi accretion radius (R_A). For R_beam >> R_A soft X-ray emission from the hot interstellar medium surrounding the black hole dominates the observed emission while for R_beam << R_A hard X-ray emission from the accretion flow dominates. I apply these models to Chandra observations of the Galactic Center, for which R_beam ~ R_A. I argue that bremsstrahlung emission accounts for most of the ``quiescent'' (non-flaring) flux observed by Chandra from Sgr A*; this emission is spatially extended on scales ~ R_A ~ 1'' and has a relatively soft spectrum, as is observed. If accretion onto the central black hole proceeds via a Bondi or ADAF flow, a hard X-ray power law should be present in deeper observations with a flux ~ 1/3 of the soft X-ray flux; nondetection of this hard X-ray component would argue against ADAF/Bondi models. I briefly discuss the application of these results to other low-luminosity AGN.

Eliot Quataert

2002-05-28

3

The Soft Gamma Repeaters as Very Strongly Magnetized Neutron Stars. II. Quiescent Neutrino, X-Ray, and Alfven Wave Emission  

Microsoft Academic Search

We calculate the quiescent X-ray, neutrino, and Alfvén wave emission from a neutron star with a very strong magnetic field, Bdipole ˜ 1014-1015 G and Binterior (5-10) x 1015 G. These results are compared with observations of quiescent emission from the soft gamma repeaters and from a small class of anomalous X-ray pulsars that we have previously identified with such

Christopher Thompson; Robert C. Duncan

1996-01-01

4

X-ray and UV correlation in the quiescent emission of Cen X-4, evidence of accretion and reprocessing  

NASA Astrophysics Data System (ADS)

We conducted the first long-term (60 days), multiwavelength (optical, ultraviolet, and X-ray) simultaneous monitoring of Cen X-4 with daily Swift observations, with the goal of understanding variability in the low mass X-ray binary Cen X-4 during quiescence. We found Cen X-4 to be highly variable in all energy bands on timescales from days to months, with the strongest quiescent variability a factor of 22 drop in the X-ray count rate in only 4 days. The X-ray, UV and optical (V band) emission are correlated on timescales down to less than 110 s. The shape of the correlation is a power law with index ? about 0.2-0.6. The X-ray spectrum is well fitted by a hydrogen NS atmosphere (kT = 59 - 80 eV) and a power law (with spectral index ? = 1.4 - 2.0), with the spectral shape remaining constant as the flux varies. Both components vary in tandem, with each responsible for about 50% of the total X-ray flux, implying that they are physically linked. We conclude that the X-rays are likely generated by matter accreting down to the NS surface. Moreover, based on the short timescale of the correlation, we also unambiguously demonstrate that the UV emission can not be due to either thermal emission from the stream impact point, or a standard optically thick, geometrically thin disc. The spectral energy distribution shows a small UV emitting region, too hot to arise from the accretion disk, that we identified as a hot spot on the companion star. Therefore, the UV emission is most likely produced by reprocessing from the companion star, indeed the vertical size of the disc is small and can only reprocess a marginal fraction of the X-ray emission. We also found the accretion disc in quiescence to likely be UV faint, with a minimal contribution to the whole UV flux.

Bernardini, F.; Cackett, E. M.; Brown, E. F.; D'Angelo, C.; Degenaar, N.; Miller, J. M.; Reynolds, M.; Wijnands, R.

2014-01-01

5

Emission processes in quiescent neutron star transients  

E-print Network

We review the observational properties of transient systems made by a neutron star primary and a late dwarf companion (known also as Soft X-ray Transients) during their quiescent state. We focus on the several emission mechanisms proposed and try to compare them with observations. Finally, we review new tools to improve our comprehension of the physics of the emission processes.

Sergio Campana

2003-11-10

6

Photoionized X-ray Emission  

NASA Astrophysics Data System (ADS)

Spectra in the 0.1 -- 10 keV energy range reveal that absorption by partially ionized gas is common in active galaxies and X-ray binaries. Modeling is key for understanding the implications of such spectra for the configuration of gas in these systems, and current models have been successfully applied to spectra from many objects. Photoionized X-ray emission spectra have been studied less thoroughly. These spectra are of interest partly because they must inevitably affect the absorption spectra and also as tests of the geometrical distribution of gas near compact objects. The modeling code xstar can be applied to both types of spectra, although an efficient treatment of emission associated with bound-bound radiative excitation was not included until recently.In this poster I will describe these recent changes and illustrate application of xstar to sample X-ray spectra.

Kallman, Timothy R.

2013-04-01

7

X-ray Emission from Massive Stars  

E-print Network

X-ray Emission from Massive Stars David Cohen Department of Physics and Astronomy Swarthmore be related to the production of X-rays on massive stars. If so, massive stars' X-rays are much different than those found our own Sun and other cooler stars like the Sun that produce X-rays via magnetic activity

Cohen, David

8

The quiescent state of the accreting X-ray pulsar SAX J2103.5+4545  

NASA Astrophysics Data System (ADS)

We present an X-ray timing and spectral analysis of the Be/X-ray binary SAX J2103.5+4545 at a time when the Be star's circumstellar disc had disappeared and thus the main reservoir of material available for accretion had extinguished. In this very low optical state, pulsed X-ray emission was detected at a level of LX ˜ 1033 erg s-1. This is the lowest luminosity at which pulsations have ever been detected in an accreting pulsar. The derived spin period is 351.13 s, consistent with previous observations. The source continues its overall long-term spin-up, which reduced the spin period by 7.5 s since its discovery in 1997. The X-ray emission is consistent with a purely thermal spectrum, represented by a blackbody with kT = 1 keV. We discuss possible scenarios to explain the observed quiescent luminosity and conclude that the most likely mechanism is direct emission resulting from the cooling of the polar caps, heated either during the most recent outburst or via intermittent accretion in quiescence.

Reig, P.; Doroshenko, V.; Zezas, A.

2014-12-01

9

On stellar X-ray emission  

NASA Technical Reports Server (NTRS)

Stellar X-ray astronomy represents an entirely new astronomical discipline which has emerged during the past five years. It lies at the crossroads of solar physics, stellar physics, and general astrophysics. The present review is concerned with the main physical problems which arise in connection with a study of the stellar X-ray data. A central issue is the extent to which the extrapolation from solar physics is justified and the definition (if possible) of the limits to such extrapolation. The observational properties of X-ray emission from stars are considered along with the solar analogy and the modeling of X-ray emission from late-type stars, the modeling of X-ray emission from early-type stars, the physics of stellar X-ray emission, stellar X-ray emission in the more general astrophysical context, and future prospects.

Rosner, R.; Golub, L.; Vaiana, G. S.

1985-01-01

10

Elemental abundances and temperatures of quiescent solar active region cores from X-ray observations  

NASA Astrophysics Data System (ADS)

A brief review of studies of elemental abundances and emission measures in quiescent solar active region cores is presented. Hinode EUV Imaging Spectrometer (EIS) observations of strong iron spectral lines have shown sharply peaked distributions around 3 MK. EIS observations of lines emitted by a range of elements have allowed good estimates of abundances relative to iron. However, X-ray observations are required to measure the plasma emission above 3 MK and the abundances of oxygen and neon. We revisit, using up-to-date atomic data, older X-ray observations obtained by a sounding rocket and by the Solar Maximum Mission (SMM) Flat Crystal Spectrometer (FCS). We find that the Fe/O and Fe/Ne ratios are normally increased by a factor of 3.2, compared to the photospheric values. Similar results are obtained from FCS observations of six quiescent active region cores. The FCS observations also indicate that the emission measure above 3 MK has a very steep negative slope, with very little plasma observed at 5 MK or above. Appendix A is available in electronic form at http://www.aanda.org

Del Zanna, G.; Mason, H. E.

2014-05-01

11

THE QUIESCENT X-RAY PROPERTIES OF THE ACCRETING MILLISECOND X-RAY PULSAR AND ECLIPSING BINARY SWIFT J1749.4-2807  

SciTech Connect

Swift J1749.4-2807 is a transient neutron star low-mass X-ray binary that contains an accreting millisecond X-ray pulsar spinning at 518 Hz. It is the first of its kind that displays X-ray eclipses, which holds significant promise to precisely constrain the mass of the neutron star. We report on a {approx_equal} 105 ks long XMM-Newton observation performed when Swift J1749.4-2807 was in quiescence. We detect the source at a 0.5-10 keV luminosity of {approx_equal}1 Multiplication-Sign 10{sup 33}(D/6.7 kpc){sup 2} erg s{sup -1}. The X-ray light curve displays three eclipses that are consistent in orbital phase and duration with the ephemeris derived during outburst. Unlike most quiescent neutron stars, the X-ray spectrum can be adequately described with a simple power law, while a pure-hydrogen atmosphere model does not fit the data. We place an upper limit on the 0.01-100 keV thermal luminosity of the cooling neutron star of {approx}< 2 Multiplication-Sign 10{sup 33} erg s{sup -1} and constrain its temperature to be {approx}< 0.1 keV (for an observer at infinity). Timing analysis does not reveal evidence for X-ray pulsations near the known spin frequency of the neutron star or its first overtone with a fractional rms of {approx}< 34% and {approx}< 28%, respectively. We discuss the implications of our findings for dynamical mass measurements, the thermal state of the neutron star, and the origin of the quiescent X-ray emission.

Degenaar, N. [Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, MI 48109 (United States); Patruno, A.; Wijnands, R., E-mail: degenaar@umich.edu [Astronomical Institute 'Anton Pannekoek', University of Amsterdam, Postbus 94249, 1090 GE Amsterdam (Netherlands)

2012-09-10

12

Accretion and nuclear activity of quiescent supermassive black holes. I: X-ray study  

E-print Network

We have studied the nuclear activity in a sample of six quiescent early-type galaxies, with new Chandra data and archival HST optical images. Their nuclear sources have X-ray luminosities ~ 10^{38} - 10^{39} erg/s (L_X/L_Edd ~ 10^{-8} - 10^{-7}), and colors or spectra consistent with accreting supermassive black holes (SMBHs)--except for the nucleus of NGC 4486B, which is softer than typical AGN spectra. In a few cases, the X-ray morphology of the nuclear sources shows hints of marginally extended structures, in addition to the surrounding diffuse thermal emission from hot gas, which is detectable on scales >~ 1 kpc. In one case (NGC 5845), a dusty disk may partially obstruct our direct view of the SMBH. We have estimated the temperature and density of the hot interstellar medium, which is one major source of fuel for the accreting SMBH; typical central densities are n_e ~ (0.02 +/- 0.01) cm^{-3}. Assuming that the hot gas is captured by the SMBH at the Bondi rate, we show that the observed X-ray luminosities are too faint to be consistent with standard disk accretion, but brighter than predicted by radiatively-inefficient solutions (eg, ADAF). In total, there are ~ 20 galaxies for which SMBH mass, hot gas density, and nuclear X-ray luminosity are simultaneously known. In some cases, the nuclear sources are brighter than predicted by the ADAF model; in other cases, they are consistent or fainter. We discuss the apparent lack of correlations between Bondi rate and X-ray luminosity, and suggest that, in order to understand the observed distribution, we need to know two additional parameters: the amount of gas supplied by the stellar population inside the accretion radius, and the fraction (possibly << 1) of the total gas available that is accreted by the SMBH. We shall discuss these issues in our Paper II.

Roberto Soria; Giuseppina Fabbiano; Alister W. Graham; Alessandro Baldi; Martin Elvis; Helmut Jerjen; Silvia Pellegrini; Aneta Siemiginowska

2005-11-10

13

The Low Quiescent X-Ray Luminosity of the Transient X-Ray Burster EXO 1747-214  

NASA Astrophysics Data System (ADS)

We report on X-ray and optical observations of the X-ray burster EXO 1747-214. This source is an X-ray transient, and its only known outburst was observed in 1984-1985 by the EXOSAT satellite. We reanalyzed the EXOSAT data to derive the source position, column density, and a distance upper limit using its peak X-ray burst flux. We observed the EXO 1747-214 field in 2003 July with the Chandra X-Ray Observatory to search for the quiescent counterpart. We found one possible candidate just outside the EXOSAT error circle, but we cannot rule out the possibility that the source is unrelated to EXO 1747-214. Our conclusion is that the upper limit on the unabsorbed 0.3-8 keV luminosity is L<7×1031 ergs s-1, making EXO 1747-214 one of the faintest neutron star transients in quiescence. We compare this luminosity upper limit to the quiescent luminosities of 19 neutron star and 14 black hole systems and discuss the results in the context of the differences between neutron stars and black holes. Based on the theory of deep crustal heating suggested by Brown and coworkers, the luminosity implies an outburst recurrence time of >1300 yr unless some form of enhanced cooling occurs within the neutron star. The position of the possible X-ray counterpart is consistent with three blended optical/IR sources with R magnitudes between 19.4 and 19.8 and J magnitudes between 17.2 and 17.6. One of these sources could be the quiescent optical/IR counterpart of EXO 1747-214.

Tomsick, John A.; Gelino, Dawn M.; Kaaret, Philip

2005-12-01

14

X-Ray and Particle Emission Techniques  

Microsoft Academic Search

\\u000a The short wavelengths and high energy of X-rays make them a highly versatile form of electromagnetic radiation. Several analytical\\u000a techniques utilize the interaction of X-rays with a substance, or their emission from excited atoms, to gain information about\\u000a sample composition. This chapter describes the production of X-rays and analytical techniques that in some way employ the\\u000a use or analysis of

Mary E. Malainey

15

X-ray Emission from Massive Stars  

E-print Network

the Sun - magnetic activity, x-ray spectra b. Hot stars c. Radiation-driven winds and the Doppler shift d #12;Spectra: continuum vs. line Visible solar spectrum: continuum, from surface X-ray/EUV solar spectrum: emission lines from hot, thin gas above the surface #12;This hot plasma is related to magnetic

Cohen, David

16

X-ray Flare Associated with a Quiescent Filament Eruption and Coronal Mass Ejection  

NASA Astrophysics Data System (ADS)

To date, solar active regions are where most flares are found to occur. We present an analysis of multi-waveband observations of the large eruption of a 'quiescent' (outside of an active region) solar filament contemporaneous with X-ray emission. The eruption covers a 2-day time span, from 2013 September 29 to 2013 September 30. The event was observed using the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI), the Solar Dynamics Observatory (SDO), and the Fermi Gamma-ray Space Telescope. Though not classified as a flare, the GOES class of the event was C1 and the X-ray light curves include a small impulsive-phase peak followed by a gradual-phase rise. The eruption produced a coronal mass ejection (CME) with a velocity of 1179 km/s. SDO Atmospheric Imaging Assembly (AIA) movies during the time span show that the filament lies outside any active region on the sun, and spans a length on the order of 600 arcseconds. Spatially resolved RHESSI emission during the gradual phase is found to come from an area along the post-eruption arcade, close to the westward expanding ribbon but confined to a length of only 150 arcseconds. No RHESSI emission is found along the eastward expanding ribbon. We infer the strength and geometry of the magnetic field during the eruption with the SDO Helioseismic and Magnetic Imager (HMI) and find a small (~ 100 arcseconds long) dipolar element within the filament channel that appears to be spatially correlated with the RHESSI emission. The dipolar element is observed to have magnetic field strengths as high as 1000 Gauss. The evolution of both the X-ray emission and AIA data support the notion that the flare was a consequence of magnetic reconnection between the dipole's magnetic field and the magnetic field supporting the filament. We conclude that solar eruptive events, which consist of both a flare and a CME, can occur outside active regions in association with a quiescent filament eruption if new, sufficiently strong magnetic flux emerges in the immediate area and reconnects with the filament's magnetic field.

Foord, Adi; Holman, Gordon D.

2015-01-01

17

Quest for quiescent neutron star low mass x-ray binaries in the Small Magellanic Cloud  

NASA Astrophysics Data System (ADS)

We present the first spectral search for neutron stars (NSs) in low-mass X-ray binaries (LMXBs) between outbursts in the Small Magellanic Cloud (SMC). We identify and discuss candidate LMXBs in quiescence in the SMC using deep Chandra X-ray observations of two portions of the SMC. We produce X-ray color-magnitude-diagrams of XRSs of these two fields and identify 10 candidates for quiescent NS LMXBs. Spectral fitting and searches for optical counterparts rule out five, leaving five candidate quiescent NS LMXBs. We estimate that we are sensitive to ˜ 10% of quiescent NS LMXBs in our fields. Our fields include 4.4 × 10^7 M? of stellar mass, giving an upper limit of 10^-6 LMXBs per M? in the SMC. We place a lower limit on the average duty cycle of NS LMXBs as ˜ 0.003.

Chowdhury, Mizanul Huq

18

Quiescent accretion disks in black hole X-ray novae  

NASA Technical Reports Server (NTRS)

We present detailed time-resolved spectroscopy of the Balmer emission lines from two black hole binary systems in quiescence, A0620-00 and Nova Muscae 1991. We find extraordinary similarities between the two systems. There are 30-40 km/s velocity variations of the emission lines over the orbital period, the phases of which are not aligned with the expected phase of the motion of the compact primary. Detailed modeling of both systems is complicated by variable hot spot components, regions of optical thickness, and intermittent excess emission in the blue line wings of the H-alpha lines. Both sources also display low velocities at the outer edge of the accretion disk, implying a large primary Roche lobe and extreme mass ratios. These complications suggest that although simple optically thin, Keplerian alpha-disk models provide a useful parameterization of emission lines from these systems, the straightforward physical models they imply should be treated with great caution.

Orosz, Jerome A.; Bailyn, Charles D.; Remillard, Ronald A.; Mcclintock, Jeffrey E.; Foltz, Craig B.

1994-01-01

19

X-ray emission from AGB stars  

NASA Astrophysics Data System (ADS)

Although the Asymptotic Giant Branch (AGB) stars are well studied in some aspects, there are several properties that remain unexplored. For instance, the role of magnetic fields for the large-scale structure and dynamics of the circumstellar envelope (CSE) has not been established. Recent results from maser polarimetry observations indicate strong magnetic fields throughout the inner CSE. These need to be confirmed by the detection of X-ray emission from coronal activity. We propose to observe three low- mass-loss rate, close (<300 pc), AGB stars, in order to detect and establish the origin of X-ray emission. The observations would be a follow-up to our recent archival search that resulted in new X-ray detections of two AGB stars.

Ramstedt, Sofia

2011-10-01

20

Soft X-ray Polarization in Thermal Magnetar Emission  

E-print Network

Emission spectra from magnetars in the soft X-ray band likely contain a thermal component emerging directly from the neutron star surface. However, the lack of observed absorption-like features in quiescent spectra makes it difficult to directly constrain physical properties of the atmosphere. We argue that future X-ray polarization measurements represent a promising technique for directly constraining the magnetar magnetic field strength and geometry. We construct models of the observed polarization signal from a finite surface hotspot, using the latest NS atmosphere models for magnetic fields B = 4 x 10^13--5 x 10^14 G. Our calculations are strongly dependent on the NS magnetic field strength and geometry, and are more weakly dependent on the NS equation of state and atmosphere composition. We discuss how the complementary dependencies of phase-resolved spectroscopy and polarimetry might resolve degeneracies that currently hamper the determination of magnetar physical parameters using thermal models.

van Adelsberg, Matthew

2009-01-01

21

X-ray emission from red quasars  

NASA Technical Reports Server (NTRS)

A dozen red quasars were observed with the Einstein Observatory in order to determine their X-ray properties. The observations show that for all these sources, the infrared-optical continuum is so steep that when extrapolated to higher frequencies, it passes orders of magnitude below the measured X-ray flux. The X-ray emission is better correlated with the radio than with the infrared flux, suggesting a connection between the two. By applying the synchrotron-self-Compton model to the data, it is found that the infrared-optical region has a size of 0.01 pc or more and a magnetic field more than 0.1 G, values considerably different than are found in the radio region. Unlike other quasars, the ionizing continuum is dominated by the X-ray emission. The peculiar line ratios seen in these objects can be understood with a photoionization model, provided that the photon to gas density ratio (ionization parameter) is an order of magnitude less than in typical quasars.

Bregman, J. N.; Glassgold, A. E.; Huggins, P. J.; Kinney, A. L.

1985-01-01

22

On the bolometric quiescent luminosity and luminosity swing of black hole candidate and neutron star low mass X-ray transients  

E-print Network

Low mass X-ray transients (LMXRTs) hosting black hole candidates (BHCs) display on average a factor of ~100 larger swing in the minimum (quiescent) to maximum (outburst) X-ray luminosity than neutron stars (NSs), despite the fact that the swing in the mass inflow rate is likely in the same range. Advection dominated accretion flows (ADAFs) were proposed to interpret such a difference. The residual optical/UV emission of quiescent LMXRTs, after subtraction of the companion star spectrum, is produced by synchrotron radiation in the (latest version) of ADAF and therefore is part of the ADAF's luminosity budget. We demonstrate that, once the residual optical/UV emission is taken into account, the bolometric luminosity swing of BHCs is consistent with that of NSs. We explore here an alternative scenario to ADAFs in which very little mass accretion onto the collapsed star takes place in the quiescence intervals. The residual optical/UV emission of BHCs are expected to derive from the energy released by the matter transferred from the companion star at radii comparable to the circularisation radius. The quiescent X-ray luminosity originates either from accretion onto the BH at very low rates and/or from coronal activity in the companion star or in the outer disk. For comparably small mass inflow rates, the NSs in these systems are likely in the radio pulsar regime. In the interaction of the radio pulsar relativistic wind with matter transferred from the companion star, a shock forms, the power law-like emission of which powers both the harder X-ray emission and most of the residual optical/UV. The soft, thermal-like X-ray component may arise from the cooling of the NS surface. This scenario matches well both the X-ray and bolometric luminosity swing of LMXRTs. (ABRIDGED).

Sergio Campana; Luigi Stella

2000-05-07

23

Studies on x-ray and UV emissions in electron cyclotron resonance x-ray sourcea)  

NASA Astrophysics Data System (ADS)

A novel electron cyclotron resonance x-ray source is constructed based on the ECR technique. In this paper, the possibility of using the ECR x-ray source for producing UV rays by optimizing the plasma parameters is explored. X-ray and UV emissions from the ECR x-ray source are carried out for argon, nitrogen, and CO2 plasma. The x-ray spectral and dose measurements are carried with NaI(Tl) based spectrometer and dosimeter, respectively. For UV measurement, a quartz window arrangement is made at the exit port and the UV intensity is measured at 5cm from the quartz plate using UV meter. The x-ray and UV emissions are carried out for different microwave power levels and gas pressures. The x-ray emission is observed in the pressure range ?10-5Torr, whereas the UV emission is found to be negligible for the gas pressures <10-5Torr and it starts increasing in the pressure range between 10-5 and 10-3Torr. At high-pressure range, collision frequency of electron-atom is large which leads to the higher UV flux. At low pressure, the electron-atom collision frequency is low and hence the electrons reach high energy and by hitting the cavity wall produces higher x-ray flux. By choosing proper experimental conditions and plasma gas species, the same source can be used as either an x-ray source or an UV source.

Baskaran, R.; Selvakumaran, T. S.

2008-02-01

24

X-Ray Emission from "Uranium" Stars  

NASA Technical Reports Server (NTRS)

The project aims to secure XMM observations of two targets with extremely low abundances of the majority of heavy elements (e.g., log[Fe/H] $\\sim$-4), but that show absorption lines of uranium. The presence of an r-process element such as uranium requires a binary star system in which the companion underwent a supernova explosion. A binary star system raises the distinct possibility of the existence of a compact object, most likely a neutron star, in the binary, assuming it survived the supernova blast. The presence of a compact object then suggests X-ray emission if sufficient matter accretes to the compact object. The observations were completed less than one year ago following a series of reobservations to correct for significant flaring that occurred during the original observations. The ROSAT all-sky survey was used to report on the initial assessment of X-ray emission from these objects; only upper limits were reported. These upper limits were used to justify the XMM observing time, but with the expectation that upper limits would merely be pushed lower. The data analysis hinges critically on the quality and degree of precision with which the background is handled. During the past year, I have spent some time learning the ins and outs of XMM data analysis. In the coming year, I can apply that learning to the analysis of the 'uranium' stars.

Schlegel, Eric; Mushotzky, Richard (Technical Monitor)

2005-01-01

25

Constraints on relativistic jets in quiescent black hole X-ray binaries from broad-band spectral modelling  

NASA Astrophysics Data System (ADS)

The nature of black hole jets at the lowest detectable luminosities remains an open question, largely due to a dearth of observational constraints. Here, we present a new, nearly simultaneous broad-band spectrum of the black hole X-ray binary (BHXB) XTE J1118+480 at an extremely low Eddington ratio (LX ˜ 10-8.5LEdd). Our new spectral energy distribution (SED) includes the radio, near-infrared, optical, ultraviolet, and X-ray wavebands. XTE J1118+480 is now the second BHXB at such a low Eddington ratio with a well-sampled SED, thereby providing new constraints on highly sub-Eddington accretion flows and jets, and opening the door to begin comparison studies between systems. We apply a multizone jet model to the new broad-band SED, and we compare our results to previous fits to the same source using the same model at 4-5 decades higher luminosity. We find that after a BHXB transitions to the so-called quiescent spectral state, the jet base becomes more compact (by up to an order of magnitude) and slightly cooler (by at least a factor of 2). Our preferred model fit indicates that jet particle acceleration is much weaker after the transition into quiescence. That is, accelerated non-thermal particles no longer reach high enough Lorentz factors to contribute significant amounts of synchrotron X-ray emission. Instead, the X-ray waveband is dominated by synchrotron self-Compton emission from a population of mildly relativistic electrons with a quasi-thermal velocity distribution that are associated with the jet base. The corresponding (thermal) synchrotron component from the jet base emits primarily in the infrared through ultraviolet wavebands. Our results on XTE J1118+480 are consistent with broad-band modelling for A0620-00 (the only other comparably low Eddington ratio BHXB with a well-sampled SED) and for Sgr A* (the quiescent supermassive black hole at the Galactic centre). The above could therefore represent a canonical baseline geometry for accreting black holes in quiescence. We conclude with suggestions for future studies to further investigate the above scenario.

Plotkin, Richard M.; Gallo, Elena; Markoff, Sera; Homan, Jeroen; Jonker, Peter G.; Miller-Jones, James C. A.; Russell, David M.; Drappeau, Samia

2015-02-01

26

X-RAY EMISSION FROM PLANETS AND COMETS: RELATIONSHIP WITH SOLAR X-RAYS AND SOLAR WIND  

E-print Network

X-RAY EMISSION FROM PLANETS AND COMETS: RELATIONSHIP WITH SOLAR X-RAYS AND SOLAR WIND ANIL BHARDWAJ Flight center, Greenbelt, MD 20771, USA Scattering of solar X-ray radiation mainly produces the non-auroral X- ray emissions from Jupiter, Saturn, and Earth, those from the disk of Mars, Venus, and Moon

Ã?stgaard, Nikolai

27

X-ray emission properties of galaxies in Abell 3128  

E-print Network

We use archival Chandra X-ray Observatory data to investigate X-ray emission from early-type galaxies in the rich z=0.06 cluster Abell 3128. By combining the X-ray count-rates from an input list of optically-selected galaxies, we obtain a statistical detection of X-ray flux, unbiased by X-ray selection limits. Using 87 galaxies with reliable Chandra data, X-ray emission is detected for galaxies down to M_B ~ -19.0, with only an upper limit determined for galaxies at M_B ~ -18.3. The ratio of X-ray to optical luminosities is consistent with recent determinations of the low-mass X-ray binary content of nearby elliptical galaxies. Taken individually, in contrast, we detect significant (3sigma) flux for only six galaxies. Of these, one is a foreground galaxy, while two are optically-faint galaxies with X-ray hardness ratios characteristic of active galactic nuclei. The remaining three detected galaxies are amongst the optically-brightest cluster members, and have softer X-ray spectra. Their X-ray flux is higher than that expected from X-ray binaries, by a factor 2-10; the excess suggests these galaxies have retained their hot gaseous haloes. The source with the highest L_X / L_B ratio is of unusual optical morphology with prominent sharp-edged shells. Notwithstanding these few exceptions, the cluster population overall exhibits X-ray properties consistent with their emission being dominated by X-ray binaries. We conclude that in rich cluster environments, interaction with the ambient intra-cluster medium acts to strip most galaxies of their hot halo gas.

Russell J. Smith

2003-07-15

28

Reabsorption of Soft X-Ray Emission at High X-Ray Free-Electron Laser Fluences  

NASA Astrophysics Data System (ADS)

We report on oxygen K-edge soft x-ray emission spectroscopy from a liquid water jet at the Linac Coherent Light Source. We observe significant changes in the spectral content when tuning over a wide range of incident x-ray fluences. In addition the total emission yield decreases at high fluences. These modifications result from reabsorption of x-ray emission by valence-excited molecules generated by the Auger cascade. Our observations have major implications for future x-ray emission studies at intense x-ray sources. We highlight the importance of the x-ray pulse length with respect to the core-hole lifetime.

Schreck, Simon; Beye, Martin; Sellberg, Jonas A.; McQueen, Trevor; Laksmono, Hartawan; Kennedy, Brian; Eckert, Sebastian; Schlesinger, Daniel; Nordlund, Dennis; Ogasawara, Hirohito; Sierra, Raymond G.; Segtnan, Vegard H.; Kubicek, Katharina; Schlotter, William F.; Dakovski, Georgi L.; Moeller, Stefan P.; Bergmann, Uwe; Techert, Simone; Pettersson, Lars G. M.; Wernet, Philippe; Bogan, Michael J.; Harada, Yoshihisa; Nilsson, Anders; Föhlisch, Alexander

2014-10-01

29

Computerized tomography with X-ray, emission, and ultrasound sources  

Microsoft Academic Search

This paper reviews the major developments that have taken place during the last three years in imaging with computed tomography (CT) using X-ray, emission, and ultrasound sources. Space limitations have resulted in some selection of topics by the author. There are four major sections dealing with algorithms, X-ray CT, emission CT, and ultrosound CT. Since most of the currently used

A. C. Kak

1979-01-01

30

X-RAY POINT-SOURCE POPULATIONS CONSTITUTING THE GALACTIC RIDGE X-RAY EMISSION  

SciTech Connect

Apparently diffuse X-ray emission has been known to exist along the central quarter of the Galactic Plane since the beginning of X-ray astronomy; this is referred to as the Galactic Ridge X-ray emission (GRXE). Recent deep X-ray observations have shown that numerous X-ray point sources account for a large fraction of the GRXE in the hard band (2-8 keV). However, the nature of these sources is poorly understood. Using the deepest X-ray observations made in the Chandra bulge field, we present the result of a coherent photometric and spectroscopic analysis of individual X-ray point sources for the purpose of constraining their nature and deriving their fractional contributions to the hard-band continuum and Fe K line emission of the GRXE. Based on the X-ray color-color diagram, we divided the point sources into three groups: A (hard), B (soft and broad spectrum), and C (soft and peaked spectrum). The group A sources are further decomposed spectrally into thermal and non-thermal sources with different fractions in different flux ranges. From their X-ray properties, we speculate that the group A non-thermal sources are mostly active galactic nuclei and the thermal sources are mostly white dwarf (WD) binaries such as magnetic and non-magnetic cataclysmic variables (CVs), pre-CVs, and symbiotic stars, whereas the group B and C sources are X-ray active stars in flares and quiescence, respectively. In the log N-log S curve of the 2-8 keV band, the group A non-thermal sources are dominant above Almost-Equal-To 10{sup -14} erg cm{sup -2} s{sup -1}, which is gradually taken over by Galactic sources in the fainter flux ranges. The Fe K{alpha} emission is mostly from the group A thermal (WD binaries) and the group B (X-ray active stars) sources.

Morihana, Kumiko [Institute of Physical and Chemical Research (RIKEN), 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan)] [Institute of Physical and Chemical Research (RIKEN), 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Tsujimoto, Masahiro; Ebisawa, Ken [Japan Aerospace Exploration Agency, Institute of Space and Astronautical Science, 3-1-1 Yoshino-dai, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan)] [Japan Aerospace Exploration Agency, Institute of Space and Astronautical Science, 3-1-1 Yoshino-dai, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan); Yoshida, Tessei, E-mail: morihana@crab.riken.jp [National Astronomical Observatory of Japan, 2-21-1, Osawa, Mitaka, Tokyo 181-8588 (Japan)] [National Astronomical Observatory of Japan, 2-21-1, Osawa, Mitaka, Tokyo 181-8588 (Japan)

2013-03-20

31

Relative probabilities of the uranium isotopes for thorium x-ray emission and fluorescence of uranium x-rays  

Microsoft Academic Search

Both thorium x-rays from decaying uranium isotopes and self-fluoresced uranium x-rays are prominent in high-resolution gamma-ray spectra of uranium-bearing materials. Useful application of the information carried by those x-rays has been curtailed because the probabilities of the uranium isotopes for thorium x-ray emission and for uranium x-ray fluorescence have not been known. By analyzing enrichment-meter geometry spectra from uranium oxide

1991-01-01

32

Relative probabilities of the uranium isotopes for thorium x-ray emission and fluorescence of uranium x-rays  

Microsoft Academic Search

This paper reports that both thorium x-rays from decaying uranium isotopes and self-fluoresced uranium x-rays are prominent in high-resolution gamma-ray spectra of uranium-bearing materials. Useful application of the information carried by those x-rays has been curtailed because the probabilities of the uranium isotopes for thorium x-ray emission and for uranium x-ray fluorescence have not been known. By analyzing enrichment-meter geometry

1991-01-01

33

Current Problems in X-Ray Emission Spectroscopy  

NASA Technical Reports Server (NTRS)

Various problems that limit X-ray analysis in the analytical electron microscope are reviewed. Major emphasis is given to the trade-off between minimum mass fraction and spatial resolution. New developments such as high-brightness electron guns, new X-ray spectrometers and clean high-vacuum analysis conditions will lead to major improvements in the accuracy and detectability limits of X-ray emission spectroscopy.

Goldstein, Joseph I.; Williams, David B.; Lyman, Charles E.

1989-01-01

34

Radio--X-ray Correlation and the "Quiescent State" of Black Hole Sources  

E-print Network

Recently a correlation between the radio and X-ray luminosities is found, $L_{\\rm R}\\propto L_{\\rm X}^{0.7}$, in black hole sources including black hole candidates in our galaxy and active galactic nuclei. We first show that the correlation can be understood in the context of an accretion-jet model developed for explaining the spectral and timing properties of XTE J1118+480. More importantly, we show that when the X-ray luminosity is below a critical value, $\\la (10^{-5}$--$10^{-6}) L_{\\rm Edd}$, if the jet persists, the correlation should turn and become steeper, $L_{\\rm R}\\propto L_{\\rm X}^{1.23}$, and the X-ray radiation of the system should be dominated by the emission from the jet, rather than by the accretion flow. Possible observational evidence for our predictions is presented and future observations to further test our predictions are proposed.

Feng Yuan; Wei Cui

2005-04-28

35

Evidence for Optical Flares in Quiescent Soft X-Ray Transients  

NASA Astrophysics Data System (ADS)

We present the results of high time resolution optical photometry of five quiescent soft X-ray transients (SXTs): V404 Cyg, A0620-00, J0422+32, GS 2000+25, and Cen X-4. We detect fast optical variations superposed on the secondary star's double-humped ellipsoidal modulation. The variability resembles typical flare activity and has amplitudes ranging from 0.06 to 0.6 mag. Flares occur on timescales of minutes to a few hours, with no dependency on orbital phase, and contribute ~19%-46% to the total veiling observed in the R band. We find that the observed level of flaring activity is veiled by the light of the companion star, and therefore, systems with cool companions (e.g., J0422+32) exhibit stronger variability. After correcting for this dilution, we do not find any correlation between the flaring activity and fundamental system parameters. We find no underlying coherent periods in the data, only quasi-periodic variations ranging between 30 and 90 minutes for the short-period SXTs and longer than 1 hr for V404 Cyg. The power-law index of the power spectra is consistent with what is observed at X-rays wavelengths, i.e., a 1/f distribution, which is compatible with the cellular automaton model. Our observed R'-band luminosities, which are in the range 1031-1033 ergs s-1, are too large to be due to chromospheric activity in the rapidly rotating companions. Since the typical timescale of the flares increases with orbital period, they are most likely produced in the accretion disk. The associated dynamical (Keplerian) timescales suggest that flares are produced at ~0.3Rd-0.7Rd. Possible formation mechanisms are magnetic loop reconnection events in the disk or, less likely, optical reprocessing of X-ray flares. In the former scenario, the maximum duration of the flares suggests that the outer disk is responsible for the flare events and so allows us to constrain the sharing timescale to ?~(5-6)?-1K.

Zurita, C.; Casares, J.; Shahbaz, T.

2003-01-01

36

X-ray emission from high temperature plasmas  

NASA Technical Reports Server (NTRS)

The physical processes occurring in plasma focus devices were investigated with particular emphasis on X-ray emission. Topics discussed include: trajectories of high energy electrons; detection of ion trajectories; spatial distribution of neutron emission; space and time resolved emission of hard X-rays from a plasma focus; the staged plasma focus as a variation of the hypocloidal pinch; formation of current sheets in a staged plasma focus; and X-ray and neutron emission from a staged plasma focus. The possibility of operating dense plasma-focus type devices in multiple arrays beyond the scaling law for a single gun is discussed.

Harries, W. L.

1977-01-01

37

X-ray Emission from Massive Stars David Cohen  

E-print Network

the Sun - magnetic activity, x-ray spectra b. Hot stars c. Radiation-driven winds and the Doppler shift d spectrum: continuum, from surface X-ray/EUV solar spectrum: emission lines from hot, thin plasma above the surface #12;This hot plasma is related to magnetic fields on the Sun: confinement, spatial structure

Cohen, David

38

X-ray emission from high temperature plasmas  

NASA Technical Reports Server (NTRS)

X-rays from a 25-hJ plasma focus apparatus were observed with pinhole cameras. The cameras consist of 0.4 mm diameter pinholes in 2 cm thick lead housing enclosing an X-ray intensifying screen at the image plane. Pictures recorded through thin aluminum foils or plastic sheets for X-ray energies sub gamma smaller than 15 keV show distributed X-ray emissions from the focussed plasma and from the anode surface. However, when thick absorbers are used, radial filamentary structure in the X-ray emission from the anode surface is revealed. Occasionally larger structures are observed in addition to the filaments. Possible mechanisms for the filamentary structure are discussed.

Harries, W. L.

1974-01-01

39

Carbon nanotube based field emission X-ray sources  

NASA Astrophysics Data System (ADS)

This dissertation describes the development of field emission (FE) x-ray sources with a carbon-nanotube (CNT) cathode. Field emission x-rays have advantages over conventional x-rays by replacing the thermionic cathode with a cold cathode so that electrons are emitted at room temperature and emission is voltage controllable. CNTs are found to be excellent electron emitters with low threshold fields and high current density which makes them ideal for generate field emission x-rays. Macroscopic CNT cold cathodes are prepared and the parameters to tune their field emission properties are studied: structure and morphology of CNT cathodes, temperature as well as electronic work function of CNT. Macroscopic CNT cathodes with optimized performance are chosen to build a high-resolution x-ray imaging system. The system can readily generate x-ray radiation with continuous variation of temporal resolution up to nanoseconds and spatial resolution down to 10 micron. Its potential applications for dynamic x-ray imaging and micro-computed tomography are also demonstrated. The performance characteristics of this compact and versatile system are promising for non-destructive testing and for non-invasive small-animal imaging for biomedical research.

Cheng, Yuan

40

The evolution of the high energy tail in the quiescent spectrum of the soft X-ray transient Aql X-1  

E-print Network

A moderate level of variability has been detected in the quiescent luminosity of several neutron star soft X-ray transients. Spectral variability was first revealed by Chandra observations of Aql X-1 in the four months that followed the 2000 X-ray outburst. By adopting the canonical model for quiescent spectrum of soft X-ray transients, i.e. an absorbed neutron star atmosphere model plus a power law tail, Rutledge et al. (2002a) concluded that the observed spectral variations can be ascribed to temperature variations of the neutron star atmosphere. These results can hardly be reconciled with the neutron star cooling that is expected to take place in between outbursts (after deep crustal heating in the accretion phase). Here we reanalyse the Chandra spectra of Aql X-1, together with a long BeppoSAX observation in the same period, and propose a different interpretation of the spectral variability: that this is due to correlated variations of the power law component and the column density (>5, a part of which might be intrinsic to the source), while the temperature and flux of the neutron star atmospheric component remained unchanged. This lends support to the idea that the power law component arises from emission at the shock between a radio pulsar wind and inflowing matter from the companion star.

Sergio Campana; Luigi Stella

2003-07-10

41

X-RAY AND GAMMA-RAY EMISSIONS FROM ROTATION POWERED MILLISECOND PULSARS  

SciTech Connect

The Fermi Large Area Telescope has revealed that rotation powered millisecond pulsars (MSPs) are a major contributor to the Galactic {gamma}-ray source population. Such pulsars may also be important in modeling the quiescent state of several low-mass X-ray binaries (LMXBs), where optical observations of the companion star suggest the possible existence of rotation powered MSPs. To understand the observational properties of the different evolutionary stages of MSPs, the X-ray and {gamma}-ray emissions associated with the outer gap model are investigated. For rotation powered MSPs, the size of the outer gap and the properties of the high-energy emission are controlled by either the photon-photon pair-creation process or magnetic pair-creation process near the surface. For these pulsars, we find that the outer gap model controlled by the magnetic pair-creation process is preferable in explaining the possible correlations between the {gamma}-ray luminosity or non-thermal X-ray luminosity versus the spin-down power. For the accreting MSPs in quiescent LMXBs, the thermal X-ray emission at the neutron star (NS) surface resulting from deep crustal heating can control the conditions in the outer gap. We argue that the optical modulation observed in the quiescent state of several LMXBs originates from the irradiation of the donor star by {gamma}-rays from the outer gap. In these systems, the irradiation luminosity required for the optical modulation of the source such as SAX J1808.4-3658 can be achieved for a NS of high mass. Finally, we discuss the high-energy emission associated with an intra-binary shock in black widow systems, e.g., PSR B1957+20.

Takata, J.; Cheng, K. S. [Department of Physics, University of Hong Kong, Pokfulam Road (Hong Kong); Taam, Ronald E., E-mail: takata@hku.hk, E-mail: hrspksc@hkucc.hku.hk, E-mail: r-taam@northwestern.edu [Department of Physics and Astronomy, Northwestern University, 2131 Tech Drive, Evanston, IL 60208 (United States)

2012-01-20

42

X-Ray Emission from the Guitar Nebula  

NASA Technical Reports Server (NTRS)

We have detected weak soft X-ray emission from the pulsar wind nebula trailing the high-velocity star PSR 2224+65 (the "Guitar Nebula"). This X-ray flux gives evidence of gamma approximately 10(exp 7) eV particles in the pulsar wind and constrains the properties of the postshock flow. The X-ray emission is most easily understood if the shocked pulsar wind is partly confined in the nebula and if magnetic fields in this zone can grow to near-equipartition values.

Romani, Roger W.; Cordes, James M.; Yadigaroglu, I.-A.

1997-01-01

43

The correlation of solar flare hard X-ray bursts with Doppler blueshifted soft X-ray flare emission  

NASA Technical Reports Server (NTRS)

We have investigated the temporal correlation between hard X-ray bursts and the intensity of Doppler blueshifted soft X-ray spectral line emission. We find a strong correlation for many events that have intense blueshifted spectral signatures and some correlation in events with modest blueshifts. The onset of hard X-rays frequently coincides to within a few seconds with the onset of blueshifted emission. The peak intensity of blueshifted emission is frequently close in time to the peak of the hard X-ray emission. Decay rates of the blueshifted and hard X-ray emission are similar, with the decay of the blueshifted emission tending to lag behind the hard X-ray emission in some cases. There are, however, exceptions to these conclusions, and, therefore, the results should not be generalized to all flares. Most of the data for this work were obtained from instruments flown on the Japanese Yohkoh solar spacecraft.

Bentley, R. D.; Doschek, G. A.; Simnett, G. M.; Rilee, M. L.; Mariska, J. T.; Culhane, J. L.; Kosugi, T.; Watanabe, T.

1994-01-01

44

Radioactive implant induced X-ray emission  

NASA Astrophysics Data System (ADS)

Two approaches with X-ray excitation sources directly inside a sample have been examined: mixing a sample in solution with a radioisotope or bombardment of a solid specimen with a radioactive ion beam. The radioisotopes used weere 3H, 35S, 125I, with detection limits of, for example, 20 ?g/g for Ag excited by a 125I implant of ˜75 kBq; 100 ?g/g for Ti excited by a 3H implant of ˜7 MBq. For comparable detection limits, the source strengths required are ˜10 3 less than that needed with external sources. The elemental coverage and the capabilities for simultaneous multielement detection are similar to "conventional" XES. In the beam implant mode, the spot size and energy of the beam provide for spatially resolved in situ X-ray excitation at a desired location inside a solid.

Joyce, J. R.; Sanni, A. O.; Schweikert, E. A.

45

What are the Origins of Quiescent Coronal Soft X-Rays?  

NASA Astrophysics Data System (ADS)

We have examined the evolution and modulation of the Sun's atmosphere from the photosphere up to the outer corona through the decline and rise of solar cycles 22, and 23 respectfully. For this we have used Yohkoh soft X-ray telescope (SXT) images, Kitt peak magnetograms and EUV spectra provided by the Coronal Diagnostic Spectrometer (CDS). We find as Hara (1996, 1997) found, that there is a modulation of the coronal brightness which varies annually in the high latitude activity zones, and that this is linked to the presence and disappearance of active regions on the sun's disk. We interpret our results with regards to the emergence and diffusion of magnetic flux. We find that the appearance of high latitude activity zones may be explained simply by the decay of diffused active region flux, We also find evidence for a positive temperature gradient within the corona from the emission profiles in the different lines.

Foley, C. R.; Culhane, J. L.; Patsourakos, S.; Yurow, R.; Moroney, C.; Mackay, D.

2002-01-01

46

Thermal X-Ray Line Emission from Accreting Black Holes  

E-print Network

We present model X-ray spectra of accreting black holes with advection-dominated accretion flows, paying attention to thermal emission lines from the hot plasma. We show that the Advanced X-ray Astrophysical Facility (AXAF) might be able to observe lines from X-ray binaries such as V404 Cyg in quiescence, the Galactic Center black hole Sagittarius A*, and the nuclei of nearby galaxies such as M87. Line intensities can provide new diagnostics to study the accreting plasma in these and related systems.

Ramesh Narayan; John Raymond

1998-11-25

47

The X-ray emission of Lyman break galaxies  

Microsoft Academic Search

We present an analysis of the X-ray emission of a large sample of z ~ 3 Lyman break galaxies (LBGs), based on Chandra\\/ACIS observations of several LBG survey fields. A total of 24 LBGs are directly detected in the X-ray, approximately doubling the number of known detections. Thirteen of the LBGs have optical spectroscopic signatures of active galactic nucleus (AGN)

E. S. Laird; K. Nandra; A. Hobbs; C. C. Steidel

2006-01-01

48

Unresolved Soft X-Ray Emission from the Galactic Disk  

NASA Astrophysics Data System (ADS)

The soft X-ray sky below 1 keV is spatially smooth after subtracting the local structure. In high galactic latitude regions, emissions from faint unresolved extragalactic point sources, i.e., the Cosmic X-ray Background (CXB), are responsible for ~40 % of the soft X-ray emission in the ROSAT R45 band 0.44-1.0 keV) (McCammom et al. 2002). Since the interstellar X-ray absorption column density is high enough 10^22 cm^-2) to block the extragalactic X-ray photons below 1 keV totally in the galactic midplane, it is naturally expected that the X-ray surface brightness in the R45 band decreases by ~40 %. However, the R45 band surface brightness reduces only by ~20 % or less from high galactic latitude regions to the midplane regions. This issue has been known as the “M band problem” (McCammom & Sanders 1990; Cox 2005). M band itself is a name of the energy band which is almost the same as the ROSAT R45 band. Masui et al. (2009) discovered the existence of an unresolved emission in its energy spectrum from a region located in the midplane for the first time and this excess emission is considered to be partly filling the decrease of the extragalactic component in the midplane. Spectral analysis revealed that this excess emission is represented well by a thin thermal emission with a temperature of abount 0.8 keV. If this excess emission is an answer for the M band problem, this should be observed in other midplane regions. We searched for this excess emission using archival data of Suzaku which has the lowest and stable background and therefore is optimum for faint soft X-ray emissions. Systematic analysis for over 100 observations with the galactic latitude of |b| < 5 was conducted and finally we detected excess emissions successfully from different 11 regions in the midplane (Mitsuishi et al. in prep). Temperatures ranges from 0.6 keV to 1.3 keV with different intensities. Our results suggests that these excess emissions are distributed in the whole galactic disk region such as CXB and the Galactic ridge X-ray emission. The origin for these excess emissions is also discussed in this conference.

Mitsuishi, Ikuyuki; Sato, T.; Kimura, S.; Mitsuda, K.; Yamasaki, N. Y.; Takei, Y.; Ohashi, T.; McCammon, D.

2013-04-01

49

X-Ray Emission from M32: X-Ray Binaries or a micro-AGN?  

E-print Network

We have analysed archival {\\it ROSAT} PSPC data for M32 in order to study the x-ray emission from this nearest elliptical galaxy. We fit spectra from three long exposures with Raymond-Smith, thermal bremsstrahlung, and power-law models. All models give excellent fits. The thermal fits have kT$\\approx$4 keV, the Raymond-Smith iron abundance is $0.4^{+0.7}_{-0.3}$ Solar, the power-law fit has $\\alpha$=1.6$\\pm$0.1, and all fits have $N_H$ consistent with the Galactic column. The source is centered on M32 to an accuracy of 9$''$, and unresolved at 27$''$ FWHM ($\\sim$90 pc). M32 is x-ray variable by a factor of 3--5 on timescales of a decade down to minutes, with evidence for a possible period of $\\sim$1.3 days. There are two plausible interpretations for these results: 1) Emission due to low-mass x-ray binaries; 2) Emission due to accretion onto a massive central black hole. Both of these possibilities are supported by arguments based on previous studies of M32 and other old stellar systems; the {\\it ROSAT} PSPC data do not allow us to unambiguously choose between them. Observations with the {\\it ROSAT} HRI and with {\\it ASCA} are required to determine which of these two very different physical models is correct.

Paul B. Eskridge; Raymond E. White III; David S. Davis

1996-03-19

50

Extended X-Ray Emission around Quasars at Intermediate Redshift  

NASA Technical Reports Server (NTRS)

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.

Fiore, Fabrizio

1998-01-01

51

X-ray emission from colliding laser plasmas  

SciTech Connect

Colliding Au, CD and Ti-Cr plasmas have been generated by illuminating two opposing foils each with a {approximately} 100J, 0.5 nsec, 2{omega} Nd-glass laser beam from the Trident laser facility at Los Alamos. The plasmas are being used to study plasma interactions which span the parameter regime from interpenetrating to collisional stagnation. X-ray emission during the laser target interaction and the subsequent collision is used to diagnose the initial plasma conditions and the colliding plasma properties. X-ray instrumentation consists of a 100 ps gated x-ray pinhole imager, a time-integratcd bremsstrahlung x-ray spectrograph and a gated x-ray spectrograph used to record isoelectronic spectra from the Ti-Cr plasmas. The imager has obtained multi-frame images of the collision and therefore, a measure of the stagnation length which is a function of the ion charge state and density and a strong function of the electron temperature. Other instrumentation includes a Thomson scattering spectrometer with probe beam, neutron detectors used to monitor the CD coated foil collisions and an ion spectrometer. We will describe the current status of the experiments and current results with emphasis on the x-ray emission diagnostics. We will also briefly describe the modeling using Lasnex and ISIS, a particle-in-cell code with massless fluid electrons and inter particle (classical) collisions.

Wilke, M.; Obst, A.W.; Winske, D. [and others

1995-09-01

52

The Evolution of Coronal X-ray Emission  

E-print Network

in luminosity by 30%, but conversely its EUV and X-ray coronal emission has declined by many orders of magnitude of B-fields and rotation. It is the dissipation of magnetic energy that heats the corona and B- fields emission. #12;2 Manifestations of the Sun s magnetic field The Sun is a magnetically active star

53

Synchrotron-Radiation Induced X-Ray Emission (SRIXE)  

SciTech Connect

Elemental analysis using emission of characteristic x rays is a well-established scientific method. The success of this analytical method is highly dependent on the properties of the source used to produce the x rays. X-ray tubes have long existed as a principal excitation source, but electron and proton beams have also been employed extensively. The development of the synchrotron radiation x-ray source that has taken place during the past 40 years has had a major impact on the general field of x-ray analysis. Even tier 40 years, science of x-ray analysis with synchrotron x-ray beams is by no means mature. Improvements being made to existing synchrotron facilities and the design and construction of new facilities promise to accelerate the development of the general scientific use of synchrotron x-ray sources for at least the next ten years. The effective use of the synchrotron source technology depends heavily on the use of high-performance computers for analysis and theoretical interpretation of the experimental data. Fortunately, computer technology has advanced at least as rapidly as the x-ray technology during the past 40 years and should continue to do so during the next decade. The combination of these technologies should bring about dramatic advances in many fields where synchrotron x-ray science is applied. It is interesting also to compare the growth and rate of acceptance of this particular research endeavor to the rates for other technological endeavors. Griibler [1997] cataloged the time required for introduction, diffusion,and acceptance of technological, economic, and social change and found mean values of 40 to 50 years. The introduction of the synchrotron source depends on both technical and non-technical factors, and the time scale at which this seems to be occurring is quite compatible with what is seen for other major innovations such as the railroad or the telegraph. It will be interesting to see how long the present rate of technological change and increase in scientific use can be maintained for the synchrotron x-ray source. A short summary of the present state of the synchrotron radiation-induced x-ray emission (SRIXE) method is presented here. Basically, SRIXE experiments can include any that depend on the detection. of characteristic x-rays produced by the incident x-ray beam born the synchrotron source as they interact with a sample. Thus, experiments done to measure elemental composition, chemical state, crystal, structure, and other sample parameters can be considered in a discussion of SRIXE. It is also clear that the experimentalist may well wish to use a variety of complementary techniques for study of a given sample. For this reason, discussion of computed microtomography (CMT) and x-ray diffraction is included here. It is hoped that this present discussion will serve as a succinct introduction to the basic ideas of SRIXE for those not working in the field and possibly help to stimulate new types of work by those starting in the field as well as by experienced practitioners of the art. The topics covered include short descriptions of (1) the properties of synchrotron radiation, (2) a description of facilities used for its production, (3) collimated microprobe, (4) focused microprobes, (5) continuum and monoenergetic excitation, (6) detection limits, (7) quantitation, (8) applications of SRIXE, (9) computed microtomography (CMT), and (10)chemical speciation using x-ray absorption near-edge structure (XANES) and extended x-ray absorption fine structure (EXAFS). An effort has been made to cite a wide variety of work from different laboratories to show the vital nature of the field.

Jones, Keith W.

1999-09-01

54

X-rayEmissionfromMassiveStars: UsingEmissionLineProfilestoConstrainWind  

E-print Network

X-rayEmissionfromMassiveStars: UsingEmissionLineProfilestoConstrainWind Kinematics Introduction:thecontextofhotstarX-rays Lineprofilediagnostics Whatdotheobservationslooklike? Whattrendsemerge? Pup:windX-rays,butlessabsorptionthanexpected OriandOri:similarsituation,verylittlewind absorption

Cohen, David

55

Diffuse X-ray emission from the Dumbbell Nebula?  

NASA Technical Reports Server (NTRS)

We have analyzed ROSAT Position Sensitive Proportional Counter pointed observations of the Dumbbell Nebula and find that the previously reported 'extended' X-ray emission is an instrumental electronic ghost image at the softest energy band. At slightly higher energy bands, the image of the Dumbbell is not very different from that of the white dwarf HZ43. We conclude that the X-ray emission of the Dumbbell Nebula comes from its central star. A blackbody model is fitted to the spectrum and the best-fit temperature of not greater than 136,000 +/- 10,000 K is in excellent agreement with the Zanstra temperatures.

Chu, You-Hua; Kwitter, Karen B.; Kaler, James B.

1993-01-01

56

Modeling X-ray Emission due to Charge Exchange  

NASA Astrophysics Data System (ADS)

Since the advent of Cravens' [1] proposal that the observed X-ray emission from comet Hyakutake was due to charge exchange (CX) of highly-charged solar wind ions with cometary neutrals, the CX-mechanism has been identified as a possible dominant contributor to the X-ray emission observed in the heliosphere, planetary exospheres, the geocorona, supernova remnants, starburst galaxies, and molecular cooling flows in galaxy clusters. To provide reliable CX-induced X-ray spectra models to simulate these and other astrophysical environments, we have undertaken a project to compute quantum-state-resolved CX cross sections of highly-charged ions colliding with H and He. Here we summarize current results for C^(5-6)+, N^6+, and O^(6-8)+ obtained with the molecular-orbital close-coupling (CC), atomic-orbital CC, and classical trajectory Monte Carlo methods. Utilizing the theoretical CX cross sections, cascade models are computed to generate X-ray spectra and compared to available measurements and observations. Comparison is also made to models assuming excitation by thermal electrons to identify diagnostics to distinguish CX-induced and electron-impact-induced X-ray emission.[4pt] [1] T. E. Cravens, Geophys. Res. Lett. 25, 105 (1997).

Stancil, P. C.; Nolte, J. L.; Porter, R. L.; Shelton, R. L.; Wu, Y.; Schultz, D. R.; Hui, Y.; Rakovic, M. J.; Ferland, G. J.; Liebermann, H. P.; Buenker, R. J.

2012-06-01

57

X-ray Emission from UVLGs and ULXs  

NASA Technical Reports Server (NTRS)

The first topic covered in this talk will be the study of GALEX-selected Ultraviolet-Luminous Galaxies (UVLGs) which appear to include an interesting subset of galaxies that are analogs to the distant (3 < z < 4) Lyman Break Galaxies (LBGs). The 2-10 keV X-ray emission of LBGs appear to be broadly similar to that of galaxies in the local Universe, possibly indicating similarity in the production of accreting binaries over large evolutionary timescales in the Universe. Given the very large distances to the LBGs, we have elected to use the the UVLGs as possible local-Universe LBG analogs. This technique is showing promise; we have detected luminous X-ray emission from one UVLG that permits basic X-ray spectroscopic analysis, and have direct X-ray constraints on a total of 6 UVLGs. The second topic for the talk is MIR diagnostics of accretion activity in Ultraluminous X-ray (ULX) sources. We have determined that the Spitzer IRS mid-infrared emission-line flux ratios for ULX sources bear similarity to those for AGN. We discuss strategies for future development of this technique using archival data and/or future observations.

Cardiff, Ann Hornschemeier

2007-01-01

58

Discovery of Diffuse Hard X-ray Emission Around Jupiter  

NASA Astrophysics Data System (ADS)

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 and the bright spot seemed to move according to the Io's motion. 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. We hence examined three mechanisms: 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 related to Io.

Ezoe, Yuichiro; Ishikawa, K.; Ohashi, T.; Terada, N.; Miyoshi, Y.; Uchiyama, Y.

2009-09-01

59

X-Ray Emission from the Galilean Satellites  

NASA Astrophysics Data System (ADS)

Analysis of Jovian system data from the ACIS camera onboard the Chandra X-Ray observatory shows emission from Io, Europa, and Ganymede, as described in Elsner et al., (to be submitted to Nature). The emission for Io and Ganymede is apparently dominated by a line near 525 ev, consistent with Kalpha (inner shell) emission from oxygen. For Europa this line may also dominate, although the observed energy seems slightly higher. For Io additional photons are apparently also seen in the 1 - 3 Kev range, which would be consistent with Kalpha emission from heavier elements Na through Ar, although photon statistics are too poor to identify specific lines and elements. In the 525 ev line the emission rates for Io through Ganymede (assuming isotropic emission) are 1.4 x 1022, 9.3 x 1021, and 9.8 x 1021 photons sec-1 respectively. This emission could arise from collisional excitation of the incoming magnetospheric oxygen atoms, or oxygen in the tenuous SO2 or O2 atmospheres or the SO2 frost, silicate, and water ice surfaces. In all cases O would be the most common element capable of X-Ray emission. The tenuous and patchy Io atmosphere would be optically thin to X-Ray photons in most locations as would the atmospheres of the other satellites. The level of incoming particle energy deposition, obtained from a crude scaling of Jovian X-Ray aurora models, suggests that most incoming ion energy would be deposited at the surfaces rather than in the atmospheres. X-Ray emission from these satellites provides a new tool for measuring their interaction with the magnetosphere and may also provide a way to directly measure the composition of their surfaces.

Howell, R. R.

2001-11-01

60

A common stochastic process rules gamma-ray burst prompt emission and X-ray flares  

E-print Network

Prompt gamma-ray and early X-ray afterglow emission in gamma-ray bursts (GRBs) are characterized by a bursty behavior and are often interspersed with long quiescent times. There is compelling evidence that X-ray flares are linked to prompt gamma-rays. However, the physical mechanism that leads to the complex temporal distribution of gamma-ray pulses and X-ray flares is not understood. Here we show that the waiting time distribution (WTD) of pulses and flares exhibits a power-law tail extending over 4 decades with index ~2 and can be the manifestation of a common time-dependent Poisson process. This result is robust and is obtained on different catalogs. Surprisingly, GRBs with many (>=8) gamma-ray pulses are very unlikely to be accompanied by X-ray flares after the end of the prompt emission (3.1 sigma Gaussian confidence). These results are consistent with a simple interpretation: an hyperaccreting disk breaks up into one or a few groups of fragments, each of which is independently accreted with the same pro...

Guidorzi, C; Frontera, F; Margutti, R; Baldeschi, A; Amati, L

2015-01-01

61

Tracking of azobenzene isomerization by X-ray emission spectroscopy.  

PubMed

Cis-trans isomerizations are among the fundamental processes in photochemistry. In azobenzene or its derivatives this dynamics is, due to its reversibility, one of the reactions widely used in photostimulation of molecular motors or in molecular electronics. Though intensively investigated in the optical regime, no detailed study exists in the X-ray regime so far. Because the X-ray emission spectroscopy echoes the electronic structure sensitive to the geometry, this theoretical report based on the density functional theory and its time-dependent version presents different nitrogen K-edge X-ray emission spectra for cis and trans isomers with close interrelation to their electron configuration. Considering the spectrum along the isomerization path, these structural signatures can be utilized to probe the isomerization dynamics in the excited molecule. The scheme can further be generalized to the element specific photoreactions. PMID:25134009

Ebadi, H

2014-09-11

62

Constraints on jet X-ray emission in low/hard state X-ray binaries  

E-print Network

We show that the combination of the similarities between the X-ray properties of low luminosity accreting black holes and accreting neutron stars, combined with the differences in their radio properties argues that the X-rays from these systems are unlikely to be formed in the relativistic jets. Specifically, the spectra of extreme island state neutron stars and low/hard state black holes are known to be indistinguishable, while the power spectra from these systems are known to show only minor differences beyond what would be expected from scaling the characteristic variability frequencies by the mass of the compact object. The spectral and temporal similarities thus imply a common emission mechanism that has only minor deviations from having all key parameters scaling linearly with the mass of the compact object, while we show that this is inconsistent with the observations that the radio powers of neutron stars are typically about 30 times lower than those of black holes at the same X-ray luminosity. We also show that an abrupt luminosity change would be expected when a system makes a spectral state transition from a radiatively inefficient jet dominated accretion flow to a thin disk dominated flow, but that such a change is not seen.

Thomas J. Maccarone

2005-03-31

63

X-RAY EMISSION ANALYSIS: SAMPLE LOSSES DURING EXCITATION  

EPA Science Inventory

Many samples of atmospheric aerosols and biological materials containing volatile or unstable species are now being examined by X-ray emission analysis, and loss of these species by sample heating is a critical consideration. The amount of heat energy deposited in a sample by the...

64

EUV and x-ray emission of nonmagnetic catacysmic variables  

SciTech Connect

Recent results are presented and discussed regarding the EUV and X-ray emission of nonmagnetic cataclysmic variables. Emphasis is given to high accretion rate systems (novalike variables and dwarf novae in outburst), and to a number of apparent discrepancies between observations and the theory of the boundary layer between the accretion disk and the surface of the white dwarf. Discussed are EUV and X-ray light curves, dwarf nova oscillations, and spectra, with new and previously unpublished results on SS Cyg and OY Car.

Mauche, C.W.

1997-09-01

65

A CHANGE IN THE QUIESCENT X-RAY SPECTRUM OF THE NEUTRON STAR LOW-MASS X-RAY BINARY MXB 1659-29  

SciTech Connect

The quasi-persistent neutron star low-mass X-ray binary MXB 1659-29 went into quiescence in 2001, and we have followed its quiescent X-ray evolution since. Observations over the first 4 yr showed a rapid drop in flux and temperature of the neutron star atmosphere, interpreted as cooling of the neutron star crust which had been heated during the 2.5 yr outburst. However, observations taken approximately 1400 and 2400 days into quiescence were consistent with each other, suggesting the crust had reached thermal equilibrium with the core. Here we present a new Chandra observation of MXB 1659-29 taken 11 yr into quiescence and 4 yr since the last Chandra observation. This new observation shows an unexpected factor of {approx}3 drop in count rate and change in spectral shape since the last observation, which cannot be explained simply by continued cooling. Two possible scenarios are that either the neutron star temperature has remained unchanged and there has been an increase in the column density, or, alternatively the neutron star temperature has dropped precipitously and the spectrum is now dominated by a power-law component. The first scenario may be possible given that MXB 1659-29 is a near edge-on system, and an increase in column density could be due to build-up of material in, and a thickening of, a truncated accretion disk during quiescence. But, a large change in disk height may not be plausible if standard accretion disk theory holds during quiescence. Alternatively, the disk may be precessing, leading to a higher column density during this latest observation.

Cackett, E. M. [Department of Physics and Astronomy, Wayne State University, 666 W. Hancock Street, Detroit, MI 48201 (United States); Brown, E. F. [Department of Physics and Astronomy, National Superconducting Cyclotron Laboratory, and the Joint Institute for Nuclear Astrophysics, Michigan State University, East Lansing, MI 48824 (United States); Cumming, A. [Department of Physics, McGill University, 3600 rue University, Montreal, QC H3A 2T8 (Canada); Degenaar, N.; Miller, J. M. [Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, MI 48109-1042 (United States); Fridriksson, J. K.; Wijnands, R. [Astronomical Institute ''Anton Pannekoek'', University of Amsterdam, Science Park 904, 1098-XH Amsterdam (Netherlands); Homan, J., E-mail: ecackett@wayne.edu [Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, 70 Vassar Street, Cambridge, MA 02139 (United States)

2013-09-10

66

X-ray Emission from Thunderstorms and Lightning  

SciTech Connect

How lightning is initiated in the relatively low electric fields inside thunderclouds and how it can then propagate for tens of kilometers through virgin air are two of the great unsolved problems in the atmospheric sciences.  Until very recently it was believed that lightning was entirely a conventional discharge, involving only low-energy (a few eV) electrons.  This picture changed completely a few years ago with the discovery of intense x-ray emission from both natural cloud-to-ground lightning and rocket-triggered lightning.  This energetic emission cannot be produced by a conventional discharge, and so the presence of x-rays strongly implies that runaway breakdown plays a role in lightning processes.  During runaway breakdown, electrons are accelerated through air to nearly the speed of light by strong electric fields.  These runaway electrons then emit bremsstrahlung x-rays and gamma-rays during collisions with air.  Indeed, the x-ray and gamma-ray emission produced by runaway breakdown near the tops of thunderstorms is bright enough to be seen from outer space, 600 km away.  As a result, the physics used for decades to describe thunderstorm electrification and lightning discharges is incomplete and needs to be revisited. 

Joseph Dwyer

2009-07-08

67

X-ray Emission from Thunderstorms and Lightning  

SciTech Connect

How lightning is initiated in the relatively low electric fields inside thunderclouds and how it can then propagate for tens of kilometers through virgin air are two of the great unsolved problems in the atmospheric sciences. Until very recently it was believed that lightning was entirely a conventional discharge, involving only low-energy (a few eV) electrons. This picture changed completely a few years ago with the discovery of intense x-ray emission from both natural cloud-to-ground lightning and rocket-triggered lightning. This energetic emission cannot be produced by a conventional discharge, and so the presence of x-rays strongly implies that runaway breakdown plays a role in lightning processes. During runaway breakdown, electrons are accelerated through air to nearly the speed of light by strong electric fields. These runaway electrons then emit bremsstrahlung x-rays and gamma-rays during collisions with air. Indeed, the x-ray and gamma-ray emission produced by runaway breakdown near the tops of thunderstorms is bright enough to be seen from outer space, 600 km away. As a result, the physics used for decades to describe thunderstorm electrification and lightning discharges is incomplete and needs to be revisited.

Dwyer, Joseph (Florida Institute of Technology) [Florida Institute of Technology

2009-08-08

68

X-ray Emission from Thunderstorms and Lightning  

ScienceCinema

How lightning is initiated in the relatively low electric fields inside thunderclouds and how it can then propagate for tens of kilometers through virgin air are two of the great unsolved problems in the atmospheric sciences.  Until very recently it was believed that lightning was entirely a conventional discharge, involving only low-energy (a few eV) electrons.  This picture changed completely a few years ago with the discovery of intense x-ray emission from both natural cloud-to-ground lightning and rocket-triggered lightning.  This energetic emission cannot be produced by a conventional discharge, and so the presence of x-rays strongly implies that runaway breakdown plays a role in lightning processes.  During runaway breakdown, electrons are accelerated through air to nearly the speed of light by strong electric fields.  These runaway electrons then emit bremsstrahlung x-rays and gamma-rays during collisions with air.  Indeed, the x-ray and gamma-ray emission produced by runaway breakdown near the tops of thunderstorms is bright enough to be seen from outer space, 600 km away.  As a result, the physics used for decades to describe thunderstorm electrification and lightning discharges is incomplete and needs to be revisited. 

Joseph Dwyer

2010-01-08

69

On X-ray Emission from Highly Loaded Hydrides  

Microsoft Academic Search

X-ray emission (1-2 keV) has been observed in various experiments using electrolytic or plasma methods for loading of hydride targets such as Pd-D to atom ratios > 0.8. Intensities vary from very low-level emission up to laser-like focused beams, depending on experimental conditions(A.G. Lipson et al, JETP Letters, (submitted)). Bremsstralung during thermalization of energetic alphas\\/protons created by nuclear reactions in

George H. Miley; Heinrich Hora; Nie Luo; Andrei Lipson

2004-01-01

70

A laboratory-based hard x-ray monochromator for high-resolution x-ray emission spectroscopy and x-ray absorption near edge structure measurements  

NASA Astrophysics Data System (ADS)

We report the development of a laboratory-based Rowland-circle monochromator that incorporates a low power x-ray (bremsstrahlung) tube source, a spherically bent crystal analyzer, and an energy-resolving solid-state detector. This relatively inexpensive, introductory level instrument achieves 1-eV energy resolution for photon energies of ˜5 keV to ˜10 keV while also demonstrating a net efficiency previously seen only in laboratory monochromators having much coarser energy resolution. Despite the use of only a compact, air-cooled 10 W x-ray tube, we find count rates for nonresonant x-ray emission spectroscopy comparable to those achieved at monochromatized spectroscopy beamlines at synchrotron light sources. For x-ray absorption near edge structure, the monochromatized flux is small (due to the use of a low-powered x-ray generator) but still useful for routine transmission-mode studies of concentrated samples. These results indicate that upgrading to a standard commercial high-power line-focused x-ray tube or rotating anode x-ray generator would result in monochromatized fluxes of order 106-107 photons/s with no loss in energy resolution. This work establishes core technical capabilities for a rejuvenation of laboratory-based hard x-ray spectroscopies that could have special relevance for contemporary research on catalytic or electrical energy storage systems using transition-metal, lanthanide, or noble-metal active species.

Seidler, G. T.; Mortensen, D. R.; Remesnik, A. J.; Pacold, J. I.; Ball, N. A.; Barry, N.; Styczinski, M.; Hoidn, O. R.

2014-11-01

71

Determination of total x-ray absorption coefficient using non-resonant x-ray emission  

PubMed Central

An alternative measure of x-ray absorption spectroscopy (XAS) called inverse partial fluorescence yield (IPFY) has recently been developed that is both bulk sensitive and free of saturation effects. Here we show that the angle dependence of IPFY can provide a measure directly proportional to the total x-ray absorption coefficient, µ(E). In contrast, fluorescence yield (FY) and electron yield (EY) spectra are offset and/or distorted from µ(E) by an unknown and difficult to measure amount. Moreover, our measurement can determine µ(E) in absolute units with no free parameters by scaling to µ(E) at the non-resonant emission energy. We demonstrate this technique with measurements on NiO and NdGaO3. Determining µ(E) across edge-steps enables the use of XAS as a non-destructive measure of material composition. In NdGaO3, we also demonstrate the utility of IPFY for insulating samples, where neither EY or FY provide reliable spectra due to sample charging and self-absorption effects, respectively. PMID:22355697

Achkar, A. J.; Regier, T. Z.; Monkman, E. J.; Shen, K. M.; Hawthorn, D. G.

2011-01-01

72

"X-Ray Transients in Star-Forming Regions" and "Hard X-Ray Emission from X-Ray Bursters"  

NASA Technical Reports Server (NTRS)

This grant funded work on the analysis of data obtained with the Burst and Transient Experiment (BATSE) on the Compton Gamma-Ray Observatory. The goal of the work was to search for hard x-ray transients in star forming regions using the all-sky hard x-ray monitoring capability of BATSE. Our initial work lead to the discovery of a hard x-ray transient, GRO J1849-03. Follow-up observations of this source made with the Wide Field Camera on BeppoSAX showed that the source should be identified with the previously known x-ray pulsar GS 1843-02 which itself is identified with the x-ray source X1845-024 originally discovered with the SAS-3 satellite. Our identification of the source and measurement of the outburst recurrence time, lead to the identification of the source as a Be/X-ray binary with a spin period of 94.8 s and an orbital period of 241 days. The funding was used primarily for partial salary and travel support for John Tomsick, then a graduate student at Columbia University. John Tomsick, now Dr. Tomsick, received his Ph.D. from Columbia University in July 1999, based partially on results obtained under this investigation. He is now a postdoctoral research scientist at the University of California, San Diego.

Halpern, Jules P.; Kaaret, Philip

1999-01-01

73

X-ray emission from high temperature plasmas  

NASA Technical Reports Server (NTRS)

The bremsstrahlung X-rays from a plasma focus device were investigated with emphasis on the emission versus position, time, energy, and angle of emission. It is shown that low energy X-rays come from the plasma focus region, but that the higher energy components come from the anode. The emission is anisotropic, the low energy polar diagram resembling a cardioid, while the high energy emission is a lobe into the anode. The plasma parameters were considered indicating that even in the dense focus, the plasma is collisionless near the axis. By considering the radiation patterns of relativistic electrons a qualitative picture is obtained, which explains the measured polar diagrams, assuming the electrons that produce the X-rays have velocity vectors lying roughly in a cone between the point of focus and the anode. The average electron energy is about 3keV at the focus and about 10 keV on the anode surface. Results are consistent with the converging beam model of neutron production.

Harries, W. L.

1975-01-01

74

Quantifying the Exospheric Component of Soft X-ray Emission  

NASA Technical Reports Server (NTRS)

High charge state heavy ions in the solar wind exchange charge with ambient neutral gas. This process creates a product ion in an excited state. During the radiative cascade process, EUV and X-ray photons are emitted with energies in the range of about 100 eV to 1 keV. Because the terrestrial exospheric density at the nominal magnetopause location is relatively high, approx. 10 cu cm, solar wind charge exchange, or SWCX, can be observed by Earth-orbiting soft X-ray instruments such as the ROSAT Position Sensitive Proportional Counters (PSPC). In this presentation, we will compare simulated and observed soft Xray emission during an event on August 18-19, 1991 and discuss the role of exospheric SWCX emission for this and other events.

Kuntz, Kip; Collier, Michael R.; Snowden, Steven L.; Robertson, Ina; Hansen, Kenneth; Cravens, Thomas

2007-01-01

75

Limits on diffuse X-ray emission from M101  

NASA Technical Reports Server (NTRS)

Observed limits on diffuse X-ray emission from M101 require that the temperature of any coronal or matrix hot gas which is radiating an appreciable part ( 10%) of the average supernova power be less than 10(5.7)K. Furthermore, the fraction of the galactic plane occupied by hot buttles similar to the one which apparently surrounds the Sun is at most 25% in the region between 10 kpc and 20 kpc from the galactic center.

Mccammon, D.; Sanders, W. T.

1984-01-01

76

Weak Hard X-Ray Emission from Broad Absorption Line Quasars: Evidence for Intrinsic X-Ray Weakness  

NASA Astrophysics Data System (ADS)

We report NuSTAR observations of a sample of six X-ray weak broad absorption line (BAL) quasars. These targets, at z = 0.148-1.223, are among the optically brightest and most luminous BAL quasars known at z < 1.3. However, their rest-frame ?2 keV luminosities are 14 to >330 times weaker than expected for typical quasars. Our results from a pilot NuSTAR study of two low-redshift BAL quasars, a Chandra stacking analysis of a sample of high-redshift BAL quasars, and a NuSTAR spectral analysis of the local BAL quasar Mrk 231 have already suggested the existence of intrinsically X-ray weak BAL quasars, i.e., quasars not emitting X-rays at the level expected from their optical/UV emission. The aim of the current program is to extend the search for such extraordinary objects. Three of the six new targets are weakly detected by NuSTAR with <~ 45 counts in the 3-24 keV band, and the other three are not detected. The hard X-ray (8-24 keV) weakness observed by NuSTAR requires Compton-thick absorption if these objects have nominal underlying X-ray emission. However, a soft stacked effective photon index (?eff ? 1.8) for this sample disfavors Compton-thick absorption in general. The uniform hard X-ray weakness observed by NuSTAR for this and the pilot samples selected with <10 keV weakness also suggests that the X-ray weakness is intrinsic in at least some of the targets. We conclude that the NuSTAR observations have likely discovered a significant population (gsim 33%) of intrinsically X-ray weak objects among the BAL quasars with significantly weak <10 keV emission. We suggest that intrinsically X-ray weak quasars might be preferentially observed as BAL quasars.

Luo, B.; Brandt, W. N.; Alexander, D. M.; Stern, D.; Teng, S. H.; Arévalo, P.; Bauer, F. E.; Boggs, S. E.; Christensen, F. E.; Comastri, A.; Craig, W. W.; Farrah, D.; Gandhi, P.; Hailey, C. J.; Harrison, F. A.; Koss, M.; Ogle, P.; Puccetti, S.; Saez, C.; Scott, A. E.; Walton, D. J.; Zhang, W. W.

2014-10-01

77

Advances in X-Ray Chemical Analysis, Japan, 45 (2014) ISSN 0911-7806 Discharge Phenomena during X-Ray Emission from Pyroelectric Crystal  

E-print Network

Advances in X-Ray Chemical Analysis, Japan, 45 (2014) ISSN 0911-7806 © X X Discharge Phenomena during X-Ray Emission from Pyroelectric Crystal and Energy Dependence of X-Ray Intensity Kengo OHIRA, Susumu IMASHUKU and Jun KAWAI #12;#12;45 181 X X Adv. X-Ray. Chem. Anal., Japan 45, pp.181-190 (2014) 606

Jun, Kawai

78

Diffuse X-ray Emission from M101  

NASA Technical Reports Server (NTRS)

The total 0.45-2.0 keV luminosity of M101 is 3.1 x 10(exp 39) ergs/s, of which 2.2 x 10(exp 39) ergs/s is due to diffuse emission. Of the diffuse emission, no more than 6% can be due to unresolved point sources such as X-ray binaries, and approx. 11% is due to dwarf stars. The diffuse emission traces the spiral arms and is roughly correlated with the H alpha and FUV (far ultraviolet) emission. The radial distribution closely follows the optical profile. The bulk of the diffuse emission is characterized by a two thermal component spectrum with kT = 0.20,0.75 keV, and the ratios of the emission measures of the two components is roughly constant as a function of both radius and surface brightness. The softer component has a sufficiently large covering factor that the bulk of the emission is likely extra-planar. We find no evidence of an extended axisymmetric X-ray halo, suggesting that any such halo has a strength much smaller than current predictions.

Kuntz, K. D.; Snowden, S. L.; Pence, W. D.; Mukai, K.; White, Nicholas E. (Technical Monitor)

2002-01-01

79

X-RAY EMISSION FROM THE SOMBRERO GALAXY: DISCRETE SOURCES  

SciTech Connect

We present a study of discrete X-ray sources in and around the bulge-dominated, massive Sa galaxy, Sombrero (M104), based on new and archival Chandra observations with a total exposure of {approx}200 ks. With a detection limit of L{sub X} {approx} 10{sup 37} erg s{sup -1} and a field of view covering a galactocentric radius of {approx}30 kpc (11.'5), 383 sources are detected. Cross-correlation with Spitler et al.'s catalog of Sombrero globular clusters (GCs) identified from HST/ACS observations reveals 41 X-ray sources in GCs, presumably low-mass X-ray binaries (LMXBs). Metal-rich GCs are found to have a higher probability of hosting these LMXBs, a trend similar to that found in elliptical galaxies. On the other hand, the four most luminous GC LMXBs, with apparently super-Eddington luminosities for an accreting neutron star, are found in metal-poor GCs. We quantify the differential luminosity functions (LFs) for both the detected GC and field LMXBs, whose power-law indices ({approx}1.1 for the GC-LF and {approx}1.6 for field-LF) are consistent with previous studies for elliptical galaxies. With precise sky positions of the GCs without a detected X-ray source, we further quantify, through a fluctuation analysis, the GC-LF at fainter luminosities down to 10{sup 35} erg s{sup -1}. The derived index rules out a faint-end slope flatter than 1.1 at a 2{sigma} significance, contrary to recent findings in several elliptical galaxies and the bulge of M31. On the other hand, the 2-6 keV unresolved emission places a tight constraint on the field LF, implying a flattened index of {approx}1.0 below 10{sup 37} erg s{sup -1}. We also detect 101 sources in the halo of Sombrero. The presence of these sources cannot be interpreted as galactic LMXBs whose spatial distribution empirically follows the starlight. Their number is also higher than the expected number of cosmic active galactic nuclei (52 {+-} 11 [1{sigma}]) whose surface density is constrained by deep X-ray surveys. We suggest that either the cosmic X-ray background is unusually high in the direction of Sombrero, or a distinct population of X-ray sources is present in the halo of Sombrero.

Li Zhiyuan; Jones, Christine; Forman, William R.; Kraft, Ralph P.; Stefano, Rosanne Di [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Spitler, Lee R. [Centre for Astrophysics and Supercomputing, Swinburne University, Hawthorn, VIC 3122 (Australia); Tang, Shikui; Wang, Q. Daniel [Department of Astronomy, University of Massachusetts, 710 North Pleasant Street, Amherst, MA 01003 (United States); Gilfanov, Marat [Max-Planck-Institut fuer Astrophysik, Karl-Schwarzschild-Str 1, 85741 Garching bei Muenchen (Germany); Revnivtsev, Mikhail, E-mail: zyli@cfa.harvard.ed [Excellence Cluster Universe, Technische Universitaet Muenchen, Boltzmannstr. 2, 85748 Garching (Germany)

2010-10-01

80

Statistical data of X-ray emission from laboratory sparks  

NASA Astrophysics Data System (ADS)

In this study we present a summary of the data of 1331 long laboratory sparks in atmospheric pressure intended for a statistical analysis. A 2 MV, 17kJ Marx generator were used to generate 1.2/52?s shape pulses positive and negative polarity. The generator was connected to a spark gap with cone-shaped electrodes. The distance between high-voltage and grounded electrodes was 1.08 meters. Breakdown voltage between electrodes was about 1MV. X-rays have been detected during the development of the discharge channel. The currents through the grounded electrode and through the high-voltage electrode were recorded separately and simultaneously with the voltage and the X-ray signal. X-rays were registered by two LaBr3(Ce+) scintillation detectors in different positions with respect to the forming discharge channel. Detector D1 was placed immediately under the grounded electrode at 15cm distance. Detector D2 was placed at horizontal distances of 143cm and 210cm, at mid-gap height. We also used lead shields of 1.5, 3, and 4 mm thickness for radiation attenuation measurements. For detector collimation we used shields up to 2 cm thickness. Also no metallic objects with pointed surfaces were present within 2 m from the spark gap. Typical plot of positive discharge presented in Figure 1a. Table 1 shows the summary of the X-ray registrations. Signal detection occurred significantly more for positive polarity discharges than for negative. This dependence was observed for both detectors. For detector D2 the probability of X-ray registration decreased proportional to 1/d2 with increasing the distance d to the breakdown gap from 1m43 to 2m10. Detailed energy spectra and time distribution of X-ray emission were obtained; see for example Fig. 1b. For both polarities of the high voltage, the X-rays only occurred when there was a current at the cathode.

Kochkin, P.; Deursen, D. V.

2011-12-01

81

OPTICAL EMISSION OF THE BLACK HOLE X-RAY TRANSIENT MAXI J1659-152 DURING QUIESCENCE  

SciTech Connect

We report on the optical detection of the black hole X-ray transient MAXI J1659-152 during its quiescent state. By using the Canada-France-Hawaii Telescope, we observed MAXI J1659-152 about seven months after the end of an X-ray outburst. The optical counterpart of MAXI J1659-152 is clearly detected with an r'-band magnitude of 23.6-23.8. The detection confirms that the optical emission of MAXI J1659-152 during quiescence is relatively bright compared to other black hole X-ray transients. This implies that the distance to MAXI J1659-152 is 4.6-7.5 kpc for an M2 dwarf companion star or 2.3-3.8 kpc for an M5 dwarf companion star. By comparing with other measurements, an M2 dwarf companion is more likely.

Kong, Albert K. H., E-mail: akong@phys.nthu.edu.tw [Institute of Astronomy and Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan (China)

2012-12-01

82

The Very-Soft X-Ray Emission of X-Ray Faint Early-Type Galaxies  

E-print Network

A recent re-analysis of Einstein data, and new ROSAT observations, have revealed the presence of at least two components in the X-ray spectra of X-ray faint early-type galaxies: a relatively hard component (kT>1.5 keV), and a very soft component (kT\\sim 0.2-0.3 keV). We address the problem of the nature of the very soft component, and whether it can be due to a hot interstellar medium (ISM), or is most likely originated by the collective emission of very soft stellar sources. To this purpose, hydrodynamical evolutionary sequences for the secular behavior of gas flows in ellipticals have been performed, and the results are compared with the observational X-ray data: the very soft component could be entirely explained with a hot ISM only in galaxies where the depth of the potential well is quite shallow, otherwise the softest contribution to the X-ray emission comes certainly from stellar sources. As stellar soft X-ray emitters, we consider late-type stellar corone, supersoft sources such as those discovered by ROSAT in the Magellanic Clouds and M31, and RSCVn systems. We finally present a model for the X-ray emission of NGC4365, to reproduce in detail the results of the ROSAT pointed observation (PSPC spectrum and radial surface brightness distribution).

S. Pellegrini; G. Fabbiano

1993-12-19

83

X-ray/UV variability and the origin of soft X-ray excess emission from II Zw 177  

NASA Astrophysics Data System (ADS)

We study a detailed broad-band X-ray/UV emission from the narrow line Seyfert 1 galaxy II Zw 177 based on two XMM-Newton and single Swift/XRT observations. Both XMM-Newton observations show the soft X-ray excess emission below 2 keV when the best-fit 2 - 10 keV power law is extrapolated down to 0.3 keV. We find the blurred reflection from an ionized accretion disc and Comptonized disc emission both describe the observed soft excess well. We find a remarkable trend of decreasing UV flux with increasing soft X-ray excess and power law emission. We suggest that this could be due to that the external edge of corona hide a fraction of accretion disk. Co-Author: Prof. Gulab C. Dewangan (IUCAA), Prof. Ranjeev Misra (IUCAA), Pramod Kumar (Nanded university)

Pal, Main

84

Chandra ACIS Observations of Jovian X-Ray Emission  

NASA Technical Reports Server (NTRS)

On November 25 and 26, 1999, the Chandra X-ray spacecraft conducted a set of four 19,000 sec observations of Jupiter. The ACIS-S instrument configuration was used for its good low energy efficiency and spatial resolution. An anomalous response was obtained which was subsequently attributed to strong jovian infrared radiation penetrating the detector and piling up spurious events across the entire X-ray range. However, the pre-observation establishment of an offsetting bias field has allowed the recovery of data from that portion of Jupiter's disc which remained within the elevated portion of the bias field during the observation. This ranges from fewer than 3000 sec to the entire observing time for about 10% of the planet. Auroral emission is seen near both poles in each observation. The northern aurora ia overall more intense than the southern, consistent with prior Einstein and ROSAT Observatory results. The southern aurora shows more modulation with Jupiter's rotation than the northern. Spatial resolution has been improved by at least a factor of two over prior measurements but convincing evidence of structure has not been seen. Lower latitude emission, first observed by ROSAT, is confirmed with flux levels averaging more than a factor of five below peak auroral values. Pronounced variation in the observed emission has occurred over the observing period. The spectral response extends from 0.24 keV, below which noise dominates, to about 1.2 keV. For all four observations the spectrum is clearly enhanced between 0.45 and 0.85 keV. This is apparently unequivocal evidence that Jupiter's X-ray emission is the result of oxygen and perhaps sulfur ions precipitating into the planet's atmosphere, where they undergo charge exchange interactions. The identification of specific transitions lines in the spectrum is among the ongoing efforts. A bremsstrahlung component has not yet been identified.

Garmire, Gordon; Elsner, Ronald; Feigelson, Eric; Ford, Peter; Gladstone, G. Randall; Hurley, Kevin; Metzger, Albert; Waite, J. Hunter, Jr.; Whitaker, Ann F. (Technical Monitor)

2001-01-01

85

Probing Multilayer Nanostructures with Photoelectron and X-Ray Emission Spectroscopies Excited by X-Ray Standing Waves  

NASA Astrophysics Data System (ADS)

We discuss a newly developed X-ray standing wave/wedge method for probing the composition, magnetization, and electronic densities of states in buried layers and interfaces of spintronic and other nanostructures. In work based on photoemission, this method has permitted determining concentration and magnetization profiles through giant magnetoresistive and magnetic tunnel junction structures, as well as individual layer densities of states near the Fermi level in a tunnel junction . Using X-ray emission and resonant inelastic X-ray scattering for detection has permitted probing deeper layers and interfaces in a giant magnetoresistance structure. Various future applications of this method in nanomagnetism and other fields of nanoscience are suggested, including using more energetic hard X-ray standing waves so as to probe more deeply below a surface and standing wave excitation in spectromicroscopy to provide depth sensitivity.

Yang, S.-H.; Sell, B. C.; Mun, B. S.; Fadley, C. S.

2013-01-01

86

Neutron Star Radius Measurement with the Quiescent Low-mass X-ray Binary U24 in NGC 6397  

NASA Astrophysics Data System (ADS)

This paper reports the spectral and timing analyses of the quiescent low-mass X-ray binary (qLMXB) U24 observed during five archived Chandra/ACIS exposures of the nearby globular cluster NGC 6397, for a total of 350 ks. We find that the X-ray flux and the parameters of the hydrogen atmosphere spectral model are consistent with those previously published for this source. On short timescales, we find no evidence of aperiodic intensity variability, with 90% confidence upper limits during five observations ranging between <8.6% rms and <19% rms, in the 0.0001-0.1 Hz frequency range (0.5-8.0 keV); and no evidence of periodic variability, with maximum observed powers in this frequency range having a chance probability of occurrence from a Poisson-deviated light curve in excess of 10%. We also report the improved neutron star (NS) physical radius measurement, with statistical accuracy of the order of ~10%: R NS = 8.9+0.9 -0.6 km for M NS = 1.4 M sun. Alternatively, we provide the confidence regions in mass-radius space as well as the best-fit projected radius R ? = 11.9+1.0 -0.8 km, as seen by an observer at infinity. The best-fit effective temperature, kT eff = 80+4 -5 eV, is used to estimate the NS core temperature which falls in the range T core = (3.0-9.8) × 107 K, depending on the atmosphere model considered. This makes U24 the third most precisely measured NS radius among qLMXBs, after those in ? Cen and M13.

Guillot, Sebastien; Rutledge, Robert E.; Brown, Edward F.

2011-05-01

87

Astrophysics Research Projects:Astrophysics Research Projects: massive star winds, x-ray emission, theoretical models,massive star winds, x-ray emission, theoretical models,  

E-print Network

Astrophysics Research Projects:Astrophysics Research Projects: massive star winds, x-ray emission, theoretical models,massive star winds, x-ray emission, theoretical models, spectroscopy, laboratory plasma-drivenhave powerful radiation-driven stellar windsstellar winds.. etaeta CarinaCarina #12;TheThe ChandraChandra X

Cohen, David

88

Solar X-ray physics  

SciTech Connect

Research on solar X-ray phenomena performed by American scientists during 1987-1990 is reviewed. Major topics discussed include solar images observed during quiescent times, the processes observed during solar flares, and the coronal, interplanetary, and terrestrial phenomena associated with solar X-ray flares. Particular attention is given to the hard X-ray emission observed at the start of the flare, the energy transfer to the soft X-ray emitting plasma, the late resolution of the flare as observed in soft X-ray, and the rate of occurrence of solar flares as a function of time and latitude. Pertinent aspects of nonflaring, coronal X-ray emission and stellar flares are also discussed. 175 refs.

Bornmann, P.L. (USAF, Geophysics Laboratory, Hanscom AFB, MA (United States))

1991-01-01

89

X-ray Emission from Eta Carinae near Periastron in 2009: Origin of the X-ray Minimum  

NASA Astrophysics Data System (ADS)

X-ray emission from the supermassive binary system, Eta Carinae, declines sharply around periastron. This X-ray minimum has two distinct phases --- the lowest flux phase in the first ~3 weeks and a slightly brighter phase thereafter. In 2009, the Chandra X-ray Observatory monitored the first phase five times and found the lowest observed flux at ~1.9e-12 ergs cm-2 s-1 (3-8 keV). The spectral shape changed such that the hard band above ~4 keV dropped quickly at the beginning and the soft band flux gradually decreased to its lowest observed value in ~2 weeks. The hard band spectrum had begun to recover by that time. This spectral variation suggests that the shocked gas producing the hottest X-ray gas near the apex of the wind-wind collision (WWC) is blocked behind the dense inner wind of the primary star, which later occults slightly cooler gas downstream. Shocked gas previously produced by the system at earlier orbital phases is suggested to produce the faint residual X-ray emission seen when the emission near the apex is completely blocked by the primary wind. The brighter phase is probably caused by the re-appearance of the WWC plasma, whose emissivity significantly declined during the occultation. We interpret this to mean that the X-ray minimum is produced by a hybrid mechanism of an occultation and a decline in emissivity of the WWC shock. We constrain timings of superior conjunction and periastron based on these results.

Hamaguchi, Kenji; Corcoran, M. F.; Russell, C. M.; Pollock, A. M.; Gull, T. R.; Teodoro, M.; Madura, T.; Damineli, A.; Pittard, J. M.

2014-01-01

90

The X-ray spectra of galaxies. II - Average spectral properties and emission mechanisms  

NASA Technical Reports Server (NTRS)

The Imaging Proportional Counter data in the Einstein database is used to study the X-ray spectra of normal galaxies. The X-ray emission temperature of spirals is found to be higher on the average than that of ellipticals. This supports the idea that accreting binaries are a major source of X-rays in spirals, while a hot interstellar medium (ISM) is present in ellipticals. The X-ray spectra of Sa galaxies are intermediate between those of ellipticals and spirals, suggesting that these galaxies contain hot gaseous emission as well as emission from accreting binaries. In E and SO galaxies the emission temperature becomes higher with a decreasing X-ray to optical luminosity ratio, which suggests that the emission of X-ray faint early-type galaxies consists of a large evolved stellar component, while the gaseous emission becomes dominant in X-ray brighter galaxies. The group with the lowest X-ray to optical ratio does not follow this trend; in these galaxies a very soft X-ray component, amounting to about half the total X-ray emission, is found in addition to the hard X-ray component. Possible explanations are integrated emission of M stars and a relatively cool ISM. A very soft component is also found in several spiral galaxies. This may indicate that some spirals contain hot gaseous components similar to those seen in NGC 253 and M82.

Kim, D.-W.; Fabbiano, G.; Trinchieri, G.

1992-01-01

91

Low energy x-ray emission from magnetic fusion plasmas  

NASA Astrophysics Data System (ADS)

Complex, transient, spatially inhomogeneous tokamak plasmas require careful diagnosis. As the reactor regime is approched, soft x rays become more important as a versatile diagnostic tool and an energy-loss mechanism. Continuum emission provides a measure of electron temperatures and light impurity content. Impurity lines serve as a probe for ion and electron temperature, impurity behavior, and radiative cooling. The entire spectrum yields vital information on instabilities and disruptions. The importance of impurities is illustrated by the extensive efforts toward understanding impurity production, effects, and control. Minute heavy impurity concentrations can prevent reactor ignition. Si(Li)-detector arrays give a broad overview of continuum and line x-ray emission (.3-50 keV) with moderate energy (200 eV) and time (50 ms) resolution. Bragg crystal and grating spectrometers provide detailed informaion on impurity lines with moderate to excellent (E/?E=100-23,000) resolving power and 1-50 ms time resolution. Imaging detector arrays measure rapid (˜10 ?s) fluctuations due to MHD instabilities and probe impurity behavior and radiative cooling. Future tokamaks require more diagnostic channels to avoid spatial scanning; higher throughput for fast, single-shot diagnosis; increased spectral information per sample period via fast scanning or use of multi-element detectors with dispersive elements; and radiation shielding and hardening of detectors.

Hill, K. W.; Bitter, M.; Eames, D.; von Goeler, S.; Sauthoff, N. R.; Silver, E.

1981-10-01

92

Soft X-ray excess emission from clusters of galaxies  

E-print Network

This is the first meeting specifically devoted to the topic of cluster soft excess and related phenomena. It calls together a group of some 40 scientists, mostly experts in the field, to present their findings on the observational aspects of emission from clusters, signature of the WHIM in the cluster, intergalactic, and local environment, theoretical modeling of the WHIM in cosmological hydrodynamic simulations, theory and observations of cluster cosmic rays, magnetic fields, radio data and the use of the Sunyaev-Zeldovich effect as a means of constraining the important parameters. We are particularly grateful to F.J. Lockman and S.L. Snowden for presenting their latest picture of the cold gas distribution in the interstellar medium, as this affects our ability to model extragalactic EUV and soft X-ray data via Galactic absorption by HI and HeI. Papers given on future hardware concepts to further the spatial and spectral diagnosis of diffuse soft X-ray emission in general are also included.

Richard Lieu; Jonathan Mittaz

2004-03-17

93

A Chandra survey of X-ray emission from radio jets: Correlations of the jet X-ray flux  

NASA Astrophysics Data System (ADS)

We have completed a Chandra survey for X-ray emission from 54 radio jets that are extended on arcsecond scales. These are in flat spectrum radio loud quasars and have redshifts in the range z=0.3 to z=2.1. We detect X-ray emission from 60% of the jets. The study reported here considers the straight part of the jet nearest to the quasar. The X-ray counting rate from this correlates very well to that from the quasar. Correlation with redshift, the jet radio flux, the radio core flux, or visual apparent magnitude is poor or non-existent.This research was supported by NASA contract NAS8-03060, SAO Grant GO9-0121B, and HST Grant HST-GO-11838.04-A

Schwartz, Daniel A.; Marshall, Herman L.; Worrall, Diana M.; Birkinshaw, Mark; Perlman, Eric S.; Lovell, Jim; Jauncey, David L.; Murphy, David William; Gelbord, Jonathan; Godfrey, Leith; Bicknell, Geoffrey V.

2015-01-01

94

Upper limits for X-ray emission from Jupiter as measured from the Copernicus satellite  

NASA Technical Reports Server (NTRS)

X-ray telescopic observations are made by the Copernicus satellite for detecting X-ray emission from Jupiter analogous to X-rays from terrestrial aurorae. Values of X-ray fluxes recorded by three Copernicus detectors covering the 0.6 to 7.5 keV energy range are reported. The detectors employed are described and the times at which the observations were made are given. Resulting upper-limit spectra are compared with previous X-ray observations of Jupiter. The upper-limit X-ray fluxes are discussed in terms of magnetospheric activity on Jupiter.

Vesecky, J. F.; Culhane, J. L.; Hawkins, F. J.

1975-01-01

95

X-Ray, UV, and Optical Observations of Supernova 2006bp with Swift: Detection of Early X-Ray Emission  

NASA Technical Reports Server (NTRS)

We present results on the X-ray and optical/UV emission from the Type IIP supernova (SN) 2006bp and the interaction of the SW shock with its environment, obtained with the X-Ray Telescope (XRT) and UV/Optical Telescope (UVOT) on-board the Swift observatory. SN 2006bp is detected in X-rays at a 4.5 sigmalevel of significance in the merged XRT data from days 1 to 12 after the explosion. If the (0.2-10 keV band) X-ray luminosity of L(sub 0.2-10) = (1.8 plus or minus 0.4) x l0(exp 39 ergs s(exp -1) is caused by interaction of the SN shock with circumstellar material (CSM), deposited by a stellar wind from the progenitor's companion star, a mass-loss rate of M is approximately 2x10(exp -6) solar mass yr(exp -1) (v(sub w)/10 km s(exp -l) is inferred. The mass-loss rate is one of the lowest ever recorded for a core-collapse SN and consistent with the non-detection in the radio with the VLA on days 2, 9, and 11 after the explosion. The Swift data further show a fading of the X-ray emission starting around day 12 after the explosion. In combination with a follow-up XMM-Newton observation obtained on day 21 after the explosion, an X-ray rate of decline Lx, varies as t(exp -n) with index n = 1.2 plus or minus 0.6 is inferred. Since no other SN has been detected in X-rays prior to the optical peak and since Type IIP SNe have an extended 'plateau' phase in the optical, we discuss the scenario that the X-rays might be due to inverse Compton scattering of photospheric optical photons off relativistic electrons produced in circumstellar shocks. However, due to the high required value of the Lorentz factor (approximately 10-100), inconsistent with the ejecta velocity inferred from optical line widths, we conclude that Inverse Compton scattering is an unlikely explanation for the observed X-ray emission. The fast evolution of the optical/ultraviolet (1900-5500A) spectral energy distribution and the spectral changes observed with Swift reveal the onset of metal line-blanketing and cooling of the expanding photosphere during the first few weeks after the outburst.

Immler, S.; Brown, P. J.; Milne, P.; Dessart, L.; Mazzali, P. A.; Landsman, W.; Gehrels, N.; Petre, R.; Burrows, D. N.; Nousek, J. A.; Chevalier, R. A.; Williams, C. L.; Koss, M.; Stockdale, C. J.; Kelley, M. T.; Weiler, K. W.; Holland, S. T.; Pian, E.; Roming, P. W. A.; Pooley, D.; Nomoto, K.; Greiner, J.; Campana, S.; Soderberg, A. M.

2007-01-01

96

Aurora and Non-Auroral X-ray Emissions from Jupiter: A Comparative View  

NASA Technical Reports Server (NTRS)

Jovian X-rays can be broadly classified into two categories: (1) auroral emission, which is confined to high-latitudes (approximately greater than 60 deg.) at both polar regions, and (2) dayglow emission, which originates from the sunlit low-latitude (approximately less than 50 deg.) regions of the disk (hereafter called disk emissions). Recent X-ray observations of Jupiter by chandra and XMM-Newton have shown that these two types of X-ray emission from Jupiter have different morphological, temporal, and spectral characteristics. In particular: 1) contrary to the auroral X-rays, which are concentrated in a spot in the north and in a band that runs half-way across the planet in the south, the low-latitude X-ray disk is almost uniform; 2) unlike the approximately 40 plus or minus 20-min periodic oscillations seen in the auroral X-ray emissions, the disk emissions do not show any periodic oscillations; 3) the disk emission is harder and extends to higher energies than the auroral spectrum; and 4) the disk X-ray emission show time variability similar to that seen in solar X-rays. These differences and features imply that the processes producing X-rays are different at these two latitude regions on Jupiter. We will present the details of these and other features that suggest the differences between these two classes of X-ray emissions from Jupiter, and discuss the current scenario of the production mechanism of them.

Bhardwal, Anil; Elsner, Ron; Gladstone, Randy; Waite, Hunter, Jr.; Lugaz, Noe; Cravens, Tom; Branduardi-Raymont, Graziella; Ramsay, Gavin; Soria, Rob; Ford, Peter

2004-01-01

97

The X-ray Emission of Planetary Nebulae M. Steffen, D. Schnberner  

E-print Network

The X-ray Emission of Planetary Nebulae M. Steffen, D. Schönberner Planetarische Nebel sind können. X-ray observations of Planetary Nebulae Over the last years, the two large X-ray space Nebulae (PNe) with high spatial and spectral resolution. These observations have shown without doubt

98

ROTATIONAL MODULATION OF X-RAY EMISSION IN ORION NEBULA YOUNG STARS E. Flaccomio,1  

E-print Network

ROTATIONAL MODULATION OF X-RAY EMISSION IN ORION NEBULA YOUNG STARS E. Flaccomio,1 G. Micela,1 S-ray­emitting plasma in a sample of young Orion Nebula Cluster stars by modulation of their X-ray light curves due-ray­bright stars with known rotational periods. We search for X-ray modulation using the Lomb Normalized

Royer, Dana

99

SEARCHING FOR NARROW EMISSION LINES IN X-RAY SPECTRA: COMPUTATION AND METHODS Taeyoung Park,1  

E-print Network

The detection and quantification of narrow emission lines in X-ray spectra is a challenging statistical task quasar emission. The detection of weak lines in noisy spectra is the main statistical problem- portant X-ray emission feature identified in AGN and quasar spectra is the iron K emission line (see

van Dyk, David

100

Gamma-Ray Emission from Be/X-ray Binaries  

NASA Astrophysics Data System (ADS)

Be/X-ray binaries are systems formed by a massive Be star and a magnetized neutron star, usually in an eccentric orbit. The Be star has strong equatorial winds occasionally forming a circumstellar disk. When the neutron star intersects the disk the accretion rate dramatically increases and a transient accretion disk can be formed around the compact object. This disk can last longer than a single orbit in the case of major outbursts. If the disk rotates faster than the neutron star, the Cheng-Ruderman mechanism can produce a current of relativistic protons that would impact onto the disk surface, producing gamma-rays from neutral pion decays and initiating electromagnetic cascades inside the disk. In this paper we present calculations of the evolution of the disk parameters during both major and minor X-ray events, and we discuss the generation of gamma-ray emission at different energies within a variety of models that include both screened and unscreened disks.

Orellana, M.; Romero, G. E.

2005-06-01

101

Gamma-Ray Emission from Be/X-Ray Binaries  

NASA Astrophysics Data System (ADS)

Be/X-ray binaries are systems formed by a massive Be star and a magnetized neutron star, usually in an eccentric orbit. The Be star has strong equatorial winds occasionally forming a circumstellar disk. When the neutron star intersects the disk the accretion rate dramatically increases and a transient accretion disk can be formed around the compact object. This disk can last longer than a single orbit in the case of major outbursts. If the disk rotates faster than the neutron star, the Cheng-Ruderman mechanism can produce a current of relativistic protons that would impact onto the disk surface, producing gamma-rays from neutral pion decays and initiating electromagnetic cascades inside the disk. In this paper we present calculations of the evolution of the disk parameters during both major and minor X-ray events, and we discuss the generation of gamma-ray emission at different energies within a variety of models that include both screened and unscreened disks.

Orellana, M.; Romero, G. E.

102

X-ray emission from young supernova remnants - Nonionization equilibrium abundances and emissivities  

NASA Technical Reports Server (NTRS)

X-ray line emission from hot, low-density plasma in young supernova remnants is strongly enhanced by departures from ionization equilibrium. The X-ray emission from a Sedov blast wave has been calculated using a nonequilibrium evolutionary treatment of the ionization structure, and the resulting spectrum has been fitted to HEAO 2 SSS data for Tycho's remnant. These models yield dramatically different elemental abundances for heavy elements (Ne, Mg, Si, S, Ar, Ca, and Fe), compared with two-temperature component equilibrium models of Becker et al. (1979, 1980). Nonequilibrium broad-band X-ray emissivities result in lower mass determinations for the supernova ejecta. Areas of further improvement of remnant X-ray modeling are suggested.

Shull, J. M.

1982-01-01

103

First Detection of Phase-dependent Colliding Wind X-ray Emission outside the Milky Way  

NASA Technical Reports Server (NTRS)

After having reported the detection of X-rays emitted by the peculiar system HD 5980, we assess here the origin of this high-energy emission from additional X-ray observations obtained with XMM-Newton. This research provides the first detection of apparently periodic X-ray emission from hot gas produced by the collision of winds in an evolved massive binary outside the Milky Way. It also provides the first X-ray monitoring of a Luminous Blue Variable only years after its eruption and shows that the source of the X-rays is not associated with the ejecta.

Naze, Yael; Koenigsberger, Gloria; Moffat, Anthony F. J.

2007-01-01

104

X-ray emission from A0-F6 spectral type stars  

Microsoft Academic Search

We use the ROSAT public data archive to study the X-ray emission of a sample of supposedly single A0-F6 spectral type stars from the Bright Star Catalogue. We detected X-ray emission from 19 A- and 33 F-type stars. However, our results are not sufficient to associate with certainty the X-ray emission to the A-type stars themselves, since the usual argument

M. R. Panzera; G. Tagliaferri; L. Pasinetti; E. Antonello

1999-01-01

105

Two component X-ray emission from RS CVn binaries  

NASA Technical Reports Server (NTRS)

A summary of results from the solid state spectrometer on the Einstein Observatory for 7 RS CVn binaries is presented. The spectra of all require two emission components, evidenced by line emission characteristic of plasma at 4 to 8 x 10 to the 6th power and bremsstrahlung characteristic of 20 to 100 x 10 to the 6th power K. The data are interpreted in terms of magnetic coronal loops similar to those seen on the Sun, although with different characteristic parameters. The emission regions could be defined by separate magnetic structures. For pressure less than approximately 10 dynes/sq cm the low temperature plasma would be confined within the stellar radii, while the high temperature plasma would, for the synchronous close binaries, fill the binary orbits. However, for loop pressures exceeding 100 dynes/sq cm, the high temperature components would also be confined to within the stellar radii, in loops covering only small fractions of the stellar surfaces. While the radio properties and the occurrence of X-ray flares suggest the larger emission regions, the observations of time variations leave the ambiguity unresolved.

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

1980-01-01

106

X-ray images of W28 and 3C400.2 - Two radio-shell supernova remnants with centrally-peaked X-ray emission  

NASA Technical Reports Server (NTRS)

X-ray images of the supernova remnants (SNRs) W28 and 3C400.2 were obtained using the Imaging Proportional Counter (IPC) on the Einstein Observatory. Despite the shell-like radio morphology of these remnants, their X-ray emission is centrally peaked. Two possible X-ray emission mechanisms are explored: synchrotron emission due to an active central pulsar, and thermal emission from a thin hot plasma filling the interior of the remnant. Comparisons of X-ray and radio properties of W28 and 3C400.2 with known Crab-like remnants suggest that synchrotron emission is not a very plausible X-ray emission mechanism. Optical and radio observations suggest that both SNRs exploded in a dense cloud and have evolved rapidly to the radiative stage. The X-ray morphology observed is similar to that predicted for SNRs in such an environment.

Matsui, Y.; Long, K. S.

1985-01-01

107

Effect of insulator sleeve material on the x-ray emission from a plasma focus device  

SciTech Connect

The effect of insulator sleeve material on x-ray emission from a 2.3 kJ Mather type plasma focus device operated in argon-hydrogen mixture is investigated. The time and space resolved x-ray emission characteristics are studied by using a three channel p-i-n diode x-ray spectrometer and a multipinhole camera. The x-ray emission depends on the volumetric ratio of argon-hydrogen mixture as well as the filling pressure and the highest x-ray emission is observed for a volumetric ratio 40% Ar to 60%H{sub 2} at 2.5 mbar filling pressure. The fused silica insulator sleeve produces the highest x-ray emission whereas nonceramic insulator sleeves such as nylon, Perspex, or Teflon does not produce focus or x-rays. The pinhole images of the x-ray emitting zones reveal that the contribution of the Cu K{alpha} line is weak and plasma x-rays are intense. The highest plasma electron temperature is estimated to be 3.3 and 3.6 keV for Pyrex glass and fused silica insulator sleeves, respectively. It is speculated that the higher surface resistivity of fused silica is responsible for enhanced x-ray emission and plasma electron temperature.

Hussain, S.; Badar, M. A. [Department of Physics, University of Sargodha, Sargodha 40100 (Pakistan); Shafiq, M.; Zakaullah, M. [Department of Physics, Quaid-i-Azam University, Islamabad 45320 (Pakistan)

2010-09-15

108

X-Ray Emission from Jupiter, Saturn, and Earth: A Short Review  

E-print Network

Jupiter, Saturn, and Earth - the three planets having dense atmosphere and a well developed magnetosphere - are known to emit X-rays. Recently, Chandra X-ray Observatory has observed X-rays from these planets, and XMM-Newton has observed them from Jupiter and Saturn. These observations have provided improved morphological, temporal, and spectral characteristics of X-rays from these planets. Both auroral and non-auroral (low-latitude) 'disk' X-ray emissions have been observed on Earth and Jupiter. X-rays have been detected from Saturn's disk, but no convincing evidence for X-ray aurora on Saturn has been observed. The non-auroral disk X-ray emissions from Jupiter, Saturn, and Earth, are mostly produced due to scattering of solar X-rays. X-ray aurora on Earth is mainly generated via bremsstrahlung from precipitating electrons and on Jupiter via charge exchange of highlyionized energetic heavy ions precipitating into the polar atmosphere. Recent unpublished work suggests that at higher (>2 keV) energies electron bremsstrahlung also plays a role in Jupiter's X-ray aurora. This paper summarizes the recent results of X-ray observations on Jupiter, Saturn, and Earth mainly in the soft energy (~0.1-2.0 keV) band and provides a comparative overview.

Anil Bhardwaj

2006-05-11

109

Nonquasineutral relativistic current filaments and their X-ray emission  

SciTech Connect

Nonquasineutral electron current filaments with the azimuthal magnetic field are considered that arise due to the generation of electron vorticity in the initial (dissipative) stage of evolution of a current-carrying plasma, when the Hall number is small ({sigma}B/en{sub e}c << 1) because of the low values of the plasma conductivity and magnetic field strength. Equilibrium filamentary structures with both zero and nonzero net currents are considered. Structures with a zero net current type form on time scales of t < t{sub sk} = (r{sub 0{omega}pe}/c){sup 2}t{sub st}, where t{sub sk} is the skin time, t{sub st} is the typical time of electron-ion collisions, and r{sub 0} is the radius of the filament. It is shown that, in nonquasineutral filaments in which the current is carried by electrons drifting in the crossed electric (E{sub r}) and magnetic (B{sub {theta}}) fields, ultrarelativistic electron beams on the typical charge-separation scale r{sub B} = B/(4{pi}en{sub e}) (the so-called magnetic Debye radius) can be generated. It is found that, for comparable electron currents, the characteristic electron energy in filaments with a nonzero net current is significantly lower than that in zero-net-current filaments that form on typical time scales of t < t{sub sk}. This is because, in the latter type of filaments, the oppositely directed electron currents repel one another; as a result, both the density and velocity of electrons increase near the filament axis, where the velocities of relativistic electrons are maximum. Filaments with a zero net current can emit X rays with photon energies h {omega} up to 10 MeV. The electron velocity distributions in filaments, the X-ray emission spectra, and the total X-ray yield per unit filament length are calculated as functions of the current and the electron number density in the filament. Analytical estimates of the characteristic lifetime of a radiating filament and the typical size of the radiating region as functions of the plasma density are obtained. The results of calculations are compared with the available experimental data.

Gordeev, A. V. [Russian Research Centre Kurchatov Institute (Russian Federation); Losseva, T. V. [Russian Academy of Sciences, Institute of Geosphere Dynamics (Russian Federation)

2009-02-15

110

Stationary digital breast tomosynthesis with distributed field emission X-ray tube  

PubMed Central

Tomosynthesis requires projection images from different viewing angles. Using a distributed x-ray source this can be achieved without mechanical motion of the source with the potential for faster image acquisition speed. A distributed x-ray tube has been designed and manufactured specifically for breast tomosynthesis. The x-ray tube consists of 31 field emission x-ray sources with an angular range of 30°. The total dose is up to 100mAs with an energy range between 27 and 45 kVp. We discuss the source geometry and results from the characterization of the first prototype. The x-ray tube uses field emission cathodes based on carbon nanotubes (CNT) as electron source. Prior to the manufacturing of the sealed x-ray tube extensive testing on the field emission cathodes has been performed to verify the requirements for commercial tomosynthesis systems in terms of emission current, focal spot size and tube lifetime. PMID:21617760

Sprenger, F.; Calderon, X.; Gidcumb, E.; Lu, J.; Qian, X.; Spronk, D.; Tucker, A.; Yang, G.; Zhou, O.

2011-01-01

111

Analysis and interpretation of diffuse x-ray emission using data from the Einstein satellite  

NASA Technical Reports Server (NTRS)

An ambitious program to create a powerful and accessible archive of the HEAO-2 Imaging Proportional Counter (IPC) database was outlined. The scientific utility of that database for studies of diffuse x ray emissions was explored. Technical and scientific accomplishments are reviewed. Three papers were presented which have major new scientific findings relevant to the global structure of the interstellar medium and the origin of the cosmic x ray background. An all-sky map of diffuse x ray emission was constructed.

Helfand, David J.

1991-01-01

112

X-ray Emission from Megamaser Galaxy IC 2560  

SciTech Connect

Observation of the H{sub 2}O megamaser galaxy IC 2560 with the Chandra Observatory reveals a complex spectrum composed of soft X-ray emission due to multi-temperature thermal plasma, and a hard continuum with strong emission lines. The continuum is most likely a Compton reflection (reprocessing) of primary emission that is completely absorbed at least up to 7 keV. The lines can be identified with fluorescence from Si, S and Fe in the lowest ionization stages. The equivalent widths of the Si and S lines are broadly compatible with those anticipated for reprocessing by optically thick cold plasma of Solar abundances, while the large equivalent width of the Fe line requires some overabundance of iron. A contribution to the line from a transmitted component cannot be ruled out, but the limits on the strength of the Compton shoulder make it less likely. From the bolometric luminosity of the nuclear region, we infer that the source radiates at 1-10% of its Eddington luminosity, for an adopted central mass of 3 x 10{sup 6} M{sub {circle_dot}}. The overall spectrum is consistent with the hypotheses that the central engines powering the detected megamsers in accretion disks are obscured from direct view by the associated accretion disk material itself, and that there is a correlation between the occurrence of megamaser emission and Compton-thick absorption columns. For the 11 known galaxies with both column density measurements and maser emission believed to arise from accretion disks, eight AGN are Compton thick.

Madejski, Greg; /SLAC /KIPAC, Menlo Park; Done, Chris; /Durham U.; Zycki, Piotr; /Warsaw, Copernicus Astron. Ctr.; Greenhill, Lincoln; /KIPAC, Menlo Park

2005-09-12

113

X-ray transients in quiescence  

E-print Network

Transient X-ray binaries remain in their quiescent state for a long time (months to hundred years) and then bright up as the most powerful sources of the X-ray sky. While it is clear that, when in outbursts, transient binaries are powered by accretion, the origin of the low luminosity X-ray emission that has been detected in the quiescent state has different interpretations and provides the unique opportunity for testing different accretion regimes. In this paper we concentrate on the various aspects of the accretion physics at low rates onto compact objects. We describe the observational panorama of quiescent emission for the three classes of X-ray transients and try to interpret these data in light of the different regimes accessible at such low mass inflow rates.

Sergio Campana

2000-12-04

114

X-ray emission from the galactic disk  

NASA Technical Reports Server (NTRS)

A search was made of a diffuse component of X-rays 1.5 keV associated with an interarm region of the galaxy at galactic longitudes in the vicinity of 60 deg. A statistically significant excess associated with a narrow disk component was detected. The angular extent of this component has a most probable value of 2 deg and may be as large as 7 deg at 90% confidence. The best fit spectrum yields an intensity of 2.9 photons 1/(cm2-sec-ster) over the 2 to 10 keV range. The 3 sigma upper limit to any emission (e.g. iron line) in a 1.5 keV band centered at 7 keV from galactic latitudes h or = 3.5 deg is .3 photons 1/(cm2-sec-ster). Several possible emission models are discussed, with the most likely candidate being a population of unresolvable low luminosity discrete sources.

Bleach, R. D.; Boldt, E. A.; Holt, S. S.; Schwartz, D. A.; Serlemitsos, P. J.

1972-01-01

115

Is optical Fe II emission related to the soft X-ray properties of quasars?  

NASA Technical Reports Server (NTRS)

Radio-quiet quasars generally show broad, blended multiplets of Fe II emission in their optical and UV spectra. Radio-loud quasars also show UV Fe II emission, but their optical Fe II emission is generally weaker. No satisfactory theory connecting the generation of Fe II and radio emission has been found to explain this effect. A second, well-established distinction between the two clases of quasar is in their X-ray properties: radio-loud quasars are more X-ray luminous, and recent results have shown that they also have systematically flatter soft X-ray slopes. Here it is proposed that the second effect causes the first; i.e., that the primary factor controlling the optical Fe II emission is the soft X-ray spectrum. This proposition is supported by X-ray and optical data for nine quasars, which shows a correlation between the soft X-ray slope and the strength of the optical Fe II emission. One of these quasars (1803+676) is radio-quiet, and yet its optical spectrum shows no evidence for Fe II emission. This quasar is also unusual in that it has a flat X-ray spectrum. This further supports the proposal that the X-ray spectrum is important in determining the relative strengths of UV and optical Fe II emission.

Wilkes, Belinda J.; Elvis, Martin; Mchardy, Ian

1987-01-01

116

Field Emission Scanning Electron Microscopy (FE-SEM) and Energy Dispersive X-Ray (EDX) Spectroscopy  

E-print Network

Field Emission Scanning Electron Microscopy (FE-SEM) and Energy Dispersive X-Ray (EDX) Spectroscopy The materials characterization facility is equipped with a Hitachi S-4700 Field Emission Scanning Electron Electron Microscope (FE-SEM). The FE-SEM is equipped with EDAX Energy Dispersive X-Ray (EDX) spectroscopy

Gelfond, Michael

117

Eclipse and Collapse of the Colliding Wind X-ray Emission from Eta Carinae  

NASA Technical Reports Server (NTRS)

X-ray emission from the massive stellar binary system, Eta Carinae, drops strongly around periastron passage; the event is called the X-ray minimum. We launched a focused observing campaign in early 2009 to understand the mechanism of causing the X-ray minimum. During the campaign, hard X-ray emission (<10 keV) from Eta Carinae declined as in the previous minimum, though it recovered a month earlier. Extremely hard X-ray emission between 15-25 keV, closely monitored for the first time with the Suzaku HXD/PIN, decreased similarly to the hard X-rays, but it reached minimum only after hard X-ray emission from the star had already began to recover. This indicates that the X-ray minimum is produced by two composite mechanisms: the thick primary wind first obscured the hard, 2-10 keV thermal X-ray emission from the wind-wind collision (WWC) plasma; the WWC activity then decays as the two stars reach periastron.

Hamaguchi, Kenji; Corcoran, Michael F.

2012-01-01

118

Beamed and Unbeamed X-ray Emission in FR1 Radio Galaxies  

NASA Technical Reports Server (NTRS)

There is good evidence for X-ray emission associated with AGN jets which are relativistically boosted towards the observer. But to what jet radius does such X-ray emission persist? To attempt to answer this question one can look at radio galaxies; their cores are sufficiently X-ray faint that any unbeamed X-ray emission in the vicinity of the central engine must be obscured. The jets of such sources are at unfavourable angles for relativistic boosting, and so their relatively weak X-ray emission must be carefully separated from the plateau of resolved X-ray emission from a hot interstellar, intragroup, or intracluster medium on which they are expected to sit. This paper presents results arguing that jet X-ray emission is generally detected in radio galaxies, even those of low intrinsic power without hot spots. The levels of emission suggest an extrapolated radio to soft X-ray spectral index, alpha(sub tao x) of about 0.85 at parsec to perhaps kiloparsec distances from the cores.

Worrall, Diana M.

1997-01-01

119

Biomedical applications of proton induced X-ray emission.  

PubMed

Apart from studies on aerosols, the majority of applications of proton induced X-ray emission (PIXE) with a normal beam or a microprobe (micro-PIXE) is found in biology and medicine. Two aspects of broad beam PIXE are often decisive for the choice of this analytical technique. Compared to other techniques capable of analysis down beyond the ppm level, PIXE can be carried out with a very small amount of material and minute fractions of the composite samples, even in the scale of micrometers and quite often with minimal sample preparation, which are important requirements for biomedical investigations. Secondly, the speed of the total analysis opens the possibility to analyze large numbers of samples in a reasonable time, which is often necessary in biomedical studies in order to obtain sufficiently significant correlations between trace element concentrations and biomedical phenomena. Few, if any, techniques can compete with micro-PIXE; quantitative trace element analysis on a micrometer scale still represent a challenging problem. The electron microprobe normally lacks the sensitivity while the laser induced techniques suffer as yet from quantification problems. This paper describes recent developments especially in micro-PIXE in biomedical research. PMID:3399860

Vis, R D

1988-06-01

120

Mapping the great attractor region in x rays and diffuse x ray emission: A possible galactic wind in the bulge of M31  

NASA Technical Reports Server (NTRS)

The NASA ADP Program to study the x ray emission in the direction of the Great Attractor and from the core of M31 has resulted in four papers; three on the Shapley Supercluster which is the dominant x ray feature in the Great Attractor region and one on the diffuse emission in M31. The results of these papers are summarized.

Forman, W. R.

1992-01-01

121

A Deep ROSAT Survey - X. X-ray-luminous narrow-emission-line galaxies  

Microsoft Academic Search

X-ray luminous narrow-emission-line galaxies (NELGs) have been previously identified and proposed as an important class of extragalactic X-ray source, with a potentially significant contribution to the total extragalactic X-ray flux at energies below ~10 keV. In order to investigate and clarify this possibility, we have used a sample of NELGs found in five deep ROSAT fields, and similar samples belonging

R. E. Griffiths; R. della Ceca; Ioannis Georgantopoulos; B. J. Boyle; G. C. Stewart; Tom Shanks; Antonella Fruscione

1996-01-01

122

Electronic Structure of In2O3 from Resonant X-ray Emission Spectroscopy  

SciTech Connect

The valence and conduction band structures of In2O3 have been measured using a combination of valence band x-ray photoemission spectroscopy, O K-edge resonant x-ray emission spectroscopy, and O K-edge x-ray absorption spectroscopy. Excellent agreement is noted between the experimental spectra and O 2p partial density of states calculated within hybrid density functional theory. Our data are consistent with a direct band gap for In2O3.

Piper, L.; DeMasi, A; Cho, S; Smith, K; Fuchs, F; Bechstedt, F; Korber, C; Klein, A; Payne, D; Egdell, R

2009-01-01

123

Chandra X-ray Observations of Jovian Low-latitude Emissions: Morphological, Temporal, and Spectral Characteristics  

NASA Technical Reports Server (NTRS)

Chandra observed X-rays from Jupiter during 24-26 February 2003 for about 40 hours with the ACIS-S and HRC-I instruments. The analysis of Jovian low-latitude "disk" Xray emissions are presented and compared with the high-latitude "auroral" emissions. We report the first Chandra ACIS-S measured X-ray spectrum (0.3-2 keV) of Jupiter's low-latitude disk The disk X-ray emission is harder and extends to higher energies than the auroral spectrum. The temporal variation in the Jovian disk X-rays is on an average consistent with those in the solar X-rays observed by GOES, and TIMED/SSE. Contrary to the auroral X-rays, the disk emissions are uniformly distributed over Jupiter; no indication of longitudinal dependence or correlation with surface magneh field strength is visible. Also, unlike the approx. 40 +/- 20 min periodic oscillations seen in the auroral X-ray emissions, the disk emissions do not show any periodic oscillations. The disk spectrum seems to be consistent with resonant and fluorescent scattering of solar X-rays by the Jovian upper atmosphere. Jupiter's disk is found to be about 50% dimmer in soft X-rays in February 2003 compared that in December 2000, which is consistent with the decrease in solar activity. No evidence of lightning-induced X-rays is seen in the Chandra X-ray data. The Jovian disk spectra observed with Chandra-ACIS is stronger than that observed with XMM-Newton two months later during April 28-29, 2003. The XMM-Newton Xray image of Jupiter shows evidence of limb darkening on the anti-sunward side as seen from Earth, as well as an asymmetry with respect to the subsolar point: suggesting a solar driven process.

Bhardwaj, Anil; Elsner, Ronald F.; Gladstone, G. Randall; Cravens, Thomas E.; Waiate J. Hunter, Jr.; Branduardi-Raymont, Graziella; Ford, Peter

2004-01-01

124

X-ray emission possibly coincident with the radio tail of PKS 0301 - 123  

NASA Technical Reports Server (NTRS)

X-ray, radio, and optical observations are reported for a very poor cluster of galaxies containing the radio source PKS 0301 - 123. A long, 100,000 second X-ray observation using the Einstein Observatory's IPC resulted in the serendipitous discovery of a peculiar extended X-ray morphology associated with the poor cluster. The X-ray emission is extended in the same direction and is approximately the same length as the radio-tailed source, PKS 0301 - 123, which was mapped at 6 and 20 cm with the VLA. Optical redshift observations with the KPNO IIDS on the 2.1 m telescope confirm the identification of the X-ray and radio emission with the poor cluster at z = 0.1. It is argued that the X-ray extension is unlikely to be a chance coincidence of a background source projected onto the foreground cluster. Therefore, four possible mechanisms which might physically link the X-ray and radio emission are considered: thermal bremsstrahlung from a cluster with a flattened potential well; inverse Compton scattering of the relativistic electrons in the radio source, X-ray synchrotron radiation; and heating the cluster gas by the turbulent wake of the radio galaxy. The prospects for future observations of such X-ray/radio coincidences are briefly discussed.

Burns, J. O.; Nelson, E. R.; White, R. A.; Gregory, S. A.

1985-01-01

125

X-ray emission possibly coincident with the radio tail of PKS 0301 - 123  

NASA Astrophysics Data System (ADS)

X-ray, radio, and optical observations are reported for a very poor cluster of galaxies containing the radio source PKS 0301 - 123. A long, 100,000 second X-ray observation using the Einstein Observatory's IPC resulted in the serendipitous discovery of a peculiar extended X-ray morphology associated with the poor cluster. The X-ray emission is extended in the same direction and is approximately the same length as the radio-tailed source, PKS 0301 - 123, which was mapped at 6 and 20 cm with the VLA. Optical redshift observations with the KPNO IIDS on the 2.1 m telescope confirm the identification of the X-ray and radio emission with the poor cluster at z = 0.1. It is argued that the X-ray extension is unlikely to be a chance coincidence of a background source projected onto the foreground cluster. Therefore, four possible mechanisms which might physically link the X-ray and radio emission are considered: thermal bremsstrahlung from a cluster with a flattened potential well; inverse Compton scattering of the relativistic electrons in the radio source, X-ray synchrotron radiation; and heating the cluster gas by the turbulent wake of the radio galaxy. The prospects for future observations of such X-ray/radio coincidences are briefly discussed.

Burns, J. O.; Nelson, E. R.; White, R. A.; Gregory, S. A.

1985-04-01

126

X-ray emission from MP Muscae: an old classical T Tauri star  

NASA Astrophysics Data System (ADS)

Aims:We study the properties of X-ray emitting plasma of MP Mus, an old classical T Tauri star. We check whether an accretion process could produce the observed X-ray emission and we derive the accretion parameters and the characteristics of the shock-heated plasma. We compare the properties of MP Mus with those of younger classical T Tauri stars to test whether age is related to the properties of the X-ray emitting plasma. Methods: XMM-Newton X-ray spectra allow us to measure plasma temperatures, abundances, and electron density. The density of cool plasma probes whether X-ray emission is produced by plasma heated in the accretion process. Results: X-ray emission from MP Mus originates from high density cool plasma but a hot flaring component is also present, suggesting that both coronal magnetic activity and accretion contribute to the observed X-ray emission. We find a Ne/O ratio similar to that observed in the much younger classical T Tauri star BP Tau. From the soft part of the X-ray emission, mostly produced by plasma heated in the accretion shock, we derive a mass accretion rate of 5×10-11 M_? yr-1.

Argiroffi, C.; Maggio, A.; Peres, G.

2007-04-01

127

EVIDENCE OF NON-THERMAL X-RAY EMISSION FROM HH 80  

SciTech Connect

Protostellar jets appear at all stages of star formation when the accretion process is still at work. Jets travel at velocities of hundreds of km s{sup –1}, creating strong shocks when interacting with the interstellar medium. Several cases of jets have been detected in X-rays, typically showing soft emission. For the first time, we report evidence of hard X-ray emission possibly related to non-thermal processes not explained by previous models of the post-shock emission predicted in the jet/ambient interaction scenario. HH 80 is located at the south head of the jet associated with the massive protostar IRAS 18162-2048. It shows soft and hard X-ray emission in regions that are spatially separated, with the soft X-ray emission region situated behind the region of hard X-ray emission. We propose a scenario for HH 80 where soft X-ray emission is associated with thermal processes from the interaction of the jet with denser ambient matter and hard X-ray emission is produced by synchrotron radiation at the front shock.

López-Santiago, J. [Instituto de Matemática Interdisciplinar, S. D. Astronomía y Geodesia, Facultad de Ciencias Matemáticas, Universidad Complutense de Madrid, E-28040 Madrid (Spain)] [Instituto de Matemática Interdisciplinar, S. D. Astronomía y Geodesia, Facultad de Ciencias Matemáticas, Universidad Complutense de Madrid, E-28040 Madrid (Spain); Peri, C. S.; Benaglia, P. [Instituto Argentino de Radioastronomía (IAR), CCT La Plata (CONICET), C.C.5, 1894 Villa Elisa, Buenos Aires (Argentina)] [Instituto Argentino de Radioastronomía (IAR), CCT La Plata (CONICET), C.C.5, 1894 Villa Elisa, Buenos Aires (Argentina); Bonito, R. [Dipartimento di Fisica e Chimica, Università di Palermo, Piazza del Parlamento 1, I-90134 Palermo (Italy)] [Dipartimento di Fisica e Chimica, Università di Palermo, Piazza del Parlamento 1, I-90134 Palermo (Italy); Miceli, M. [INAF-Osservatorio Astronomico di Palermo, Piazza del Parlamento 1, I-90134 Palermo (Italy)] [INAF-Osservatorio Astronomico di Palermo, Piazza del Parlamento 1, I-90134 Palermo (Italy); Albacete-Colombo, J. F. [Universidad Nacional del COMAHUE, Monseñor Esandi y Ayacucho, 8500 Viedma, Río Negro (Argentina)] [Universidad Nacional del COMAHUE, Monseñor Esandi y Ayacucho, 8500 Viedma, Río Negro (Argentina); De Castro, E. [Dpto. de Astrofísica y CC. de la Atmósfera, Universidad Complutense de Madrid, E-28040 Madrid (Spain)] [Dpto. de Astrofísica y CC. de la Atmósfera, Universidad Complutense de Madrid, E-28040 Madrid (Spain)

2013-10-20

128

Local magnetic moments at Mn 2p X-ray photoelectron and Mn L_?,? X-ray emission spectra  

NASA Astrophysics Data System (ADS)

The Mn L_?,_? (3darrow 2p_3/2,1/2) resonant X-ray emission spectra (RXES) and Mn 2p_3/2,1/2 X-ray photoelectron spectra of proposed as half metallic ferromagnets Mn-based Heusler alloys Ni_2MnZ (Z=In, Sn, Sb) are found to be different from ones of La_1-xSm_xMn_2Si2 compounds. Linearly polarized resonant excitation establishes that the distinctive feature in Mn L_? RXES of Heusler alloys is due to the nearly half-metallic character of Mn 3d states [1]. For intermetallides with metallic like valence band the Mn L_? RXES behave as metallic. However, the magnitude of the Mn 2p_3/2 core level splitting follows the magnitude of local magnetic moment ?_Mn increasing from La_1-xSm_xMn_2Si2 (2.3-2.5 ?_B) to Heusler alloys (3-4 ?_B). In contrast to RXES and XPS data, Mn L_3,2 X-ray absorption spectra shows typically metallic behavior for all materials. [1] J. Kübler, et.al., Phys. Rev. B 28, 1745 (1983)

Yablonskikh, Mikhail; Denlinger, Jonathan; Neumann, Manfred; Moewes, Alexander

2004-03-01

129

X-Ray Emission from Magnetic Massive Stars  

NASA Astrophysics Data System (ADS)

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-{\\dot{M}} B stars and flattens for the more luminous, higher-{\\dot{M}} 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. Based on data collected with XMM-Newton and Chandra.

Nazé, Yaël; Petit, Véronique; Rinbrand, Melanie; Cohen, David; Owocki, Stan; ud-Doula, Asif; Wade, Gregg A.

2014-11-01

130

High energy X-ray emission driven by high voltage circuit system  

NASA Astrophysics Data System (ADS)

The x-rays are produced by high voltage discharge applied inside plasma source interaction chamber; the control circuit system of high voltage is composed of a power supply and a LC-inverter. The goal of the project is based on the production of x-rays by a plasma to increase the efficiency of a classic x-ray tube with hot filament. Preliminary results of high energy x-rays emission, the layout and simulation with p-spice of the high voltage system are presented.

Emilio, M. Di Paolo; Palladino, L.

2014-04-01

131

Hard X-ray and Infrared Emission from Apparently Single White Dwarfs  

E-print Network

The photospheric emission of a white dwarf (WD) is not expected to be detectable in hard X-rays or the mid-IR. Hard X-ray (~1 keV) emission associated with a WD is usually attributed to a binary companion; however, emission at 1 keV has been detected from three WDs without companions: KPD 0005+5106, PG 1159, and WD 2226-210. The origin of their hard X-ray emission is unknown, although it has been suggested that WD 2226-210 has a late-type companion whose coronal activity is responsible for the hard X-rays. Recent Spitzer observations of WD 2226-210 revealed mid-IR excess emission indicative of the existence of a dust disk. It now becomes much less clear whether WD 2226-210's hard X-ray emission originates from the corona of a late-type companion or from the accretion of the disk material. High-quality X-ray observations and mid-IR observations of KPD 0005+5106 and PG 1159 are needed to help us understand the origin of their hard X-ray emission.

Y. -H. Chu; R. A. Gruendl; M. A. Guerrero; K. Y. -L. Su

2007-01-01

132

A Search for X-ray emission from Saturn, Uranus and Neptune  

E-print Network

We present an analysis of X-ray observations of the trans-Jovian planets Saturn, Uranus and Neptune with the ROSAT PSPC in comparison with X-ray observations of Jupiter. For the first time a marginal X-ray detection of Saturn was found and 95% confidence upper limits for Uranus and Neptune were obtained. These upper limits show that Jupiter-like X-ray luminosities can be excluded for all three planets, while they are consistent assuming intrinsic Saturn-like X-ray luminosities. Similar X-ray production mechanisms on all trans-Jovian planets can therefore not be ruled out, and spectral shape and total luminosity observed from Saturn are consistent with thick-target bremsstrahlung caused by electron precipitation as occurring in auroral emission from the Earth.

Jan-Uwe Ness; Juergen H. M. M. Schmitt

2000-01-08

133

Evaluation of photoelectron emission direction reconstruction algorithm for a soft x-ray polarimeter  

NASA Astrophysics Data System (ADS)

X-ray polarimetry has been an unexplored field of X-ray astronomy. The GEM (Gas electron multiplier) based X-ray polarimeter brings high sensitivity measurement of x-ray polarization from most popular classes of celestial X-ray sources. It derives the polarization information from the track of the photoelectron imaged by finely subdivided gas pixel detector. Either pixel or TPC based readout is used in polarimeter. TPC based soft X-ray polarimeter was planned for the NASA's GEMS Mission. Garfield simulations have been carried out for both pixel readout geometry and TPC readout geometry. The images of primary electron cloud obtained in simulation have been used for photoelectron emission direction reconstruction. We discuss the reconstruction algorithm, which has been developed and this algorithm is evaluated with the known inputs for simulation. Effect of operating parameters on the performance of both TPC readout method and pixel readout method will be compared.

Koushal, V.

134

Two component model for X-ray emission of radio selected QSO's  

NASA Technical Reports Server (NTRS)

Using a large database of radio, optical, and x ray luminosities of AGNs with survival analysis, it was found that the x ray emission of the radio selected quasars has two components. One is related to the optical luminosity and the other is related to the radio luminosity.

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

1986-01-01

135

A Study of Nonthermal X-Ray and Radio Emission from the O Star 9 Sgr  

NASA Technical Reports Server (NTRS)

The observed X-ray and highly variable nonthermal radio emission from OB stars has eluded explanation for more than 18 years. The most favorable model of X-ray production in these stars (shocks) predicts both nonthermal radio and X-ray emission. The nonthermal X-ray emission should occur above 2 keV and the variability of this X-ray component should also be comparable to the observed radio variability. To test this scenario, we proposed an ASC/VLA monitoring program to observe the OB star, 9 Sgr, a well known nonthermal, variable radio source and a strong X-ray source. We requested 625 ks ASCA observations with a temporal spacing of approximately 4 days which corresponds to the time required for a density disturbance to propagate to the 6 cm radio free-free photosphere. The X-ray observations were coordinated with 5 multi-wavelength VLA observations. These observations represent the first systematic attempt to investigate the relationship between the X-ray and radio emission in OB stars.

Waldron, Wayne L.; Corcoran, Michael F.; Drake, Stephen A.

1999-01-01

136

X-Ray Emission from the Halo of M31  

NASA Technical Reports Server (NTRS)

Our goal was to use short (10 ksec) observations of selected fields in the halo of M31, to determine the size and characteristics of its X-ray population and to study the connection between globular clusters and X-ray sources. The program of observations has yet to be successfully completed. We received acceptable data from just 2 of the 5 approved fields. Nevertheless, the results were intriguing and we have submitted a paper based on this data to Nature. We find that the X-ray source density is significantly enhanced in the vicinity of one GC, providing the first observational evidence supporting the ejection hypothesis. We also find additional X-ray sources, including some which are very soft, in large enough numbers to suggest that not all could have been formed in GCs. That is, some must be descended from the same primordial halo population that produced any compact stars comprising part of the halo's dark matter. Extrapolating fiom the X-ray source population, we estimate that stellar remnants and dim old stars in the halo could comprise as much as 25% of the estimated mass (approx. 10(exp 12) Solar Mass) of the halo. These results suggest that the other approved fields should be observed soon and also provide strong motivation for the future XMM-Newton programs.

Mushotzky, Richard (Technical Monitor); DiStefano, Rosanne

2004-01-01

137

Waiting in the Wings: Reflected X-Ray Emission from the Homunculus Nebula  

Microsoft Academic Search

We report the first detection of X-ray emission associated with the Homunculus nebula that surrounds the supermassive star eta Car. The emission is characterized by a temperature in excess of 100 MK and is consistent with scattering of the time-delayed X-ray flux associated with the star. The nebular emission is bright in the northwestern lobe and near the central regions

M. F. Corcoran; K. Hamaguchi; T. Gull; K. Davidson; R. Petre; D. J. Hillier; N. Smith; A. Damineli; J. A. Morse; N. R. Walborn; E. Verner; N. Collins; S. White; J. M. Pittard; K. Weis; D. Bomans; Y. Butt

2004-01-01

138

Stellar Wind Induced Soft X-Ray Emission from Close-in Exoplanets  

NASA Astrophysics Data System (ADS)

In this Letter, we estimate the X-ray emission from close-in exoplanets. We show that the Solar/Stellar Wind Charge Exchange Mechanism (SWCX), which produces soft X-ray emission, is very effective for hot Jupiters. In this mechanism, X-ray photons are emitted as a result of the charge exchange between heavy ions in the solar wind and the atmospheric neutral particles. In the solar system, comets produce X-rays mostly through the SWCX mechanism, but it has also been shown to operate in the heliosphere, in the terrestrial magnetosheath, and on Mars, Venus, and the Moon. Since the number of emitted photons is proportional to the solar wind mass flux, this mechanism is not very effective for the solar system giants. Here we present a simple estimate of the X-ray emission intensity that can be produced by close-in extrasolar giant planets due to charge exchange with the heavy ions of the stellar wind. Using the example of HD 209458b, we show that this mechanism alone can be responsible for an X-ray emission of ?1022 erg s–1, which is 106 times stronger than the emission from the Jovian aurora. We discuss also the possibility of observing the predicted soft X-ray flux of hot Jupiters and show that despite high emission intensities they are unobservable with current facilities.

Kislyakova, K. G.; Fossati, L.; Johnstone, C. P.; Holmström, M.; Zaitsev, V. V.; Lammer, H.

2015-02-01

139

Resonant Soft-x-ray Emission Spectroscopy of Liquids  

NASA Astrophysics Data System (ADS)

We present now a possible way to carry out soft-x-ray fluorescence spectroscopy of liquids. The liquid cell has a window to attain compatibility with UHV conditions of the spectrometer and beamline, The synchrotron radiation enters the liquid cell through a 100 nm-thick silicon nitride window and the emitted x-rays exit through the same window. This allows in particular liquid-solid interfaces to be studied. Such a liquid cell has been used to study the electronic structure of a variety of systems ranging from water solutions of inorganic salts and inertial drugs to nano materials and actinide compounds in their wet conditions.

Guo, J.-H.; Augustsson, A.; Englund, C.-J.; Nordgren, J.

2004-05-01

140

Detection of x-ray emission in a nanosecond discharge in air at atmospheric pressure.  

PubMed

Measurement of x-ray emission is an important parameter to investigate runaway behavior of fast electrons produced in nanosecond-pulse gas discharge. An online detection system of x rays is described in this paper, and the system consists of an x-ray detector with NaI (Tl) scintillator and photomultiplier tube, and an integrated multichannel analyzer. The system is responsible for detecting x-ray emission signal, processing the detected signals, and scaling the energy distribution. The calibration results show that every channel of the detection system represents a given x-ray energy and various x rays can be divided into different energy ranges between 10 and 130 keV. For a repetitive nanosecond-pulse breakdown between highly nonuniform gaps in open air, an energy distribution is obtained using the online detection system. It shows that the x-ray emission is a continuous spectrum and the x rays of above 60 keV dominate in the detected energy distribution. PMID:21198017

Zhang, Cheng; Shao, Tao; Yu, Yang; Niu, Zheng; Yan, Ping; Zhou, Yuanxiang

2010-12-01

141

A Comparison of X-Ray and Optical Emission in Cassiopeia A  

NASA Astrophysics Data System (ADS)

Broadband optical and narrowband Si XIII X-ray images of the young Galactic supernova remnant Cassiopeia A (Cas A) obtained over several decades are used to investigate spatial and temporal emission correlations on both large and small angular scales. The data examined consist of optical and near-infrared ground-based and Hubble Space Telescope images taken between 1951 and 2011, and of X-ray images from Einstein, ROSAT, and Chandra taken between 1979 and 2013. We find weak spatial correlations between the remnant's X-ray and optical emission features on large scales, but several cases of good optical/X-ray correlations on small scales for features which have brightened due to recent interactions with the reverse shock. We also find instances (1) where a time delay is observed between the appearance of a feature's optical and X-ray emissions, (2) of displacements of several arcseconds between a feature's X-ray and optical emission peaks, and (3) of regions showing no corresponding X-ray or optical emissions. To explain this behavior, we propose a highly inhomogeneous density model for Cas A's ejecta consisting of small, dense optically emitting knots (n ~102-3 cm-3) and a much lower density (n ~0.1-1 cm-3) diffuse X-ray emitting component often spatially associated with optical emission knots. The X-ray emitting component is sometimes linked to optical clumps through shock-induced mass ablation generating trailing material leading to spatially offset X-ray/optical emissions. A range of ejecta densities can also explain the observed X-ray/optical time delays since the remnant's ?5000 km s-1 reverse shock heats dense ejecta clumps to temperatures around 3 × 104 K relatively quickly, which then become optically bright while more diffuse ejecta become X-ray bright on longer timescales. Highly inhomogeneous ejecta as proposed here for Cas A may help explain some of the X-ray/optical emission features seen in other young core-collapse supernova remnants.

Patnaude, Daniel J.; Fesen, Robert A.

2014-07-01

142

Thermal X-Ray Iron Line Emission from the Galactic Center Black Hole Sagittarius A*  

E-print Network

We model thermal X-ray emission from the accreting supermassive black hole Sagittarius A* at the Galactic Center. For the region inside $1.^{\\prime\\prime}5$ of the center, we use a {generalized} radiatively inefficient accretion flow (RIAF) model, and for the region out to $10^{\\prime\\prime}$ we use published models of the ambient hot gas. We calculate the equivalent widths of Hydrogen-like and Helium-like emission lines of various elements, notably iron. We predict that a strong Helium-like iron line with an equivalent width $\\sim1$ keV should be emitted by both the external medium and the RIAF. The equivalent width in the external medium is sensitive to the metallicity $Z$ of the gas as well as the mean temperature. For reasonable choices of these parameters, the calculated results agree with Chandra's detection of an iron line with an equivalent width of 1.3 keV within $10^{\\prime\\prime}$. The emission from within $1.^{\\prime\\prime}5$ is not sensitive to the external temperature, but is sensitive to the density and, especially, temperature profile inside the Bondi radius. For the range of profiles we consider, we calculate the equivalent width of the iron line to be $\\sim0.6-1.5 (Z/Z_\\odot)$ keV, where $Z_\\odot$ is the solar metallicity. We present a new Chandra spectrum of the quiescent emission within $1.^{\\prime\\prime}5$ of Sgr A*. The measured equivalent width of the iron line is 0.7 keV. Although this measurement has a large uncertainty, it is consistent with our predictions, provided the metallicity of the gas is approximately solar.

Ya-Di Xu; Ramesh Narayan; Eliot Quataert; Feng Yuan; Frederick K. Baganoff

2005-11-19

143

X-Ray Emission from Nitrogen-Rich Wolf-Rayet Stars  

NASA Astrophysics Data System (ADS)

Wolf-Rayet (WR) stars are massive evolved stars approaching the end of their lives as supernovae. Previous studies have focused on X-ray bright WR+OB colliding wind binaries, but much less is known about the X-ray emission of single WR stars. We have initiated a survey of single (non-binary) nitrogen-rich (WN-type) stars aimed at determining their X-ray properties and identifying possible emission processes. We have recently detected X-rays from a WN2 and a WN6 star with Chandra and an observation of a WN4 star is pending. We propose here to use XMM EPIC to extend this exploratory survey to the later WN7 - WN9 spectral types, thus providing a first-look at X-ray properties across the full spectral sequence.

Skinner, Stephen

2008-10-01

144

On the diffuse X-ray emission from the Wolf-Rayet bubble NGC 2359  

NASA Astrophysics Data System (ADS)

A recent XMM-Newton observation has revealed diffuse X-ray emission inside the nebula NGC 2359 around the Wolf-Rayet star WR 7. Taking advantage of an improved point-source rejection and background subtraction, and a detailed comparison of optical and X-ray morphology, we have reanalysed these X-ray observations. Our analysis reveals diffuse X-ray emission from a blowout and the presence of emission at energies from 1.0 to 2.0 keV. The X-ray emission from NGC 2359 can be described by an optically thin plasma emission model, but contrary to previous analysis, we find that the chemical abundances of this plasma are similar to those of the optical nebula, with no magnesium enhancement, and that two components at temperatures T1 = 2 × 106 K and T2 = 5.7 × 107 K are required. The estimated X-ray luminosity in the 0.3-2.0 keV energy range is LX = 2 × 1033 erg s-1. The averaged rms electron density of the X-ray-emitting gas (ne ? 0.6 cm-3) reinforces the idea of mixing of material from the outer nebula into the hot bubble.

Toalá, J. A.; Guerrero, M. A.; Chu, Y.-H.; Gruendl, R. A.

2015-01-01

145

Impulsive phase of flares in soft X-ray emission  

NASA Technical Reports Server (NTRS)

Observations using the bent crystal spectrometer instrument on the Solar Maximum Mission show that turbulence and blue-shifted motions are characteristic of the soft X-ray plasma during the impulsive phase of flares, and are coincident with the hard X-ray bursts observed by the hard X-ray burst spectrometer. A method for analysing the Ca XIX and Fe XXV spectra characteristic of the impulsive phase is presented. Nonthermal widths and blue-shifted components in the spectral lines of Ca XIX and Fe XXV indicate the presence of turbulent velocities exceeding 100 km/s and upward motions of 300-400 km/s. The April 10, May 9, and June 29, 1980 flares are studied. The April 10 flare has two separated footpoints bright in hard X-rays. Plasma heated to temperatures greater than ten million K rises from the footpoints. During the three minutes in which the evaporation process occurs an energy of 3.7 x 10 to the 30th ergs. This is consistent with the above figures, allowing for loss by radiation and conduction.

Antonucci, E.; Gabriel, A. H.; Acton, L. W.; Leibacher, J. W.; Culhane, J. L.; Rapley, C. G.; Doyle, J. G.; Machado, M. E.; Orwig, L. E.

1982-01-01

146

The Chandra Planetary Nebula Survey (CHANPLANS). II. X-Ray Emission from Compact Planetary Nebulae  

NASA Astrophysics Data System (ADS)

We present results from the most recent set of observations obtained as part of the Chandra X-ray observatory Planetary Nebula Survey (CHANPLANS), the first comprehensive X-ray survey of planetary nebulae (PNe) in the solar neighborhood (i.e., within ~1.5 kpc of the Sun). The survey is designed to place constraints on the frequency of appearance and range of X-ray spectral characteristics of X-ray-emitting PN central stars and the evolutionary timescales of wind-shock-heated bubbles within PNe. CHANPLANS began with a combined Cycle 12 and archive Chandra survey of 35 PNe. CHANPLANS continued via a Chandra Cycle 14 Large Program which targeted all (24) remaining known compact (R neb <~ 0.4 pc), young PNe that lie within ~1.5 kpc. Results from these Cycle 14 observations include first-time X-ray detections of hot bubbles within NGC 1501, 3918, 6153, and 6369, and point sources in HbDs 1, NGC 6337, and Sp 1. The addition of the Cycle 14 results brings the overall CHANPLANS diffuse X-ray detection rate to ~27% and the point source detection rate to ~36%. It has become clearer that diffuse X-ray emission is associated with young (lsim 5 × 103 yr), and likewise compact (R neb <~ 0.15 pc), PNe with closed structures and high central electron densities (ne >~ 1000 cm-3), and is rarely associated with PNe that show H2 emission and/or pronounced butterfly structures. Hb 5 is one such exception of a PN with a butterfly structure that hosts diffuse X-ray emission. Additionally, two of the five new diffuse X-ray detections (NGC 1501 and NGC 6369) host [WR]-type central stars, supporting the hypothesis that PNe with central stars of [WR]-type are likely to display diffuse X-ray emission.

Freeman, M.; Montez, R., Jr.; Kastner, J. H.; Balick, B.; Frew, D. J.; Jones, D.; Miszalski, B.; Sahai, R.; Blackman, E.; Chu, Y.-H.; De Marco, O.; Frank, A.; Guerrero, M. A.; Lopez, J. A.; Zijlstra, A.; Bujarrabal, V.; Corradi, R. L. M.; Nordhaus, J.; Parker, Q. A.; Sandin, C.; Schönberner, D.; Soker, N.; Sokoloski, J. L.; Steffen, M.; Toalá, J. A.; Ueta, T.; Villaver, E.

2014-10-01

147

Characterization of nuclear physics targets using Rutherford backscattering and particle induced x-ray emission  

E-print Network

Rutherford backscattering and particle induced x-ray emission have been utilized to precisely characterize targets used in nuclear fission experiments. The method allows for a fast and non destructive determination of target thickness, homogeneity and element composition.

Th. Rubehn; G. J. Wozniak; L. Phair; L. G. Moretto; Kin M. Yu

1996-09-23

148

Chandra Observations of Nuclear X-ray Emission from a Sample of Radio Sources  

E-print Network

We present the X-ray properties of a sample of 17 radio sources observed with the Chandra X-ray Observatory as part of a project aimed at studying the X-ray emission from their radio jets. In this paper, we concentrate on the X-ray properties of the unresolved cores. The sample includes 16 quasars (11 core-dominated and 5 lobe-dominated) in the redshift range z=0.30--1.96, and one low-power radio-galaxy at z=0.064. No diffuse X-ray emission is present around the cores of the quasars, except for the nearby low-power galaxy that has diffuse emission on a scale and with a luminosity consistent with other FRIs. No high-amplitude, short-term variability is detected within the relatively short Chandra exposures. However, 1510-089 shows low-amplitude flux changes with a timescale of $\\sim$25 minutes. The X-ray spectra of the quasar cores are generally well described by a single power law model with Galactic absorption. However, in six quasars we find soft X-ray excess emission below 1.6 keV. Interestingly, we detect...

Gambill, J K; Chartas, G; Cheung, C C; Maraschi, L; Tavecchio, F; Urry, C M; Pesce, J E

2003-01-01

149

Measurements of Peak X-ray Emission of imploding DT capsules using X-ray Diagnostics at the National Ignition Facility  

NASA Astrophysics Data System (ADS)

The absolute time (bang time) and burn width of the x-ray emission from the imploding cores of deuterium-tritium capsules near peak compression are measured by several different but complimentary diagnostic instruments. These instruments report independent measurements for the bang time (BT) and burn width (BW). A summary of the results from recent DT experiments is presented contrasting the BT and BW reported by: SPIDER, an x-ray streak camera; Gamma Ray History, a gamma ray detector; and Hardened X-ray Gated Imager (HGXI), a gated micro-channel plate coupled to film camera. An evaluation of the shielding and design of the instruments is presented in order to compare the spectral sensitivity of the instruments. Simulations of the x-ray emission spectrum are examined with the results reported by these x-ray diagnostics.

Khan, Shahab; Macphee, Andrew; Izumi, Nobuhiko; Glenn, Steve; Kimbrough, Joe; Herrmann, Hans; Church, Jennifer; Bell, Perry; Bradley, David

2012-10-01

150

Laboratory simulation of charge exchange-produced X-ray emission from comets.  

PubMed

In laboratory experiments using the engineering spare microcalorimeter detector from the ASTRO-E satellite mission, we recorded the x-ray emission of highly charged ions of carbon, nitrogen, and oxygen, which simulates charge exchange reactions between heavy ions in the solar wind and neutral gases in cometary comae. The spectra are complex and do not readily match predictions. We developed a charge exchange emission model that successfully reproduces the soft x-ray spectrum of comet Linear C/1999 S4, observed with the Chandra X-ray Observatory. PMID:12791989

Beiersdorfer, P; Boyce, K R; Brown, G V; Chen, H; Kahn, S M; Kelley, R L; May, M; Olson, R E; Porter, F S; Stahle, C K; Tillotson, W A

2003-06-01

151

Design of a novel transmission-grating spectrometer for soft X-ray emission studies  

Microsoft Academic Search

The design of a transmission-grating spectrometer for high-resolution soft X-ray emission studies has been proposed. It is different from conventional types of soft X-ray emission spectrometers; that is, the spectrometer has a Wolter type I mirror, a free-standing transmission grating, and a back-illuminated CCD. A high collection angle up to 1.5×10?3sr is achieved by utilizing the Wolter mirror as a

Takaki Hatsui; Hiroyuki Setoyama; Eiji Shigemasa; Nobuhiro Kosugi

2005-01-01

152

X-ray emission from clusters and groups of galaxies  

NASA Technical Reports Server (NTRS)

Recent major advances in x-ray imaging and spectroscopy of clusters have allowed the determination of their mass and mass profile out to approximately 1/2 the virial radius. In rich clusters, most of the baryonic mass is in the gas phase, and the ratio of mass in gas/stars varies by a factor of 2-4. The baryonic fractions vary by a factor of approximately 3 from cluster to cluster and almost always exceed 0.09 h50-[3/2] and thus are in fundamental conflict with the assumption of Omega = 1 and the results of big bang nucleosynthesis. The derived Fe abundances are 0.2-0.45 solar, and the abundances of O and Si for low redshift systems are 0.6-1.0 solar. This distribution is consistent with an origin in pure type II supernova. The amount of light and energy produced by these supernovae is very large, indicating their importance in influencing the formation of clusters and galaxies. The lack of evolution of Fe to a redshift of z approximately 0.4 argues for very early enrichment of the cluster gas. Groups show a wide range of abundances, 0.1-0.5 solar. The results of an x-ray survey indicate that the contribution of groups to the mass density of the universe is likely to be larger than 0.1 h50-2. Many of the very poor groups have large x-ray halos and are filled with small galaxies whose velocity dispersion is a good match to the x-ray temperatures.

Mushotzky, R.

1998-01-01

153

Varieties of WN star X-ray Emission Mechanisms  

NASA Astrophysics Data System (ADS)

The extreme range of physical conditions in the winds of Wolf-Rayet stars of the nitrogen sequence in terms of density, velocity and chemical composition gives more leverage to attack the unsolved origin of X-rays from hot stars than available through the more homogenous O stars. We propose to obtain EPIC spectra of 4 prominent WN stars, including two single stars and two binaries, in order to explore both ends of the luminosity distribution.

Pollock, Andrew

2007-10-01

154

Molybdenum and chlorine x-ray emission from Alcator A  

SciTech Connect

High-resolution (..delta..lambda/lambda approx. = 0.015) x-ray spectra in the wavelength region 3.7 ..-->.. 6.2 A (3.4 ..-->.. 2.0 keV) have been collected from the Alcator tokamak using a flat crystal Bragg monochromator. Molybdenum L lines and chlorine K lines have been observed and charge-state identifications have been made by comparison with calculations.

Rice, J.E.; Marmar, E.S.; Coan, T.; Allen, S.L.; Cowan, R.D.

1980-07-01

155

Alpha Particle Induced X-ray Emission in the Classroom  

SciTech Connect

We report on an experimental demonstration in an introductory modern physics course to elucidate the X-ray line spectra, and how they arise from transitions of electrons to inner shells. We seek to determine the effect of limited use of an interactive component as a supplement to a traditional lecture, and how it would improve the student achievement. In this preliminary study the students were exposed to traditional lectures on X-ray production and Bohr's model, they then were given a homework on the abc of X-ray spectra, after which they were given a pre-test on the materials, followed by an in-class demonstration, and a final post-exam. The gain, as measured from pre- to post-exams appears to remark the differences in how students approached the subject before and after the use of the demonstration. This initial study shows the validity of in-class demonstrations as teaching tools and opens a wide new area of research in modern physics teaching.

Lopez, Jorge A.; Borunda, Mario F.; Morales, Jaime [Department of Physics, University of Texas at El Paso, El Paso, Texas 79968 (United States)

2003-08-26

156

Discovery of Oxygen Kalpha X-ray Emission from the Rings of Saturn  

E-print Network

Using the Advanced CCD Imaging Spectrometer (ACIS), the Chandra X-ray Observatory (CXO) observed the Saturnian system for one rotation of the planet (~37 ks) on 20 January, 2004, and again on 26-27 January, 2004. In this letter we report the detection of X-ray emission from the rings of Saturn. The X-ray spectrum from the rings is dominated by emission in a narrow (~130 eV wide) energy band centered on the atomic oxygen K-alpha fluorescence line at 0.53 keV. The X-ray power emitted from the rings in the 0.49-0.62 keV band is 84 MW, which is about one-third of that emitted from Saturn disk in the photon energy range 0.24-2.0 keV. Our analysis also finds a clear detection of X-ray emission from the rings in the 0.49-0.62 keV band in an earlier (14-15 April, 2003) Chandra ACIS observation of Saturn. Fluorescent scattering of solar X-rays from oxygen atoms in the H2O icy ring material is the likely source mechanism for ring X-rays, consistent with the scenario of solar photo-production of a tenuous ring oxygen atmosphere and ionosphere recently discovered by Cassini.

Anil Bhardwaj; Ronald F. Elsner; J. Hunter Waite, Jr.; G. Randall Gladstone; Thomas E. Cravens; Peter G. Ford

2005-05-19

157

A unified model of accretion flows and X ray emission in low mass X ray binary systems  

NASA Technical Reports Server (NTRS)

Recent work on a unified model of accretion flows and X-ray emission in low mass X-ray binaries is summarized. In this model, a weakly magnetic neutron star accretes gas simultaneously from a Keplerian disk and a corona above the inner part of the disk. Photons are produced and escape through an approximately radial inflow of gas captured from the inner disk corona. Changes in the optical depths of the central corona and the radial flow may explain the Z-shaped hardness-intensity and color-color tracks observed in the most luminous sources. Numerical simulations show that the radial flow oscillates when the luminosity rises to within a few percent of the Eddington critical luminosity L sub E, and that the oscillation frequency is approximately 5 to 10 Hz if the radial flow develops approximately 300 km from the neutron star. The 10 to 20 Hz oscillations observed in Sco X-1 when it is on the flaring branch are discussed.

Lamb, F. K.

1989-01-01

158

Waiting in the Wings: Reflected X-ray Emission from the Homunculus Nebula  

E-print Network

We report the first detection of X-ray emission associated with the Homunculus Nebula which surrounds the supermassive star Eta Carinae. The emission is characterized by a temperature in excess of 100 MK, and is consistent with scattering of the time-delayed X-ray flux associated with the star. The nebular emission is bright in the northwestern lobe and near the central regions of the Homunculus, and fainter in the southeastern lobe. We also report the detection of an unusually broad Fe K fluorescent line, which may indicate fluorescent scattering off the wind of a companion star or some other high velocity outflow. The X-ray Homunculus is the nearest member of the small class of Galactic X-ray reflection nebulae, and the only one in which both the emitting and reflecting sources are distinguishable.

M. F. Corcoran; K. Hamaguchi; T. Gull; K. Davidson; R. Petre; D. J. Hillier; N. Smith; A. Damineli; J. A. Morse; N. R. Walborn; E. Verner; N. Collins; S. White; J. M. Pittard; K. Weis; D. Bomans; Y. Butt

2004-06-07

159

Waiting in the Wings: Reflected X-ray Emission from the Homunculus Nebula  

NASA Technical Reports Server (NTRS)

We report the first detection of X-ray emission associated with the Homunculus Nebula which surrounds the supermassive star eta Carinae. The emission is characterized by a temperature in excess of 100 MK, and is consistent with scattering of the time-delayed X-ray flux associated with the star. The nebular emission is bright in the northwestern lobe and near the central regions of the Homunculus, and fainter in the southeastern lobe. We also report the detection of an unusually broad Fe K fluorescent line, which may indicate fluorescent scattering off the wind of a companion star or some other high velocity outflow. The X-ray Homunculus is the nearest member of the small class of Galactic X-ray reflection nebulae, and the only one in which both the emitting and reflecting sources are distinguishable.

Corcoran, M. F.; Hamaguchi, K.; Gull, T.; Davidson, K.; Petre, R.; Hillier, D. J.; Smith, N.; Damineli, A.; Morse, J. A.; Walborn, N. R.

2004-01-01

160

Waiting in the Wings: Reflected X-ray Emission from the Homunculus Nebula  

E-print Network

We report the first detection of X-ray emission associated with the Homunculus Nebula which surrounds the supermassive star Eta Carinae. The emission is characterized by a temperature in excess of 100 MK, and is consistent with scattering of the time-delayed X-ray flux associated with the star. The nebular emission is bright in the northwestern lobe and near the central regions of the Homunculus, and fainter in the southeastern lobe. We also report the detection of an unusually broad Fe K fluorescent line, which may indicate fluorescent scattering off the wind of a companion star or some other high velocity outflow. The X-ray Homunculus is the nearest member of the small class of Galactic X-ray reflection nebulae, and the only one in which both the emitting and reflecting sources are distinguishable.

Corcoran, M F; Gull, T R; Davidson, K; Petre, R; Hillier, D J; Smith, N; Damineli, A; Morse, J A; Walborn, N R; Verner, E; Collins, N; White, S; Pittard, J M; Weis, K; Bomans, D; Butt, Y

2004-01-01

161

Recurrent X-ray Emission Variations of Eta Carinae and the Binary Hypothesis  

NASA Technical Reports Server (NTRS)

Recent studies suggest that, the super-massive star eta Carinae may have a massive stellar companion (Damineli, Conti, and Lopes 1997), although the dense ejecta surrounding the star make this claim hard to test using conventional methods. Settling this question is critical for determining the current evolutionary state and future evolution of the star. We address this problem by an unconventional method: If eta Carinae is a binary, X-ray emission should be produced in shock waves generated by wind-wind collisions in the region between eta Carinae and its companion. Detailed X-ray monitoring of eta Carinae for more that) 2 years shows that the observed emission generally resembles colliding-wind X-ray emission, but with some significant discrepancies. Furthermore, periodic X-ray "flaring" may provide an additional clue to determine the presence of a companion star and for atmospheric pulsation in eta Carinae.

Ishibashi, K.; Corcoran, M. F.; Davidson, K.; Swank, J. H.; Petre, R.; Drake, S. A.; Damineki, A.; White, S.

1998-01-01

162

Generation Mechanisms UV and X-ray Emissions During SL9 Impact  

NASA Technical Reports Server (NTRS)

The purpose of this grant was to study the ultraviolet and X-ray emissions associated with the impact of comet Shoemaker-Levy 9 with Jupiter. The University of Michigan task was primarily focused on theoretical calculations. The NAGW-4788 subtask was to be largely devoted to determining the constraints placed by the X-ray observations on the physical mechanisms responsible for the generation of the X-rays. Author summarized below the ROSAT observations and suggest a physical mechanism that can plausibly account for the observed emissions. It is hoped that the full set of activities can be completed at a later date. Further analysis of the ROSAT data acquired at the time of the impact was necessary to define the observational constraints on the magnetospheric-ionospheric processes involved in the excitation of the X-ray emissions associated with the fragment impacts. This analysis centered around improvements in the pointing accuracy and improvements in the timing information. Additional pointing information was made possible by the identification of the optical counterparts to the X-ray sources in the ROSAT field-of-view. Due to the large number of worldwide observers of the impacts, a serendipitous visible plate image from an observer in Venezuela provided a very accurate location of the present position of the X-ray source, virtually eliminating pointing errors in the data. Once refined, the pointing indicated that the two observed X-ray brightenings that were highly correlated in time with the K and P2 events were brightenings of the X-ray aurora (as identified in images prior to the impact).Appendix A "ROSAT observations of X-ray emissions from Jupiter during the impact of comet Shoemaker-Levy 9' also included.

Waite, J. Hunter, Jr.

1997-01-01

163

SphinX Measurements of the 2009 Solar Minimum X-Ray Emission  

NASA Astrophysics Data System (ADS)

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.

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

2012-06-01

164

A Chandra X-ray Study of NGC 1068 - I. Observations of Extended Emission  

E-print Network

We report sub arc-second resolution X-ray imaging-spectroscopy of the archetypal type 2 Seyfert galaxy NGC 1068 with the Chandra X-ray Observatory. The observations reveal the detailed structure and spectra of the 13 kpc-extent nebulosity previously imaged at lower resolution with ROSAT. The Chandra image shows a bright, compact source coincident with the brightest radio and optical emission; this source is extended by \\simeq 1.5 arcsec (165 pc) in the same direction as the nuclear optical line and radio continuum emission. Bright X-ray emission extends \\simeq 5 arcsec (550 pc) to the NE and coincides with the NE radio lobe and gas in the narrow line region. The large-scale emission shows trailing spiral arms and other structures. Numerous point sources associated with NGC 1068 are seen. There is a very strong correlation between the X-ray emission and the high excitation ionized gas seen in HST and ground-based [O III] \\lambda 5007 images. The X-rays to the NE of the nucleus are absorbed by only the Galactic column density and thus originate from the near side of the disk of NGC 1068. In contrast the X-rays to the SW are more highly absorbed and must come from gas in the disk or on the far side of it. This geometry is similar to that inferred for the narrow line region and radio lobes. (Abstract truncated).

A. J. Young; A. S. Wilson; P. L. Shopbell

2001-04-02

165

SphinX MEASUREMENTS OF THE 2009 SOLAR MINIMUM X-RAY EMISSION  

SciTech Connect

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 Multiplication-Sign 10{sup 47} cm{sup -3} and 1.1 Multiplication-Sign 10{sup 48} cm{sup -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.

Sylwester, J.; Kowalinski, M.; Gburek, S.; Siarkowski, M.; Bakala, J.; Gryciuk, M.; Podgorski, P.; Sylwester, B. [Space Research Centre, Polish Academy of Sciences, 51-622, Kopernika 11, Wroclaw (Poland); Kuzin, S. [P. N. Lebedev Physical Institute (FIAN), Russian Academy of Sciences, Leninsky Prospect 53, Moscow 119991 (Russian Federation); Farnik, F. [Astronomical Institute, Ondrejov Observatory (Czech Republic); Reale, F. [Dipartimento di Fisica, Universita di Palermo, Palermo, Italy, and INAF, Osservatorio Astronomico di Palermo, Palermo (Italy); Phillips, K. J. H., E-mail: js@cbk.pan.wroc.pl [Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, Surrey RH5 6NT (United Kingdom)

2012-06-01

166

Evolution of X-ray emission from young massive star clusters  

E-print Network

The evolution of X-ray emission from young massive star clusters is modeled, taking into account the emission from the stars as well as from the cluster wind. It is shown that the level and character of the soft (0.2-10 keV) X-ray emission change drastically with cluster age and are tightly linked with stellar evolution. Using the modern X-ray observations of massive stars we show that the correlation between bolometric and X-ray luminosity known for single O stars also holds for O+O and O+Wolf-Rayet (WR) binaries. The diffuse emission originates from the cluster wind heated by the kinetic energy of stellar winds and supernova explosions. To model the evolution of the cluster wind, the mass and energy yields from a population synthesis are used as input to a hydrodynamic model. It is shown that in a very young clusters the emission from the cluster wind is low. When the cluster evolves, WR stars are formed. Their strong stellar winds power an increasing X-ray emission of the cluster wind. Subsequent supernova explosions pump the level of diffuse emission even higher. Clusters at this evolutionary stage may have no X-ray bright stellar point sources, but a relatively high level of diffuse emission. A supernova remnant may become a dominant X-ray source, but only for a short time interval of a few thousand years. We retrieve and analyse Chandra and XMM-Newton observations of six massive star clusters located in the Large Magellanic Cloud. Our model reproduces the observed diffuse and point-source emission from these LMC clusters, as well as from the Galactic clusters Arches, Quintuplet and NGC 3603.

L. M. Oskinova

2005-05-25

167

Clumped X-ray emission around radio galaxies in Abell clusters  

NASA Technical Reports Server (NTRS)

We have made a comparison of the X-ray and radio morphologies for a sample of 41 rich cluster fields using Einstein Observatory Imaging Proportional Counter (IPC) and Very Large Array (VLA) 20 cm images. Surprisingly, we find that 75% of the radio galaxies have a statistically significant X-ray peak or subclump within 5 min of the radio galaxy position. The X-ray luminosity and the generally extended nature of the X-ray subclumps suggest that these subclumps are overdense regions emitting free-free radiation, although there is also evidence for Active Galactic Nuclei (AGN) X-ray emission coming from some of the more compact, high surface brightness X-ray peaks. Some interesting correlations with radio morphology were also discovered. For clusters which contain wide-angle-tailed radio sources associated with centrally dominant galaxies, there are significant elongations or clumps in the central X-ray emission which are unusual for this type of cluster. We suggest that cluster radio galaxies are pointers to particular clusters or regions within clusters that have recently undergone mergers between cluster subsystems.

Burns, Jack O.; Rhee, George; Owen, Frazer N.; Pinkney, Jason

1994-01-01

168

Relation between X-Ray and ?-Ray Emissions for Fermi Blazars  

NASA Astrophysics Data System (ADS)

Using ?-ray band data detected by Fermi Large Area Telescope (LAT) and X-ray band data for 78 blazars, we find a medium correlation between X-ray and ?-ray fluxes in the average state. A medium anticorrelation is also found between X-ray (1KeV) mean spectral index ? x and ?-ray mean spectral index ? ? for blazars. Our results suggest that the most likely radiation mechanism for the high energy ?-ray would be SSC. And that the ?-ray emission mechanism may be somewhat different for BL Lacs and FSRQs.

Li, Bijun; Zhang, Xiong

2014-11-01

169

RX J1838.4-0301: an accreting pulsar or coronal X-ray emission?  

NASA Astrophysics Data System (ADS)

The X-ray source RX J1838.4-0301 is of particular interest since it is a possible member of a small subclass of pulsars with anomalous properties. A spectroscopic study of its proposed optical counterpart and a reanalysis of the ROSAT data indicate that the observed optical and X-ray properties, with the exception of the reported ~5 s periodicity (Schwentker 1994), are consistent with coronal emission from an active late type star. In the lack of an independent confirmation, the presence of X-ray pulsations in RX J1838.4-0301 should be considered with caution.

Mereghetti, S.; Belloni, T.; Nasuti, F. P.

1997-05-01

170

Chandra Observations and Modeling of Geocoronal Charge Exchange X-Ray Emission During Solar Wind Gusts  

NASA Astrophysics Data System (ADS)

Solar wind charge exchange (SWCX) X-rays are emitted when highly charged solar wind ions such as O7+ collide with neutral gas. The best known examples of this occur around comets, but SWCX emission also arises in the Earth's tenuous outer atmosphere and throughout the heliosphere as neutral H and He from the interstellar medium flows into the solar system. This geocoronal and heliospheric emission comprises much of the soft X-ray background and is seen in every X-ray observation. Geocoronal emission, although usually weaker than heliospheric emission, arises within a few tens of Earth radii and therefore responds much more quickly (on time scales of less than an hour) to changes in solar wind intensity than the widely distributed heliospheric emission.We have studied a dozen Chandra observations when the flux of solar wind protons and O7+ ions was at its highest. These gusts of wind cause correspondingly abrupt changes in geocoronal SWCX X-ray emission,which may or may not be apparent in Chandra data depending on a given observation's line of sight through the magnetosphere. We compare observed changes in the X-ray background with predictions from a fully 3D analysis of SWCX emission based on magnetospheric simulations using the BATS-R-US model.

Kornbleuth, Marc; Wargelin, Bradford J.; Juda, Michael

2014-06-01

171

Galactic Ridge X-ray Emission study with NuSTAR  

NASA Astrophysics Data System (ADS)

The paradigm of the Galactic Ridge X-ray Emission (GRXE) or hard X-ray background of the Milky Way has been dramatically changed over the past years. The stellar origin of the GRXE has been strongly supported by morphological and spectral studies with RXTE, INTEGRAL and Chandra observatories. The GRXE does not arise from the interaction of cosmic rays with the interstellar medium, as was believed before, but is associated with the (predominantly old) stellar population of the Galaxy, namely with hard X-ray emission from accreting white dwarfs and coronaly active stars. I will present results of the GRXE spectral study with NuSTAR hard X-ray mission launched into the orbit in 2012. The GRXE measurements have been done in a part of the Galactic Center survey program 2012-2014. New data allow us to reconstruct both GRXE spatial distribution and broadband (3-80 keV) spectrum, providing another test for its interpretation.

Krivonos, Roman; NuSTAR

2015-01-01

172

The origin of the X-ray emission from the enigmatic multiple system HBC 515  

NASA Astrophysics Data System (ADS)

HBC 515 is a recently discovered, intriguing, multiple pre-main sequence system located in the L1622 molecular cloud and, with an X-ray luminosity of Lx 10^{32} erg/s, it is one of the brightest X-ray sources in Orion. HBC 515 is composed of a very young (age<1 Myr) intermediate-mass ( 2 M_sun) binary, whose circumstellar disk has already dispersed and a class I/II object surrounded by a thick envelope of gas and dust. It is not clear what physical mechanism has triggered the fast disk dispersal. There are two possibilities: dynamical interaction between the components of the multiple system, or photoevaporation due to its X-ray emission. We propose a 30 ks ACIS-I observation of HBC 515 to pinpoint the sources of its X-ray emission and, thereby, distinguish between these alternatives.

Sacco, Giuseppe

2010-09-01

173

A carbon nanotube field emission multipixel x-ray array source for microradiotherapy application  

PubMed Central

The authors report a carbon nanotube (CNT) field emission multipixel x-ray array source for microradiotherapy for cancer research. The developed multipixel x-ray array source has 50 individually controllable pixels and it has several distinct advantages over other irradiation source including high-temporal resolution (millisecond level), the ability to electronically shape the form, and intensity distribution of the radiation fields. The x-ray array was generated by a CNT cathode array (5×10) chip with electron field emission. A dose rate on the order of >1.2 Gy?min per x-ray pixel beam is achieved at the center of the irradiated volume. The measured dose rate is in good agreement with the Monte Carlo simulation result. PMID:21691440

Wang, Sigen; Calderon, Xiomara; Peng, Rui; Schreiber, Eric C.; Zhou, Otto; Chang, Sha

2011-01-01

174

The Morphology of the X-ray Emission above 2 keV from Jupiter's Aurorae  

NASA Technical Reports Server (NTRS)

The discovery in XMM-Newton X-ray data of X-ray emission above 2 keV from Jupiter's aurorae has led us to reexamine the Chandra ACIS-S observations taken in Feb 2003. Chandra's superior spatial resolution has revealed that the auroral X-rays with E > 2 keV are emitted from the periphery of the region emitting those with E < 1 keV. We are presently exploring the relationship of this morphology to that of the FUV emission from the main auroral oval and the polar cap. The low energy emission has previously been established as due to charge exchange between energetic precipitating ions of oxygen and either sulfur or carbon. It seems likely to us that the higher energy emission is due to precipitation of energetic electrons, possibly the same population of electrons responsible for the FUV emission. We discuss our analysis and interpretation.

Elsner, R.; Branduardi-Raymont, G.; Galand, M.; Grodent, D.; Waite, J. H.; Cravens, T.; Ford, P.

2007-01-01

175

The Morphology of the X-ray Emission above 2 keV from Jupiter's Aurorae  

NASA Technical Reports Server (NTRS)

The discovery in XMM-Newton X-ray data of X-ray emission above 2 keY from Jupiter's aurorae has led us to reexamine the Chandra ACIS-S observations taken in Feb 2003. Chandra's superior spatial resolution has revealed that the auroral X-rays with E > 2 keV are emitted from the periphery of the region emitting those with E < 1 keV. We are presently exploring the relationship of this morphology to that of the FUV emission from the main auroral oval and the polar cap. The low energy emission has previously been established as due to charge exchange between energetic precipitating ions of oxygen and either sulfur or carbon. It seems likely to us that the higher energy emission is due to precipitation of energetic electrons, possibly the same population of electrons responsible for the FUV emission. We discuss our analysis and interpretation.

Elsner, R.; Branduardi-Raymont, G.; Galand, M.; Grodent, D.; Gladstone, G. R.; Waite, J. H.; Cravens, T.; Ford, P.

2007-01-01

176

Extended X-ray emission from the BL Lac object PKS 0521-365  

E-print Network

Models that seek to unify BL Lacs and low-power radio galaxies predict that the two types of object should show similar isotropically emitted X-ray emission. Testing this is usually limited by difficulties in separating strong X-ray emission from a BL Lac nucleus and surrounding low-surface brightness emission. In this paper we report ROSAT HRI observations of the z=0.055 BL Lac object PKS 0521-365. We are able to separate a luminous extended X-ray component from the bright nucleus. Using a new radio map, we show that it is unlikely that the extended emission is due to inverse-Compton scattering of photons from the active nucleus, and instead interpret it as thermal emission from dense, rapidly cooling gas. This is a more extreme environment than is found in typical FRI radio galaxies, and may pose a problem for unified models.

M. J. Hardcastle; D. M. Worrall; M. Birkinshaw

1998-12-08

177

Thermal X-Ray Emission and Cosmic-Ray Production in Young Supernova Remnants  

Microsoft Academic Search

We have developed a simple model to investigate the modifications of the hydrodynamics and nonequilibrium ionization X-ray emission in young supernova remnants due to nonlinear particle acceleration. In nonlinear, diffusive shock acceleration, the heating of the gas to X-ray-emitting temperatures is strongly coupled to the acceleration of cosmic-ray ions. If the acceleration is efficient and a significant fraction of the

Anne Decourchelle; Donald C. Ellison; Jean Ballet

2000-01-01

178

X-ray emission from Ap/Bp stars Bridging cool and hot stars  

E-print Network

overlap with late B-type stars X-rays from magnetic Ap/Bp stars IQ Aur (A0p) as prototype latest X Aur and the MCWS model X-ray emission from magnetically confined wind-shocks MCWS model (Babel Ap/Bp stars 27.06.2011 7 / 16 #12;A0p stars - not just wind shocks?! XMM-Newton observation of IQ Aur

Robrade, Jan

179

A model of hard X-rays emission from free expanding Plasma-Focus discharges  

NASA Astrophysics Data System (ADS)

A planar-piston model of the hard x-ray production in Plasma-Focus devices is presented. The model applies Von Karman approximations to represent the inner structure of the pinch. The hard x-ray emission is calculated assuming Bremsstrahlung from the collision on the anode base of an electron current running away from the pinch. The model was applied to analyse the experimental data of a small Plasma Focus without surrounding cathode, founding good agreement.

Fogliatto, E.; González, J.; Barbaglia, M.; Clausse, A.

2014-05-01

180

Chasing coronaij x-ray emission to the end of the pleiades main sequence ... and beyond?  

Microsoft Academic Search

We have used a 40-ks XMM-Newton observation to examine the X-ray emission of 33 proposed M-type members in. the core of the Pleiades. We reach a limiting X-ray luminosity of LX ~ × 1027 erg s-1 in the field centre and detect 17 of 19 members with MIc < 10.5 (where MIc is absolute magnitude in the Cousins I band,

K. R. Briggs; J. P. Pye

2003-01-01

181

Chasing coronaij x-ray emission to the end of the pleiades main sequence … and beyond?  

Microsoft Academic Search

We have used a 40-ks XMM-Newton observation to examine the X-ray emission of 33 proposed M-type members in. the core of the Pleiades. We reach a limiting X-ray luminosity of LX ? × 1027 erg s?1 in the field centre and detect 17 of 19 members with MIc < 10.5 (where MIc is absolute magnitude in the Cousins I band,

K. R. Briggs; J. P. Pye

2003-01-01

182

Soft x-ray emission studies of the electronic structure in silicon nanoclusters  

SciTech Connect

Density of states changes in the valence and conduction band of silicon nanoclusters were monitored using soft x-ray emission and absorption spectroscopy as a function of cluster size. a progressive increase in the valence band edge toward lower energy is found fro clusters with decreasing diameters. A similar but smaller shift is observed in the near-edge x-ray absorption data of the silicon nanoclusters.

Van Buuren, T.; Dinh, L.N.; Chase, L.L.; Siekhaus, W.J.; Jumenez, I.; Terminello, L.J.; Grush, M.; Callcott, T.A.; Carlisle, J.A.

1997-02-01

183

X-ray emission from laser-generated plasmas recorded by a transmission crystal spectrometer  

Microsoft Academic Search

A transmission crystal spectrometer was utilized to record the hard x-ray spectra from laser-produced plasmas in the 12 keV to 60 keV energy range and with a resolving power of E\\/DeltaE?100. This emission is of interest for the development of hard x-ray backlighters and hot electron diagnostics. Planar foils of U and Pb were irradiated at the OMEGA laser facility

John F. Seely; Rami Doron; Avi Bar-Shalom; Lawrence T. Hudson; Christian Stoeckl

2004-01-01

184

X-ray Emission from Pre-Main-Sequence Stars - Testing the Solar Analogy  

NASA Technical Reports Server (NTRS)

This LTSA award funded my research on the origin of stellar X-ray emission and the validity of the solar-stellar analogy. This research broadly addresses the relevance of our current understanding of solar X-ray physics to the interpretation of X-ray emission from stars in general. During the past five years the emphasis has been on space-based X-ray observations of very young stars in star-forming regions (T Tauri stars and protostars), cool solar-like G stars, and evolved high-mass Wolf-Rayet (WR) stars. These observations were carried out primarily with the ASCA and ROSAT space-based observatories (and most recently with Chandra), supplemented by ground-based observations. This research has focused on the identification of physical processes that are responsible for the high levels of X-ray emission seen in pre-main-sequence (PMS) stars, active cool stars, and WR stars. A related issue is how the X-ray emission of such stars changes over time, both on short timescales of days to years and on evolutionary timescales of millions of years. In the case of the Sun it is known that magnetic fields play a key role in the production of X-rays by confining the coronal plasma in loop-like structures where it is heated to temperatures of several million K. The extent to which the magnetically-confined corona interpretation can be applied to other X-ray emitting stars is the key issue that drives the research summarized here.

Skinner, Stephen L.

2000-01-01

185

Relating magnetic field strengths to hard X-ray emission in solar flares  

Microsoft Academic Search

The observation of hard X-ray (HXR) emission in solar flares provides important diagnostic information about the acceleration and subsequent transport of energetic electrons in the flare process. However, while hard X-rays are thought to be emitted from the flare footpoints through thick-target bremsstrahlung interactions, the details of the transport of accelerated electrons through the solar atmosphere still remains unclear. Trapping

C. P. Goff; S. A. Matthews; L. van Driel-Gesztelyi; L. K. Harra

2004-01-01

186

Hard X-Ray Emission and the Ionizing Source in LINERs  

NASA Technical Reports Server (NTRS)

We report X-ray luminosities of 21 LINERs (low-ionization nuclear emission-line regions) and 17 low-luminosity Seyferts obtained with ASCA and discuss the ionizing source in LINERs. Most LINERs with broad H-alpha emission in their optical spectra (LINER 1s) have a compact hard X-ray source and their 2-10 keV X-ray luminosities (LX) are proportional to their H alpha luminosities (L-H-alpha). This correlation strongly supports the hypothesis that the dominant ionizing source in LINER 1s is photoionization by hard photons from low-luminosity AGNs. Although some LINERs without broad H-alpha emission (LINER 2s) have X-ray properties similar to LINER 1s, the X-ray luminosities of many 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 something other than an AGN, or that an AGN, if present, is obscured even at energies above 2 keV. LINER 2s having small LX/LH-alpha occupy a localized region with small [OI]/H-alpha on the excitation diagram. Such LINER spectra can be reproduced by photoionization by very hot stars.

Terashima, Y.; Ho, L. C.; Ptak, A. F.

2004-01-01

187

ChanPlaNS: Investigating the Diffuse X-ray Emission within Compact Planetary Nebulae  

NASA Astrophysics Data System (ADS)

We present highlights of results from the Chandra Planetary Nebula Survey (ChanPlaNS), the first comprehensive X-ray survey of planetary nebulae (PNe) in the solar neighborhood (i.e., within ~ 1.5 kpc of the Sun). We are finding that diffuse X-ray emission is restricted to compact (Rneb <~0.15 pc) nebulae; this characteristic size scale corresponds to a PN-shaping wind collision timescale of <~ 5 x 103 yr. Furthermore, we find that all ChanPlaNS PNe that display diffuse X-ray emission have closed structures and characteristic nebular densities ne >~ 1000 cm-3, while older, lower-n_e nebulae remain difficult to detect. This relationship between nebular density and energetic wind interactions suggests that optical spectroscopy of density-sensitive lines (e.g., [O II], [S II]) can be used to establish whether a PN might be in an active wind-collision phase. Of the diffuse X-ray detections, 100% (5/5) of PNe with [WR]-type central stars (CSPNe) within ~ 1.5 kpc have detected. We present preliminary results from 3D structural reconstructions of PNe that are designed to investigate the apparent systematic differences between the diffuse X-ray emission morphologies of [WR] and non-[WR] CSPNe, as well as the possibility of enhanced X-ray absorption due to photoionized and neutral nebular gas.

Freeman, Marcus; Montez, Rodolfo; Kastner, Joel H.; ChanPlaNS Team

2015-01-01

188

X-ray emission from hot accretion flows  

NASA Astrophysics Data System (ADS)

Radiatively inefficient, hot accretion flows are widely considered as a relevant accretion mode in low-luminosity AGNs. We study spectral formation in such flows using a refined model with a fully general relativistic description of both the radiative (leptonic and hadronic) and hydrodynamic processes, as well as with an exact treatment of global Comptonization. We find that the X-ray spectral index-Eddington ratio anticorrelation as well as the cut-off energy measured in the best-studied objects favor accretion flows with rather strong magnetic field and with a weak direct heating of electrons. Furthermore, they require a much stronger source of seed photons than considered in previous studies. The nonthermal synchrotron radiation of relativistic electrons seems to be the most likely process capable of providing a sufficient flux of seed photons. Hadronic processes, which should occur due to basic properties of hot flows, provide an attractive explanation for the origin of such electrons.

Nied?wiecki, Andrzej; Xie, Fu-Guo; St?pnik, Agnieszka

2014-07-01

189

Fabrication, characterization and integration of carbon nanotube cathodes for field emission X-ray source  

NASA Astrophysics Data System (ADS)

Carbon nanotube (CNT) field emitters are now being evaluated for a wide range of vacuum electronic applications. Our laboratory pioneer in the development of CNT based field emission X-ray source technology, which has the potential to fundamentally change how X-ray radiation is generated and utilized. Applications of the CNT field emission X-ray source technology in a wide range of applications including biomedical imaging, radiation therapy, and homeland security are being actively pursued. However, problems with the performance of the CNT cathodes for X-ray generation including short lifetime at high current density, instability under high voltage, poor emission uniformity, and cathode-to-cathode inconsistency are still major obstacles for device applications. The goal of this thesis work is the development and optimization of an electrophoretic process to fabricate composite CNT films with controlled nanotube orientation and surface density, and enhanced adhesion. The CNT cathode fabrication process consist in a combination of photolithography and electrophoretic deposition (EPD) method where parameters such as SU-8 photoresist thickness, deposition time, and deposition voltage were varied to fabricate CNT cathodes with the required properties for X-ray generation. Also the development of CNT alcohol-based suspensions in context of the EPD method requirements with excellent long term stability has been accomplished. The CNT cathodes fabricated by EPD have significantly enhanced macroscopic field emission current density and long-term stability under high operating voltages. Also these CNT cathodes compared to others reported previously show significant improved field emission properties with small cathode-to-cathode variation. The integration, characterization, and evaluation of these CNT cathodes into a micro focus field emission X-ray source has been achieved with excellent X-ray source characteristics and performance including X-ray flux and stability at the maximum current and power allowed for a fixed anode. Also, with similar performance afforded in comparison with a conventional thermionic X-ray tube operating at the same focal spot size. The application of this CNT electron source for high-resolution X-ray imaging has been demonstrated.

Calderon-Colon, Xiomara

190

X-Ray Emission from a Simulated Cluster of Galaxies  

NASA Technical Reports Server (NTRS)

Using the 1993 cluster simulation of Katz & White, we analyze the intracluster medium and investigate the accuracy of the standard hydrostatic method for determining cluster masses. We show that the simulated cluster gas is in hydrostatic equilibrium with a subsonic flow toward the center. Inside a radius of (approx.) 100 kpc, this flow is in a steady state. The cooling time is shorter than a Hubble time within the central 50 kpc. The flow rate is regulated by the gas sink in the middle of the cluster and the PdV work done as the gas flows in, verifying the standard cooling flow scenario. We simulate observations of the cluster using the instrument parameters of the EXOSAT ME detector and the Einstein IPC detector. Even though the intracluster gas is not isothermal, isothermal models of the cluster, excluding regions within 100 kpc of galaxies, fit the EXOSAT X-ray spectra as well as they fit real clusters. The X- ray surface brightness distribution is similar to that of real clusters, again excluding the galaxies. We simulate the procedure used to determine the masses of real clusters. We use the equation of hydrostatic equilibrium together with the temperature derived from an isothermal fit to the simulated EXOSAT spectrum and the density profile derived from a fit to the simulated IPC surface brightness profile to determine the mass. A comparison of the derived mass profile to the actual mass profile shows that errors of a factor of 2 are possible. If the actual temperature profile is used, the cluster mass is found to an accuracy of better than 25% within the virial radius.

Tsai, John C.; Katz, Neal; Bertschinger, Edmund

1994-01-01

191

Origin of Thermal and Non-Thermal Hard X-Ray Emission from the Galactic Center  

NASA Astrophysics Data System (ADS)

We analyse new results of Chandra and Suzaku Observatories which found a flux of hard X-ray emission from the compact region around Sgr A* (r ˜ 100 pc). We suppose that this emission is generated by accretion processes onto the central supermassive blackhole when an unbound part of captured stars obtains an additional momentum. As a result a flux of subrelativistic protons is generated near the galactic center which heats the background plasma up to temperatures about 6-10 keV and produces by inverse bremsstrahlung a flux of non-thermal X-ray emission in the energy range above 10 keV.

Dogiel, Vladimir A.; Chernyshov, Dmitrii O.; Yuasa, Takayuki; Prokhorov, Dmitrii; Cheng, Kwong-Sang; Bamba, Aya; Inoue, Hajime; Ko, Chung-Ming; Kokubun, Motohide; Maeda, Yoshitomo; Mitsuda, Kazuhisa; Nakazawa, Kazuhiro; Yamasaki, Noriko Y.

2009-10-01

192

FADING HARD X-RAY EMISSION FROM THE GALACTIC CENTER MOLECULAR CLOUD Sgr B2  

SciTech Connect

The center of our Galaxy harbors a four million solar mass black hole that is unusually quiet: its present X-ray luminosity is more than 10 orders of magnitude less than its Eddington luminosity. The observation of iron fluorescence and hard X-ray emission from some of the massive molecular clouds surrounding the Galactic center has been interpreted as an echo of a past 10{sup 39} erg s{sup -1} flare. Alternatively, low-energy cosmic rays propagating inside the clouds might account for the observed emission, through inverse bremsstrahlung of low-energy ions or bremsstrahlung emission of low-energy electrons. Here, we report the observation of a clear decay of the hard X-ray emission from the molecular cloud Sgr B2 during the past seven years, thanks to more than 20 Ms of INTEGRAL exposure. This confirms the decay previously observed comparing the 6.4 keV line fluxes measured by various X-ray instruments, but without intercalibration effects. The measured decay time is 8.2 {+-} 1.7 yr, compatible with the light crossing time of the molecular cloud core. Such a short timescale rules out inverse bremsstrahlung by cosmic-ray ions as the origin of the X ray emission. We also obtained 2-100 keV broadband X-ray spectra by combining INTEGRAL and XMM-Newton data and compared them with detailed models of X-ray emission due to irradiation of molecular gas by (1) low-energy cosmic-ray electrons and (2) hard X-rays. Both models can reproduce the data equally well, but the time variability constraints and the huge cosmic-ray electron luminosity required to explain the observed hard X-ray emission strongly favor the scenario in which the diffuse emission of Sgr B2 is scattered and reprocessed radiation emitted in the past by Sgr A*. The spectral index of the illuminating power-law source is found to be {Gamma} {approx} 2 and its luminosity 1.5-5 x 10{sup 39} erg s {sup -1}, depending on the relative positions of Sgr B2 and Sgr A*. Using recent parallax measurements that place Sgr B2 in front of Sgr A*, we find that the period of intense activity of Sgr A* ended between 75 and 155 years ago.

Terrier, R.; Ponti, G.; Goldwurm, A.; Trap, G. [Astroparticule et Cosmologie, Universite Paris7/CNRS/CEA, Batiment Condorcet, 75013 Paris (France); Belanger, G. [European Space Agency, ESAC, P.O. Box 78, 28691, Villanueva de la Canada, Madrid (Spain); Decourchelle, A. [Service d'Astrophysique (SAp)/IRFU/DSM/CEA Saclay, Bt. 709, 91191 Gif-sur-Yvette Cedex (France); Tatischeff, V. [Centre de Spectrometrie Nucleaire et de Spectrometrie de Masse, CNRS/IN2P3 and Univ Paris-Sud, 91405 Orsay (France); Morris, M. R. [Department of Physics and Astronomy, University of California, Los Angeles, CA 90095-1547 (United States); Warwick, R., E-mail: rterrier@in2p3.f [Department of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH (United Kingdom)

2010-08-10

193

Extended X-ray Emission From a Quasar-driven Superbubble  

NASA Astrophysics Data System (ADS)

We propose to look for the X-ray component of a bona-fide quasar-driven wind, manifested as a 20 kpc-scale superbubble in the warm ionized gas. With ALMA and JVLA observations, we have ruled out star formation or a radio jet as the source of the outflow, and we have detected very soft (<1 keV) X-ray photons spatially coincident with the superbubble. With our existing 20 ks observation, we cannot determine whether the X-rays arise from the hot outflow or photoionized gas. With an additional 80ks observation (100 ks total), we will use the X-ray morphology and spectrum to distinguish these two possibilities. A single-orbit HST observation will allow us to both build a pure emission line map of the outflow and (via scattered light) teach us about the ambient density in the outflow.

Greene, Jenny

2014-09-01

194

The buddies of Babcock's star - X-ray emission from extreme magnetic ApBp stars?  

NASA Astrophysics Data System (ADS)

We propose XMM-Newton observations of two extreme magnetic Ap/Bp stars, HD 75049 and HD 137509, that exhibit surface field strengths of about 30 kG. HD 75049 is an Ap star and its extraordinary large magnetic field is dominated by a strong dipole component. The B9p star HD 137509 exhibits a similar surface field strength, but the underlying magnetic structure has a far more complex field geometry. Our targets have magnetic fields that rival famous Babcock's star that was recently established as a bright X-ray source. X-ray emission from intermediate mass stars is thought to originate from magnetically confined wind-shocks and the aim of this proposal is to test, whether HD 75049 and HD 137509 emit X-rays and if so, to determine their basic X-ray properties.

Robrade, Jan

2009-10-01

195

X-RAY EMISSION FROM THE FU ORIONIS STAR V1735 CYGNI  

SciTech Connect

The variable star V1735 Cyg (=Elias 1-12) lies in the IC 5146 dark cloud and is a member of the class of FU Orionis objects whose dramatic optical brightenings are thought to be linked to episodic accretion. We report the first X-ray detections of V1735 Cyg and a deeply embedded class I protostar lying 24'' to its northeast. X-ray spectra obtained with EPIC on XMM-Newton reveal very high-temperature plasma (kT > 5 keV) in both objects, but no large flares. Such hard X-ray emission is not anticipated from accretion shocks and is a signature of magnetic processes. We place these new results into the context of what is presently known about the X-ray properties of FU Orionis stars and other accreting young stellar objects.

Skinner, Stephen L.; Sokal, Kimberly R. [Center for Astrophysics and Space Astronomy (CASA), University of Colorado, Boulder, CO 80309-0389 (United States); Guedel, Manuel; Briggs, Kevin R. [Institute of Astronomy, ETH Zurich, Wolfgang-Pauli-Str. 27, 8093 Zurich (Switzerland)

2009-05-01

196

Diagnosing residual motion via the x-ray self emission from indirectly driven inertial confinement implosionsa)  

NASA Astrophysics Data System (ADS)

In an indirectly driven implosion, non-radial translational motion of the compressed fusion capsule is a signature of residual kinetic energy not coupled into the compressional heating of the target. A reduction in compression reduces the peak pressure and nuclear performance of the implosion. Measuring and reducing the residual motion of the implosion is therefore necessary to improve performance and isolate other effects that degrade performance. Using the gated x-ray diagnostic, the x-ray Bremsstrahlung emission from the compressed capsule is spatially and temporally resolved at x-ray energies of >8.7 keV, allowing for measurements of the residual velocity. Here details of the x-ray velocity measurement and fitting routine will be discussed and measurements will be compared to the velocities inferred from the neutron time of flight detectors.

Pak, A.; Field, J. E.; Benedetti, L. R.; Caggiano, J.; Hatarik, R.; Izumi, N.; Khan, S. F.; Knauer, J.; Ma, T.; Spears, B. K.; Town, R. P. J.; Bradley, D. K.

2014-11-01

197

Discovery of Diffuse Hard X-ray Emission associated with Jupiter  

NASA Astrophysics Data System (ADS)

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.

Ezoe, Y.; Miyoshi, Y.; Ishikawa, K.; Ohashi, T.; Terada, N.; Uchiyama, Y.; Negoro, H.

2009-12-01

198

Observation and Modeling of Geocoronal Charge Exchange X-Ray Emission during Solar Wind Gusts  

NASA Astrophysics Data System (ADS)

Solar wind charge exchange (SWCX) X-rays are emitted when highly charged solar wind ions such as O7 + collide with neutral gas, including the Earth's tenuous outer atmosphere (exosphere or geocorona) and hydrogen and helium from the local interstellar medium drifting through the heliosphere. This geocoronal and heliospheric emission comprises a significant and varying fraction of the soft X-ray background (SXRB) and is seen in every X-ray observation, with the intensity dependent on solar wind conditions and observation geometry. Under the right conditions, geocoronal emission can increase the apparent SXRB by roughly an order of magnitude for an hour or more. In this work, we study a dozen occasions when the near-Earth solar wind flux was exceptionally high. These gusts of wind lead to abrupt changes in SWCX X-ray emission around Earth, which may or may not be seen by X-ray observatories depending on their line of sight. Using detailed three-dimensional magnetohydrodynamical simulations of the solar wind's interaction with the Earth's magnetosphere, and element abundances and ionization states measured by ACE, we model the time-dependent brightness of major geocoronal SWCX emission lines during those gusts and compare with changes in the X-ray background measured by the Chandra X-ray Observatory. We find reasonably good agreement between model and observation, with measured geocoronal line brightnesses averaged over 1 hr of up to 136 photons s–1 cm–2 sr–1 in the O VII K? triplet around 564 eV.

Wargelin, B. J.; Kornbleuth, M.; Martin, P. L.; Juda, M.

2014-11-01

199

CHANDRA REVEALS VARIABLE MULTI-COMPONENT X-RAY EMISSION FROM FU ORIONIS  

SciTech Connect

FU Orionis is the prototype of a class of eruptive young stars ('FUors') characterized by strong optical outbursts. We recently completed an exploratory survey of FUors using XMM-Newton to determine their X-ray properties, about which little was previously known. The prototype FU Ori and V1735 Cyg were detected. The X-ray spectrum of FU Ori was found to be unusual, consisting of a cool moderately absorbed component plus a hotter component viewed through an absorption column density that is an order of magnitude higher. We present here a sensitive (99 ks) follow-up X-ray observation of FU Ori obtained at higher angular resolution with Chandra ACIS-S. The unusual multi-component spectrum is confirmed. The hot component is centered on FU Ori and dominates the emission above 2 keV. It is variable (a signature of magnetic activity) and is probably coronal emission originating close to FU Ori's surface viewed through cool gas in FU Ori's strong wind or accretion stream. In contrast, the X-ray centroid of the soft emission below 2 keV is offset 0.''20 to the southeast of FU Ori, toward the near-IR companion (FU Ori S). This offset amounts to slightly less than half the separation between the two stars. The most likely explanation for the offset is that the companion contributes significantly to the softer X-ray emission below 2 keV (and weakly above 2 keV). The superimposed X-ray contributions from FU Ori and the companion resolve the paradox posed by XMM-Newton of an apparently single X-ray source viewed through two different absorption columns.

Skinner, Stephen L. [CASA, University of Colorado, Boulder, CO 80309-0389 (United States); Guedel, Manuel [Department of Astronomy, University of Vienna, Tuerkenschanzstr. 17, A-1180 Vienna (Austria); Briggs, Kevin R. [Institute of Astronomy, ETH Zuerich, Wolfgang-Pauli-Strasse 27, 8093 Zuerich (Switzerland); Lamzin, Sergei A., E-mail: stephen.skinner@colorado.ed [Sternberg Astronomical Institute, Universitetski Pr. 13, Moscow 119992 (Russian Federation)

2010-10-20

200

Early magnetic B-type stars: X-ray emission and wind properties  

NASA Astrophysics Data System (ADS)

We present a comprehensive study of X-ray emission by, and wind properties of, massive magnetic early B-type stars. Dedicated XMM-Newton observations were obtained for three early-type B-type stars, ?1 CMa, V2052 Oph and ? Cas, with recently discovered magnetic fields. We report the first detection of X-ray emission from V2052 Oph and ? Cas. The latter is one the softest X-ray sources among the early-type stars, while the former is one of the X-ray faintest. The observations show that the X-ray spectra of our programme stars are quite soft with the bulk of X-ray emitting material having a temperature of about 1 MK. We compile the complete sample of early B-type stars with detected magnetic fields to date and existing X-ray measurements, in order to study whether the X-ray emission can be used as a general proxy for stellar magnetism. We find that the X-ray properties of early massive B-type magnetic stars are diverse, and that hard and strong X-ray emission does not necessarily correlate with the presence of a magnetic field, corroborating similar conclusions reached earlier for the classical chemically peculiar magnetic Bp-Ap stars. We analyse the ultraviolet (UV) spectra of five non-supergiant B stars with magnetic fields (? Sco, ? Cep, ?1 CMa, V2052 Oph and ? Cas) by means of non-local thermodynamic equilibrium (non-LTE) iron-blanketed model atmospheres. The latter are calculated with the Potsdam Wolf-Rayet (PoWR) code, which treats the photosphere as well as the wind, and also accounts for X-rays. With the exception of ? Sco, this is the first analysis of these stars by means of stellar wind models. Our models accurately fit the stellar photospheric spectra in the optical and the UV. The parameters of X-ray emission, temperature and flux are included in the model in accordance with observations. We confirm the earlier findings that the filling factors of X-ray emitting material are very high. Our analysis reveals that the magnetic early-type B stars studied here have weak winds with velocities not significantly exceeding vesc. The mass-loss rates inferred from the analysis of UV lines are significantly lower than predicted by hydrodynamically consistent models. We find that, although the X-rays strongly affect the ionization structure of the wind, this effect is not sufficient in reducing the total radiative acceleration. When the X-rays are accounted for at the intensity and temperatures observed, there is still sufficient radiative acceleration to drive a stronger mass-loss than we empirically infer from the UV spectral lines.

Oskinova, L. M.; Todt, H.; Ignace, R.; Brown, J. C.; Cassinelli, J. P.; Hamann, W.-R.

2011-09-01

201

Origin of the X-ray Emission in the Nuclei of FR Is  

E-print Network

We investigate the X-ray origin in FRIs using the multi-waveband high resolution data of eight FR I sources, which have very low Eddington ratios. We fit their multi-waveband spectrum using a coupled accretion-jet model. We find that X-ray emission in the source with the highest L_X (~1.8*10^-4 L_Edd) is from the advection-dominated accretion flow (ADAF). Four sources with moderate L_X(~several*10^-6 L_Edd) are complicated. The X-ray emission of one FR I is from the jet, and the other three is from the sum of the jet and ADAF. The X-ray emission in the three least luminous sources (L_X<1.0*10^-6L_Edd) is dominated by the jet. These results roughly support the predictions of Yuan and Cui(2005) where they predict that when the X-ray luminosity of the system is below a critical value, the X-radiation will not be dominated by the emission from the ADAF any longer, but by the jet. We also find that the accretion rates in four sources must be higher than the Bondi rates, which implies that other fuel supply (e.g., stellar winds) inside the Bondi radius should be important.

Qingwen Wu; Feng Yuan; Xinwu Cao

2008-09-17

202

X-RAY EMISSION FROM SN 2004dj: A TALE OF TWO SHOCKS  

SciTech Connect

Type IIP (Plateau) supernovae are the most commonly observed variety of core-collapse events. They have been detected in a wide range of wavelengths from radio, through optical to X-rays. The standard picture of a Type IIP supernova has the blastwave interacting with the progenitor's circumstellar matter to produce a hot region bounded by a forward and a reverse shock. This region is thought to be responsible for most of the X-ray and radio emission from these objects. Yet the origin of X-rays from these supernovae is not well understood quantitatively. The relative contributions of particle acceleration and magnetic field amplification in generating the X-ray and radio emission need to be determined. In this work, we analyze archival Chandra observations of SN 2004dj, one of the nearest supernovae since SN 1987A, along with published radio and optical information. We determine the pre-explosion mass-loss rate, blastwave velocity, electron acceleration, and magnetic field amplification efficiencies. We find that a greater fraction of the thermal energy goes into accelerating electrons than into amplifying magnetic fields. We conclude that the X-ray emission arises out of a combination of inverse Compton scattering by non-thermal electrons accelerated in the forward shock and thermal emission from supernova ejecta heated by the reverse shock.

Chakraborti, Sayan; Yadav, Naveen; Ray, Alak [Tata Institute of Fundamental Research, 1 Homi Bhabha Road, Colaba, Mumbai 400 005 (India); Smith, Randall [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Chandra, Poonam [Department of Physics, Royal Military College of Canada, Kingston, ON K7K 7B4 (Canada); Pooley, David, E-mail: schakraborti@fas.harvard.edu [Department of Physics, Sam Houston State University, Huntsville, TX (United States)

2012-12-20

203

Modeling Diffuse X-ray Emission around the Galactic Center from Colliding Stellar Winds  

NASA Astrophysics Data System (ADS)

The Galactic center is a hotbed of astrophysical phenomena. The ~30 evolved massive stars orbiting the SMBH on scales <10" inject a large fraction of the matter that accretes onto the SMBH, and potentially creates large swaths of hot, X-ray emitting material around Sgr A* from their wind-wind collisions. Using the Gadget-2 SPH simulations of these evolved stars ejecting their winds over the last 1100 years from Cuadra et al. 2008, we solve the formal solution to the equation of radiative transfer for a grid of rays through the 6"x6" simulation volume to calculate the thermal X-ray emission from the diffuse hot gas. We then fold each of these energy-dependent pixel maps through the Chandra ACIS-S response function to directly compare with the recent 3Ms X-ray Visionary Program observations of the Galactic center (Wang et al. 2013). The model X-ray flux, in absolute units, agrees well with the observations just outside the SMBH (whose emission is not included in this modeling), indicating that the shocked wind material from the evolved massive stars is indeed the source of diffuse X-ray emission at the Galactic center. The emission of the IRS13 cluster, though, is overestimated by two orders of magnitude, indicating a potential revision in the cluster stellar parameters. We will conclude by discussing future work, such as implementing the “pressure-entropy” formulation of SPH for this calculation and including O stars and closely orbiting binaries.

Post Russell, Christopher Michael; Cuadra, Jorge; Wang, Q. Daniel; Owocki, Stanley P.

2015-01-01

204

Modeling Diffuse X-ray Emission around the Galactic Center from Colliding Stellar Winds  

NASA Astrophysics Data System (ADS)

The Galactic center is a hotbed of astrophysical phenomena. The ~30 evolved massive stars orbiting the SMBH on scales <10" inject a large fraction of the matter that accretes onto the SMBH, and potentially creates large swaths of hot, X-ray emitting material around Sgr A* from their wind-wind collisions. Using the Gadget-2 SPH simulations of these evolved stars ejecting their winds over the last 1100 years from Cuadra et al. 2008, we solve the formal solution to the equation of radiative transfer for a grid of rays through the 6"x6" simulation volume to calculate the thermal X-ray emission from the diffuse hot gas. We then fold each of these energy-dependent pixel maps through the Chandra ACIS-S response function to directly compare with the recent 3Ms X-ray Visionary Program observations of the Galactic center (Wang et al. 2013). The model X-ray flux, in absolute units, agrees well with the observations just outside the SMBH (whose emission is not included in this modeling), indicating that the shocked wind material from the evolved massive stars is indeed the source of diffuse X-ray emission at the Galactic center. The emission of the IRS13 cluster, though, is overestimated by two orders of magnitude, indicating a potential revision in the cluster stellar parameters. We will conclude by discussing future work, such as implementing the 'pressure-entropy' formulation of SPH for this calculation and including O stars and closely orbiting binaries.

Russell, Christopher Michael Post; Cuadra, Jorge; Wang, Q. Daniel; Owocki, Stanley P.

2015-01-01

205

Low- to Middle-Latitude X-Ray Emission from Jupiter  

NASA Technical Reports Server (NTRS)

The Chandra X-ray Observatory (CXO) observed Jupiter during the period 24-26 February 2003 for approx. 40 hours (4 Jupiter rotations), using both the spectroscopy array of the Advanced CCD Imaging Spectrometer (ACIS-S) and the imaging array of the High-Resolution Camera (HRC-I). Two ACIS-S exposures, each -8.5 hours long, were separated by an HRC-I exposure of approx. 20 hours. The low- to middle-latitude nonauroral disk X-ray emission is much more spatially uniform than the auroral emission. However, the low- to middle-latitude X-ray count rate shows a small but statistically significant hour angle dependence and depends on surface magnetic field strength. In addition, the X-ray spectra from regions corresponding to 3-5 gauss and 5-7 gauss surface fields show significant differences in the energy band 1.26-1.38 keV, perhaps partly due to line emission occurring in the 3-5 gauss region but not the 5-7 gauss region. A similar correlation of surface magnetic field strength with count rate is found for the 18 December 2000 HRC-I data, at a time when solar activity was high. The low- to middle-latitude disk X-ray count rate observed by the HRC-I in the February 2003 observation is about 50% of that observed in December 2000, roughly consistent with a decrease in the solar activity index (F10.7 cm flux) by a similar amount over the same time period. The low- to middle-latitude X-ray emission does not show any oscillations similar to the approx. 45 min oscillations sometimes seen from the northern auroral zone. The temporal variation in Jupiter's nonauroral X-ray emission exhibits similarities to variations in solar X-ray flux observed by GOES and TIMED/SEE. The two ACIS-S 0.3-2.0 keV low- to middle-latitude X-ray spectra are harder than the auroral spectrum and are different from each other at energies above 0.7 keV, showing variability in Jupiter's nonauroral X-ray emission on a timescale of a day. The 0.3-2.0 keV X-ray power emitted at low to middle latitudes is 0.21 GW and 0.39 GW for the first and second ACIS-S exposures, respectively. We suggest that X-ray emission from Jupiter's disk may be largely generated by the scattering and fluorescence of solar X rays in its upper atmosphere, especially at times of high incident solar X-ray flux. However, the dependence of count rate on surface magnetic-field strength may indicate the presence of some secondary component, possibly ion precipitation from radiation belts close to the planet.

Bhardwaj, Anil; Elsner, Ronald F.; Gladstone, G. Randall; Waite, J. Hunter, Jr.; Branduardi-Raymont, Graziella; Cravens, Thomas E.; Ford, Peter G.

2006-01-01

206

Quiescent Diffusive and Fumarolic Volcanic Bromocarbon Emissions  

NASA Astrophysics Data System (ADS)

Future scenarios of declining atmospheric burdens of Ozone Depleting Substances (ODS) such as halocarbons after phase-out following international regulation (Montreal Protocol) vary strongly depending on what contribution from natural sources is taken into account. In addition, current and pre-industrial global atmospheric budgets of ODS are poorly balanced by known natural and anthropogenic sources of halocarbons (Butler, 2000). Brominated halocarbons have a high Ozone Depletion Potential, Br is at least 40x as efficient as Cl in polar stratospheric ozone destruction (Solomon et al., 1992). CH3Br is the dominant Br carrier to the stratosphere with sources being ca.: 32% anthropogenic, 39% natural, but ca. 29% unaccounted for (WMO, 1998). Natural sources have been reviewed recently (Gribble, 2000, Butler, 2000), including magmatic inorganic (Bureau, 2000) and volcanic organic sources (Rassmussen et al., 1980; Schwandner et al., 2002). CH3Br and other bromocarbons have been reported in non-eruptive volcanic gases previously (Jordan et al., 2000; Schwandner et al., 2000). Due to its capability to extremely rapidly hydrolyse (Gan et al., 1995), CH3Br should not be sampled by the caustic soda bottle technique as used by Jordan et al. (2000) whose samples also show signs of air contamination, but by cryogenic separation of steam with subsequent sorbent trapping, as used by Isidorov (1990), Wahrenberger (1996) and Schwandner et al. (2000, 2001). To contribute significantly to the natural Br budget, volcanic gases would have to at least contain 2 ppmv (dry gas) CH3Br, scaled to a global CO2 emission of 66 Tgy-1 (Stoiber, 1995) based on CO2 flux to halocarbon concentration correlations (e.g. CFC-11: R2=0.91, Schwandner et al., 2002). However, CH3Br is not the only volcanogenic bromocarbon. Analysis of diffusive flank and crater degassing on Vulcano island (Italy) showed a strong diffusive component of CH3Br and C2H5Br emissions in 60-100°C hot pristine unvegetated volcanic "soil" close to high-temperature fumaroles. Other ODS found significantly above air, field and analytical system blanks include CH3Cl, CH3I, chlorophenols and chlorobenzenes. Abundances range from upper pptv to ppmv (e.g. CFC-11: max. 1200 pptv diffusive, 3700 pptv fumarolic/dry gas, dry air: 268 pptv). References\\ Bureau H. et al. (2000), EPSL 183 (1-2):51-60.\\Butler J.H. (2000), Nature 403:560-261.\\Gan J. Y. et al. (1995), J. Agric. Food Chem. 43:1361-1367.\\Gribble G. W. (2000), Environ. Sci. Pollut. Res. 7(1), 37-49.\\Isidorov V. A. et al. (1990), J. Atmos. Chem. 10(3):329-340.\\Jordan A. et al.(2000), ES&T 34:1122-1124.\\Rasmussen R. A. et al. (1980), EOS Transact. 61(6):67.\\Schwandner F. M. et al. (2000), J. Conf. Abs. 5(2):898.\\Schwandner F. M. et al. (2001), Chimia 55(7-8):590.\\Schwandner F.M. et al. (2002), Geoch. Soc. Spec. Publ. 8 (subm.).\\Solomon S. et al. (1992), JGR-A. 97:825-842.\\Stoiber R. E. (1995), In: A handbook of physical constants, AGU Reference Shelf 1:308-319.\\Wahrenberger C. et al. (1996), EOS Trans. 77(46):804.\\WMO (1998) Scientific assessment of ozone depletion. WMO Rep. No. 44, World Meteorological Organisation (WMO), Geneva.

Schwandner, F. M.; Gi?e, A. P.; Seward, T. M.; Hall, P. A.; Dietrich, V. J.

2002-12-01

207

Discovery of X-ray emission associated with the Gum Nebula  

NASA Technical Reports Server (NTRS)

The Gum Nebula was observed by the A-2 LED proportional counters on the HEAO-1 satellite as part of the all-sky survey. The first detection of X-ray emission associated with the Gum Nebula is reported. Soft X-ray spectra were constructed from the A-2 LED PHA data. Single temperature Raymond-Smith models were fitted to the observed spectra to yield temperature, column density and emission measure. The temperature is 6 x 10 exp 5 K, the column density 4 x 10 exp 20/sq cm, and the emission measure 5 cm exp-6 pc. The X-ray and optical properties of the Gum Nebula are consistent with a supernova remnant in the shell stage of evolution, which was the product of an energetic (3 x 10 exp 51 ergs) supernova explosion which occurred about 2 x 10 exp 6 yr ago.

Leahy, D. A.; Nousek, J.; Garmire, G.

1992-01-01

208

Relativistic calculations of x-ray emission following a Xe-Bi83+ collision  

NASA Astrophysics Data System (ADS)

We study the x-ray emission following the collision of a Bi83+ ion with a neutral Xe atom at the projectile energy 70 MeV/u. The collisional and post-collisional processes are treated separately. The probabilities of various many-electron processes at the collision are calculated within a relativistic independent electron model using the coupled-channel approach with atomiclike Dirac-Fock-Sturm orbitals. The analysis of the post-collisional processes resulting in the x-ray emission is based on the fluorescence yields, the radiation, and Auger decay rates, and allows one to derive intensities of the x-ray emission and compare them with experimental data. A reasonable agreement between the theoretical results and the recent experimental data is observed. The role of the relativistic effects is investigated.

Kozhedub, Y. S.; Shabaev, V. M.; Tupitsyn, I. I.; Gumberidze, A.; Hagmann, S.; Plunien, G.; Stöhlker, Th.

2014-10-01

209

X-ray emission from relativistically moving electron density cusps  

SciTech Connect

We report on novel methods to generate ultra-short, coherent, X-rays using a laserplasma interaction. Nonlinear interaction of intense laser pulses with plasma creates stable, specific structures such as electron cusps. For example, wake waves excited in an underdense plasma by an intense, short-pulse laser become dense and propagate along with the laser pulse. This is called a relativistic flying mirror. The flying mirror can reflect a counter-propagating laser pulse and directly convert it into high-frequency radiation, with a frequency multiplication factor of {approx} 4{gamma}{sup 2} and pulse shortening with the same factor. After the proof-of-principle experiments, we observed that the photon number generated in the flying mirror is close to the theoretical estimate. We present the details of the experiment in which a 9 TW laser pulse focused into a He gas jet generated the Flying Mirror, which partly reflected a 1 TW pulse, giving up to {approx} 10{sup 10} photons, 60 nJ (1.4 Multiplication-Sign 10{sup 12} photons/sr) in the XUV spectral region (12.8-22 nm).

Kando, M.; Pirozhkov, A. S.; Nakamura, T.; Hayashi, Y.; Kotaki, H.; Kawase, K.; Esirkepov, T. Zh.; Fukuda, Y.; Kiriyama, H.; Okada, H.; Daito, I.; Kameshima, T.; Mori, M.; Koga, J. K.; Daido, H.; Faenov, A. Ya.; Pikuz, T.; Ma, J.; Chen, L.-M.; Ragozin, E. N. [Japan Atomic Energy Agency (Japan); Osaka University (Japan); Joint Institute for High Temperature of the Russian Academy of Science, Moscow (Russian Federation); Institute of Physics, Chinese Academy of Sciences, Beijing (China); P. N. Lebedev Physical Institute of the Russian Academy of Sciences, Leninsky prospekt 53, 119991 Moscow (Russian Federation); Japan Atomic Energy Agency and Graduate School for the Creation of New Photonics Industries (Japan); Ludwig-Maximilians-University (Germany); and others

2012-07-11

210

Search of X-ray emission from roAp stars: the case of ? Equulei  

NASA Astrophysics Data System (ADS)

Context. Rapidly oscillating Ap (roAp) stars represent a subclass of magnetic, chemically peculiar stars. The explanation for their pulsations includes suppressed convection due to the strong magnetic field. These stars rotate slowly such that a solar-like dynamo and ensuing magnetic activity is unlikely to be present. On the other hand, magnetic activity could provide the particle acceleration suspected to be responsible for the presence of short-lived radionuclides on some roAp stars. Aims: The detection of X-ray emission from Ap stars can be an indicator for the presence of magnetic activity and dynamo action, provided different origins for the emission, such as wind shocks and close late-type companions, can be excluded. Here we report on results for ? Equ, the only roAp star for which an X-ray detection is reported in ROSAT catalogs. Methods: We use high resolution imaging in X-rays with Chandra and in the near-infrared with NACO/VLT that allow us to spatially resolve companions down to ? 1'' and ~0.06'' separations, respectively. Results: The bulk of the X-ray emission is associated with a companion of ? Equ identified in our NACO image. Assuming coevality with the primary roAp star (~900 Myr), the available photometry for the companion points at a K-type star with ~0.6 M?. Its X-ray properties are in agreement with the predictions for its age and mass. An excess of photons with respect to the expected background and contribution from the nearby companion is observed near the optical position of ? Equ. We estimate an X-ray luminosity of log Lx [erg/s] = 26.6 and log (Lx/Lbol) = -7.9 for this emission. A small offset between the optical and the X-ray image leaves some doubt on its association with the roAp star. Conclusions: The faint X-ray emission that we tentatively ascribe to the roAp star is difficult to explain as a solar-like stellar corona due to its very low Lx/Lbol level and the very long rotation period of ? Equ. It could be produced in magnetically confined wind shocks implying a mass loss rate of ~10-14 M?/yr or from an additional unknown late-type companion at separation ? 0.4''. If confirmed by future deeper X-ray observations this emission could point at the origin for the presence of radioactive elements on some roAp stars.

Stelzer, B.; Hummel, C. A.; Schöller, M.; Hubrig, S.; Cowley, C.

2011-05-01

211

X-ray emission from T Tauri stars attributable to an accretion shock wave  

NASA Astrophysics Data System (ADS)

We consider the X-ray emission of an accretion shock wave for classical T Tauri stars. The absorption of the emission by cold preshock gas is shown to make its spectrum harder than that in the formation zone. However, since the effect is not too large, the shock wave can be responsible only for the soft component of the observed X-ray emission. The observed emission with E > 1 keV is assumed to be produced by a coronal plasma with T ~ 10^7 K, which is confined by closed field lines of the large-scale stellar magnetic field near the magnetic equator. The contribution of this region to the ultraviolet and optical emission is discussed. We also show that, in contrast to the optical emission, the intensity of the X-ray emission generated by a shock wave depends only slightly on the accreted-gas density. This is consistent with the lack of correlation between the optical and X-ray variability detected in BP Tau.

Lamzin, S. A.

1999-07-01

212

New Chandra observations of the jet in 3C273. 1. Softer X-ray than radio spectra and the X-ray emission mechanism  

SciTech Connect

The jet in 3C273 is a high-power quasar jet with radio, optical and X-ray emission whose size and brightness allow a detailed study of the emission processes acting in it. We present deep Chandra observations of this jet and analyze the spectral properties of the jet emission from radio through X-rays. We find that the X-ray spectra are significantly softer than the radio spectra in all regions of the bright part of the jet except for the first bright ''knot A'', ruling out a model in which the X-ray emission from the entire jet arises from beamed inverse-Compton scattering of cosmic microwave background photons in a single-zone jet flow. Within two-zone jet models, we find that a synchrotron origin for the jet's X-rays requires fewer additional assumptions than an inverse-Compton model, especially if velocity shear leads to efficient particle acceleration in jet flows.

Jester, Sebastian; /Fermilab; Harris, D.E.; /Smithsonian Astrophys. Observ.; Marshall, H.L.; /MIT, MKI; Meisenheimer, K.; /Heidelberg, Max Planck Inst. Astron.

2006-05-01

213

X-ray Emission from Eta Carinae near Periastron in 2009 I: A Two State Solution  

E-print Network

X-ray emission from the supermassive binary system Eta Carinae declines sharply around periastron. This X-ray minimum has two distinct phases - the lowest flux phase in the first ~3 weeks and a brighter phase thereafter. In 2009, the Chandra X-ray Observatory monitored the first phase five times and found the lowest observed flux at ~1.9e-12 ergs cm-2 s-1 (3-8 keV). The spectral shape changed such that the hard band above ~4 keV dropped quickly at the beginning and the soft band flux gradually decreased to its lowest observed value in ~2 weeks. The hard band spectrum had begun to recover by that time. This spectral variation suggests that the shocked gas producing the hottest X-ray gas near the apex of the wind-wind collision (WWC) is blocked behind the dense inner wind of the primary star, which later occults slightly cooler gas downstream. Shocked gas previously produced by the system at earlier orbital phases is suggested to produce the faint residual X-ray emission seen when the emission near the apex is ...

Hamaguchi, Kenji; Russell, Christopher; Pollock, Andrew M T; Gull, Theodore R; Teodoro, Mairan; Madura, Thomas I; Damineli, Augusto; Pittard, Julian M

2014-01-01

214

Hard X-Ray Emission and the Ionizing Source in LINERs  

NASA Technical Reports Server (NTRS)

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.

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

2000-01-01

215

X-ray emission from gamma-ray sources in the galactic anticentre region  

NASA Technical Reports Server (NTRS)

An X-ray survey of three high energy gamma-ray sources in the galactic anticenter region conducted using the large area sky survey instrument on HEAO 1 is presented. The sensitivity of this survey is highest reported, and two, and possibly three, X-ray sources were detected in the vicinity of gamma 195+5. Three new X-ray sources have been discovered within a few degrees of CG176-7, but none overlaps the gamma-ray error box. These results demonstrate that gamma-ray sources like CG195+4 and CG176-7 have emission characteristics different from the Crab pulsar, but may be similar to the Vela pulsar. Alternatively, the lack of detectable X-ray flux suggests that the gamma-ray emission arises from cosmic-ray interactions in dense interstellar clouds. An interesting feature of the new X-ray sources is that four of them may be associated with early-type stars which exhibit emission lines.

Share, G. H.; Bonnardeau, M.; Wood, K.; Meekins, J. F.; Yentis, D. J.; Evans, W. D.; Johnson, W. N.; Shulman, S.; Byram, E. T.; Chubb, T. A.

1979-01-01

216

Evolution of the X-ray Emission of Radio-Quiet Quasars  

E-print Network

We report new Chandra observations of seven optically faint, z \\sim 4 radio-quiet quasars. We have combined these new observations with previous Chandra observations of radio-quiet quasars to create a sample of 174 sources. These sources have 0.1 < z < 4.7, and 10^{44} ergs s^{-1} < nu L_{nu} (2500 \\AA) < 10^{48} ergs s^{-1}. The X-ray detection fraction is 90%. We find that the X-ray loudness of radio-quiet quasars decreases with UV luminosity and increases with redshift. The model that is best supported by the data has a linear dependence of optical-to-X-ray ratio, alpha_{ox}, on cosmic time, and a quadratic dependence of alpha_{ox} on log L_{UV}, where alpha_{ox} becomes X-ray quiet more rapidly at higher log L_{UV}. We find no significant evidence for a relationship between the X-ray photon index, Gamma_X, and the UV luminosity, and we find marginally significant evidence that the X-ray continuum flattens with increasing z (2 sigma). The Gamma_X-z anti-correlation may be the result of X-ray spectral curvature, redshifting of a Compton reflection component into the observed Chandra band, and/or redshifting of a soft excess out of the observed Chandra band. Using the results for Gamma_X, we show that the alpha_{ox}-z relationship is unlikely to be a spurious result caused by redshifting of the observable X-ray spectral region. A correlation between alpha_{ox} and z implies evolution of the accretion process. We present a qualitative comparison of these new results with models for accretion disk emission.

Brandon C. Kelly; Jill Bechtold; Aneta Siemiginowska; Tom Aldcroft; Malgorzata Sobolewska

2006-11-03

217

An X-Ray Reprocessing Model of Disk Thermal Emission in Type 1 Seyfert Galaxies  

NASA Technical Reports Server (NTRS)

Using a geometry consisting of a hot central Comptonizing plasma surrounded by a thin accretion disk, we model the optical through hard X-ray spectral energy distributions of the type 1 Seyfert. galaxies NGC 3516 and NGC 7469. As in the model proposed by Poutanen, Krolik, and Ryde for the X-ray binary Cygnus X-1 and later applied to Seyfert galaxies by Zdziarski, Lubifiski, and Smith, feedback between the radiation reprocessed by the disk and the thermal Comptonization emission from the hot central plasma plays a pivotal role in determining the X-ray spectrum, and as we show, the optical and ultraviolet spectra as well. Seemingly uncorrelated optical/UV and X-ray light curves, similar to those which have been observed from these objects can, in principle, be explained by variations in the size, shape, and temperature of the Comptonizing plasma. Furthermore, by positing a disk mass accretion rate which satisfies a condition for global energy balance between the thermal Comptonization luminosity and the power available from accretion, one can predict the spectral properties of the heretofore poorly measured hard X-ray continuum above approximately 50 keV in type 1 Seyfert galaxies. Conversely, forthcoming measurements of the hard X-ray continuum by more sensitive hard X-ray and soft gamma-ray telescopes, such as those aboard the International Gamma-Ray Astrophysics Laboratory (INTEGRAL) in conjunction with simultaneous optical, UV, and soft X-ray monitoring, will allow the mass accretion rates to be directly constrained for these sources in the context of this model.

Chiang, James; White, Nicholas E. (Technical Monitor)

2002-01-01

218

X-ray Emission From Eta Carinae near Periastron in 2009 I: A Two State Solution  

NASA Technical Reports Server (NTRS)

X-ray emission from the supermassive binary system Eta Carinae declines sharply around periastron. This X-ray minimum has two distinct phases the lowest flux phase in the first 3 weeks and a brighter phase thereafter. In 2009, the Chandra X-ray Observatory monitored the first phase five times and found the lowest observed flux at 1.91012 ergs/sq cm/s (38 keV). The spectral shape changed such that the hard band above 4 keV dropped quickly at the beginning and the soft band flux gradually decreased to its lowest observed value in 2 weeks. The hard band spectrum had begun to recover by that time. This spectral variation suggests that the shocked gas producing the hottest X-ray gas near the apex of the wind-wind collision (WWC) is blocked behind the dense inner wind of the primary star, which later occults slightly cooler gas down-stream. Shocked gas previously produced by the system at earlier orbital phases is suggested to produce the faint residual X-ray emission seen when the emission near the apex is completely blocked by the primary wind. The brighter phase is probably caused by the re-appearance of the WWC plasma, whose emissivity significantly declined during the occultation. We interpret this to mean that the X-ray minimum is produced by a hybrid mechanism of an occultation and a decline in emissivity of the WWC shock. We constrain timings of superior conjunction and periastron based on these results.

Hamaguchi, Kenji; Corcoran, Michael F.; Russell, Christopher; Pollock, Andrew M. T.; Gull, Theodore R.; Teodoro, Mairan; Madura, Thomas I.; Damineli, Augusto; Pittard, Julian M.

2014-01-01

219

Feedback from winds and supernovae in massive stellar clusters - II. X-ray emission  

NASA Astrophysics Data System (ADS)

The X-ray emission from a simulated massive stellar cluster is investigated. The emission is calculated from a 3D hydrodynamical model which incorporates the mechanical feedback from the stellar winds of three O stars embedded in a giant molecular cloud (GMC) clump containing 3240 M? of molecular material within a 4 pc radius. A simple prescription for the evolution of the stars is used, with the first supernova (SN) explosion at t = 4.4 Myr. We find that the presence of the GMC clump causes short-lived attenuation effects on the X-ray emission of the cluster. However, once most of the material has been ablated away by the winds, the remaining dense clumps do not have a noticeable effect on the attenuation compared with the assumed interstellar medium (ISM) column. We determine the evolution of the cluster X-ray luminosity, LX, and spectra, and generate synthetic images. The intrinsic X-ray luminosity drops from nearly 1034 erg s-1 while the winds are `bottled up', to a near-constant value of 1.7 × 1032 erg s-1 between t = 1 and 4 Myr. LX reduces slightly during each star's red supergiant stage due to the depressurization of the hot gas. However, LX increases to ?1034 erg s-1 during each star's Wolf-Rayet stage. The X-ray luminosity is enhanced by two to three orders of magnitude to ˜1037 erg s-1 for at least 4600 yr after each SN explosion, at which time the blast wave leaves the grid and the X-ray luminosity drops. The X-ray luminosity of our simulation is generally considerably fainter than predicted from spherically symmetric bubble models, due to the leakage of hot gas material through gaps in the outer shell. This process reduces the pressure within our simulation and thus the X-ray emission. However, the X-ray luminosities and temperatures which we obtain are comparable to similarly powerful massive young clusters.

Rogers, H.; Pittard, J. M.

2014-06-01

220

Water maser emission from X-ray-heated circumnuclear gas in active galaxies  

NASA Technical Reports Server (NTRS)

We have modeled the physical and chemical conditions present within dense circumnuclear gas that is irradiated by X-rays from an active galactic nucleus. Over a wide range of X-ray fluxes and gas pressures, the effects of X-ray heating give rise to a molecular layer at temperatures of 400-1000 K within which the water abundance is large. The physical conditions within this molecular layer naturally give rise to collisionally pumped maser emission in the 6(sub 16) - 5(sub 23) 22 GHz transition of ortho-water, with predicted maser luminosities of 10(exp 2 +/- 0.5) solar luminosity per sq. pc of illuminated area. Given plausible assumptions about the geometry of the source and about the degree to which the maser emission is anisotropic, such surface luminosities are sufficient to explain the large apparent luminosities observed in water maser sources that are associated with active galactic nuclei.

Neufeld, David A.; Maloney, Philip R.; Conger, Sarah

1994-01-01

221

X-ray emission from old and intermediate age brown dwarfs  

E-print Network

According to the paradigm of solar-type dynamo action brown dwarfs should not exhibit magnetic activity as they are fully convective. Indeed, Halpha observations of ultracool field dwarfs indicate a decline of activity setting in near the substellar limit. X-ray emission traditionally serves as another means to examine magnetic activity on stars. The substellar regime can now be accessed with the new generation of X-ray instruments onboard XMM-Newton and Chandra. We report on two recent XMM-Newton observations of brown dwarfs in the Pleiades cluster and in the field aiming to constrain the age and effective temperature dependence of X-ray emission from substellar objects.

B. Stelzer; R. Neuhaeuser

2002-06-17

222

X-RAY EMISSION FROM NITROGEN-TYPE WOLF-RAYET STARS  

SciTech Connect

We summarize new X-ray detections of four nitrogen-type Wolf-Rayet (WR) stars obtained in a limited survey aimed at establishing the X-ray properties of WN stars across their full range of spectral subtypes. None of the detected stars is so far known to be a close binary. We report Chandra detections of WR 2 (WN2), WR 18 (WN4), and WR 134 (WN6), and an XMM-Newton detection of WR79a (WN9ha). These observations clearly demonstrate that both WNE and WNL stars are X-ray sources. We also discuss Chandra archive detections of the WN6h stars WR 20b, WR 24, and WR 136 and ROSAT non-detections of WR 16 (WN8h) and WR 78 (WN7h). The X-ray spectra of all WN detections show prominent emission lines and an admixture of cool (kT < 1 keV) and hot (kT > 2 keV) plasma. The hotter plasma is not predicted by radiative wind shock models and other as yet unidentified mechanisms are at work. Most stars show X-ray absorption in excess of that expected from visual extinction (A {sub V}), likely due to their strong winds or cold circumstellar gas. Existing data suggest a falloff in X-ray luminosity toward later WN7-9 subtypes, which have higher L {sub bol} but slower, denser winds than WN2-6 stars. This provides a clue that wind properties may be a more crucial factor in determining emergent X-ray emission levels than bolometric luminosity.

Skinner, Stephen L.; Sokal, Kimberly R. [Center for Astrophysics and Space Astronomy (CASA), University of Colorado, Boulder, CO 80309-0389 (United States); Zhekov, Svetozar A. [JILA, University of Colorado, Boulder, CO 80309-0440 (United States); Guedel, Manuel [Institute of Astronomy, ETH Zuerich, Wolfgang-Pauli-Str. 27, 8093 Zuerich (Switzerland); Schmutz, Werner [Physikalisch-Meteorologisches Observatorium Davos and World Radiation Center (PMOD/WRC), Dorfstrasse 33, CH-7260 Davos Dorf (Switzerland)], E-mail: Stephen.Skinner@colorado.edu

2010-03-15

223

X-ray continuum and iron K emission line from the radio galaxy 3C 390.3  

NASA Technical Reports Server (NTRS)

X-ray properties of the radio galaxy 3C 390.3 were investigated using the European X-ray Observatory Satellite (EXOSAT) and Ginga satellites. Long-term, large-amplitude X-ray intensity changes were detected over a period extending from 1984 through 1991, and high-quality X-ray spectra were obtained especially with Ginga. The X-ray continuum spectra were described with power-law model with photon slope in the range 1.5-1.8, and the slope flattened as the 2-20 keV luminosity decreased by 40%. There was a first detection of the iron emission line from this source at the 90% confidence level. An upper limit was derived on the thermal X-ray component. X-ray emission mechanisms and possible origins of the long-term variation are discussed.

Inda, M.; Makishima, K.; Kohmura, Y.; Tashiro, M.; Ohashi, T.; Barr, P.; Hayashida, K.; Palumbo, G. G. C.; Trinchieri, G.; Elvis, M.

1994-01-01

224

Solar Control on Jupiter's Equatorial X-ray Emissions: 26-29 November 2003 XMM-Newton Observation  

E-print Network

During November 26-29, 2003 XMM-Newton observed soft (0.2-2 keV) X-ray emission from Jupiter for 69 hours. The low-latitude X-ray disk emission of Jupiter is observed to be almost uniform in intensity with brightness that is consistent with a solar-photon driven process. The simultaneous lightcurves of Jovian equatorial X-rays and solar X-rays (measured by the TIMED/SEE and GOES satellites) show similar day-to-day variability. A large solar X-ray flare occurring on the Jupiter-facing side of the Sun is found to have a corresponding feature in the Jovian X-rays. These results support the hypothesis that X-ray emission from Jovian low-latitudes are solar X-rays scattered from the planet's upper atmosphere, and suggest that the Sun directly controls the non-auroral X-rays from Jupiter's disk. Our study also suggests that Jovian equatorial X-rays can be used to monitor the solar X-ray flare activity on the hemisphere of the Sun that is invisible to space weather satellites.

Anil Bhardwaj; Graziella Branduardi-Raymont; Ronald F. Elsner; G. Randall Gladstone; Gavin Ramsay; Pedro Rodriguez; Roberto Soria; J. Hunter Waite Jr.; Thomas E. Cravens

2005-04-29

225

WEAK HARD X-RAY EMISSION FROM TWO BROAD ABSORPTION LINE QUASARS OBSERVED WITH NuSTAR: COMPTON-THICK ABSORPTION OR INTRINSIC X-RAY WEAKNESS?  

SciTech Connect

We present Nuclear Spectroscopic Telescope Array (NuSTAR) hard X-ray observations of two X-ray weak broad absorption line (BAL) quasars, PG 1004+130 (radio loud) and PG 1700+518 (radio quiet). Many BAL quasars appear X-ray weak, probably due to absorption by the shielding gas between the nucleus and the accretion-disk wind. The two targets are among the optically brightest BAL quasars, yet they are known to be significantly X-ray weak at rest-frame 2-10 keV (16-120 times fainter than typical quasars). We would expect to obtain Almost-Equal-To 400-600 hard X-ray ({approx}> 10 keV) photons with NuSTAR, provided that these photons are not significantly absorbed (N{sub H} {approx}< 10{sup 24} cm{sup -2}). However, both BAL quasars are only detected in the softer NuSTAR bands (e.g., 4-20 keV) but not in its harder bands (e.g., 20-30 keV), suggesting that either the shielding gas is highly Compton-thick or the two targets are intrinsically X-ray weak. We constrain the column densities for both to be N{sub H} Almost-Equal-To 7 Multiplication-Sign 10{sup 24} cm{sup -2} if the weak hard X-ray emission is caused by obscuration from the shielding gas. We discuss a few possibilities for how PG 1004+130 could have Compton-thick shielding gas without strong Fe K{alpha} line emission; dilution from jet-linked X-ray emission is one likely explanation. We also discuss the intrinsic X-ray weakness scenario based on a coronal-quenching model relevant to the shielding gas and disk wind of BAL quasars. Motivated by our NuSTAR results, we perform a Chandra stacking analysis with the Large Bright Quasar Survey BAL quasar sample and place statistical constraints upon the fraction of intrinsically X-ray weak BAL quasars; this fraction is likely 17%-40%.

Luo, B.; Brandt, W. N. [Department of Astronomy and Astrophysics, 525 Davey Lab, The Pennsylvania State University, University Park, PA 16802 (United States); Alexander, D. M.; Hickox, R. [Department of Physics, Durham University, South Road, Durham DH1 3LE (United Kingdom); Harrison, F. A.; Fuerst, F.; Grefenstette, B. W.; Madsen, K. K. [Cahill Center for Astronomy and Astrophysics, California Institute of Technology, Pasadena, CA 91125 (United States); Stern, D. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Bauer, F. E. [Departamento de Astronomia y Astrofisica, Pontificia Universidad Catolica de Chile, Casilla 306, Santiago 22 (Chile); Boggs, S. E.; Craig, W. W. [Space Sciences Laboratory, University of California, Berkeley, CA 94720 (United States); Christensen, F. E. [DTU Space-National Space Institute, Technical University of Denmark, Elektrovej 327, DK-2800 Lyngby (Denmark); Comastri, A. [INAF-Osservatorio Astronomico di Bologna, Via Ranzani 1, I-40127 Bologna (Italy); Fabian, A. C. [Institute of Astronomy, Madingley Road, Cambridge CB3 0HA (United Kingdom); Farrah, D. [Department of Physics, Virginia Tech, Blacksburg, VA 24061 (United States); Fiore, F. [Osservatorio Astronomico di Roma, via Frascati 33, I-00040 Monteporzio Catone (Italy); Hailey, C. J. [Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027 (United States); Matt, G. [Dipartimento di Matematica e Fisica, Universita degli Studi Roma Tre, via della Vasca Navale 84, I-00146 Roma (Italy); Ogle, P. [IPAC, California Institute of Technology, Mail Code 220-6, Pasadena, CA 91125 (United States); and others

2013-08-01

226

A compact wavelength-dispersive X-ray spectrometer for particle-induced X-ray emission analysis  

Microsoft Academic Search

A new compact wavelength-dispersive X-ray spectrometer has been developed for our compact high energy ion microprobe system (“mikro-i”). This spectrometer is designed to detect four light elements, boron, carbon, nitrogen and oxygen. Using two multilayer X-ray analyzers, multilayer benders cut from a single metal block and a gas-proportional counter with a 150 mm × 20 mm wide, 1 ?m thick

Y. Furukawa; K. Yokoyama; K. Inoue; K. Ishibashi; H. Fukuyama

1996-01-01

227

Chandra Observation of an X-ray Flare at Saturn: Evidence for Direct Solar Control on Saturn's Disk X-ray Emissions  

E-print Network

Saturn was observed by Chandra ACIS-S on 20 and 26-27 January 2004 for one full Saturn rotation (10.7 hr) at each epoch. We report here the first observation of an X-ray flare from Saturn's non-auroral (low-latitude) disk, which is seen in direct response to an M6-class flare emanating from a sunspot that was clearly visible from both Saturn and Earth. Saturn's disk X-ray emissions are found to be variable on time scales of hours to weeks to months, and correlated with solar F10.7 cm flux. Unlike Jupiter, X-rays from Saturn's polar (auroral) region have characteristics similar to those from its disk. This report, combined with earlier studies, establishes that disk X-ray emissions of the giant planets Saturn and Jupiter are directly regulated by processes happening on the Sun. We suggest that these emissions could be monitored to study X-ray flaring from solar active regions when they are on the far side and not visible to Near-Earth space weather satellites.

Anil Bhardwaj; Ronald F. Elsner; J. Hunter Waite Jr; G. Randall Gladstone; Thomas E. Cravens; Peter G. Ford

2005-04-05

228

Hard X-ray diffuse emission from the Galactic Center seen by INTEGRAL  

E-print Network

We study the hard X-ray (20-100 keV) variability of the Galactic Center (GC) and of the nearby sources on the time scale of 1000 s. We find that 3 of the 6 hard X-ray sources detected by INTEGRAL within the central 1 degree of the Galaxy are not variable on this time scale: the GC itself (the source IGR J1745.6-2901) as well as the source 1E 1743.1-2843 and the molecular cloud Sgr B2. We put an upper limit of 5 x 10^{-12} erg/(cm^2 sec) (in 20 to 60 keV band) on the variable emission form the supermassive black hole (the source Sgr A*) which powers the activity of the GC(although we can not exclude the possibility of rare stronger flares). The non-variable 20-100 keV emission from the GC turns out to be the high-energy non-thermal tail of the diffuse hard ``8 keV'' component of emission from Sgr A region. Combining the XMM-Newton and INTEGRAL data we find that the size of the extended hard X-ray emission region is about 20 pc. The only physical mechanism of production of diffuse non-thermal hard X-ray flux, which does not contradict the multi-wavelength data on the GC, is the synchrotron emission from electrons of energies 10-100 TeV.

A. Neronov; M. Chernyakova; T. J. -L. Courvoisier; R. Walter

2005-06-18

229

Very high energy ?-ray emission from X-ray transients during major outbursts  

NASA Astrophysics Data System (ADS)

Context: Some high mass X-ray binaries (HMXB) have been recently confirmed as ?-ray sources by ground based Cherenkov telescopes. In this work, we discuss the ?-ray emission from X-ray transient sources formed by a Be star and a highly magnetized neutron star. This kind of systems can produce variable hadronic ?-ray emission through the mechanism proposed by Cheng and Ruderman, where a proton beam accelerated in the pulsar magnetosphere impacts the transient accretion disk. We choose as case of study the best known system of this class: A0535+26. Aims: We aim at making quantitative predictions about the very high-energy radiation generated in Be-X ray binary systems with strongly magnetized neutron stars. Methods: We study the gamma-ray emission generated during a major X-ray outburst of a HMXB adopting for the model the parameters of A0535+26. The emerging photon signal from the disk is determined by the grammage of the disk that modulates the optical depth. The electromagnetic cascades initiated by photons absorbed in the disk are explored, making use of the so-called "Approximation A" to solve the cascade equations. Very high energy photons induce Inverse Compton cascades in the photon field of the massive star. We implemented Monte Carlo simulations of these cascades, in order to estimate the characteristics of the resulting spectrum. Results: TeV emission should be detectable by Cherenkov telescopes during a major X-ray outburst of a binary formed by a Be star and a highly magnetized neutron star. The ?-ray light curve is found to evolve in anti-correlation with the X-ray signal.

Orellana, M.; Romero, G. E.; Pellizza, L. J.; Vidrih, S.

2007-04-01

230

Modeling of X-ray emissions produced by stepping lightning leaders  

NASA Astrophysics Data System (ADS)

Intense and brief bursts of X-ray emissions have been measured during the stepping process of both natural cloud-to-ground (CG) and rocket-triggered lightning flashes. In this paper, we investigate theoretically the energy spectra of X-rays produced by the bremsstrahlung emission of thermal runaway electrons accelerated in the inhomogeneous electric field produced around lightning leader tips. The X-ray energy spectrum depends on the physical properties of the associated lightning leaders. Consequently, X-ray measurements can be used for diagnostics of the electrical properties of lightning stepped leaders. We report simulation results of the photon energy spectra produced by 5 and 10 MV negative CG lightning discharges that would be measured from the ground using ideal detectors. We also quantify theoretically the radial dependence of X-ray energy spectra received at ground level during the leader stepping process. Moreover, it is found that the ground radiation generated in this process is harmless to humans.

Xu, Wei; Celestin, Sebastien; Pasko, Victor P.

2014-10-01

231

Femtosecond Laser-Induced X-Ray Emission from Gold Nano-Colloidal Solutions  

NASA Astrophysics Data System (ADS)

By irradiating droplets of chloroauric acid aqueous solution (˜ 1{0}^{-3} mol/l) and those of gold nano-colloidal solution with near-IR (˜800 nm) femtosecond (35 fs) laser light, the X-ray intensity and the X-ray emission spectra were recorded. The laser pulses were focused onto the surface of droplets (˜90?m in diameter) ejected from an ink-jet nozzle by an off-axis parabolic mirror. The X-ray intensity was about 660 times higher with the gold nano-colloidal solution than with the chloroauric acid aqueous solution. Electron temperatures calculated from the X-ray emission spectra on the basis of the assumption of the Boltzmann distribution were 0.074 keV for the chloroauric acid aqueous solution and 2.9 keV for the gold nano-colloidal solution. The significantly high X-ray intensity and electron temperature obtained with the gold nano-colloidal solution can be ascribed to the enhancement of the laser field intensity by surface plasmon resonance at the gold nano-particles.

Hatanaka, K.; Yoshida, K.; Iwasaki, A.; Yamanouchi, K.

232

Investigating the hard X-ray emission from the hottest Abell cluster A2163 with Suzaku  

NASA Astrophysics Data System (ADS)

Context. We present the results from Suzaku of the hottest Abell galaxy cluster A2163 at z = 0.2. Aims: To study the physics of gas heating in cluster mergers, we investigated hard X-ray emission from the merging cluster A2163, which hosts the brightest synchrotron radio halo. Methods: We analyzed hard X-ray emission spectra accumulated from two-pointed Suzaku observations. Non-thermal hard X-ray emission should result from the inverse Compton scattering of relativistic electrons by photons in the cosmic microwave background. To measure this emission, the dominant thermal emission in the hard X-ray band must be modeled in detail. To this end, we analyzed the combined broadband X-ray data of A2163 collected by Suzaku and XMM-Newton, assuming single- and multi-temperature models for thermal emission and the power-law model for non-thermal emission. Comparing the non-thermal hard X-ray flux to radio synchrotron emission, we also estimated the magnetic field in the cluster. Results: From the Suzaku data, we detected significant hard X-ray emission from A2163 in the 12-60 keV band at the 28? level (or at the 5.5? level if a systematic error of the non-X-ray background model is considered). The Suzaku HXD spectrum alone is consistent with the single-temperature thermal model of gas temperature kT = 14 keV. From the XMM-Newton data, we constructed a multi-temperature model including a very hot (kT = 18 keV) component in the north-east region. Incorporating the multi-temperature and the power-law models into a two-component model with a radio-band photon index, where ? = 2.18, the 12-60 keV energy flux of non-thermal emission is constrained within 5.3 ± 0.9 (±3.8) × 10-12 erg s-1cm-2 (the first and second errors refer to the 1? statistical and systematic uncertainties, respectively). The 90% upper limit of detected inverse Compton emission is marginal (FNT < 1.2 × 10-11 erg s-1cm-2 in the 12-60 keV band). The estimated magnetic field in A2163 is B > 0.098 ?G. While the present results represent a three-fold increase in the accuracy of the broadband (0.3-60 keV) spectral model of A2163, more sensitive hard X-ray observations are needed to decisively test for the presence of hard X-ray emission due to inverse Compton emission.

Ota, N.; Nagayoshi, K.; Pratt, G. W.; Kitayama, T.; Oshima, T.; Reiprich, T. H.

2014-02-01

233

X-Ray Emission From Comet McNaught-Hartley (C/1999 T1)  

NASA Astrophysics Data System (ADS)

Comet McNaught-Hartley was observed in five one-hour sessions from January 8 to 14 2001 using the advanced CCD imaging spectrometer on board the Chandra X-ray Observatory. The X-ray image of the comet does not show a crescent-like shape. Two brightness maxima are offset from the nucleus between the sunward and comet velocity directions. The comet mean X-ray luminosity is equal to 7.8x 1015 erg s-1 for photon energy E > 150 eV and aperture 1.5x 105 km where the comet X-ray brightness is 20% of the peak value. Day-to-day variations in X-rays reach a factor of 5. The comet and Earth were seeing different faces of the Sun, and the expected time delay between the solar wind events on the Earth and the comet was 6 days. The best correlation between the X-ray luminosity and the solar wind proton density is for the delay of 5.5 days and may be explained by the higher velocity of heavy ions. Gas production rate was 1029 s-1 during the observations, and the efficiency of X-ray excitation adjusted to the proton density of 10 cm-3 is equal to 5x 10-14 erg AU3/2. The strongest short-term variation was by a factor of 1.75 for 1600 s. This variation may be explained by a sudden (for a few minutes) decrease in the solar wind flux by a factor of 3. Careful background subtraction made it possible to extract the comet spectrum from 150 to 1000 eV. No signal was detected at E > 1000 eV, and an upper limit to any emission with E > 1000 eV is 0.3% of the emission at 150-1000 eV. The best ?2-fit model to the spectrum consists of 9 narrow emissions. The emission energies and intensities are in good agreement with a charge exchange spectrum calculated by us for the slow solar wind. Using this spectrum, we identify the observed emissions as (Ne7+ + Mg7+ + Mg8+) 195 eV, (Mg8+ + Mg9+ + Si8+) 250 eV, C5+ 370 and 460 eV, O6+ 560 eV, O7+ 650, 780, and 840 eV, and Ne8+ 940 eV. X-ray spectroscopy of comets may be used to diagnose the solar wind composition and its interaction with comets.

Krasnopolsky, V.; Christian, D.; Kharchenko, V.; Dalgarno, A.; Wolk, S.; Lisse, C.; Stern, A.

2002-05-01

234

Measurement of the Radius of Neutron Stars with High Signal-to-noise Quiescent Low-mass X-Ray Binaries in Globular Clusters  

NASA Astrophysics Data System (ADS)

This paper presents the measurement of the neutron star (NS) radius using the thermal spectra from quiescent low-mass X-ray binaries (qLMXBs) inside globular clusters (GCs). Recent observations of NSs have presented evidence that cold ultra dense matter—present in the core of NSs—is best described by "normal matter" equations of state (EoSs). Such EoSs predict that the radii of NSs, R NS, are quasi-constant (within measurement errors, of ~10%) for astrophysically relevant masses (M NS>0.5 M ?). The present work adopts this theoretical prediction as an assumption, and uses it to constrain a single R NS value from five qLMXB targets with available high signal-to-noise X-ray spectroscopic data. Employing a Markov chain Monte-Carlo approach, we produce the marginalized posterior distribution for R NS, constrained to be the same value for all five NSs in the sample. An effort was made to include all quantifiable sources of uncertainty into the uncertainty of the quoted radius measurement. These include the uncertainties in the distances to the GCs, the uncertainties due to the Galactic absorption in the direction of the GCs, and the possibility of a hard power-law spectral component for count excesses at high photon energy, which are observed in some qLMXBs in the Galactic plane. Using conservative assumptions, we found that the radius, common to the five qLMXBs and constant for a wide range of masses, lies in the low range of possible NS radii, R_NS =9.1^{+ 1.3}_{- 1.5} \\,km (90%-confidence). Such a value is consistent with low-R NS equations of state. We compare this result with previous radius measurements of NSs from various analyses of different types of systems. In addition, we compare the spectral analyses of individual qLMXBs to previous works.

Guillot, Sebastien; Servillat, Mathieu; Webb, Natalie A.; Rutledge, Robert E.

2013-07-01

235

X-ray emission from a high-atomic-number z-pinch plasma created from compact wire arrays  

Microsoft Academic Search

Thermal and nonthermal x-ray emission from the implosion of compact tungsten wire arrays in 5-MA Saturn discharges is reported. The timing of multiple implosions and the thermal x-ray spectra (1 to 10 keV) agree with 2D radiation-hydrocode simulations. Nonthermal x-ray emission (10 to 100 keV) correlates with pinch spots distributed along the z-axis. The similarities of the measured nonthermal spectrum,

T. W. L. Sanford; D. Mosher; J. S. De Groot

1996-01-01

236

The Detection of Circumnuclear X-Ray Emission from the Seyfert Galaxy NGC 3516  

NASA Technical Reports Server (NTRS)

We present the first high-resolution, X-ray image of the circumnuclear regions of the Seyfert 1 galaxy NGC 3516, using the Chandra X-ray Observatory (CXO). All three of the CXO observations reported were performed with one of the two grating assemblies in place, and here we restrict our analysis to undispersed photons (i.e. those detected in the zeroth-order). A previously-unknown X-ray source is detected approximately 6 arcsec (1.1h(sub 75)(exp -1) kpc) NNE of the nucleus (position angle approximately 29 degrees) which we designate CXOU 110648.1 + 723412. Its spectrum can be characterized as a power law with a photon index (Gamma) approximately 1.8 - 2.6, or as thermal emission with a temperature kT approximately 0.7 - 3 keV. Assuming a location within NGC 3516, isotropic emission implies a luminosity L approximately 2 - 8 x 10(exp 39)h(sub 75)(exp-2) erg s(exp -1) in the 0.4 - 2 keV band. If due to a single point source, the object is super-Eddington for a 1.4 solar mass neutron star. However, multiple sources or a small, extended source cannot be excluded using the current data. Large-scale extended S-ray emission is also detected out to approximately 10 arcsec (approximately 2h(sub 75)(exp -1) kpc) from the nucleus to the NE and SW, and is approximately aligned with the morphologies of the radio emission and extended narrow emission line region (ENLR). The mean luminosity of this emission is 1 - 5 x 10(exp 37)h(sub 75)(exp -2) erg s(exp -1) arcsec(exp -2), in the 0.4 - 2 keV band. Unfortunately the current data cannot usefully constrain its spectrum. These results are consistent with earlier suggestions of circumnuclear X-ray emissi in NGC 3516 based on ROSAT observations, and thus provide the first clear detection of extended X-ray emission in a Seyfert 1.0 galaxy. If the extended emission is due to scattering of the nuclear X-ray continuum, then the pressure in the X-ray emitting gas is at least two orders of magnitude too small to provide the confining medium for the ENLR clouds.

George, I. M.; Turner, T. J.; Netzer, H.; Kraemer, S. B.; Ruiz, J.; Chelouche, D.; Crenshaw, D. M.; Yaqoob, T.; Nandra, K.; Mushotzky, R. F.; White, Nicholas E. (Technical Monitor)

2001-01-01

237

Discrete sources as the origin of the Galactic X-ray ridge emission.  

PubMed

An unresolved X-ray glow (at energies above a few kiloelectronvolts) was discovered about 25 years ago and found to be coincident with the Galactic disk-the Galactic ridge X-ray emission. This emission has a spectrum characteristic of a approximately 10(8) K optically thin thermal plasma, with a prominent iron emission line at 6.7 keV. The gravitational well of the Galactic disk, however, is far too shallow to confine such a hot interstellar medium; instead, it would flow away at a velocity of a few thousand kilometres per second, exceeding the speed of sound in the gas. To replenish the energy losses requires a source of 10(43) erg s(-1), exceeding by orders of magnitude all plausible energy sources in the Milky Way. An alternative is that the hot plasma is bound to a multitude of faint sources, which is supported by the recently observed similarities in the X-ray and near-infrared surface brightness distributions (the latter traces the Galactic stellar distribution). Here we report that at energies of approximately 6-7 keV, more than 80 per cent of the seemingly diffuse X-ray emission is resolved into discrete sources, probably accreting white dwarfs and coronally active stars. PMID:19407795

Revnivtsev, M; Sazonov, S; Churazov, E; Forman, W; Vikhlinin, A; Sunyaev, R

2009-04-30

238

The X-Ray Emissions from the M87 Jet: Diagnostics and Physical Interpretation  

Microsoft Academic Search

We reanalyze the deep Chandra observations of the M87 jet, first examined by Wilson & Yang in 2002. By employing an analysis chain that also includes image deconvolution, knots HST-1 and I are fully separated from adjacent emission. We derive the spatially resolved X-ray spectrum of the jet using the most recent response functions and find slight but significant variations

Eric S. Perlman; Andrew S. Wilson

2005-01-01

239

Detections of hard X-ray emissions from bright early-type galaxies with ASCA  

NASA Technical Reports Server (NTRS)

Five bright elliptical galaxies in the Virgo Cluster, NGC 4365, NGC 4374 (M84), NGC 4406 (M86), NGC 4472 (M49), and NGC 4636, were observed with ASCA. In addition to the extended thermal X-ray emission of temperature kT approximately 1 keV, harder X-rays with color temperature kT greater than or equal to 2 keV were detected from all of them. The 2-10 keV luminosities of this hard component for the five galaxies, integrated within 5 min, are distributed within a relatively narrow range of (1-4) x 10(exp 40) ergs/s. The hard X-ray component is primarily attributed to the integrated emission from discrete X-ray sources. In NGC 4406 and NGC 4374 the data indicate that the hard component is contributed additionally by foreground/background emission from the hot intracluster medium (ICM) of the Virgo Cluster. The hard component of NGC 4472 seems also contributed by the Virgo ICM emission, but in this case there is evidence that the ICM brightness is locally enhanced within approximately 10 min of NGC 4472.

Matsushita, K.; Makishima, K.; Awaki, H.; Canizares, C. R.; Fabian, A. C.; Fukazawa, Y.; Loewenstein, M.; Matsumoto, H.; Mihara, T.; Mushotzky, R. F.

1994-01-01

240

THE MULTIELEMENTAL ANALYSIS OF DRINKING WATER USING PROTON-INDUCED X-RAY EMISSION (PIXE)  

EPA Science Inventory

A new, rapid, and economical method for the multielemental analysis of drinking water samples is described. The concentrations of 76 elements heavier than aluminum are determined using proton-induced x-ray emission (PIXE) technology. The concentration of sodium is evaluated using...

241

Implications of the non-detection of X-ray emission from HD 149427  

NASA Astrophysics Data System (ADS)

HD 149427 is a very enigmatic object. It has been classified either as a planetary nebula or as a D'-type symbiotic star. Its distance is also highly uncertain. Furthermore, HD 149427 is a potential jet source. We report the non-detection of X-ray emission from HD 149427 and explore the implications to its nature. We observed the object with XMM-Newton with an effective exposure time of 33.5 ks. The upper limit for the flux of the X-ray emission in the soft band (<2 keV) is 10^-15 erg s^-1 cm^-2, while in the hard band (>2 keV) it is about 10^-14 erg s^-1 cm^-2. We discuss the implication of our results in light of the possible natures of HD 149427 - being a planetary nebula or a symbiotic star, close or very distant. The derived upper limits on the mass accretion rate of the white dwarf are untypical for symbiotic stars and may favor the picture of HD 149427 being a young PN. HD 149427 might be a symbiotic star in hibernation - if a symbiotic star at all. We estimate the possible mass-loss rate and kinetic luminosity of the jet and find no contradiction with our upper limit of soft X-ray emission. Therefore the jet may be still present but it was too faint to be detected via soft X-ray emission.

Stute, M.; Luna, G. J. M.

2011-11-01

242

Relationship between Hard X-ray Emissions and Magnetic Field Strengths in Solar Flares  

Microsoft Academic Search

An asymmetric hard X-ray (HXR) characteristic in conjugate footpoints of newly reconnected magnetic fields, i.e. stronger HXR emissions with weaker magnetic fields and vice versa, is commonly observed in solar flares. It can be explained by the asymmetric magnetic mirroring that weaker magnetic fields would result in higher precipitation rate of energetic electrons from corona to chromosphere and thus stronger

M. Hsieh; Y. Yang; C. Z. Cheng

2009-01-01

243

The Relationship Between Solar Radio and Hard X-Ray Emission  

NASA Technical Reports Server (NTRS)

This review discusses the complementary relationship between radio and hard Xray observations of the Sun using primarily results from the era of the Reuven Ramaty High Energy Solar Spectroscopic Imager satellite. A primary focus of joint radio and hard X-ray studies of solar flares uses observations of nonthermal gyrosynchrotron emission at radio wavelengths and bremsstrahlung hard X-rays to study the properties of electrons accelerated in the main flare site, since it is well established that these two emissions show very similar temporal behavior. A quantitative prescription is given for comparing the electron energy distributions derived separately from the two wavelength ranges: this is an important application with the potential for measuring the magnetic field strength in the flaring region, and reveals significant differences between the electrons in different energy ranges. Examples of the use of simultaneous data from the two wavelength ranges to derive physical conditions are then discussed, including the case of microflares, and the comparison of images at radio and hard X-ray wavelengths is presented. There have been puzzling results obtained from observations of solar flares at millimeter and submillimeter wavelengths, and the comparison of these results with corresponding hard X-ray data is presented. Finally, the review discusses the association of hard X-ray releases with radio emission at decimeter and meter wavelengths, which is dominated by plasma emission (at lower frequencies) and electron cyclotron maser emission (at higher frequencies), both coherent emission mechanisms that require small numbers of energetic electrons. These comparisons show broad general associations but detailed correspondence remains more elusive.

White, S. M.; Benz, A. O.; Christe, S.; Farnik, F.; Kundu, M. R.; Mann, G.; Ning, Z.; Raulin, J.-P.; Silva-Valio, A. V. R.; Saint-Hilaire, P.; Vilmer, N.; Warmuth, A.

2011-01-01

244

10 micron detection of the hard X-ray transient GRO J0422+32: Free-free emission from an X-ray-driven accretion disk wind?  

NASA Technical Reports Server (NTRS)

We report the detection of 10 micrometer emission from the transient low-mass X-ray binary (LMXB) and optical nova GRO J0422+32 near the maximum of its outburst. We discuss this result in terms of (1) a 'standard' model according to which low-energy radiation of LMXB is caused by reprocessing of X-rays in an accretion disk; (2) emission from a cool secondary star; (3) emission from dust grains heated by the transient X-rays, and (4) free-free emission from an X-ray-driven wind from the accretion disk. Only the fourth alternative provides a viable explanation for the observed 10 micrometer emission, with a mass-loss rate in the disk wind that may be substantially higher than the rate of accretion onto the compact star. The presence of such a wind may have a profound effect on the evolution of the binary, and contribute to the solution of the 'birthrate problem' of millisecond ratio pulsars.

Paradijs, Van J.; Telesco, C. M.; Kouveliotou, C.; Fishman, G. J.

1994-01-01

245

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

NASA Technical Reports Server (NTRS)

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.

Rawley, Gayle L.

1993-01-01

246

Modeling of the EUV and X-Ray Emission Spectra Induced by the Solar Winds Ions in the Heliosphere  

NASA Technical Reports Server (NTRS)

We have carried out investigation of the EUV and X-ray emission spectra induced in interaction between the Solar Wind (SW) and interstellar neutral gas. The spectra of most important SW ions have been computed for the charge-exchange mechanism of X-ray emission using new accurate spectroscopic data from recent laboratory measurements and theoretical calculations. Total spectra have been constructed as a sum of spectra induced in the charge-exchange collisions by individual O(exp q+), C(exp q+), N(exp q+), Ne(exp q+), Mg (exp q+) and Fe(exp q+) ions. Calculations have been performed for X-ray emission from the heliospheric hydrogen and helium gas. X-ray maps of the heliosphere have been computed. The power density of X-ray sources in the heliospheric ecliptic plane is shown for the H gas and for the He gas. Distances from the Sun (0,0) are given in AU. The helium cone is clear seen in the X-ray map of the charge-exchange emission induced by the solar wind. X-ray emission spectra detected by the Chandra X-ray telescope from the "dark" side of Moon has been identified as a X-ray background emission induced by the solar wind from the geocorona. Spectra and intensities of this charge-exchange X-rays have been compared with the heliospheric component of the X-ray background. Observations and modeling of the SW spectra induced from the geocorona indicate a strong presence of emission lines of highly charged oxygen ions. Anisotropy in distribution of heliospheric X-rays has been predicted and calculated for the regions of the fast and slow solar winds.

Kharchenko, Vasili

2005-01-01

247

Current sheath curvature correlation with the neon soft x-ray emission from plasma focus device  

Microsoft Academic Search

The insulator sleeve length is one of the major parameters that can\\u000a severely affect the neon soft x-ray yield from a plasma focus. The\\u000a effect of the insulation sleeve length on various characteristic timings\\u000a of plasma focus discharges and hence the soft x-ray emission\\u000a characteristics has been investigated using a resistive divider. The\\u000a pinhole images and laser shadowgraphy are used

T. Zhang; X. Lin; K. A. Chandra; T. L. Tan; S. V. Springham; A. Patran; P. Lee; S. Lee; R. S. Rawat

2005-01-01

248

Binarity and Accretion: X-Ray Emission from AGB stars with FUV Excesses  

NASA Astrophysics Data System (ADS)

We propose a pilot survey for X-ray emission from AGB stars that are candidates for having binary companions with active accretion. These objects were identified via our innovative technique to search for FUV/NUV excesses in AGB stars using GALEX. The detection (or non-detection) of X-rays from this sample will enable us to begin testing models for the origin of the UV-excesses, leading to vital breakthroughs in our understanding of accretion-related phenomena and binarity in AGB stars. A larger survey, optimised using results fron this study, will be proposed in future cycles.

Sahai, Raghvendra

2012-10-01

249

Infrared emission from X-ray binaries - IRAS observations  

NASA Technical Reports Server (NTRS)

Theoretical calculations show that detectable amounts of FIR radiation can be produced by accretion disks around compact sources. Here, the HEAO A-1 Catalog (Wood et al., 1984) and Bradt and McClintock (1983) are used to select a likely set of candidate sources, and the IRAS Point Source Catalog and IRAS Serendipitous Survey Catalog are used to search for characteristic IR emission from sources in fields around them. Eighty-one candidates with 242 IRAS field sources were examined and color corrected. Eight of these have IR flux measurements which are consistent with emisison from an accretion disk S/N, although other mechanisms for their IR emission cannot yet be ruled out. Most have poor positional corespondences and must be considered suspect as identifications.

Smith, Howard A.; Beall, J. H.; Swain, Mark R.

1990-01-01

250

A waveguide electron cyclotron resonance source of X-ray emission for low-dose introscopy  

NASA Astrophysics Data System (ADS)

It is shown that a "point" target in a conventional evacuated waveguide in the magnetic field of a mirror trap formed by two disk magnets axially magnetized in the direction perpendicular to the electric field vector represents a source of X-ray bremsstrahlung of electrons accelerated in an ECR discharge with a broad range of photon energies up to 0.8 MeV. The dosage rate of the source is ˜1 R/h. The source fed from a conventional microwave oven has small dimensions and a low weight. It is easy-to-use and is suitable as a laboratory tool, in particular, in radiobiology and introscopy. After passing through the object, X-ray emission is recorded by a digital camera with the help of a highly sensitive X-ray fluorescent screen, which converts it into an optical image.

Sergeichev, K. F.; Ionidi, V. Yu.; Karfidov, D. M.; Lukina, N. A.

2013-12-01

251

Photospheric soft X-ray emission from hot DA white dwarfs  

NASA Technical Reports Server (NTRS)

The Einstein Observatory's imaging proportional counter has detected 150-eV soft X-ray radiation from the four hot DA white dwarfs EG 187, Gr 288 and 289, and LB 1663. The observed pulse height spectra suggest that the emission is generated by hot photospheres whose T(eff) lie in the 30,000-60,000 K range. The IUE spacecraft UV spectra and H-beta line profiles for the four stars have been fitted, along with the X-ray fluxes, with a grid of hot, high gravity, homogeneous model atmospheres of mixed H-He composition. In all cases, the data require the presence of some X-ray opacity in the photosphere. Attention is given to the implications of this result in the context of white dwarf surface layer diffusion theories. Also noted are the limits imposed on the hot white dwarf population by the Einstein Medium Sensitivity Survey.

Wesemael, F.; Raymond, J. C.; Kahn, S. M.; Liebert, J.; Steiner, J. E.; Shipman, H. L.

1984-01-01

252

X-ray Emission from Supernovae in Dense Circumstellar Matter Environments: a Search for Collisionless Shocks  

NASA Technical Reports Server (NTRS)

The optical light curve of some supernovae (SNe) may be powered by the outward diffusion of the energy deposited by the explosion shock (the so-called shock breakout) in optically thick (Tau approx > 30) circumstellar matter (CSM). Recently, it was shown that the radiation-mediated and radiation-dominated shock in an optically thick wind must transform into a collisionless shock and can produce hard X-rays. The X-rays are expected to peak at late times, relative to maximum visible light. Here we report on a search, using Swift/XRT and Chandra, for X-ray emission from 28 SNe that belong to classes whose progenitors are suspected to be embedded in dense CSM. Our sample includes 19 Type IIn SNe, one Type Ibn SN, and eight hydrogen-poor superluminous SNe (SLSN-I such as SN 2005ap). Two SNe (SN 2006jc and SN 2010jl) have X-ray properties that are roughly consistent with the expectation for X-rays from a collisionless shock in optically thick CSM. However, the X-ray emission from SN 2006jc can also be explained as originating in an optically thin region. Thus, we propose that the optical light curve of SN 2010jl is powered by shock breakout in CSM. We suggest that two other events (SN 2010al and SN 2011ht) were too X-ray bright during the SN maximum optical light to be explained by the shock-breakout model.We conclude that the light curves of some, but not all, SNe IIn/Ibn are powered by shock breakout in CSM. For the rest of the SNe in our sample, including all of the SLSN-I events, our X-ray limits are not deep enough and were typically obtained too early (i.e., near the SN maximum light) for definitive conclusions about their nature. Late-time X-ray observations are required in order to further test whether these SNe are indeed embedded in dense CSM. We review the conditions required for a shock breakout in a wind profile. We argue that the timescale, relative to maximum light, for the SN to peak in X-rays is a probe of the column density and the density profile above the shock region. In SNe whose X-ray emission slowly rises, and peaks at late times, the optical light curve is likely powered by the diffusion of shock energy in a dense CSM. We note that if the CSM density profile falls faster than a constant-rate wind-density profile, then X-rays may escape at earlier times than estimated for the wind-profile case. Furthermore, if the CSM has a region in which the density profile is very steep relative to a steady wind-density profile, or if the CSM is neutral, then the radio free-free absorption may be sufficiently low for radio emission to be detected.

Ofek, E. O.; Fox, D.; Cenko, Stephen B.; Sullivan, M; Gnat, O.; Frail, D. A.; Horesh, A.; Corsi, A.; Quimby, R. M.; Gehrels, N.; Kulkarni, S. R.; Gal-Yam, A.; Nugent, P. E.; Yaron, O.; Fillippenko, A. V; Kasliwal, M. M.; Bildsten, L.; Bloom, J. S.; Poznanski, D.; Arcavi, I.; Laher, R. R.; Levitan, D.; Sesar, B.; Surace, J..

3013-01-01

253

X-ray emission of brown dwarfs: Towards constraining the dependence on age, luminosity, and temperature  

E-print Network

Three brown dwarfs in different evolutionary stages have been observed with the Chandra X-ray Observatory. Combining the new observations with previous studies presented in the literature yields a brown dwarf sample that reaches well down into the cooling phase of brown dwarfs, allowing to investigate the possible influence of effective temperature on X-ray activity. Combining our results with published data allows us to consider a subsample of high-mass brown dwarfs (with 0.05-0.07 Msun), and another one characterized by similar effective temperature (with 2400-2800 K). Our findings support the idea that effective temperature plays a critical role for the X-ray activity in brown dwarfs. This underlines an earlier suggestion based on observations of chromospheric Ha emission in ultracool dwarfs that the low ionization fraction in the cool brown dwarf atmospheres may suppress magnetic activity.

B. Stelzer; G. Micela; E. Flaccomio; R. Neuhaeuser; R. Jayawardhana; ;; - Uni Palermo; - OA Palermo; - Uni Jena; - Uni Toronto

2005-11-07

254

X-ray Emission from Supernovae in Dense Circumstellar Matter Environments: a Search for Collisionless Shocks  

NASA Technical Reports Server (NTRS)

The optical light curve of some supernovae (SNe) may be powered by the outward diffusion of the energy deposited by the explosion shock (the so-called shock breakout) in optically thick (Tau approx > 30) circumstellar matter (CSM). Recently, it was shown that the radiation-mediated and radiation-dominated shock in an optically thick wind must transform into a collisionless shock and can produce hard X-rays. The X-rays are expected to peak at late times, relative to maximum visible light. Here we report on a search, using Swift/XRT and Chandra, for X-ray emission from 28 SNe that belong to classes whose progenitors are suspected to be embedded in dense CSM. Our sample includes 19 Type IIn SNe, one Type Ibn SN, and eight hydrogen-poor superluminous SNe (SLSN-I such as SN 2005ap). Two SNe (SN 2006jc and SN 2010jl) have X-ray properties that are roughly consistent with the expectation for X-rays from a collisionless shock in optically thick CSM. However, the X-ray emission from SN 2006jc can also be explained as originating in an optically thin region. Thus, we propose that the optical light curve of SN 2010jl is powered by shock breakout in CSM. We suggest that two other events (SN 2010al and SN 2011ht) were too X-ray bright during the SN maximum optical light to be explained by the shock-breakout model.We conclude that the light curves of some, but not all, SNe IIn/Ibn are powered by shock breakout in CSM. For the rest of the SNe in our sample, including all of the SLSN-I events, our X-ray limits are not deep enough and were typically obtained too early (i.e., near the SN maximum light) for definitive conclusions about their nature. Late-time X-ray observations are required in order to further test whether these SNe are indeed embedded in dense CSM. We review the conditions required for a shock breakout in a wind profile. We argue that the timescale, relative to maximum light, for the SN to peak in X-rays is a probe of the column density and the density profile above the shock region. In SNe whose X-ray emission slowly rises, and peaks at late times, the optical light curve is likely powered by the diffusion of shock energy in a dense CSM. We note that if the CSM density profile falls faster than a constant-rate wind-density profile, then X-rays may escape at earlier times than estimated for the wind-profile case. Furthermore, if the CSM has a region in which the density profile is very steep relative to a steady wind-density profile, or if the CSM is neutral, then the radio free-free absorption may be sufficiently low for radio emission to be detected.

Ofek, E. O.; Fox, D.; Cenko, Stephen B.; Sullivan, M; Gnat, O.; Frail, D. A.; Horesh, A.; Corsi, A.; Quimby, R. M.; Gehrels, N.; Kulkarni, S. R.; Gal-Yam, A.; Nugent, P. E.; Yaron, O.; Fillippenko, A. V; Kasliwal, M. M.; Bildsten, L.; Bloom, J. S.; Poznanski, D.; Arcavi, I.; Laher, R. R.; Levitan, D.; Sesar, B.; Surace, J..

2013-01-01

255

Characterization of ceramics and glass using proton-induced X-ray emission  

SciTech Connect

Proton-induced X-ray emission (PIXE) is one of various chemical analysis tools that uses X-rays to identify individual elements. It is closely related to X-ray fluorescence (XRF) and electron microprobe analysis (EMA). Although XRF and EMA are routinely used by materials engineers, PIXE is relatively uncommon. On the other hand, PIXE has proved to be the preferred technique in several specialized applications in environmental and biological studies. Many of the authors of this paper have recently demonstrated the utility of the technique in analyzing various commercial glass plates with and without transition-metal oxide coatings. The recent development of focused proton beams increases the potential of PIXE for the analysis of engineering materials.

Shackelford, J.F.; Risbud, S.H. (Univ. of California, Davis, CA (United States). Dept. of Chemical Engineering and Materials Science); Kusko, B.H.; Cahill, T.A. (Univ. of California, Davis, CA (United States). Crocker Nuclear Lab); Bihuniak, P.P.; Hanson, M.E. (PPG Industries, Inc., Pittsburgh, PA (United States). Advanced Research Div.)

1993-11-01

256

Measuring the X-ray Emission Impacting the Planets Orbiting Nearby Low-mass Stars  

NASA Astrophysics Data System (ADS)

M dwarf planetary systems present a truly exciting opportunity to discover and study the first habitable extrasolar planets in the next 5-10 years. As part of our larger HST MUSCLES project, we propose ACIS-S observations of 4 low-mass exoplanet hosts (3 M dwarfs -- GJ581, GJ1214, GJ849, and 1 K dwarf -- HD97658) that have no existing measurements of their coronal X-ray emission. We will measure their X-ray luminosities and coronal temperatures, and derive the high energy radiation field to facilitate exoplanet atmospheric modeling. These planetary systems allow study of exoplanet atmospheric chemistry and evolution under a wide diversity of physical situations. X-ray heating enhances evaporation and atmospheric escape, which can impact the long-term stability of exoplanetary atmospheres.

Brown, Alexander

2013-09-01

257

The origin of X-ray emission from T Tauri stars  

E-print Network

Several aspects concerning the origin of the very strong X-ray activity of T Tauri Stars (TTS) are still not well understood. Important new insight came recently from the Chandra Orion Ultradeep Project (COUP), a unique 10-day long Chandra observation of the Orion Nebula Cluster, and the XMM-Newton Extended Survey of the Taurus Molecular Cloud (XEST). Based mainly on the results of these two large projects, I will discuss our current knowledge about the location of the X-ray emitting structures in TTS, the nature of their coronal magnetic fields, inferences for pre-main-sequence magnetic dynamos, and the relation between accretion processes and X-ray emission.

Thomas Preibisch

2007-04-24

258

Discovery of X-Ray Emission in the Old Classical Nova DK Lacertae  

NASA Astrophysics Data System (ADS)

We report the discovery of X-ray emission at the position of the old classical nova DK Lacertae using the Swift satellite. Three observations were conducted using the X-Ray Telescope 62 years after the discovery of the nova, yielding 46 source signals in an exposure time of 4.8 ks. A background-subtracted count rate was 9 ± 2 × 10-3 counts s-1, corresponding to a detection significance level of 5?. The X-ray spectrum was characterized by a continuum extending up to about 7 keV, which can be modeled by a power-law component with a photon index of 1.4-5.6, or by a thermal bremsstrahlung component with a temperature of 0.7-13.3 keV, convolved with interstellar absorption with an equivalent hydrogen column density of 0.3-2.4 × 1022 cm-2. Assuming a distance of 3900 pc to the source, the luminosity was 1032-1034 erg s-1 in the 0.3-10 keV energy band. The origin of X-rays is considered to be either mass accretion on the white dwarf or adiabatic shocks in nova ejecta, with the former appearing much more likely. In either case, DK Lacertae represents a rare addition to the exclusive club of X-ray emitting old novae.

Takei, D.; Sakamoto, T.; Drake, J. J.

2013-01-01

259

X-ray emission processes in stars and their immediate environment  

PubMed Central

A decade of X-ray stellar observations with Chandra and XMM-Newton has led to significant advances in our understanding of the physical processes at work in hot (magnetized) plasmas in stars and their immediate environment, providing new perspectives and challenges, and in turn the need for improved models. The wealth of high-quality stellar spectra has allowed us to investigate, in detail, the characteristics of the X-ray emission across the Hertzsprung-Russell (HR) diagram. Progress has been made in addressing issues ranging from classical stellar activity in stars with solar-like dynamos (such as flares, activity cycles, spatial and thermal structuring of the X-ray emitting plasma, and evolution of X-ray activity with age), to X-ray generating processes (e.g., accretion, jets, magnetically confined winds) that were poorly understood in the preChandra/XMM-Newton era. I will discuss the progress made in the study of high energy stellar physics and its impact in a wider astrophysical context, focusing on the role of spectral diagnostics now accessible. PMID:20360562

Testa, Paola

2010-01-01

260

X-RAY AND TeV EMISSIONS FROM HIGH-FREQUENCY-PEAKED BL LAC OBJECTS  

SciTech Connect

The majority of the extragalactic sources yet detected at TeV photon energies belong to the class of 'high-frequency-peaked BL Lac objects' (HBLs) that exhibit a spectral energy distribution with a lower peak in the X-ray band. Such spectra are well described in terms of a log-parabolic shape with considerable curvature, and widely interpreted as synchrotron emission from ultrarelativistic electrons outflowing in a relativistic jet; these are expected to radiate also in {gamma}-rays through the inverse Compton process. Recently, we have compared the X-ray spectral parameter distributions of TeV detected HBLs (TBLs) with those undetected (UBLs), and found that the distributions of the peak energies E{sub p} are similarly symmetric around a value of a few keVs for both subclasses, while the X-ray spectra are broader for TBLs than for UBLs. Here we propose an acceleration scenario to interpret both the E{sub p} and the spectral curvature distributions in terms of a coherent and a stochastic acceleration mechanisms, respectively. We show how the curvature parameter b {approx_equal} 0.3-0.7 of the synchrotron X-rays, which depends only on the latter acceleration component, can be related to the inverse Compton luminosity in {gamma}-rays, thus introducing a link between the X-ray and the TeV observations of HBLs.

Massaro, F.; Paggi, A. [Harvard-Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, MA 02138 (United States); Cavaliere, A. [Dipartimento di Fisica, Universita di Roma Tor Vergata, Via della Ricerca Scientifica 1, I-00133 Roma (Italy)

2011-12-15

261

X-ray emission from the terrestrial magnetosheath  

E-print Network

as the proton thermal speed and is given by: #23; thermal = p 3k B T=m (2) and the total relative speed is given by #24; = p u 2 sw +#23; 2 thermal (3) T is the temperature, k B is Boltzmann's constant, m is the proton mass, and u sw is the bulk ow speed...umper and R. G. West, Discovery of X{rayand extreme ultraviolet emission from Comet C/Hyakutake 1996 B2, Science, 274, 205, 1996. Lisse, C. M., K. Dennerl, J. Englhauser, J. Trumper, F. E. Mar- shall, R. Petre, A. Valina, B. J. Kellett, and R. Bingham, X...

Robertson, Ina Picket; Cravens, Thomas Edward

2003-04-29

262

Charge-Exchange Emission and the Soft X-ray Background  

NASA Astrophysics Data System (ADS)

The Soft X-ray Background (SXRB) is composed of multiple elements, from the putative Local Hot Bubble (LHB), to the Galactic halo, to the Warm Hot Intergalactic Medium (WHIM). Each of these components fill the FOV of a typical X-ray detector, and must be separated from the other components, foreground emission, and instrumental backgrounds on the basis of spectral, spatial, and temporal variation. Since every neutral atom in the solar system can charge-exchange with highly ionized species in the solar wind, solar wind charge-exchange (SWCX) emission is a ubiquitous foreground. Since the SWCX spectrum is qualitatively identical to that of a very diffuse recombining plasma, which one might expect to see in the LHB or the Galactic halo, it is a significant impediment to study of the SXRB. I will describe our current understanding of the three major components of the SWCX emission and the major outstanding issues concerning the SWCX emission. I will discuss the observational techniques for diffuse X-ray emission that avoid problems with the SWCX emission, describe an ambitious program to characterize the SWCX emission, and outline the fundamental limitations of this program.

Kuntz, K. D.

2013-04-01

263

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

NASA Astrophysics Data System (ADS)

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.

Heard, Victoria; Warwick, Robert

2012-09-01

264

Detection of X-ray Emission From Galaxies Inside The Bootes Void  

NASA Technical Reports Server (NTRS)

We report the x-ray properties of Bootes void galaxies detected by the ROSAT All-Sky Survey (RASS). By searching the fields of 26 radio and 27 emission-line-selected void galaxies, we have detected 9 x-ray emitting void galaxies at >2.7-sigma confidence level. Five of these 9 galaxies are in the IP,AS subsample. We expect 2 detections at the redshift of the Bootes void based on previous positional cross-correlation studies of the RASS and IRAS Point Source Catalogue sources. Three of the x-ray emitting galaxies are AGNs (IRAS14288+5255, Mrk845, and IRAS 15195+5050), and the remaining 6 are all likely emission line galaxies (PC1357+4641, CG547, CG922, IRAS14SOO+4804, CG637, and IRAS15092+3940). The far infrared flux levels of the AGN sources implies most of the observed x-ray emissivity is from starburst activity. We have carried out timing and spectral analysis for the narrow-line Seyfert 1 galaxy Mrk845. Poor statistics prevents detailed analysis of the remaining sources. only two galaxies in our sample, BHI 1514+3819 and FSS 1515+3823, were observed during ROSAT pointed observations resulting in a nondetection at the 1-sigma level.

Kim, Chulhee; Boller, Thomas; Ghosh, Kajal K.; Swartz, Douglas A.; Ramsey, Brian D.; Rose, M. Franklin (Technical Monitor)

2000-01-01

265

Detection of X-Ray Emission from Galaxies Inside the Bootes Void  

NASA Technical Reports Server (NTRS)

We report the X-ray properties of Bootes void galaxies detected by the ROSAT All-Sky Survey (RASS). By searching the fields of 26 radio and 27 emission-line-selected void galaxies, we have detected nine X-ray-emitting void galaxies at greater than 2.7 sigma confidence level. Five of these nine galaxies are in the IRAS subsample. Two of the IRAS galaxies were previously identified in positional cross-correlation studies of the RASS and IRAS Point Source Catalogue sources. Three of the X-ray-emitting galaxies are active galactic nuclei (AGNs; IRAS 14288+5255, Mrk 845, and IRAS 15195+5050), three are emission-line galaxies (PC 1357+4641, CG 547, and CG 922), and the remaining three are of unknown spectral type (IRAS 14500+4804, CG 637, and MAS 15092+3940). The far-infrared flux levels of the AGN sources imply that most of the observed X-ray emissivity is from starburst activity. We have carried out timing and spectral analysis for the Seyfert 1 galaxy Mrk 845. Poor statistics prevents detailed analysis of the remaining sources. Only two galaxies in our sample, BHI 1514+3819 and FSS 1515+3823, were observed during ROSAT pointed observations resulting in a nondetection at the 1 sigma level.

Kim, Chulhee; Boller, T.; Ghosh, K.; Swartz, Douglas A.; Ramsey, Brian D.

2001-01-01

266

Charge Exchange Induced X-Ray Emission of Fe XXVI and Fe XXV  

NASA Astrophysics Data System (ADS)

Charge exchange is a vital process to consider in the modeling of X-ray spectra obtained by the Chandra, XMM Newton and Suzaku X-ray Space Observatories. The process is largely relevant in many astrophysical environments including comets (whose emission is primarily a product of charge exchange alone), the heliosphere, astropheres of stars, supernova remnants, the Galactic Center and the Galactic Ridge. The understanding of the X-ray spectra produced by these environments is crippled by the current lack of atomic and molecular data– especially for charge exchange. Here, we apply the Landau-Zener method to calculate total, n-resolved, n?-resolved and S-resolved cross sections for Fe26+ and Fe25+ collisions with H, He, H2, N2, H2O and CO. Using this data in a cascade model for X-ray emission, theoretical spectra for each system are predicted. The resulting spectra are then compared to experimental data for Fe26+ and Fe25+ collisions with N2. Fe XXVI and Fe XXV have been selected for study as iron emission lines have been detected in the galactic plane. Further, these systems illustrate computational difficulties for high projectile charges. In the Landau-Zener calculations, several ?-distribution models have been tested for the electron capture by the bare ion, Fe26+. Quantum defect methods are also employed to estimate excitation energies and transition probabilities for high-lying Rydberg levels of the He-like Fe24+.

Wargelin, B. J.

2015-01-01

267

Charge exchange x-ray emission: Astrophysical observations and potential diagnostics  

NASA Astrophysics Data System (ADS)

Interest in astrophysical sources of charge exchange X-rays has been growing steadily since the discovery of X-ray emission from the comet Hyakutake with ROSAT in 1996. Since then, charge exchange has been observed between solar wind ions and neutrals in the geocorona and in the atmospheres of Mars and Jupiter. Charge exchange with interstellar neutrals within the heliosphere between solar wind ions and neutral hydrogen and helium from the interstellar medium is now acknowledged as contributing a considerable (although currently unknown) fraction of the soft X-ray background. We make a brief survey of the heliospheric, Galactic, and extragalactic systems in which charge exchange has been observed or is predicted to take place. Experiments measuring velocity dependent cross-section and line ratios for Lyman-series lines and He-like triplets are needed to check current theoretical models of charge exchange emission and aid interpretation of observations. We point out a number of systems that are of astrophysical interest that could be the subject of future laboratory investigations, particularly velocity dependent line ratios of the X-ray emission produced by charge exchange between highly ionized common elements (such as O, C, Ne, and Fe) and atomic hydrogen and helium. To begin to address the need for laboratory data we have measured velocity dependent Ly-series line ratios for C6+ ions interacting with H2, He, and Kr gas targets at Oak Ridge National Laboratory's Ion-Atom Merged-Beams Apparatus.

Morgan, K.; Andrianarijaona, V.; Draganic, I. N.; Defay, X.; Fogle, M.; Galindo-Uribarri, A.; Guillen, C. I.; Havener, C. C.; Hokin, M.; McCammon, D.; Nader, D. J.; Romano, S. L.; Carcoba, F. Salces; Sauter, P.; Seely, D.; Stancil, P. C.; Vane, C. R.; Vassantachart, A. K.; Wulf, D.

2013-04-01

268

Structure of the X-Ray Emission from the Jet of 3C 273  

NASA Technical Reports Server (NTRS)

We present images from four Chandra observations of the quasar 3C 273. The zeroth order images from two grating observations using the AXAF CCD Imaging Spectrometer (ACIS-S) detector are used to examine the structure and spectrum of the jet. The jet has at least four distinct features which are not resolved in previous observations. Using jet feature nomenclature based on HST observations, we find that knot Al is very bright in X-rays. We have measured the X-ray spectrum of this X-ray knot for the first time, obtaining a photon index of 1.36 +/- 0.11 and a flux density of 37 +/- 4 nJy at 1 keV. Combining this measurement with lower frequency data shows that a pure synchrotron model can fit the spectrum of knot Al from 4 GHz to 5 keV (over nine decades in energy) without a change of spectral slope. Knot A2 is also detected and is somewhat blended with knot B1 but synchrotron emission is not likely to explain the X-ray emission due to the spectral turnover observed in the optical-UV band. No other knots are clearly detected but there is an indication of weak emission from the eastern portion of knot H3. near the "head," which is radio-bright. There is diffuse flux which extends from 14 arcsec to 20 arcsec which shows curvature that is comparable to the optical flux found by Bahcall, et al.

Marshall, H. L.; Lee, J. C.; Ogle, P. M.; Drake, J. J.; Fruscione, A.; Grimes, J.; Harris, D.; Kraft, R.; Pease, D.; Schwartz, D.; Siemiginowska, A.; Lavoie, Anthony R. (Technical Monitor)

2000-01-01

269

Charge Exchange Induced X-Ray Emission of Fe XXVI and Fe XXV  

NASA Astrophysics Data System (ADS)

Charge exchange is a vital process to consider in the modeling of X-ray spectra obtained by the Chandra, XMM Newton and Suzaku X-ray Space Observatories. The process is largely relevant in many astrophysical environments including comets (whose emission is primarily a product of charge exchange alone), the heliosphere, astropheres of stars, supernova remnants, the Galactic Center and the Galactic Ridge. The understanding of the X-ray spectra produced by these environments is crippled by the current lack of atomic and molecular data- especially for charge exchange. Here, we apply the Landau-Zener method to calculate total, n-resolved, n?-resolved and S-resolved cross sections for Fe26+ and Fe25+ collisions with H, He, H2, N2, H2O and CO. Using this data in a cascade model for X-ray emission, theoretical spectra for each system are predicted. The resulting spectra are then compared to experimental data for Fe26+ and Fe25+ collisions with N2. Fe XXVI and Fe XXV have been selected for study as iron emission lines have been detected in the galactic plane. Further, these systems illustrate computational difficulties for high projectile charges. In the Landau-Zener calculations, several ?-distribution models have been tested for the electron capture by the bare ion, Fe26+. Quantum defect methods are also employed to estimate excitation energies and transition probabilities for high-lying Rydberg levels of the He-like Fe24+.

Mullen, Patrick Dean; Cumbee, Renata; Lyons, David; Stancil, Phillip C.; B. J. Wargelin

2015-01-01

270

X-RAY EMISSION FROM THE WOLF-RAYET BUBBLE S 308  

SciTech Connect

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, map most of the nebula. The X-ray emission from S 308 displays a limb-brightened morphology, with a central cavity {approx}22' in size 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 0.43 keV and O VII at 0.57 keV, and declines toward high energies, with a faint tail up to 1 keV. This spectrum can be described by a two-temperature optically thin plasma emission model (T{sub 1} {approx} 1.1 Multiplication-Sign 10{sup 6} K, T{sub 2} {approx} 13 Multiplication-Sign 10{sup 6} K), with a total X-ray luminosity {approx}2 Multiplication-Sign 10{sup 33} erg s{sup -1} at the assumed distance of 1.5 kpc.

Toala, J. A.; Guerrero, M. A. [Instituto de Astrofisica de Andalucia, IAA-CSIC, Glorieta de la Astronomia s/n, 18008 Granada (Spain); Chu, Y.-H.; Gruendl, R. A. [Department of Astronomy, University of Illinois, 1002 West Green Street, Urbana, IL 61801 (United States); Arthur, S. J. [Centro de Radioastronomia y Astrofisica, Universidad Nacional Autonoma de Mexico, Campus Morelia, Apartado Postal 3-72, 58090, Morelia, Michoacan (Mexico); Smith, R. C. [NOAO/CTIO, 950 N. Cherry Avenue, Tucson, AZ 85719 (United States); Snowden, S. L., E-mail: toala@iaa.es [NASA Goddard Space Flight Center, Code 662, Greenbelt, MD 20771 (United States)

2012-08-10

271

Electronic emission of radio-sensitizing gold nanoparticles under X-ray irradiation : experiment and simulations  

E-print Network

In this paper we present new results on electronic emission of Gold Nanoparticles (GNPs) using X-ray photoelectron spectroscopy (XPS) and compare them to the gold bulk electron emission. This subject has undergone new interest within the perspective of using GNPs as a radiotherapy enhancer. The experimental results were simulated using various models (Livermore and PENELOPE) of the Geant 4 simulation toolkit dedicated to the calculation of the transportation of particles through the matter. Our results show that the GNPs coating is a key parameter to correctly construe the experimental GNPs electronic emission after X-ray irradiation and point out some limitations of the PENELOPE model. Using XPS spectra and Geant4 Livermore simulations,we propose a method to determine precisely the coating surface density of the GNPs. We also show that the expected intrinsic nano-scale electronic emission enhancement effect - suspected to contribute to the GNPs radio-sensitizing properties - participates at most for a few pe...

Casta, R; Sence, M; Moretto-Capelle, P; Cafarelli, P; Amsellem, A; Sicard-Roselli, C

2014-01-01

272

X-ray Emission Processes in Extragalactic Jets, Lobes and Hot Spots  

E-print Network

This paper is a brief review of the processes responsible for X-ray emission from radio jets, lobes and hot spots. Possible photons in inverse Compton scattering models include the radio synchrotron radiation itself (i.e. synchrotron self-Compton [SSC] emission), the cosmic microwave background (CMB), the galaxy starlight and radiation from the active nucleus. SSC emission has been detected from a number of hot spots. Scattering of the CMB is expected to dominate for jets (and possibly hot spots) undergoing bulk relativistic motion close to the direction towards the observer. Scattering of infrared radiation from the AGN should be observable from radio lobes, especially if they are close to the active nucleus. Synchrotron radiation is detected in some sources, most notably the jet of M87. I briefly discuss why different hot spots emit X-rays by different emission mechanisms and the nature of the synchrotron spectra.

Andrew S. Wilson

2003-01-07

273

X-ray-emission measurements following charge exchange between C6+ and H2  

NASA Astrophysics Data System (ADS)

Lyman x-ray spectra following charge exchange between C6+ and H2 are presented for collision velocities between 400 and 2300 km/s (1-30 keV/amu). Spectra were measured by a microcalorimeter x-ray detector capable of fully resolving the C vi Lyman series emission lines though Lyman-?. The ratios of the measured emission lines are sensitive to the angular momentum l states populated during charge exchange and are used to gauge the effectiveness of different l-distribution models in predicting Lyman emission due to charge exchange. At low velocities, we observe that both single-electron-capture and double-electron-capture autoionization contribute to Lyman emission and that a statistical l distribution best describes the measured line ratios. At higher velocities single-electron capture dominates with the l distribution peaked at the maximum l.

Fogle, M.; Wulf, D.; Morgan, K.; McCammon, D.; Seely, D. G.; Dragani?, I. N.; Havener, C. C.

2014-04-01

274

Chandra X-ray Grating Spectrometry of Eta Carinae near X-ray Minimum: I. Variability of the Sulfur and Silicon Emission Lines  

NASA Technical Reports Server (NTRS)

We report on variations in important X-ray emission lines in a series of Chandra grating spectra of the supermassive colliding wind binary star eta Car, including key phases around the X-ray minimum/periastron passage in 2003.5. The X-rays arise from the collision of the slow, dense wind of eta Car with the fast, low-density wind of an otherwise hidden companion star. The X-ray emission lines provide the only direct measure of the flow dynamics of the companion's wind along the wind-wind collision zone. We concentrate here on the silicon and sulfur lines, which are the strongest and best resolved lines in the X-ray spectra. Most of the line profiles can be adequately fit with symmetric Gaussians with little significant skewness. Both the silicon and sulfur lines show significant velocity shifts and correlated increases in line widths through the observations. The R = forbidden-to-intercombination ratio from the Si XIII and S XV triplets is near or above the low-density limit in all observations, suggesting that the line-forming region is > 1.6 stellar radii from the companion star, and that the emitting plasma may be in a non-equilibrium state. We show that simple geometrical models cannot simultaneously fit both the observed centroid variations and changes in line width as a function of phase. We show that the observed profiles can be fitted with synthetic profiles with a reasonable model of the emissivity along the wind-wind collision boundary. We use this analysis to help constrain the line formation region as a function of orbital phase, and the orbital geometry. Subject headings: X-rays: stars -stars: early-type-stars: individual (q Car)

Henley, D. B.; Corcoran, M. F.; Pittard, J. M.; Stevens, I. R.; Hamaguchi, K.; Gull, T. R.

2008-01-01

275

DETECTION OF DIFFUSE X-RAY EMISSION FROM PLANETARY NEBULAE WITH NEBULAR O VI  

SciTech Connect

The presence of O VI ions can be indicative of plasma temperatures of a few Multiplication-Sign 10{sup 5} K that are expected in heat conduction layers between the hot shocked stellar wind gas at several 10{sup 6} K and the cooler (10{sup 4} K) nebular gas of planetary nebulae (PNe). We have used FUSE observations of PNe to search for nebular O VI emission or absorption as a diagnostic of the conduction layer to ensure the presence of hot interior gas. Three PNe showing nebular O VI, namely IC 418, NGC 2392, and NGC 6826, have been selected for Chandra observations and diffuse X-ray emission is indeed detected in each of these PNe. Among the three, NGC 2392 has peculiarly high diffuse X-ray luminosity and plasma temperature compared with those expected from its stellar wind's mechanical luminosity and terminal velocity. The limited effects of heat conduction on the plasma temperature of a hot bubble at the low terminal velocity of the stellar wind of NGC 2392 may partially account for its high plasma temperature, but the high X-ray luminosity needs to be powered by processes other than the observed stellar wind, probably the presence of an unseen binary companion of the central star of the PN (CSPN) of NGC 2392. We have compiled relevant information on the X-ray, stellar, and nebular properties of PNe with a bubble morphology and found that the expectations of bubble models including heat conduction compare favorably with the present X-ray observations of hot bubbles around H-rich CSPNe, but have notable discrepancies for those around H-poor [WR] CSPNe. We note that PNe with more massive central stars can produce hotter plasma and higher X-ray surface brightness inside central hot bubbles.

Ruiz, N.; Guerrero, M. A. [Instituto de Astrofisica de Andalucia, IAA-CSIC, c/ Glorieta de la Astronomia s/n, E-18008 Granada (Spain)] [Instituto de Astrofisica de Andalucia, IAA-CSIC, c/ Glorieta de la Astronomia s/n, E-18008 Granada (Spain); Chu, Y.-H.; Gruendl, R. A. [Department of Astronomy, University of Illinois, 1002 West Green Street, Urbana, IL 61801 (United States)] [Department of Astronomy, University of Illinois, 1002 West Green Street, Urbana, IL 61801 (United States); Jacob, R.; Schoenberner, D.; Steffen, M., E-mail: nieves@iaa.es [Leibniz-Institut fuer Astrophysik Potsdam (AIP), An der Sternwarte 16, D-14482 Potsdam (Germany)

2013-04-10

276

On the origin of X-ray emission in some FR Is: ADAF or jet?  

E-print Network

We investigate the X-ray origin in FR Is using the radio, submillimetre, optical, and {\\em Chandra} X-ray data of a small sample consisting of eight FR I sources. These sources are very dim, with X-ray luminosities $L_{\\rm X}/L_{\\rm Edd} \\sim 10^{-4}-10^{-8}$ ($L_{\\rm X}$ is the X-ray luminosity between 2-10 keV). We try to fit the multiwaveband spectrum using a coupled accretion-jet model. In this model, the accretion flow is described by an advection-dominated accretion flow (ADAF) while in the innermost region of ADAF a fraction of accretion flow is transferred into the vertical direction and forms a jet. We find that X-ray emission in the source with the highest $L_{\\rm X}$ ($\\sim 1.8 \\times 10^{-4}L_{\\rm Edd}$) is from the ADAF. The results for the four sources with moderate $L_{\\rm X}$ ($\\sim$ several $\\times 10^{-6}L_{\\rm Edd}$) are complicated. Two are mainly from the ADAFs, one from the jet, and the other from the sum of the jet and ADAF. The X-ray emission in the three least luminous sources ($L_{\\rm X} \\lesssim 1.0\\times 10^{-6}L_{\\rm Edd}$) is dominated by the jet although for one source it can also be interpreted by the ADAF since the quality of X-ray data is low. We conclude that these results roughly support the predictions of Yuan & Cui (2005) where they predict that when the X-ray luminosity of the system is below a critical value, the X-radiation will not be dominated by the emission from the ADAF any longer, but by the jet. We also investigate the fuel supply in these sources. We find that the accretion rates in four sources among the five in which we can have good constraints to their accretion rates must be higher than the Bondi rates. This implies that other fuel supply, such as the gas released by the stellar population inside the Bondi radius, should be important.

Qingwen Wu; Feng Yuan; Xinwu Cao

2007-06-28

277

The Discovery of X-ray Emission from Active Galactic Nuclei  

NASA Astrophysics Data System (ADS)

Back in 1974 the UHURU catalog (3U) had been published with many UHGLS - unidentified high galactic latitude sources. Identifications were hampered by the square degree sized error boxes (positional uncertainties). Could these explain the cosmic X-ray background? Could UHGLS be "X-ray galaxies"? Only three active galaxies (AGNs) had been found as X-ray sources: 3C273, Cen A and NGC 4151, while others had upper limits. What was the difference between X-ray and non-X-ray AGNs? It turned out that the slightly better positioning capability and slightly deeper sensitivity of the Ariel V Sky Survey Instrument (SSI), launched in October 1974, were just enough to show that the UHGLS were Seyfert galaxies. And I was lucky enough that I'd joined the Leicester X-ray group and had taken on the UHGLS for my PhD thesis, with Ken Pounds as my supervisor. With the SSI we made a catalog of high latitude sources, the "2A" catalog, including about a dozen known Seyfert galaxies (lowish luminosity nearby AGNs) and, with Mike Penston and Martin Ward, we went on to identify many of them with both newly discovered normal broad emission line AGNs and a few new "narrow emission line galaxies", or NELGs, as we called them. We are now convinced that it is summation of many obscured NELGs that produce the flat spectrum of the X-ray background, and we are still searching for them in Chandra deep surveys and at higher energies with NuSTAR. There was an obvious connection between the X-ray obscuration and the optical reddening, which must lie outside the region emitting the broad optical spectral lines. Andy Lawrence and I, following a clue from Bill Keel, put this together into what we now call the Unified Scheme for AGN structure. This idea of a flattened torus obscuring the inner regions of the AGN was so dramatically confirmed a few years later -- by Ski Antonucci and Joe Miller's discovery of polarized broad emission lines in NGC1068 -- that the precursor papers became irrelevant. But Ariel V had provided the seeds for this advance too. Not bad for 100cm2 and 1/2 degree collimators.

Elvis, Martin

2013-01-01

278

Comparative study of X ray and microwave emissions during solar flares  

NASA Astrophysics Data System (ADS)

The work supported by the grant consisted of two projects. The first project involved making detailed case studies of two flares using SMM data in conjunction with ground based observations. The first flare occurred at 1454 UT on June 20, 1989 and involved the eruption of a prominence near the limb. In the study we used data from many wavelength regimes including the radio, H-alpha, hard X-rays, and soft X-rays. We used a full gyrosynchrotron code to model the apparent presence of a 1.4 GHz source early in the flare that was in the form of a large coronal loop. The model results lead us to conclude that the initial acceleration occurs in small, dense loops which also produced the flare's hard X-ray emission. We also found evidence that a source at 1.4 GHz later in the event was due to second harmonic plasma emission. This source was adjacent to a leg of the prominence and comes from a dense column of material in the magnetic structure supporting the prominence. Finally, we investigated a source of microwaves and soft X-rays, occurring approximately 10 min after the hard X-ray peak, and calculate a lower limit for the density of the source. The second flare that was studied occurred at 2156 UT on June 20, 1989 and was observed with the VLA and the Owens Valley Radio Observatory (OVRO) Frequency Agile Array. We have developed a gyrosynchrotron model of the sources at flare peak using a new gyrosynchrotron approximation which is valid at very low harmonics of the gyrofrequency. We found that the accelerated particle densities of the sources decreased much more with radius from the source center than had been supposed in previous work, while the magnetic field varied less. We also used the available data to analyze a highly polarized source which appeared late in the flare. The second project involved compiling a statistical base for the relative timing of the hard X-ray peak, the turbulent and blue-shift velocities inferred from soft X-ray line emissions observed by SMM and the microwave peak as determined from ground-based observations. This timing was then used to aid the testing of newly developed global models for flares that incorporate the global magnetic topology as well as the electron dynamics that are responsible for the hard X-rays and microwaves.

Winglee, Robert M.

279

EUV and soft x-ray excess emission from clusters of galaxies  

NASA Astrophysics Data System (ADS)

Extreme ultra-violet and soft X-ray radiation (~60-400 eV) from extragalactic sources suffers from severe Galactic absorption losses, rendering the detection of radiation at these energies a complicated task. Clusters are well known to be X-ray emitters; some EUV and soft X-rays are therefore expected as the low- energy `tail' of this emission. The first detection of excess EUV emission, i.e., above that expected fro the X-ray emitting gas, was achieved only very recently (1996), nearly thirty years after cluster X-rays were detected. Basic dynamic and energetic properties of clusters of galaxies are reviewed in Chapter 2. Clusters analyzed in this Dissertation (A2199, A1795, Coma and Virgo) all lie along directions of low line-of-sight Galactic HI column density (NH <= 1-2 × 1020 cm-2), and diffuse excess EUV emission from them was detected in the 60-200 eV band by the Extreme Ultraviolet Explorer (EUVE). Instrumental issues concerning the Deep Survey detector aboard EUVE are therefore scrutinised in Chapter 3 in order to devise a correct method of data analysis. Relevant issues to the ROSAT Position-sensitive Proportional Counter (PSPC) detector, used for its soft X-ray sensitivity, are also considered. The EUV and soft X-ray excess emission (the cluster soft excess phenomenon, CSE) is found for all four clusters in the sample (Chapter 4). Some of the clusters show a peculiar trend of the CSE emission, resulting in the increase of the relative importance of the CSE emission with radial distance (the soft-excess radial trend, SERT). Two alternative explanations of the CSE emission are explored: non-thermal radiation due to Inverse Compton (IC) scattering of relativistic electrons and radiation from a warm (~106 K) gas. A detailed treatment of IC scattering (off the microwave background field, the MWB) in the cluster environment is described in Chapter 5, where cluster spectra are fitted to IC models. It is initially shown that the soft excess of some clusters (e.g., A2199 and A1795) can be explained in the context of an adiabatic gas and cosmic ray (CR) atmosphere. It is however found that not all clusters allow an interpretation of the CSE emission as non- thermal radiation; in some cases (e.g., Coma, A1795), severe energetic problems, such as equipartition of thermal and non-thermal energy, arise. A more likely interpretation of the CSE is as emission from a second phase of the ICM (warm ~ 106 K gas). The thermal interpretation is possible for all clusters in the sample (Chapter 6) and requires a significant fraction of a cluster's mass to reside in this warm gas. Interesting clues are also gained by the imaging of the excess emission. In particular, analysis of ROSAT PSPC images (Chapter 6) reveals evidence for cold, absorbing gas in clusters of galaxies. It is concluded that a self-consistent interpretation of EUV and soft X-ray emission from clusters is that of an ICM composed of three thermal components: hot (~108 K, the X-ray emitting gas), warm (~10 6 K) and cold (<=105 K) gas.

Bonamente, Massimiliano

2000-08-01

280

Energy-dispersive X-ray emission spectroscopy using an X-ray free-electron laser in a shot-by-shot mode  

PubMed Central

The ultrabright femtosecond X-ray pulses provided by X-ray free-electron lasers open capabilities for studying the structure and dynamics of a wide variety of systems beyond what is possible with synchrotron sources. Recently, this “probe-before-destroy” approach has been demonstrated for atomic structure determination by serial X-ray diffraction of microcrystals. There has been the question whether a similar approach can be extended to probe the local electronic structure by X-ray spectroscopy. To address this, we have carried out femtosecond X-ray emission spectroscopy (XES) at the Linac Coherent Light Source using redox-active Mn complexes. XES probes the charge and spin states as well as the ligand environment, critical for understanding the functional role of redox-active metal sites. K?1,3 XES spectra of MnII and Mn2III,IV complexes at room temperature were collected using a wavelength dispersive spectrometer and femtosecond X-ray pulses with an individual dose of up to >100 MGy. The spectra were found in agreement with undamaged spectra collected at low dose using synchrotron radiation. Our results demonstrate that the intact electronic structure of redox active transition metal compounds in different oxidation states can be characterized with this shot-by-shot method. This opens the door for studying the chemical dynamics of metal catalytic sites by following reactions under functional conditions. The technique can be combined with X-ray diffraction to simultaneously obtain the geometric structure of the overall protein and the local chemistry of active metal sites and is expected to prove valuable for understanding the mechanism of important metalloproteins, such as photosystem II. PMID:23129631

Alonso-Mori, Roberto; Kern, Jan; Gildea, Richard J.; Sokaras, Dimosthenis; Weng, Tsu-Chien; Lassalle-Kaiser, Benedikt; Tran, Rosalie; Hattne, Johan; Laksmono, Hartawan; Hellmich, Julia; Glöckner, Carina; Echols, Nathaniel; Sierra, Raymond G.; Schafer, Donald W.; Sellberg, Jonas; Kenney, Christopher; Herbst, Ryan; Pines, Jack; Hart, Philip; Herrmann, Sven; Grosse-Kunstleve, Ralf W.; Latimer, Matthew J.; Fry, Alan R.; Messerschmidt, Marc M.; Miahnahri, Alan; Seibert, M. Marvin; Zwart, Petrus H.; White, William E.; Adams, Paul D.; Bogan, Michael J.; Boutet, Sébastien; Williams, Garth J.; Zouni, Athina; Messinger, Johannes; Glatzel, Pieter; Sauter, Nicholas K.; Yachandra, Vittal K.; Yano, Junko; Bergmann, Uwe

2012-01-01

281

X-ray secondary heating and ionization in quasar emission-line clouds  

Microsoft Academic Search

Accurate Monte Carlo computations of the X-ray secondary electron heating, ionization, and excitation of H and He gas in interstellar space and in quasar emission-line clouds, are presented. The fraction of energy deposited in each form is sensitive to the background ionization fraction, x = n(H+)\\/n(Htot), and can affect the temperature, ionization state, and line emissivities at large depths in

J. M. Shull; M. E. van Steenberg

1985-01-01

282

The evolution of planetary nebulae. V. The diffuse X-ray emission  

NASA Astrophysics Data System (ADS)

Context: Observations with space-borne X-ray telescopes revealed the existence of soft, diffuse X-ray emission from the inner regions of planetary nebulae. Although the existing images support the idea that this emission arises from the hot shocked central-star wind which fills the inner cavity of a planetary nebula, existing models have difficulties to explain the observations consistently. Aims: We investigate how the inclusion of thermal conduction changes the physical parameters of the hot shocked wind gas and the amount of X-ray emission predicted by time-dependent hydrodynamical models of planetary nebulae with central stars of normal, hydrogen-rich surface composition. Methods: We upgraded our 1D hydrodynamics code NEBEL by to account for energy transfer due to heat conduction, which is of importance at the interface separating the hot shocked wind gas (“hot bubble”) from the much cooler nebular material. With this new version of NEBEL we recomputed a selection of our already existing hydrodynamical sequences and obtained synthetic X-ray spectra for representative models along the evolutionary tracks by means of the freely available CHIANTI package. Results: Heat conduction leads to lower temperatures and higher densities within a bubble and brings the physical properties of the X-ray emitting domain into close agreement with the values derived from observations. The amount of X-rays emitted during the course of evolution depends on the energy dumped into the bubble by the fast stellar wind, on the efficiency of “evaporating” cool nebular gas via heat conduction, and on the bubble's expansion rate. We find from our models that the X-ray luminosity of a planetary nebula increases during its evolution across the HR diagram until stellar luminosity and wind power decline. Depending on the central-star mass and the evolutionary phase, our models predict X-ray [ 0.45-2.5 keV] luminosities between 10-8 and 10-4 of the stellar bolometric luminosities, in good agreement with the observations. Less than 1% of the wind power is radiated away in this X-ray band. Although temperature, density, and also the mass of the hot bubble is significantly altered by heat conduction, the dynamics of the whole system remains practically the same. Conclusions: Heat conduction allows the construction of nebular models which predict the correct amount of X-ray emission and at the same time are fully consistent with the observed mass-loss rate and wind speed. Thermal conduction must be considered as a viable physical process for explaining the diffuse X-ray emission from planetary nebulae with closed inner cavities. Magnetic fields must then be absent or extremely weak. Dedicated to the memory of M. Perinotto, a dear friend and esteemed colleague who died unexpectedly and much too early on August 15, 2007.

Steffen, M.; Schönberner, D.; Warmuth, A.

2008-10-01

283

Local magnetic moments at Mn 2p X-ray photoelectron and Mn L_alpha,beta X-ray emission spectra  

Microsoft Academic Search

The Mn L_alpha,_beta (3darrow 2p_3\\/2,1\\/2) resonant X-ray emission spectra (RXES) and Mn 2p_3\\/2,1\\/2 X-ray photoelectron spectra of proposed as half metallic ferromagnets Mn-based Heusler alloys Ni_2MnZ (Z=In, Sn, Sb) are found to be different from ones of La_1-xSm_xMn_2Si2 compounds. Linearly polarized resonant excitation establishes that the distinctive feature in Mn L_alpha RXES of Heusler alloys is due to the nearly

Mikhail Yablonskikh; Jonathan Denlinger; Manfred Neumann; Alexander Moewes

2004-01-01

284

Investigating X-ray Emission from PPN and PN using numerical simulations  

NASA Astrophysics Data System (ADS)

The shaping of Pre-planetary nebulae (PPN) and Planetary Nebulae (PN) is believed to result from the interaction of a fast, collimated post-AGB wind (CFW) plowing into the slow, dense wind emitted during the AGB phase, followed by an isotropic tenuous wind during the PN phase (Sahai & Trauger 1998). The expanding shell which forms the PPN and later the PN is expected to produce extended X-ray emission due to the large speed of the fast wind and resulting high temperatures in the shocked gas. X-ray emission was only detected in 3 of 60 PNs observed with ROSAT, followed by a few more from CHANDRA and XMM (e.g. Guerrero et al. 2005). In the case of PPNs, there is so far only one confirmed X-ray detection (Sahai et al. 2003), although many have been observed with CHANDRA. The general problem of understanding the formation and shaping of PNs has been addressed analytically and numerically (see Balick & Frank 2002, and references therein). X-ray emission is one of the most direct probes of the fast wind and the interaction process which drives PN formation. However, this probe has not been fully exploited in previous modeling studies. Very recently, Akashi et al. (2006, hereafter ASB06) used analytical, self-similar, spherically symmetric models to address this problem. We are performing numerical simulations with the hydrodynamics code FLASH varying the basic parameters of the fast and slow wind over an extensive parameter grid and computing the X-ray emission as a function of these parameters and the time history of the fast wind.

Stute, Matthias; Sahai, Raghvendra

285

On the variability of the Arches diffuse X-ray emission  

NASA Astrophysics Data System (ADS)

The Arches cluster is a massive star cluster located within the Galactic center region and characterized by a strong thermal emission in the X-ray band. A diffuse non thermal X-ray emission, including the neutral iron fluorescent line at 6.4 keV, has also been detected in a region surrounding the star cluster, towards dense molecular clouds which are visible in radio. This emission could be created either by a strong X-ray irradiation of the clouds by a bright source or by the interaction of low energy cosmic-ray protons, possibly produced by the nearby star cluster, with the clouds. Using XMM observations collected up to 2009, previous studies did not find significant variations of the non-thermal emission and concluded that the low energy cosmic-ray bombardment was the most likely scenario. We are now adding three more years of observation to the analysis and we will present our latest results on the variability of the Arches non-thermal emission, a crucial diagnostic for understanding the origin of this emission.

Clavel, Maïca; Ponti, Gabriele; Tatischeff, Vincent; Terrier, Regis; Goldwurm, Andrea; Soldi, Simona; Maurin, Gilles

286

RS Ophiuchi in Quiescence: Why Is It X-ray Faint?  

NASA Technical Reports Server (NTRS)

The short interval between successive outbursts of RS Oph strongly suggests that it has a high mass white dwarf accreting at a high rate. This, in turn, suggests the possibility of prominent X-ray emission from RS Oph in quiescence. However, archival quiescent X-ray observations of RS Oph show it to be a modest soft X-ray source but not a strong 2-10 keV X-ray source. In this aspect, RS Oph differs markedly from T CrB. We speculate on the possible mechanisms that could significantly suppress the 2-10 keV X-ray emission in RS Oph.

Mukai, Koji

2007-01-01

287

A thin diffuse component of the Galactic ridge X-ray emission and heating of the interstellar medium contributed by the radiation of Galactic X-ray binaries  

NASA Astrophysics Data System (ADS)

We predict a thin diffuse component of the Galactic ridge X-ray emission (GRXE) arising from the scattering of the radiation of bright X-ray binaries (XBs) by the interstellar medium. This scattered component has the same scale height as that of the gaseous disk (~80 pc) and is therefore thinner than the GRXE of stellar origin (scale height ~130 pc). The morphology of the scattered component is furthermore expected to trace the clumpy molecular and HI clouds. We calculate this contribution to the GRXE from known Galactic XBs assuming that they are all persistent. The known XBs sample is incomplete, however, because it is flux limited and spans the lifetime of X-ray astronomy (~50 years), which is very short compared with the characteristic time of 1000-10 000 years that would have contributed to the diffuse emission observed today due to time delays. We therefore also use a simulated sample of sources, to estimate the diffuse emission we should expect in an optimistic case assuming that the X-ray luminosity of our Galaxy is on average similar to that of other galaxies. In the calculations we also take into account the enhancement of the total scattering cross-section due to coherence effects in the elastic scattering from multi-electron atoms and molecules. This scattered emission can be distinguished from the contribution of low X-ray luminosity stars by the presence of narrow fluorescent K-? lines of Fe, Si, and other abundant elements present in the interstellar medium and by directly resolving the contribution of low X-ray luminosity stars. We find that within 1° latitude of the Galactic plane the scattered emission contributes on average 10 - 30% of the GRXE flux in the case of known sources and over 50% in the case of simulated sources. In the latter case, the scattered component is found to even dominate the stellar emission in certain parts of the Galactic plane. X-rays with energies ?1 keV from XBs should also penetrate deep inside the HI and molecular clouds, where they are absorbed and heat the interstellar medium. We find that this heating rate dominates the heating by cosmic rays (assuming a solar neighborhood energy density) in a considerable part of the Galaxy. Appendices are available in electronic form at http://www.aanda.org

Molaro, Margherita; Khatri, Rishi; Sunyaev, Rashid A.

2014-04-01

288

X-ray Line Emission from Evaporating and Condensing Accretion Disk Atmospheres  

E-print Network

We model the X-rays reprocessed by an accretion disk in a fiducial low-mass X-ray binary system with a neutron star primary. An atmosphere, or the intermediate region between the optically thick disk and a Compton-temperature corona, is photoionized by the neutron star continuum. X-ray lines from the recombination of electrons with ions dominate the atmosphere emission and should be observable with the Chandra and XMM-Newton high-resolution spectrometers. The self-consistent disk geometry agrees well with optical observations of these systems, with the atmosphere shielding the companion from the neutron star. At a critical depth range, the disk gas has one thermally unstable and two stable solutions. A clear difference between the model spectra exists between evaporating and condensing disk atmospheres. This difference should be observable in high-inclination X-ray binaries, or whenever the central continuum is blocked by absorbing material and the extended disk emission is not.

M. A. Jimenez-Garate; J. C. Raymond; D. A. Liedahl; C. J. Hailey

2001-05-02

289

X-RAY EMISSION FROM THE SUPERGIANT SHELL IN IC 2574  

SciTech Connect

The M81 group member dwarf galaxy IC 2574 hosts a supergiant shell of current and recent star formation activity surrounding a 1000 Multiplication-Sign 500 pc hole in the ambient H I gas distribution. Chandra X-ray Observatory imaging observations reveal a luminous, L{sub X} {approx} 6.5 Multiplication-Sign 10{sup 38} erg s{sup -1} in the 0.3-8.0 keV band, point-like source within the hole but offset from its center and fainter diffuse emission extending throughout and beyond the hole. The star formation history at the location of the point source indicates a burst of star formation beginning {approx}25 Myr ago and currently weakening and there is a young nearby star cluster, at least 5 Myr old, bracketing the likely age of the X-ray source at between 5 and {approx}25 Myr. The source is thus likely a bright high-mass X-ray binary-either a neutron star or black hole accreting from an early B star undergoing thermal-timescale mass transfer through Roche lobe overflow. The properties of the residual diffuse X-ray emission are consistent with those expected from hot gas associated with the recent star formation activity in the region.

Yukita, Mihoko [Department of Physics and Astronomy, University of Alabama, Tuscaloosa, AL (United States); Swartz, Douglas A. [Universities Space Research Association, NASA Marshall Space Flight Center, ZP12 Huntsville, AL 35812 (United States)

2012-05-01

290

Internal Energy Dissipation of Gamma-Ray Bursts Observed with Swift: Precursors, Prompt Gamma-rays, Extended emission and Late X-ray Flares  

E-print Network

We jointly analyze the gamma-ray burst (GRB) data observed with BAT and XRT on board the Swift mission to present a global view on the internal energy dissipation processes in GRBs, including precursors, prompt gamma-ray emission, extended soft gamma-ray emission, and late X-ray flares. The Bayesian block method is utilized to analyze the BAT lightcurves to identify various emission episodes. Our results suggest that these emission components likely share a same physical origin, which is repeated activation of the GRB central engine. What we observe in the gamma-ray band may be the tip-of-iceberg of more extended underlying activities. The precursor emission, which is detected in about 10% of {\\em Swift} GRBs, is preferably detected in those GRBs that have a massive star core-collapse origin. The soft extended emission (EE) tail, on the other hand, is preferably detected in those GRBs that have a compact star merger origin. Bright X-ray emission is detected during the BAT quiescent phases prior to subsequent ...

Hu, You-Dong; Xi, Shao-Qiang; Peng, Fang-Kun; Lu, Rui-Jing; LV, Lian-Zhong; Zhang, Bing

2014-01-01

291

Equation of motion coupled cluster theory calculations of the X-ray emission spectroscopy of water  

NASA Astrophysics Data System (ADS)

The equation of motion coupled cluster theory including single and double excitations (EOM-CCSD) method is applied to study the X-ray emission spectroscopy of water. For the 1b1 orbital, a difference of about 0.7 eV is predicted between a tetrahedrally coordinated water molecule and a water molecule in which water molecules accepting hydrogen bonds are absent, and as a proton is dissociated emission from the 1b1 and 3a1 orbitals become closer in energy. The resonantly excited X-ray emission spectrum for the 4a1 orbital shows a red-shift in the bands and a reduction in intensity for the 3a1 band.

Besley, Nicholas A.

2012-07-01

292

Measurement of charge exchange and X-ray emission cross sections for solar wind-comet interactions  

NASA Technical Reports Server (NTRS)

X-ray emission from a comet was observed for the first time in 1996. One of the mechanisms believed to be contributing to this surprisingly strong emission is the interaction of highly charged solar wind ions with cometary gases.

Greenwood, J.; Willaims, I.; Smith, S.; Chutjian, A.

2000-01-01

293

Search for X-Ray Emission in the Nearest Known Brown Dwarf  

NASA Technical Reports Server (NTRS)

The XMM observation were obtained on 2001 January 07-08 for 51767 s. The Optical Monitor (OM) was used with the V filter for 4 exposures of 5000 s each in imaging mode. We used the data given by the OM to confirm the presence of the source in the field of view. The European Photon Imaging Camera (EPIC) MOS 1 and MOS2 were used 48724 s each in prime full window mode with 2.5 s time resolution. The EPIC PN was used 46618 s in prime full window mode with 73.4 ms time resolution. The X-ray source closest to the expected position of our target is offset by delta R.A=2.5 arcsec and delta Dec=-28.37 arcsec. This offset is high in comparison with the 0.4 arcsec observed with the optical data. So at this point we already knew that the target was not detected. To confirm that conclusion, we performed the identification of all X-ray sources in the field of view by comparing source to source our image with the one obtained by Rutledge et al. with Chandra. This allowed us to identify all the X-ray sources in our field of view in an area of 20 arcsec times 10 arcsec centered on the expected coordinates of LP944-20. We were then able to conclude that the target was not detected during this observation. This result allowed us to determine a new and better 3 sigma upper limit of X-Ray emission for this object. We have also derived duty cycles for X-ray flares as a function of X-ray luminosity by comparing the XMM data with Chandra and ROSAT data. One student has been supported with the grant during four months (Herve Bouy). A Sun workstation was purchased for him.

Martin, Eduardo

2003-01-01

294

Multibeam field emission x-ray system with half-scan reconstruction algorithm  

SciTech Connect

Purpose: In this article, the authors propose a multibeam field emission x-ray (MBFEX) system along with a half-scan fan-beam reconstruction algorithm. Methods: The proposed system consists of a linear CNT-based MBFEX source array, a single large area detector that is divided into same number of segments as the number of x-ray beams, a multihole collimator that aligns each beam with a corresponding detector segment, and a sample rotation stage. The collimator is placed between the source and the object to restrict the x-ray radiations through the target object only. In this design, all the x-ray beams are activated simultaneously to provide multiple projection views of the object. The detector is virtually segmented and synchronized with the x-ray exposure and the physiological signals when gating is involved. The transmitted x-ray intensity from each beam is collected by the corresponding segment on the detector. After each exposure, the object is rotated by a step angle until sufficient data set is collected. The half-scan reconstruction formula for MBFEX system is derived from the conventional filtered backprojection algorithm. To demonstrate the advantages of the system and method in reducing motion artifacts, the authors performed simulations with both standard and dynamic Shepp-Logan phantoms. Results: The numerical results indicate that the proposed multibeam system and the associated half-scan algorithm can effectively reduce the scanning time and improve the image quality for a time-varying object. Conclusions: The MBFEX technique offers an opportunity for the innovation of multisource imaging system.

Lu Yang; Yu Hengyong; Cao Guohua; Zhao Jun; Wang Ge; Zhou, Otto [Department of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China); SBES Division and ICTAS Center for Biomedical Imaging, Virginia Tech, Blacksburg, Virginia 24061 (United States); Department of Physics and Astronomy, University of North Carolina, Chapel Hill, North Carolina 27599 (United States); Department of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China); SBES Division and ICTAS Center for Biomedical Imaging, Virginia Tech, Blacksburg, Virginia 24061 (United States); Department of Physics and Astronomy, University of North Carolina, Chapel Hill, North Carolina 27599 (United States)

2010-07-15

295

Chandra Observations of Extended X-Ray Emission in ARP 220  

NASA Technical Reports Server (NTRS)

We resolve the extended X-ray emission from the prototypical ultraluminous infrared galaxy Arp 220. Extended, faint, edge-brightened, soft X-ray lobes outside the optical galaxy are observed to a distance of 1CL 15 kpc on each side of the nuclear region. Bright plumes inside the optical isophotes coincide with the optical line emission and extend 1 1 kpc from end to end across the nucleus. The data for the plumes cannot be fitted by a single-temperature plasma and display a range of temperatures from 0.2 to 1 keV. The plumes emerge from bright, diffuse circumnuclear emission in the inner 3 kpc centered on the Ha peak, which is displaced from the radio nuclei. There is a close morphological correspondence between the Ha and soft X-ray emission on all spatial scales. We interpret the plumes as a starburst-driven superwind and discuss two interpretations of the emission from the lobes in the context of simulations of the merger dynamics of Arp 220.

McDowell, J. C.; Clements, D. L.; Lamb, S. A.; Shaked, S.; Hearn, N. C.; Colina, L.; Mundell, C.; Borne, K.; Baker, A. C.; Arribas, S.

2003-01-01

296

Calcium L(III) and L(II) region x-ray and electron emissions for near threshold electron excitation  

Microsoft Academic Search

An x-ray excitation spectrometer (XRES) was constructed and used to record the Lsb{III} and Lsb{II} region x-ray emissions under near threshold electron excitation for samples of pure calcium metal and samples of calcium in various stages of oxidation. X-ray yield measurements were also made using a lithium-drifted silicon detector. An electron spectrometer was used to observe Auger, electron loss, and

Robert A. Wagner

1997-01-01

297

Discovery of X-ray and Extreme Ultraviolet Emission from Comet C\\/Hyakutake 1996 B2  

Microsoft Academic Search

During its close approach to Earth, comet C\\/Hyakutake 1996 B2 was observed at extreme ultraviolet and x-ray wavelengths with the Rontgen X-ray Satellite and Rossi X-ray Timing Explorer. The emission morphology was symmetric with respect to a vector from the comet's nucleus toward the sun, but not symmetric around the direction of motion of the comet with respect to interplanetary

C. M. Lisse; K. Dennerl; J. Englhauser; M. Harden; F. E. Marshall; M. J. Mumma; R. Petre; J. P. Pye; M. J. Ricketts; J. Schmitt; J. Trumper; R. G. West

1996-01-01

298

X-Ray Emission from Supernovae in Dense Circumstellar Matter Environments: A Search for Collisionless Shock  

NASA Technical Reports Server (NTRS)

The optical light curve of some supernovae (SNe) may be powered by the outward diffusion of the energy deposited by the explosion shock (so-called shock breakout) in optically thick (tau approx > 30) circumstellar matter (CSM). Recently, it was shown that the radiation-mediated and -dominated shock in an optically thick wind must transform into 8. collisionless shock and can produce hard X-rays. The X-rays are expected to peak at late times, relative to maximum visible light. Here we report on a search, using Swift-XRT and Chandra, for X-ray emission from 28 SNe that belong to classes whose progenitors are suspected to be embedded in dense CSM. Our sample includes 19 type-IIn SNe, one type-Ibn SN and eiht hydrogen-poor super-luminous SNe (SLSN-I; SN 2005ap like). Two SNe (SN 2006jc and SN 2010jl) have X-ray properties that are roughly consistent with the expectation for X-rays from a collisionless shock in optically thick CSl\\l. Therefore, we suggest that their optical light curves are powered by shock breakout in CSM. We show that two other events (SN 2010al and SN 2011ht) were too X-ray bright during the SN maximum optical light to be explained by the shock breakout model. We conclude that the light curves of some, but not all, type-IIn/Ibn SNe are powered by shock breakout in CSM. For the rest of the SNe in our sample, including all the SLSN-I events, our X-ray limits are not deep enough and were typically obtained at too early times (i.e., near the SN maximum light) to conclude about their nature. Late time X-ray observations are required in order to further test if these SNe are indeed embedded in dense CSM. We review the conditions required for a shock breakOut in a wind profile. We argue that the time scale, relative to maximum light, for the SN to peak in X-rays is a probe of the column density and the density profile above the shock region. The optical light curves of SNe, for which the X-ray emission peaks at late times, are likely powered by the diffusion of shock energy from a dense CSM. We note that if the CSM density profile falls faster than a constant-rate wind density profile, then X-rays may escape at earlier times than estimated for the wind profile case. Furthermore, if the CSM have a region in which the density profile is very steep, relative to a steady wind density profile, or the CSM is neutral, then the radio free-free absorption may be low enough, and radio emission may be detected.

Ofek, E.O; Fox, D.; Cenko, B.; Sullivan, M.; Gnat, O.; Frail A.; Horesh, A.; Corsi, A; Quimby, R. M.; Gehrels, N.; Kulkarni, S. R.; Gal-Yam, A.; Nugent, P. E.; Yaron, O.; Filippenko, A. V.; Kasliwal, M. M.; Bildsten, L.; Bloom, J. S.; Poznanski, D; Arcavi, L.; Laher, R. R.; Levitan, D.; Sesar, B.; Surace, J.

2012-01-01

299

Possible Charge-Exchange X-Ray Emission in the Cygnus Loop Detected with Suzaku  

NASA Technical Reports Server (NTRS)

X-ray spectroscopic measurements of the Cygnus Loop supernova remnant indicate that metal abundances throughout most of the remnant s rim are depleted to approx.0.2 times the solar value. However, recent X-ray studies have revealed in some narrow regions along the outermost rim anomalously "enhanced" abundances (up to approx. 1 solar). The reason for these anomalous abundances is not understood. Here, we examine X-ray spectra in annular sectors covering nearly the entire rim of the Cygnus Loop using Suzaku (21 pointings) and XMM-Newton (1 pointing). We find that spectra in the "enhanced" abundance regions commonly show a strong emission feature at approx.0.7 keV. This feature is likely a complex of He-like O K(gamma + delta + epsilon), although other possibilities cannot be fully excluded. The intensity of this emission relative to He-like O K(alpha) appears to be too high to be explained as thermal emission. This fact, as well as the spatial concentration of the anomalous abundances in the outermost rim, leads us to propose an origin from charge-exchange processes between neutrals and H-like O. We show that the presence of charge-exchange emission could lead to the inference of apparently "enhanced" metal abundances using pure thermal emission models. Accounting for charge-exchange emission, the actual abundances could be uniformly low throughout the rim. The overall abundance depletion remains an open question. Subject headings: ISM: abundances ISM: individual objects (Cygnus Loop) ISM: supernova remnants X-rays: ISM atomic processes

Katsuda, Satoru; Tsunemi, Hiroshi; Mori, Koji; Uchida, Hiroyuki; Kosugi, Hiroko; Kimura, Masashi; Nakajima, Hiroshi; Takakura, Satoru; Petre, Robert; Hewitt. John W.; Yamaguchi, Hiroya

2011-01-01

300

Accretion and Outflows in X-ray Binaries: What's Really Going on During X-ray Quiescence  

NASA Astrophysics Data System (ADS)

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.

MacDonald, Rachel K. D.; Bailyn, Charles D.; Buxton, Michelle

2015-01-01

301

Diffuse X-Ray Emission from the Superbubbles N70 and N185 in the Large Magellanic Cloud  

NASA Astrophysics Data System (ADS)

We present a study of the diffuse X-ray emission from superbubbles (SBs) N70 (DEM L301) and N185 (DEM L25) located in the Large Magellanic Cloud, based on data from the XMM-Newton Satellite. We obtained spectra and images of these objects in the soft X-ray energy band. These X-ray spectra were fitted by a thermal plasma model, with temperatures of 2.6× {{10}6} K and 2.3× {{10}6} K, for N70 and N185, respectively. For N70, images show that X-ray emission comes from the inner regions of the SB when we compare the distribution of the X-ray and the optical emission, while for N185, the X-ray emission is partially confined by the optical shell. We suggest that the observed X-ray emission is caused by shock-heated gas, inside of the optical shells. We also obtained X-ray luminosities which exceed the values predicted by the standard analytical model. This fact shows that, in addition to the winds of the interior stars, it is necessary to consider another ingredient in the description, such as a supernova explosion, as has been proposed in previous numerical models.

Reyes-Iturbide, J.; Rosado, M.; Rodríguez-González, A.; Velázquez, P. F.; Sánchez-Cruces, M.; Ambrocio-Cruz, P.

2014-11-01

302

Iron line and diffuse hard X-ray emission from the starburst galaxy M82  

E-print Network

We examine the properties of the diffuse hard X-ray emission in the classic starburst galaxy M82. We use new Chandra ACIS-S observations in combination with reprocessed archival Chandra ACIS-I and XMM-Newton observations. We find E~6.7 keV Fe He-alpha emission is present in the central |r| iron line fluxes in the 2004 April 21 XMM-Newton observation are consistent with those of the Chandra-derived diffuse component, but in the 2001 May 6 XMM-Newton observation they are significantly higher and also both E=6.4 and E=6.9 keV iron lines are detected. We attribute the excess iron line emission to the Ultra-Luminous X-ray source in its high state. In general the iron K-shell luminosity of M82 is dominated by the diffuse component. The total X-ray luminosity of the diffuse hard X-ray emission (corrected for emission by unresolved low luminosity compact objects) is L_X ~ 4.4 x 10^39 erg/s in the E=2-8 keV energy band, and the 6.7 keV iron line luminosity is L_X ~ (1.1 -- 1.7) x 10^38 erg/s. The 6.7 keV iron line luminosity is consistent with that expected from the previously unobserved metal-enriched merged supernova ejecta that is thought to drive the larger-scale galactic superwind. The iron line luminosity implies a thermal pressure within the starburst region of P/k ~ 2 x 10^7 K/cm^3, which is consistent with independent observational estimates of the starburst region pressure [Abstract abridged].

D. K. Strickland; T. M. Heckman

2006-11-28

303

Enhancement of Terrestrial Diffuse X-Ray Emission Associated with Coronal Mass Ejection and Geomagnetic Storm  

NASA Astrophysics Data System (ADS)

We present an analysis of a Suzaku observations taken during the geomagnetic storm of 2005 August 23-24. We found a time variation of diffuse soft X-ray emission when a coronal mass ejection hit Earth and caused a geomagnetic storm. The diffuse emission consisted of fluorescent scattering of solar X-rays and an exospheric solar wind charge exchange. The former is characterized by a neutral oxygen emission line due to strong heating of the upper atmosphere during the storm time, while the latter is dominated by the sum of C V, C VI, N VI, N VII, O VII, and O VIII emission lines due to an enhanced solar wind flux in the vicinity of the exosphere. Using the solar-wind data taken with the ACE and WIND satellites, a time correlation between the solar wind and the strong O VII line flux was investigated. We estimated necessary column densities for the solar X-ray scattering and exospheric SWCX. From these results, we argue that a part of the solar-wind ions enters inside the magnetosphere and causes the SWCX reaction.

Ezoe, Yuichiro; Miyoshi, Yoshizumi; Yoshitake, Hiroshi; Mitsuda, Kazuhisa; Terada, Naoki; Oishi, Shihoko; Ohashi, Takaya

2011-11-01

304

X-ray Emission from Charge Exchange in the Cygnus Loop SNR  

E-print Network

The Cygnus Loop has been the focus of substantial debate concerning the contribution of charge exchange (CX) to supernova remnant (SNR) X-ray emission. We take advantage of a distinct feature of CX, enhanced K{\\alpha} forbidden line emission, and employ the energy centroid of the OVII K{\\alpha} triplet as a diagnostic. Based on X-ray spectra extracted from an extensive set of Suzaku observations, we measure the energy centroid shifts of the triplet on and off the shock rim of the remnant. We find that enhanced forbidden to resonance line emission exists throughout much of the rim and this enhancement azimuthally correlates with non-radiative H{\\alpha} filaments, a tracer of strong neutral-plasma interaction in the optical. We also show that alternative mechanisms cannot explain the enhancement observed. These results demonstrate the need to model the CX contribution to the X-ray emission of SNRs, particularly for shocks propagating in a partially neutral medium. Such modeling may be critically important to th...

Roberts, Shawn R

2015-01-01

305

MEASUREMENT OF THE RADIUS OF NEUTRON STARS WITH HIGH SIGNAL-TO-NOISE QUIESCENT LOW-MASS X-RAY BINARIES IN GLOBULAR CLUSTERS  

SciTech Connect

This paper presents the measurement of the neutron star (NS) radius using the thermal spectra from quiescent low-mass X-ray binaries (qLMXBs) inside globular clusters (GCs). Recent observations of NSs have presented evidence that cold ultra dense matter-present in the core of NSs-is best described by ''normal matter'' equations of state (EoSs). Such EoSs predict that the radii of NSs, R{sub NS}, are quasi-constant (within measurement errors, of {approx}10%) for astrophysically relevant masses (M{sub NS}>0.5 M{sub Sun }). The present work adopts this theoretical prediction as an assumption, and uses it to constrain a single R{sub NS} value from five qLMXB targets with available high signal-to-noise X-ray spectroscopic data. Employing a Markov chain Monte-Carlo approach, we produce the marginalized posterior distribution for R{sub NS}, constrained to be the same value for all five NSs in the sample. An effort was made to include all quantifiable sources of uncertainty into the uncertainty of the quoted radius measurement. These include the uncertainties in the distances to the GCs, the uncertainties due to the Galactic absorption in the direction of the GCs, and the possibility of a hard power-law spectral component for count excesses at high photon energy, which are observed in some qLMXBs in the Galactic plane. Using conservative assumptions, we found that the radius, common to the five qLMXBs and constant for a wide range of masses, lies in the low range of possible NS radii, R{sub NS}=9.1{sup +1.3}{sub -1.5} km (90%-confidence). Such a value is consistent with low-R{sub NS} equations of state. We compare this result with previous radius measurements of NSs from various analyses of different types of systems. In addition, we compare the spectral analyses of individual qLMXBs to previous works.

Guillot, Sebastien; Rutledge, Robert E. [Department of Physics, McGill University, 3600 rue University, Montreal, QC, H2X-3R4 (Canada); Servillat, Mathieu [Laboratoire AIM (CEA/DSM/IRFU/SAp, CNRS, Universite Paris Diderot), CEA Saclay, Bat. 709, F-91191 Gif-sur-Yvette (France); Webb, Natalie A., E-mail: guillots@physics.mcgill.ca, E-mail: rutledge@physics.mcgill.ca [Universite de Toulouse, UPS-OMP, IRAP, Toulouse (France)

2013-07-20

306

Optimization of neon soft X-ray emission from 200 J plasma focus device for application in soft X-ray lithography  

NASA Astrophysics Data System (ADS)

The Fast Miniature Plasma Focus (FMPF) device is basically made up of coaxial electrodes with centrally placed anode and six cathode rods surrounding them concentrically. They are enclosed in a vacuum chamber, filled with low pressure operating gas. However, in our experiments, these cathode rods were removed to investigate the influence of them on neon soft X-ray (SXR) and hard X-ray (HXR) emission from the device. On removal of cathode rods, the cathode base plate serves as cathode and the plasma sheath is formed between the anode and the base plate of cathode. Neon was used as the operating gas for our experiments and the FMPF device used is of 235 J energy capacities. The experimental results showed that the FMPF device was able to focus better and the SXR emission efficiency was five times higher without cathode rods than with cathode rods. On the contrary, HXR emission did not vary with and without cathode rods. This observed phenomenon was further cross-checked through imaging of plasma dynamics, with and without cathode rods. FMPF device consists of 4 Pseudo Spark Gap (PSG) switches, which need to operate synchronously to deliver high voltage from capacitors to the anode. It was also seen that, the presence or absence of cathode rods also influence the synchronous operation of PSG switches. It also implies that this is one definite way to optimize the SXR emission from the FMPF device. This study reveals an important finding that, cathode rods play a vital role in the formation of plasma sheath with consequential influence on the radiation emission from plasma focus devices. Enhancement of the X-ray emission from this device is definitely a stepping stone in the realization of this device for industrial applications such as X-ray lithography for semiconductor industries.

Kalaiselvi, S. M. P.; Tan, T. L.; Talebitaher, A.; Lee, P.; Rawat, R. S.

2014-08-01

307

Detection of X-ray emission from the PSR 1259-63/SS 2883 binary system  

NASA Technical Reports Server (NTRS)

Nonpulsed but variable X-ray emission has been detected from the binary system containing the radio pulsar PSR 1259-63 during two pointed ROSAT observations, taken 5 months apart. This 47.7 ms radio pulsar is in a highly eccentric (epsilon approximately 0.85) binary system with the 10-15 solar mass Be star SS 2883. It is the first radio pulsar found to be in a binary system with a massive main-sequence companion; it is also the most highly eccentric binary system known to contain a neutron star. The level of X-ray flux detected in the ROSAT observations has increased with orbital phase by a factor of at least 10 between 1992 February and 1993 February. The X-ray flux is significantly greater than expected from the Be star's corona and seems likely to originate either from low-level stellar wind accretion onto the neutron star or from the shock between the stellar wind and the relativistic pulsar wind. The system may be the progenitor of the more slowly rotating Be X-ray binary pulsar systems.

Cominsky, Lynn; Roberts, Mallory; Johnston, Simon

1994-01-01

308

Experimental study of hard-X ray emission from laboratory sparks  

NASA Astrophysics Data System (ADS)

We present the characterization of hard-X rays produced by meter-long laboratory sparks carried out at the high-voltage laboratory of RSE, Milano, Italy. Sparks are known to emit X-rays when positive and negative streamers connect, before breakdown. Numerical simulations suggest that X-rays are produced by Bremsstrahlung in air by electrons accelerated to the runaway regime in the high electric field at the streamers tip. Positive meter-long discharges are produced by a Marx generator loaded by a meter-long air gap formed by a spherical anode and a conical-shaped cathode. Maximum voltage at breakdown is about 1 MV. We investigate the production of X-rays by means of an array of scintillation detectors deployed around the cathode. Each detector is a 2'' NaI(Tl) scintillating crystal coupled to a photomultiplier tube (PMT). Each detector is battery-powered and enclosed in a metallic housing for EM shielding. Analog signal output is trasmitted to a shielded control room by means of optical fibre tranceivers, and then collected by a fast digitizer. We present the experimental setup and first results concerning detection efficiency, energy spectra, and geometrical distribution of the emission.

Marisaldi, Martino; Rizzi, Rolando; Levi, Giuseppe; Malgesini, Roberto; Villa, Andrea; Mazza, Paolo; Labanti, Claudio; Fuschino, Fabio; Campana, Riccardo; Bianchini, David; Brancaccio, Rossella; Montanari, Alessandro; Patrizii, Laura

2014-05-01

309

On the X-ray Baldwin effect for narrow Fe Kalpha emission line  

E-print Network

Most Active Galactic Nuclei (AGN) exhibit a narrow Fe Kalpha line at ~ 6.4 keV in the X-ray spectra, due to the fluorescent emission from cold material far from the inner accretion disk. Using XMM-Newton observations, Page et al. found that the equivalent width (EW) of the narrow Fe Kalpha line decreases with increasing luminosity (EW ~ L^-0.17pm0.08), suggesting a decrease in the covering factor of the material emitting the line (presumably the torus). By combining the archival Chandra HETG observations of 34 type 1 AGNs with XMM observations in literature, we build a much large sample with 101 AGNs. We find a similar X-ray Baldwin effect in the sample (EW ~ L^-0.2015pm0.0426), however, we note that the anti-correlation is dominated by the radio loud AGN in the sample, whose X-ray spectra might be contaminated by the relativistic jet. Excluding the radio loud AGN, we find a much weaker anti-correlation (EW ~ L^-0.1019pm0.0524). We present Monte-Carlo simulations showing that such a weak anti-correlation can be attributed to the relative short time scale variations of the X-ray continuum.

P. Jiang; J. X. Wang; T. G. Wang

2006-03-14

310

Detection of parametric X-ray emission from a GaAs single crystal  

NASA Astrophysics Data System (ADS)

The paper reports the experimental observation of parametric X-ray emission (PXE) from a perfect GaAs single crystal at an angle of 90 deg to the electron-velocity direction. Measurements were performed on the Sirius synchrotron; the target was a 0.4-mm-thick GaAs single crystal in Bragg geometry. The PXE spectrum of GaAs was evaluated for an electron energy of 250 MeV in the case of diffraction on (400) planes. In addition, the energy dependence of the ratio of PXE intensity to the intensity of characteristic X-ray emission was examined in the 250-900 MeV range.

Afanasenko, V. P.; Baryshevskii, V. G.; Gradovskii, O. T.; Livshits, M. G.; Lobko, A. S.

1988-01-01

311

Electrochemical flowcell for in-situ investigations by soft x-ray absorption and emission spectroscopy  

SciTech Connect

A new liquid flow-cell designed for electronic structure investigations at the liquid-solid interface by soft X-ray absorption and emission spectroscopy is presented. A thin membrane serves simultaneously as a substrate for the working electrode and solid state samples as well as for separating the liquid from the surrounding vacuum conditions. In combination with counter and reference electrodes this approach allows in-situ studies of electrochemical deposition processes and catalytic reactions at the liquid-solid interface in combination with potentiostatic measurements. As model system in-situ monitoring of the deposition process of Co metal from a 10 mM CoCl{sub 2} aqueous solution by X-ray absorption and emission spectroscopy is presented.

Schwanke, C.; Lange, K. M., E-mail: Kathrin.lange@helmholtz-berlin.de [Helmholtz-Zentrum Berlin für Materialien und Energie, Institute of Solar Fuels, Albert-Einstein-Straße 15, 12489 Berlin (Germany); Golnak, R.; Xiao, J. [Helmholtz-Zentrum Berlin für Materialien und Energie, Institute of Methods for Material Development, Albert-Einstein-Straße 15, 12489 Berlin (Germany)

2014-10-15

312

X-ray observations of high-excitation emission-line galaxies with the HEAO 1 scanning modulation collimator  

NASA Technical Reports Server (NTRS)

Data from the scanning modulation collimator on HEAO 1 are presented which firmly establish high-excitation emission-line galaxies as a class of X-ray source. For NGC 5506 and M82, the X-ray emission (1-13 keV) is shown to originate in the nuclear region of the galaxy; NGC 2992 and NGC 526a are also identified as X-ray emitters, but are not resolved. The latter is a new identification for 2A 0120-353, previously associated with the NGC 526/527 group. In these four particular cases, the observed X-ray-emitting galaxies have a close companion, and the X-ray emission may have been triggered by a close encounter

Griffiths, R. E.; Schwartz, D. A.; Schwarz, J.; Doxsey, R. E.; Johnston, M. D.; Blades, J. C.

1979-01-01

313

Design of a transmission grating spectrometer and an undulator beamline for soft x-ray emission studies  

SciTech Connect

A soft x-ray undulator beamline and an x-ray emission spectrometer have been designed for soft x-ray emission studies. The beamline has a varied-line-spacing plane grating monochromator, which enables the energy resolution over 104 with a beam size down to 10 x 60 {mu}m2. The x-ray emission spectrometer has a Wolter type I mirror, a free-standing transmission grating, and a back-illuminated CCD. A high collection angle up to 1.5 x 10-3 sr is achieved by utilizing the Wolter mirror as a prefocusing system. The CCD is mounted at 1400 mm downstream of the grating on a Rowland torus mount. Diffracted x-rays are detected in the normal incidence geometry, resulting in high detection efficiency. The energy resolution is limited by the figure errors of the optical elements and the spatial resolution of the detector.

Hatsui, Takaki; Kosugi, Nobuhiro [Institute for Molecular Sciences, Myodaiji, Okazaki 444-8585 (Japan); Graduate University for Advanced Studies, Myodaiji, Okazaki 444-8585 (Japan); Shigemasa, Eiji [Institute for Molecular Sciences, Myodaiji, Okazaki 444-8585 (Japan)

2004-05-12

314

X-ray continuum emission spectroscopy from hot dense matter at Gbar pressuresa)  

NASA Astrophysics Data System (ADS)

We have measured the time-resolved x-ray continuum emission spectrum of ˜30 times compressed polystyrene created at stagnation of spherically convergent shock waves within the Gbar fundamental science campaign at the National Ignition Facility. From an exponential emission slope between 7.7 keV and 8.1 keV photon energy and using an emission model which accounts for reabsorption, we infer an average electron temperature of 375 ± 21 eV, which is in good agreement with HYDRA-1D simulations.

Kraus, D.; Döppner, T.; Kritcher, A. L.; Bachmann, B.; Chapman, D. A.; Collins, G. W.; Glenzer, S. H.; Hawreliak, J. A.; Landen, O. L.; Ma, T.; Le Pape, S.; Neumayer, P.; Swift, D. C.; Falcone, R. W.

2014-11-01

315

X-ray continuum emission spectroscopy from hot dense matter at Gbar pressures.  

PubMed

We have measured the time-resolved x-ray continuum emission spectrum of ?30 times compressed polystyrene created at stagnation of spherically convergent shock waves within the Gbar fundamental science campaign at the National Ignition Facility. From an exponential emission slope between 7.7 keV and 8.1 keV photon energy and using an emission model which accounts for reabsorption, we infer an average electron temperature of 375 ± 21 eV, which is in good agreement with HYDRA-1D simulations. PMID:25430182

Kraus, D; Döppner, T; Kritcher, A L; Bachmann, B; Chapman, D A; Collins, G W; Glenzer, S H; Hawreliak, J A; Landen, O L; Ma, T; Le Pape, S; Neumayer, P; Swift, D C; Falcone, R W

2014-11-01

316

Novel Cell Design for Combined In Situ Acoustic Emission and X-ray Diffraction of Cycling Lithium Ion Batteries  

Microsoft Academic Search

An in situ acoustic emission (AE) and X-ray diffraction (XRD) cell for use in the study of battery electrode materials has been devised and tested. This cell uses commercially available coin cell hardware retrofitted with a metalized polyethylene terephthalate (PET) disk which acts as both an X-ray window and a current collector. In this manner the use of beryllium and

Kevin J Rhodes; Melanie J Kirkham; Roberta Ann Meisner; Chad M Parish; Nancy J Dudney; Claus Daniel

2011-01-01

317

Proton-induced X-ray emission analysis of munitions disposal residues  

Microsoft Academic Search

Residues from several unservicible munitions and chemical agents disposed of by incineration and chemical conversion have been quantitatively analyzed for elemental content using proton-induced X-ray emission (PIXE). Carbonaceous residues were first digested by a single-acid, wet-oxidation procedure and silicious residues were prepared using a lithium metaborate fusion-acid dissolution procedure. The resulting solutions were applied to a polycarbonate film and analyzed

N. W. Lytle; M. W. Hill; K. E. Lambert; N. F. Mangelson; S. S. W. Kwak

1985-01-01

318

Resolved X-ray emission line profiles Clumping in Hot Star Winds  

E-print Network

Resolved X-ray emission line profiles Clumping in Hot Star Winds W.-R. Hamann, A. Feldmeier & L and wind porosity. We find that reducing the mass-loss rate of Pup by roughly a factor of four, to 1.5 Ã? 10-6 M yr-1 , enables simple non-porous wind models to provide good fits to the data. If

Cohen, David

319

Bulk band gaps in divalent hexaborides: A soft x-ray emission study  

SciTech Connect

Boron K-edge soft x-ray emission and absorption are used to address the fundamental question of whether divalent hexaborides are intrinsic semimetals or defect-doped bandgap insulators. These bulk sensitive measurements, complementary and consistent with surface-sensitive angle-resolved photoemission experiments, confirm the existence of a bulk band gap and the location of the chemical potential at the bottom of the conduction band.

Denlinger, Jonathan D.; Gweon, Gey-Hong; Allen, James W.; Bianchi, Andrea D.; Fisk, Zachary

2001-10-03

320

Correlation of solar radio pulsations with hard X-ray emission  

NASA Technical Reports Server (NTRS)

A systematic study of the correlation of quasi-periodic broad-band decimetric pulsations with hard X-ray (HXR) emission is carried out. It is found that, in 11 out of 56 simultaneously observed events, the decimetric quasi-periodic pulsations in the impulsive phase of flares are correlated. If events with concurring type III bursts are included, 19 cases of radio pulsations are correlated with HXR.

Aschwanden, M. J.; Benz, A. O.; Kane, S. R.

1990-01-01

321

Parametric X-ray emission under conditions of extremely asymmetric diffraction  

NASA Astrophysics Data System (ADS)

The spectral and angular distributions of parametric X-ray emission (PXE) are found under conditions of extremely asymmetric diffraction. An expression is derived for the total number of photons recorded by a detector with a given angular resolution. The influence that multiple electron scattering and the mosaic structure of real crystals has on the nature of PXE is discussed. It was found that the theory explaining PXE in the case of extreme asymmetry agrees well with experimental measurements.

Baryshevskii, V. G.; Grubich, A. O.; Feranchuk, I. D.

1986-05-01

322

X-rays emission from a compact diode energized by capacitor discharge  

NASA Astrophysics Data System (ADS)

X-ray emission from a compact diode consisting of a sharp edged cathode and flat anode of copper and lead, energized by simple capacitor discharge is reported. With a sewing machine needle cathode, and lead target, the generation efficiency upto 0.4% is obtained. The efficiency is expected to enhance further with the increase in discharge energy, charging voltage and reducing the parasitic inductance.

Zakaullah, M.; Ahmed, S.; Hussain, S.; Afzal, M.; Waheed, A.

2005-01-01

323

Non-thermal emissions from accreting X-ray binary pulsars  

NASA Astrophysics Data System (ADS)

We study non-thermal emissions from cascade processes in accreting X-ray binary pulsars. In the framework of the magnetospheric gap model, we consider three photon fields, which are respectively from the polar cap of a pulsar, its surrounding accretion disk and a massive companion star with a circumstellar disk, to shield the gap. The gap-accelerated ultra-relativistic electrons emit high-energy photons via curvature radiation and an inverse Compton scattering process, in which part of these high-energy photons absorbed by interactions with the surrounding photon fields can facilitate the following electromagnetic cascades. We first carry out numerical calculations of the cascade processes in order to obtain the predicted emission spectra. As an example, we subsequently apply this model to reproduce observations of LS I +61° 303. We find that the results can fit observations ranging from hard X-ray to ?-ray bands. In particular, they can explain the spectral cutoff feature at a few GeV. Finally, we suggest that the emissions detected by the Fermi Large Area Telescope from X-ray binary pulsars originate in the magnetosphere region of the pulsar.

Zhang, Jian-Fu; Jin, Hui; Dong, Ai-Jun

2014-03-01

324

Suzaku Observation of Diffuse X-ray Emission from the Carina Nebula  

NASA Technical Reports Server (NTRS)

We studied extended X-ray emission from the Carina Nebula taken with the Suzaku CCD camera XIS on 2005 Aug. 29. The X-ray morphology, plasma temperature and absorption to the plasma are consistent with the earlier Einstein results. The Suzaku spectra newly revealed emission lines from various spices including oxygen, but not from nitrogen. This result restricts the N/O ratio significantly low, compared with evolved massive stellar winds, suggesting that the diffuse emission is originated in an old supernova remnant or a super shell produced by multiple supernova remnants. The X-ray spectra from the north and south of eta Car showed distinct differences between 0.3-2 keV. The south spectrum shows strong L-shell lines of iron ions and K-shell lines of silicon ions, while the north spectrum shows them weak in intensity. This means that silicon and iron abundances are a factor of 2-4 higher in the south region than in the north region. The abundance variation may be produced by an SNR ejecta, or relate to the dust formation around the star forming core.

Hamaguchi, Kenji; Petre, Robert; Matsumoti, Hironori; Tsujimoto, Masahiro; Holt, Stephan S.; Ezoe, Yuichiro; Ozawa, Hideki; Tsuboi, Yohko; Soong, Yang; Kitamoto, Shunji; Sekiguchi, Akiko; Kokubun, Motohide

2007-01-01

325

X-ray photo-emission and energy dispersive spectroscopy of HA coated titanium  

SciTech Connect

The purpose of this study was to determine the chemical composition changes of hydroxyapatite (HA) coated titanium using surface analysis (x-ray photo-emission) and bulk analysis (energy dispersive spectroscopy). The specimens examined were controls, 30 minutes and 3 hours aged specimens in distilled water or 0.2M sodium phosphate buffer (pH 7.2) at room temperature. Each x-ray photo-emission cycle consisted of 3 scans followed by argon sputtering for 10 minutes for a total of usually 20 cycles, corresponding to a sampling depth of {approximately} 1500 {angstrom}. The energy dispersive spectroscopy analysis was on a 110 by 90 {mu}m area for 500 sec. Scanning electron microscopy examination showed crystal formation (3P{sub 2}O{sub 5}*2CAO*?H{sub 2}O by energy dispersive spectroscopy analysis) on the HA coating for the specimens aged in sodium phosphate buffer. The x-ray photo-emission results indicated the oxidation effect of water on the titanium (as TiO{sub 2}) and the effect of the buffer to increase the surface concentration of phosphorous. No differences in the chemical composition were observed by energy dispersive spectroscopy analysis. The crystal growth was only observed for the sodium phosphate buffer specimens and only on the HA surface.

Drummond, J.L.; Steinberg, A.D. [Univ. of Illinois, Chicago, IL (United States); Krauss, A.R. [Argonne National Lab., IL (United States)] [and others

1997-08-01

326

Soft X-ray synchrotron radiation investigations of actinidematerials systems utilizing X-ray emission spectroscopy and resonantinelastic X-ray scattering  

SciTech Connect

Synchrotron radiation (SR) methods have been utilized with increasing frequency over the past several years to study topics in actinide science, ranging from those of a fundamental nature to those that address a specifically-targeted technical need. In particular, the emergence of microspectroscopic and fluorescence-based techniques have permitted investigations of actinide materials at sources of soft x-ray SR. Spectroscopic techniques with fluorescence-based detection are useful for actinide investigations since they are sensitive to small amounts of material and the information sampling depth may be varied. These characteristics also serve to simplify both sample preparation and safety considerations. Examples of investigations using these fluorescence techniques will be described along with their results, as well as the prospects for future investigations utilizing these methodologies.

Shuh, D.K.; Butorin, S.M.; Guo, J.-H.; Nordgren, J.

2004-01-03

327

INVERSE COMPTON X-RAY EMISSION FROM SUPERNOVAE WITH COMPACT PROGENITORS: APPLICATION TO SN2011fe  

SciTech Connect

We present a generalized analytic formalism for the inverse Compton X-ray emission from hydrogen-poor supernovae and apply this framework to SN 2011fe using Swift X-Ray Telescope (XRT), UVOT, and Chandra observations. We characterize the optical properties of SN 2011fe in the Swift bands and find them to be broadly consistent with a 'normal' SN Ia, however, no X-ray source is detected by either XRT or Chandra. We constrain the progenitor system mass-loss rate M-dot < 2 x 10{sup -9} M{sub Sun }yr{sup -1} (3{sigma} c.l.) for wind velocity v{sub w} = 100 km s{sup -1}. Our result rules out symbiotic binary progenitors for SN 2011fe and argues against Roche lobe overflowing subgiants and main-sequence secondary stars if {approx}> 1% of the transferred mass is lost at the Lagrangian points. Regardless of the density profile, the X-ray non-detections are suggestive of a clean environment (n{sub CSM} < 150 cm{sup -3}) for 2 Multiplication-Sign 10{sup 15} {approx}< R {approx}< 5 Multiplication-Sign 10{sup 16} cm around the progenitor site. This is either consistent with the bulk of material being confined within the binary system or with a significant delay between mass loss and supernova explosion. We furthermore combine X-ray and radio limits from Chomiuk et al. to constrain the post-shock energy density in magnetic fields. Finally, we searched for the shock breakout pulse using gamma-ray observations from the Interplanetary Network and find no compelling evidence for a supernova-associated burst. Based on the compact radius of the progenitor star we estimate that the shock breakout pulse was likely not detectable by current satellites.

Margutti, R.; Soderberg, A. M.; Chomiuk, L.; Milisavljevic, D.; Foley, R. J.; Slane, P.; Moe, M. [Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138 (United States); Chevalier, R. [Department of Astronomy, University of Virginia, Charlottesville, VA 22904-4325 (United States); Hurley, K. [Space Sciences Laboratory, University of California, 7 Gauss Way, Berkeley, CA 94720-7450 (United States); Hughes, J. P. [Department of Physics and Astronomy, Rutgers University, Piscataway, NJ 08854-8019 (United States); Fransson, C. [Department of Astronomy, Stockholm University, AlbaNova, SE-106 91 Stockholm (Sweden); Barthelmy, S.; Cummings, J. [NASA/Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Boynton, W.; Enos, H.; Fellows, C. [Department of Planetary Sciences, University of Arizona, Tucson, AZ 85721 (United States); Briggs, M.; Connaughton, V. [Physics Department, The University of Alabama in Huntsville, Huntsville, AL 35809 (United States); Costa, E.; Del Monte, E. [INAF/IASF-Roma, via Fosso del Cavaliere 100, 00133 Roma (Italy); and others

2012-06-01

328

Physical Conditions in the X-Ray Emission-line Gas in NGC 1068  

NASA Astrophysics Data System (ADS)

We present a detailed, photoionization modeling analysis of XMM-Newton/Reflection Grating Spectrometer observations of the Seyfert 2 galaxy NGC 1068. The spectrum, previously analyzed by Kinkhabwala et al., reveals a myriad of soft X-ray emission lines, including those from H- and He-like carbon, nitrogen, oxygen, and neon, and M- and L-shell iron. As noted in the earlier analysis, based on the narrowness of the radiative recombination continua, the electron temperatures in the emission-line gas are consistent with photoionization, rather than collisional ionization. The strengths of the carbon and nitrogen emission lines, relative to those of oxygen, suggest unusual elemental abundances, which we attribute to the star formation history of the host galaxy. Overall, the emission lines are blueshifted with respect to systemic, with radial velocities ~160 km s–1, similar to that of [O III] ?5007, and thus consistent with the kinematics and orientation of the optical emission-line gas and, hence, likely part of an active galactic nucleus driven outflow. We were able to achieve an acceptable fit to most of the strong emission lines with a two-component photoionization model, generated with CLOUDY. The two components have ionization parameters and column densities of logU = –0.05 and 1.22 and logN H = 20.85 and 21.2 and covering factors of 0.35 and 0.84, respectively. The total mass of the X-ray gas is roughly an order of magnitude greater than the mass of ionized gas determined from optical and near-IR spectroscopy, which indicates that it may be the dominant component of the narrow-line region. Furthermore, we suggest that the medium that produces the scattered/polarized optical emission in NGC 1068 possesses similar physical characteristics to those of the more highly ionized of the X-ray model components.

Kraemer, S. B.; Sharma, N.; Turner, T. J.; George, Ian M.; Crenshaw, D. Michael

2015-01-01

329

Discovery of X-Ray Emission from the First Be/Black Hole System  

NASA Astrophysics Data System (ADS)

MWC 656 (=HD 215227) was recently discovered to be the first binary system composed of a Be star and a black hole (BH). We observed it with XMM-Newton, and detected a faint X-ray source compatible with the position of the optical star, thus proving it to be the first Be/BH X-ray binary. The spectrum analysis requires a model fit with two components, a blackbody plus a power law, with k_BT = 0.07^{+0.04}_{-0.03} keV and a photon index ? = 1.0 ± 0.8, respectively. The non-thermal component dominates above sime0.8 keV. The obtained total flux is F(0.3-5.5\\, keV) = (4.6^{+1.3}_{-1.1})\\times 10^{-14} erg cm-2 s-1. At a distance of 2.6 ± 0.6 kpc the total flux translates into a luminosity L X = (3.7 ± 1.7) × 1031 erg s-1. Considering the estimated range of BH masses to be 3.8-6.9 M ?, this luminosity represents (6.7 ± 4.4) × 10-8 L Edd, which is typical of stellar-mass BHs in quiescence. We discuss the origin of the two spectral components: the thermal component is associated with the hot wind of the Be star, whereas the power-law component is associated with emission from the vicinity of the BH. We also find that the position of MWC 656 in the radio versus X-ray luminosity diagram may be consistent with the radio/X-ray correlation observed in BH low-mass X-ray binaries. This suggests that this correlation might also be valid for BH high-mass X-ray binaries (HMXBs) with X-ray luminosities down to ~10-8 L Edd. MWC 656 will allow the accretion processes and the accretion/ejection coupling at very low luminosities for BH HMXBs to be studied.

Munar-Adrover, P.; Paredes, J. M.; Ribó, M.; Iwasawa, K.; Zabalza, V.; Casares, J.

2014-05-01

330

The height of flare emissions in white light and in hard X-rays  

NASA Astrophysics Data System (ADS)

Hard X-ray emission has long been known to correlate well with white-light continuum emission by a solar flare, providing support for the thick-target model of interactions by nonthermal electrons accelerated in the impulsive phase of a solar flare. This model makes specific predictions for the height, in the solar atmosphere, where such emissions can form. In this presentation we extend our earlier work (Martinez Oliveros et al., ApJ 753, 26, 2012) on the determination of the absolute heights of white-light flares and their associated hard X-ray sources. The new work makes use of surveys of the HMI flare observations, which provide a new database with excellent properties for this purpose in conjunction with STEREO and RHESSI. In the earlier work, based on the flare SOL2011-02-24, we found the white-light and hard X-ray sources to coincide, and to occur close to their minimum possible heights in terms of model optical depth. This conclusion is now confirmed with three additional flares: SOL2011-01-28T01:03 (M1.3), SOL2013-05-13T02:17 (X1.7), and SOL2013-05-13T16:01 (X2.8). The relatively low absolute altitude of the hard X-ray sources (of order 500 km above the level of the photosphere, at 500 nm optical depth unity) presents a puzzle for the standard thick-target model, and we discuss some possible explanations.

Hudson, H. S.; Martinez Oliveros, J.; Glesener, L.; Krucker, S.; Bogart, R. S.; Couvidat, S. P.; Prochnow, B.; Scherrer, P. H.

2013-12-01

331

X-ray emission from star-forming galaxies - signatures of cosmic rays and magnetic fields  

NASA Astrophysics Data System (ADS)

The evolution of magnetic fields in galaxies is still an open problem in astrophysics. In nearby galaxies the far-infrared-radio correlation indicates the coupling between magnetic fields and star formation. The correlation arises from the synchrotron emission of cosmic ray electrons travelling through the interstellar magnetic fields. However, with an increase of the interstellar radiation field (ISRF), inverse Compton scattering becomes the dominant energy loss mechanism of cosmic ray electrons with a typical emission frequency in the X-ray regime. The ISRF depends on the one hand on the star formation rate and becomes stronger in starburst galaxies, and on the other hand increases with redshift due to the higher temperature of the cosmic microwave background. With a model for the star formation rate of galaxies, the ISRF, and the cosmic ray spectrum, we can calculate the expected X-ray luminosity resulting from the inverse Compton emission. Except for galaxies with an active galactic nucleus the main additional contribution to the X-ray luminosity comes from X-ray binaries. We estimate this contribution with an analytical model as well as with an observational relation, and compare it to the pure inverse Compton luminosity. Using data from the Chandra Deep Field Survey and far-infrared observations from Atacama Large Millimeter/Submillimeter Array, we then determine upper limits for the cosmic ray energy. Assuming that the magnetic energy in a galaxy is in equipartition with the energy density of the cosmic rays, we obtain upper limits for the magnetic field strength. Our results suggest that the mean magnetic energy of young galaxies is similar to the one in local galaxies. This points towards an early generation of galactic magnetic fields, which is in agreement with current dynamo evolution models.

Schober, J.; Schleicher, D. R. G.; Klessen, R. S.

2015-01-01

332

THE BURSTY NATURE OF SOLAR FLARE X-RAY EMISSION. II. THE NEUPERT EFFECT  

SciTech Connect

We carry out a novel statistical test of the Neupert effect based on multifractal spectra. The multifractal spectrum is the number distribution of the strengths (i.e., the Hölder exponents) of bursts in a signal. This is tested on simulations and carried out on RHESSI X-ray data from a well observed GOES X4.8 magnitude flare. The multifractal spectra is ideally suited to quantifying the relative smooth and bursty signals typically found in (thermal) soft X-ray and (non-thermal) hard X-ray data of solar flares. We show that light curves from all energies between 3 keV and 25 keV are statistically similar, suggesting that all these signals are dominated by the same (presumably thermal) emission. Emission lying between 25 keV and 100 keV probably contains some contribution from both thermal and non-thermal sources. The multifractal spectrum of a signal and that of its (cumulative) temporal integration are statistically similar (i.e., low residuals upon subtraction), but shifted by one in the peak Hölder exponent. We find the pairs of 3-6 keV and 100-300 keV emissions, the 6-12 keV and 100-300 keV emissions and the 12-25 keV and 100-300 keV emissions are all consistent with the Neupert effect. The best agreement with the Neupert effect is between the 12-25 keV and 100-300 keV pair, although possibly with some secondary source of thermal emission present.

McAteer, R. T. James [Department of Astronomy, New Mexico State University, MSC 4500, NM 88003-8001 (United States); Bloomfield, D. Shaun, E-mail: mcateer@nmsu.edu [Astrophysics Research Group, School of Physics, Trinity College Dublin, College Green, Dublin 2 (Ireland)

2013-10-20

333

Charge Exchange Signatures in X-Ray Line Emission Accompanying Plasma-Wall Interaction  

NASA Astrophysics Data System (ADS)

Directional flows of well-collimated energetic ions produced at laser-burnt-through foils were used to investigate transient phenomena accompanying the plasma interaction with surfaces of solid targets (generally known as plasma-wall interaction, PWI). The plasma jet launched from the rear surface of the 0.8-um-thick Al foil irradiated at oblique laser incidence with an intensity of 3×1014 W/cm2 was incident on the quasi-massive C target. The plasma x-ray self-emission was analyzed by focusing survey and high-dispersion spectrometers. The time-integrated, spatially resolved narrow-band spectra recorded close to the C surface exhibit a dip structure in the red-wing profiles of the hydrogenic Al Ly? line which was attributed to the charge exchange between two stationary Coulomb centers represented by the Al XIII and fully stripped C ions. This identification of the charge exchange signatures in x-ray line emission is supported by hydrodynamic simulations of environmental conditions in the near-wall plasma and by predictions of the dips positions following from complementary theoretical models. The agreement between the experiment and theory validates the first high precision x-ray spectroscopic identification of charge exchange phenomena accompanying the PWI.

Renner, O.; Dalimier, E.; Liska, R.; Oks, E.; Šmíd, M.

2012-12-01

334

On binary-driven hypernovae and their nested late X-ray emission  

NASA Astrophysics Data System (ADS)

Context. The induced gravitational collapse (IGC) paradigm addresses the very energetic (1052-1054 erg) long gamma-ray bursts (GRBs) associated to supernovae (SNe). Unlike the traditional "collapsar" model, an evolved FeCO core with a companion neutron star (NS) in a tight binary system is considered as the progenitor. This special class of sources, here named "binary-driven hypernovae" (BdHNe), presents a composite sequence composed of four different episodes with precise spectral and luminosity features. Aims: We first compare and contrast the steep decay, the plateau, and the power-law decay of the X-ray luminosities of three selected BdHNe (GRB 060729, GRB 061121, and GRB 130427A). Second, to explain the different sizes and Lorentz factors of the emitting regions of the four episodes, for definiteness, we use the most complete set of data of GRB 090618. Finally, we show the possible role of r-process, which originates in the binary system of the progenitor. Methods: We compare and contrast the late X-ray luminosity of the above three BdHNe. We examine correlations between the time at the starting point of the constant late power-law decay t*a, the average prompt luminosity ? Liso ?, and the luminosity at the end of the plateau La. We analyze a thermal emission (~ 0.97-0.29 keV), observed during the X-ray steep decay phase of GRB 090618. Results: The late X-ray luminosities of the three BdHNe, in the rest-frame energy band 0.3-10 keV, show a precisely constrained "nested" structure. In a space-time diagram, we illustrate the different sizes and Lorentz factors of the emitting regions of the three episodes. For GRB 090618, we infer an initial dimension of the thermal emitter of ~ 7 × 1012 cm, expanding at ? ? 2. We find tighter correlations than the Dainotti-Willingale ones. Conclusions: We confirm a constant slope power-law behavior for the late X-ray luminosity in the source rest frame, which may lead to a new distance indicator for BdHNe. These results, as well as the emitter size and Lorentz factor, appear to be inconsistent with the traditional afterglow model based on synchrotron emission from an ultra-relativistic (? ~ 102-103) collimated jet outflow. We argue, instead, for the possible role of r-process, originating in the binary system, to power the mildly relativistic X-ray source.

Ruffini, R.; Muccino, M.; Bianco, C. L.; Enderli, M.; Izzo, L.; Kovacevic, M.; Penacchioni, A. V.; Pisani, G. B.; Rueda, J. A.; Wang, Y.

2014-05-01

335

Resonance scattering in the X-ray emission lines profiles of ? Puppis  

NASA Astrophysics Data System (ADS)

We present XMM-Newton Reflection Grating Spectrometer observations of pairs of X-ray emission line profiles from the O star ? Pup that originate from the same He-like ion. The two profiles in each pair have different shapes and cannot both be consistently fit by models assuming the same wind parameters. We show that the differences in profile shape can be accounted for in a model including the effects of resonance scattering, which affects the resonance line in the pair but not the intercombination line. This implies that resonance scattering is also important in single resonance lines, where its effect is difficult to distinguish from a low effective continuum optical depth in the wind. Thus, resonance scattering may help reconcile X-ray line profile shapes with literature mass-loss rates.

Leutenegger, M. A.; Cohen, D. H.; Kahn, S. M.; Owocki, S. P.; Paerels, F. B. S.

2008-04-01

336

Chemical Analysis of Impurity Boron Atoms in Diamond Using Soft X-ray Emission Spectroscopy  

SciTech Connect

To analyze the local structure and/or chemical states of boron atoms in boron-doped diamond, which can be synthesized by the microwave plasma-assisted chemical vapor deposition method (CVD-B-diamond) and the temperature gradient method at high pressure and high temperature (HPT-B-diamond), we measured the soft X-ray emission spectra in the CK and BK regions of B-diamonds using synchrotron radiation at the Advanced Light Source (ALS). X-ray spectral analyses using the fingerprint method and molecular orbital calculations confirm that boron atoms in CVD-B-diamond substitute for carbon atoms in the diamond lattice to form covalent B-C bonds, while boron atoms in HPT-B-diamond react with the impurity nitrogen atoms to form hexagonal boron nitride. This suggests that the high purity diamond without nitrogen impurities is necessary to synthesize p-type B-diamond semiconductors.

Muramatsu, Yasuji; Iihara, Junji; Takebe, Toshihiko; Denlinger, Jonathan D.

2008-03-29

337

X-ray Fluorescence Emission Tomography (XFET) with Novel Imaging Geometries – A Monte Carlo Study  

PubMed Central

This paper presents a feasibility study for using two new imaging geometries for synchrotron X-ray fluorescence emission tomography (XFET) applications. In the proposed approaches, the object is illuminated with synchrotron X-ray beams of various cross-sectional dimensions. The resultant fluorescence photons are detected by high-resolution imaging-spectrometers coupled to collimation apertures. To verify the performance benefits of the proposed methods over the conventional line-by-line scanning approach, we have used both Monte Carlo simulations and an analytical system performance index to compare several different imaging geometries. This study has demonstrated that the proposed XFET approach could lead to a greatly improved imaging speed, which is critical for making XFET a practical imaging modality for a wide range of applications. PMID:22228913

Meng, L. J.; Li, Nan; La Riviere, P. J.

2011-01-01

338

Cometary X-Rays: Line Emission Cross Sections for Multiply Charged Solar Wind Ion Charge Exchange  

SciTech Connect

Absolute line emission cross sections are presented for 1 keV/amu charge exchange collisions of multiply charged solar wind ions with H{sub 2}O, H, O, CO{sub 2}, and CO cometary targets. The present calculations are contrasted with available laboratory data. A parameter-free model is used to successfully predict the recently observed x-ray spectra of comet C/LINEAR 1999 S4. We show that the resulting spectrum is extremely sensitive to the time variations of the solar wind composition. Our results suggest that orbiting x-ray satellites may be a viable way to predict the solar wind intensities and composition on the Earth many hours before the ions reach the earth.

Otranto, S; Olson, R E; Beiersdorfer, P

2006-12-22

339

On the distribution of radio emission in the X-ray cluster of galaxies Abell 401  

NASA Technical Reports Server (NTRS)

The study deals with 4885-MHz very large array (VLA) observations of four galaxies in the rich cluster Abell 401. High-resolution VLA maps reveal several new features in the radion galaxies, e.g., 4C13.17A is unusually highly polarized near the galaxy nucleus unlike other head-tail sources. 4C13.17B is shown for the first time to have characteristics similar to the U-shaped source NGC 1265. From these maps models are produced that required the hot ICM that has been detected by X-ray observations. It is noted that there should be a correlation between the radio and X-ray emission from massive galaxies in clusters.

Burns, J. O.; Ulmer, M. P.

1980-01-01

340

X-ray emission of a xenon gas jet plasma diagnosed with Thomson scattering.  

PubMed

We present the results of a benchmark experiment aimed at validating recent calculation techniques for the emission properties of medium and high-Z multicharged ions in hot plasmas. We use space- and time-resolved M-shell x-ray spectroscopy of a laser-produced gas jet xenon plasma as a primary diagnostic of the ionization balance dynamics. We perform measurements of the electron temperature, electron density, and average charge state by recording simultaneous spectra of ion acoustic and electron plasma wave Thomson scattering. A comparison of the experimental x-ray spectra with calculations performed ab initio with a non-local-thermodynamic-equilibrium collisional-radiative model based on the superconfiguration formalism, using the measured plasma parameters, is presented and discussed. PMID:12006034

Chenais-Popovics, C; Malka, V; Gauthier, J-C; Gary, S; Peyrusse, O; Rabec-Le Gloahec, M; Matsushima, I; Bauche-Arnoult, C; Bachelier, A; Bauche, J

2002-04-01

341

A Versatile Medium-Resolution X-ray Emission Spectrometer for Diamond Anvil Cell Applications  

SciTech Connect

We present design and performance details for a polycapillary-coupled x-ray spectrometer that provides very high collection efficiency at a moderate energy resolution suitable for many studies of nonresonant x-ray emission spectroscopy, especially for samples of heavy elements under high pressures. Using a single Bragg analyzer operating close to a backscattering so as to minimize the effect of the weak divergence of the quasicollimated exit beam from the polycapillary optic, this instrument can maintain a typical energy resolution of 5 eV over photon energies from 5 keV to 10 keV. We find dramatically improved count rates as compared to a traditional higher-resolution instrument based on a single spherically-bent crystal analyzer.

Mortensen, Devon R.; Seidler, G. T.; Bradley, J. A.; Lipp, M. J.; Evans, W. J.; Chow, P.; Xiao, Y. M.; Boman, G.; Bowden, Mark E.

2013-08-28

342

Generation of hard X-ray emission by the electron beam in plasma focus facilities  

NASA Astrophysics Data System (ADS)

The results of measurements of the temporal characteristics of hard X-ray emission generated at plasma focus (PF) facilities are presented. Mechanisms of electron beam generation in the PF pinch are analyzed. On the basis of the known mechanisms and experimental data on the measured temporal characteristics of hard X-ray pulses, a mechanism of fast electron generation that takes into account both the effect of the anomalous pinch resistance and the current redistribution in the near-pinch region is proposed. The processes occurring in the pinch plasma are simulated on the basis of the proposed mechanism by using the MicroCap code. It is shown that only a small fraction of the discharge current (1-10%) can be transformed into the electron beam current.

Dulatov, A. K.; Lemeshko, B. D.; Mikhailov, Yu. V.; Prokuratov, I. A.; Selifanov, A. N.

2014-11-01

343

[Particle Induced X-ray Emission (PIXE) for analysis of trace elements in biological materials].  

PubMed

Outline of Particle Induced X-ray Emission (PIXE) and its application to biomedical samples are described. Charged particles from cyclotron or van de Graaff generator bombards analytical samples and semiconductor detector measures energy and intensity of induced characteristic x-ray. Simultaneous determination for 22Na to 92U is possible by PIXE. 100 nA of 3 MeV protons bombards biomedical samples and detection limits for almost all trace essential elements are sub microgram/g. Only 1 mg of biomedical sample is necessary for determination of trace elements and no chemical procedure is necessary for preparation of analytical sample. PIXE is powerful tool for determination of essential elements and applied for diagnosis for several diseases. PMID:8587194

Iwata, Y

1996-01-01

344

An improved model for ultraviolet- and x-ray-induced electron emission from CsI  

NASA Astrophysics Data System (ADS)

A microscopic theoretical model is proposed for calculating the characteristics of ultraviolet photoemission and x-ray secondary electron emission induced from CsI photoconverters. This approach is based on a realistic picture of the basic interactions of photons and induced electrons within the material. Both differential and integral emission characteristics, such as energy spectra and quantum efficiencies, are estimated according to the model and are found to agree, in general, with experimental data. The model-calculated photoemission enhancement under high external electric fields is also considered and is fairly compatible with measured values. The applicability of the model in the field of radiation detectors incorporating solid photoconverters is discussed.

Boutboul, T.; Akkerman, A.; Gibrekhterman, A.; Breskin, A.; Chechik, R.

1999-11-01

345

Survey of the K-shell emission from heliumlike ions with an X-ray microcalorimeter  

NASA Astrophysics Data System (ADS)

The Electron Beam Ion Trap Microcalorimeter Spectrometer (ECS) routinely surveys the K-shell x-ray spectra that fall into the energy range between 200 eV and 14,000 eV. The spectra serve as in situ energy references and include the K-shell emission from ions between boron at the low-energy end and krypton at the high end. Example spectra are presented of the n = 2 ? n = 1 emission from heliumlike noble gas ions neon, argon, and krypton, from the heliumlike transition metals iron and nickel, as well as the heliumlike ions of boron, silicon, sulfur, and germanium.

Beiersdorfer, P.; Brown, G. V.; Clementson, J. H. T.; Frankel, M.; Gu, M. F.; Kahn, S. M.; Kelley, R.; Kilbourne, C. A.; Porter, F. S.; Thorn, D.; Träbert, E.

2009-04-01

346

Optimization of neon soft X-rays emission from 200 J fast miniature dense plasma focus device: A potential source for soft X-ray lithography  

NASA Astrophysics Data System (ADS)

The neon soft X-ray (SXR) emission characteristics of a Fast Miniature Plasma Focus (FMPF-3) device have been investigated. The FMPF-3 device used for our experiment is of sub-kilojoule energy capacity, which is an order of magnitude lesser than the other well established plasma focus devices. The influence of different geometrical parameters of the anode and the pressure of the filling gas on the SXR emission was investigated to optimize the neon SXR yield and thereby make it a potential source for X-ray lithography. The SXR signal, solely from the desired, characteristic spectral range (900-1600) eV was selectively extracted and acquired using appropriate X-ray absorption filters on diode X-ray spectrometer. It was found that the neon SXR emission from 17 mm long cylindrical anode, which produced best neutron yields, was rather poor, in a very narrow pressure range and that too at low operating pressure. With decrease in the length of cylindrical anode, the optimum operating pressure shifts to higher pressure side, the working pressure range widens and the SXR yield also increases until the anode length is reduced to 12 mm, after which, the SXR yield and working pressure range start to degrade. The highest neon SXR yield of 1.1 J/shot, corresponding to a wall plug efficiency of 0.57%, was obtained for 12 mm long cylindrical anode. The tapered anodes with different length were also designed and tested, but they did not show any significant improvement in neon SXR yield.

Kalaiselvi, S. M. P.; Tan, T. L.; Talebitaher, A.; Lee, P.; Rawat, R. S.

2013-08-01

347

X-ray Emission From Planets Venus and Mars: Theoretical Model and Numerical Simulations  

NASA Astrophysics Data System (ADS)

Recently X-ray emission from non-magnetic planets Venus and Mars have been discovered by Chandra X-ray telescopes [1,2]. Analysis of observational data shows that either charge exchange model or fluorescent scattering of solar x-rays cannot explain the whole set of observational data. The premise of this paper is that x-ray emission of both planets is a combination of line k-shell radiation and Bremmstrahlung produced by energetic electrons interacting with planetary atmospheres. Due to the absence of their planetary magnetospheres, planetary bow shocks are located quite close to the ionospheres and on both planets their ionospheres are directly exposed to the shocked solar wind flow. In situ observations revealed the existence at the ionospheric boundaries of strongly turbulent layer -- the so-called plasma mantle. Previous hybrid simulations (kinetic ions and hydro dynamical electrons) have shown that mantle turbulence is produced by interaction of counterstreaming ion populations of the solar wind and planetary ionospheres. Recently developed particle in cell (fully kinetic) code demonstrated that mantle turbulence is responsible for electron acceleration in an agreement with in-situ observations that revealed the presence in mantle electrons with energies up to several hundred eV.[3] In the present paper we incorporated energetic electron distribution obtained by numerical simulations into ADAS code [4] and compared results with observations. 1. K. Dennerl et.al. A&A 286, 319 (2002). 2. K. Dennerl, A&A 394, 1119-1128 (2002). 3. K. Szego et.al. J6R 112, 2175 (1997) 4. http: adas.phystretch ac.uk

Bryans, P.; Quest, K. B.; Shapiro, V. D.; Bingham, R.; Tourner, M.

2003-12-01

348

X-ray emission from a nanosecond-pulse discharge in an inhomogeneous electric field at atmospheric pressure  

SciTech Connect

This paper describes experimental studies of the dependence of the X-ray intensity on the anode material in nanosecond high-voltage discharges. The discharges were generated by two nanosecond-pulse generators in atmospheric air with a highly inhomogeneous electric field by a tube-plate gap. The output pulse of the first generator (repetitive pulse generator) has a rise time of about 15 ns and a full width at half maximum of 30-40 ns. The output of the second generator (single pulse generator) has a rise time of about 0.3 ns and a full width at half maximum of 1 ns. The electrical characteristics and the X-ray emission of nanosecond-pulse discharge in atmospheric air are studied by the measurement of voltage-current waveforms, discharge images, X-ray count and dose. Our experimental results showed that the anode material rarely affects electrical characteristics, but it can significantly affect the X-ray density. Comparing the density of X-rays, it was shown that the highest x-rays density occurred in the diffuse discharge in repetitive pulse mode, then the spark discharge with a small air gap, and then the corona discharge with a large air gap, in which the X-ray density was the lowest. Therefore, it could be confirmed that the bremsstrahlung at the anode contributes to the X-ray emission from nanosecond-pulse discharges.

Zhang Cheng; Shao Tao; Ren Chengyan; Zhang Dongdong [Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing 100190 (China); Key Laboratory of Power Electronics and Electric Drive, Chinese Academy of Sciences, Beijing 100190 (China); Tarasenko, Victor; Kostyrya, Igor D. [Institute of High Current Electronics, Russian Academy of Science, Tomsk 634055 (Russian Federation); Ma Hao [Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing 100190 (China); Yan Ping [Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing 100190 (China); Key Laboratory of Power Electronics and Electric Drive, Chinese Academy of Sciences, Beijing 100190 (China); State Key Laboratory of Electrical Insulation and Power Equipment, Xi'an Jiaotong University, Xi'an 710049 (China)

2012-12-15

349

X-ray emission from a nanosecond-pulse discharge in an inhomogeneous electric field at atmospheric pressure  

NASA Astrophysics Data System (ADS)

This paper describes experimental studies of the dependence of the X-ray intensity on the anode material in nanosecond high-voltage discharges. The discharges were generated by two nanosecond-pulse generators in atmospheric air with a highly inhomogeneous electric field by a tube-plate gap. The output pulse of the first generator (repetitive pulse generator) has a rise time of about 15 ns and a full width at half maximum of 30-40 ns. The output of the second generator (single pulse generator) has a rise time of about 0.3 ns and a full width at half maximum of 1 ns. The electrical characteristics and the X-ray emission of nanosecond-pulse discharge in atmospheric air are studied by the measurement of voltage-current waveforms, discharge images, X-ray count and dose. Our experimental results showed that the anode material rarely affects electrical characteristics, but it can significantly affect the X-ray density. Comparing the density of X-rays, it was shown that the highest x-rays density occurred in the diffuse discharge in repetitive pulse mode, then the spark discharge with a small air gap, and then the corona discharge with a large air gap, in which the X-ray density was the lowest. Therefore, it could be confirmed that the bremsstrahlung at the anode contributes to the X-ray emission from nanosecond-pulse discharges.

Zhang, Cheng; Shao, Tao; Tarasenko, Victor; Ma, Hao; Ren, Chengyan; Kostyrya, Igor D.; Zhang, Dongdong; Yan, Ping

2012-12-01

350

CORONAL THICK TARGET HARD X-RAY EMISSIONS AND RADIO EMISSIONS  

SciTech Connect

A distinctive class of hard X-ray (HXR) sources located in the corona was recently found, which implies that the collisionally thick target model (CTTM) applies even to the corona. We investigated whether this idea can be independently verified by microwave radiations which have been known as the best companion to HXRs. This study is conducted on the GOES M2.3 class flare which occurred on 2002 September 9 and was observed by the Reuven Ramaty High-Energy Solar Spectroscopic Imager and the Owens Valley Solar Array. Interpreting the observed energy-dependent variation of HXR source size under the CTTM, the coronal density should be as high as 5 Multiplication-Sign 10{sup 11} cm{sup -3} over a distance of up to 12''. To explain the cutoff feature of the microwave spectrum at 3 GHz, however, we require a density no higher than 1 Multiplication-Sign 10{sup 11} cm{sup -3}. Additional constraints must be placed on the temperature and magnetic field of the coronal source in order to reproduce the microwave spectrum as a whole. First, a spectral feature called the Razin suppression requires a magnetic field in a range of 250-350 G along with high viewing angles around 75 Degree-Sign . Second, to avoid excess fluxes at high frequencies due to the free-free emission that was not observed, we need a high temperature {>=}2 Multiplication-Sign 10{sup 7} K. These two microwave spectral features, Razin suppression and free-free emissions, become more significant at regions of high thermal plasma density and are essential for validating and determining additional parameters of the coronal HXR sources.

Lee, Jeongwoo [Physics Department, New Jersey Institute of Technology, Newark, NJ 07102 (United States); Lim, Daye; Choe, G. S.; Kim, Kap-Sung [School of Space Research, Kyung Hee University, Yongin 446-701 (Korea, Republic of); Jang, Minhwan [Department of Astronomy and Space Science, Kyung Hee University, Yongin 446-701 (Korea, Republic of)

2013-05-20

351

Unique Properties of Thermally Tailored Copper: Magnetically Active Regions and Anomalous X-ray Fluorescence Emissions  

PubMed Central

When high-purity copper (?99.98%wt) is melted, held in its liquid state for a few hours with iterative thermal cycling, then allowed to resolidify, the ingot surface is found to have many small regions that are magnetically active. X-ray fluorescence analysis of these regions exhibit remarkably intense lines from “sensitized elements” (SE), including in part or fully the contiguous series V, Cr, Mn, Fe, and Co. The XRF emissions from SE are far more intense than expected from known impurity levels. Comparison with blanks and standards show that the thermal “tailoring” also introduces strongly enhanced SE emissions in samples taken from the interior of the copper ingots. For some magnetic regions, the location as well as the SE emissions, although persistent, vary irregularly with time. Also, for some regions extraordinarily intense “sensitized iron” (SFe) emissions occur, accompanied by drastic attenuation of Cu emissions. PMID:20037657

2009-01-01

352

EMISSION LINES BETWEEN 1 AND 2 keV IN COMETARY X-RAY SPECTRA  

SciTech Connect

We present the detection of new cometary X-ray emission lines in the 1.0-2.0 keV range using a sample of comets observed with the Chandra X-Ray Observatory and ACIS spectrometer. We have selected five comets from the Chandra sample with good signal-to-noise spectra. The surveyed comets are C/1999 S4 (LINEAR), C/1999 T1 (McNaught-Hartley), 153P/2002 (Ikeya-Zhang), 2P/2003 (Encke), and C/2008 8P (Tuttle). We modeled the spectra with an extended version of our solar wind charge exchange (SWCX) emission model. Above 1 keV, we find Ikeya-Zhang to have strong emission lines at 1340 and 1850 eV which we identify as being created by SWCX lines of Mg XI and Si XIII, respectively, and weaker emission lines at 1470, 1600, and 1950 eV formed by SWCX of Mg XII, Mg XI, and Si XIV, respectively. The Mg XI and XII and Si XIII and XIV lines are detected at a significant level for the other comets in our sample (LS4, MH, Encke, 8P), and these lines promise additional diagnostics to be included in SWCX models. The silicon lines in the 1700-2000 eV range are detected for all comets, but with the rising background and decreasing cometary emission, we caution that these detections need further confirmation with higher resolution instruments.

Ewing, Ian; Christian, Damian J. [Department of Physics and Astronomy, California State University, 18111 Nordhoff Street, Northridge, CA 91330 (United States)] [Department of Physics and Astronomy, California State University, 18111 Nordhoff Street, Northridge, CA 91330 (United States); Bodewits, Dennis [Department of Astronomy, University of Maryland, College Park, MD 20742 (United States)] [Department of Astronomy, University of Maryland, College Park, MD 20742 (United States); Dennerl, Konrad [Max-Planck-Institut fuer extraterrestrische Physik, Postfach 1312, D-85741 Garching Germany (Germany)] [Max-Planck-Institut fuer extraterrestrische Physik, Postfach 1312, D-85741 Garching Germany (Germany); Lisse, Carey M. [Planetary Exploration Group, Space Department, Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Rd, Laurel, MD 20723 (United States)] [Planetary Exploration Group, Space Department, Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Rd, Laurel, MD 20723 (United States); Wolk, Scott J., E-mail: ian.ewing.794@my.csun.edu, E-mail: daman.christian@csun.edu [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)

2013-01-20

353

Modulated X-ray emission of the magnetic O8.5V-star Tr16-22  

NASA Astrophysics Data System (ADS)

Using an extensive X-ray dataset, we analyzed the X-ray emission of the massive O-star Tr16-22, which was recently found to be magnetic. Its bright X-ray emission is found to be modulated with a ~54 d period. This timescale should represent the rotational timescale of the star, as it does for other magnetic massive stars. In parallel, new spectropolarimetric data confirm the published magnetic detection. Based on observations collected with the ESA science mission XMM-Newton, Chandra, and ESO-FORS2 instrument.Tables 1-3 are available in electronic form at http://www.aanda.org

Nazé, Yaël; Wade, Gregg A.; Petit, Véronique

2014-09-01

354

Hot Spectral Emissions in Quiescent Active Regions and Nanoflare Heating  

NASA Astrophysics Data System (ADS)

A leading candidate for the heating of active region (AR) coronal loops is the nanoflare model. This model treats coronal loops as collections of impulsively heated sub-resolution strands and explains several key observational aspects of warm (1-2 MK) coronal loops. However, the basic requirement of this model is that the strands initially reach very high temperatures of several MK before they cool down to canonical coronal temperatures. Therefore, the detection of hot plasmas in AR loops represents a stringest test of the nanoflare model. Previous work has shown that the best way to observe the postulated hot plasmas is by the means of spectroscopic observations in hot lines (T > 3 MK). The emission is predicted to be quite faint, but the EIS spectrometer onboard Hinode has sufficient sensitivity to allow us to perform such a test for the first time. We will present an analysis of the emission characteristics of quiescent coronal loops in a number of hot lines spanning approximately 3-12 MK (Ni XVII, Ca XV, Fe XVII, Ca XVII, Fe XXIII). We will show that hot plasmas are ubiquitous over entire active regions, and we will compare the measured intensities of both hot and warm lines with predictions of nanoflare models.

Patsourakos, S.; Klimchuk, J. A.

2008-05-01

355

The X-Ray Emissions from the M87 Jet: Diagnostics and Physical Interpretation  

NASA Astrophysics Data System (ADS)

We reanalyze the deep Chandra observations of the M87 jet, first examined by Wilson & Yang in 2002. By employing an analysis chain that also includes image deconvolution, knots HST-1 and I are fully separated from adjacent emission. We derive the spatially resolved X-ray spectrum of the jet using the most recent response functions and find slight but significant variations in the spectral shape, with values of ?X(S?~?-?) ranging from ~1.2-1.4 (in the nucleus and knots HST-1, D, and C) to ~1.6 (in knots F, A, and B). We make use of VLA radio observations, as well as HST imaging and polarimetry data, to examine the jet's broadband spectrum and inquire as to the nature of particle acceleration in the jet. As shown in previous papers, a simple continuous injection model for the synchrotron-emitting knots, in which one holds constant both the filling factor facc of the regions within which particles are accelerated and the energy spectrum of the injected particles, cannot account for the flux or spectrum of the X-ray emission. Instead, we propose that facc is a function of both position and energy and find that in the inner jet, facc~E-0.4+/-0.2?~E-0.2+/-0.1e, and in knots A and B, facc~E-0.7+/-0.2?~E-0.35+/-0.1e, where E? is the energy of the emitted photon and Ee is the energy of the emitting electron. In this model, the index p of the relativistic electron energy spectrum at injection [n(Ee)~E-pe] is p=2.2 at all energies and all locations along the jet, in excellent agreement with the predictions of models of cosmic-ray acceleration by ultrarelativistic shocks (p=2.23). There is a strong correlation between the peaks of X-ray emission and minima of optical percentage polarization, i.e., regions where the jet magnetic field is not ordered. We suggest that the X-ray peaks coincide with shock waves that accelerate the X-ray-emitting electrons and cause changes in the direction of the magnetic field; the polarization is thus small because of beam averaging.

Perlman, Eric S.; Wilson, Andrew S.

2005-07-01

356

X-ray spectra from magnetar candidates - III. Fitting SGR/AXP soft X-ray emission with non-relativistic Monte Carlo models  

NASA Astrophysics Data System (ADS)

Within the magnetar scenario, the `twisted magnetosphere' model appears very promising in explaining the persistent X-ray emission from soft gamma repeaters (SGRs) and anomalous X-ray pulsars (AXPs). In the first two papers of the series, we have presented a 3D Monte Carlo code for solving radiation transport as soft, thermal photons emitted by the star surface are resonantly upscattered by the magnetospheric particles. A spectral model archive has been generated and implemented in XSPEC. Here, we report on the systematic application of our spectral model to different XMM-Newton and INTEGRAL observations of SGRs and AXPs. We find that the synthetic spectra provide a very good fit to the data for the nearly all the source (and source states) we have analysed.

Zane, S.; Rea, N.; Turolla, R.; Nobili, L.

2009-09-01

357

Diffuse X-Ray Emission from Late-Type Galaxy Haloes  

E-print Network

Current theories of galaxy formation predict that spiral galaxies are embedded in a reservoir of hot gas. This gas is able to cool onto the galaxy replenishing cold gas that is consumed by star formation. Estimates of the X-ray luminosity emitted in the cooling region suggest a bolometric luminosity of order 10 x 10^41 ergs/s in massive systems. We have used ROSAT PSPC data to search for extended X-ray emission from the haloes of three nearby, massive, late-type galaxies: NGC 2841, NGC 4594 and NGC 5529. We infer 95 per cent upper limits on the bolometric X-ray luminosities of the haloes of NGC 2841, NGC 4594 and NGC 5529 of 0.4, 1.2 and 3.8 x 10^41 ergs/s respectively. Thus the true luminosity lies well below the straightforward theoretical prediction. We discuss this discrepancy and suggest a number of ways in which the theoretical model can be brought into agreement with the observational results. A possible solution is that the gravitational potentials of the dark matter haloes of these galaxies are weaker than assumed in the current model. Alternatively, the present day accretion may be substantially less than is required on average to build the disk over the Hubble time. Our results are, however, based on only three galaxies, none of which is ideal for this kind of study. A larger data set is required to explore this important problem further.

A. J. Benson; R. G. Bower; C. S. Frenk; S. D. M. White

2000-03-15

358

Intravenous coronary angiography utilizing K-emission and bremsstrahlung X-rays produced by electron bombardment  

SciTech Connect

The screening of the general population for coronary artery disease would be practical if a method existed for visualizing the extent of occlusion after an intravenous injection of contrast agent. Measurements performed with synchrotron radiation at SSRL and NSLS have shown that such an intravenous angiography procedure would be possible with an intense source of monochromatic X-rays. Because of the high cost of an electron synchrotron, theoretical analysis and experiments using inanimate phantoms has been undertaken to demonstrate the feasibility of using the spectrum produced by two appropriately chosen anode materials when bombarded with electrons in the 100--500 keV energy range for angiography. By using the X-rays emitted at 120{degree} to the incident electron direction, about 20--30% of the X-ray intensity would be due to K-emission lines. Calculations using the TIGERP Monte Carlo Code, have shown that high quality angiograms of human coronary arteries should be possible with a contrast agent containing ytterbium, if an electron beam pulses of 16 kJ were used for each anode target. The experimental program supported in part by the DOE has consisted of these theoretical calculations and experiments at the Dynamitron Electron Accelerator Facility at BNL.

NONE

1992-12-31

359

Calcium L(III) and L(II) region x-ray and electron emissions for near threshold electron excitation  

NASA Astrophysics Data System (ADS)

An x-ray excitation spectrometer (XRES) was constructed and used to record the Lsb{III} and Lsb{II} region x-ray emissions under near threshold electron excitation for samples of pure calcium metal and samples of calcium in various stages of oxidation. X-ray yield measurements were also made using a lithium-drifted silicon detector. An electron spectrometer was used to observe Auger, electron loss, and secondary electron emissions. The principal threshold region resonance feature seen in the oxidized calcium integrated XRES spectrum agreed well with that obtained from the x-ray yield measurement. No threshold region electron resonance signals were discernable above background for incident electron energies which gave rise to the x-ray resonance signals seen in both the XRES and x-ray yield experiments. The x-ray resonance emission spectrum for threshold electron excitation differed substantially from that of a photo-electron yield spectrum obtained by Barth, et al. The differences are attributed to two bound electron processes similar to those observed in the lanthanides.

Wagner, Robert A.

360

Intrinsic disc emission and the soft X-ray excess in active galactic nuclei  

NASA Astrophysics Data System (ADS)

Narrow-line Seyfert 1 (NLS1) galaxies have low-mass black holes and mass accretion rates close to (or exceeding) Eddington, so a standard blackbody accretion disc should peak in the extreme ultraviolet. However, the lack of true absorption opacity in the disc means that the emission is better approximated by a colour temperature corrected blackbody, and this colour temperature correction is large enough (˜2.4) that the bare disc emission from a zero spin black hole can extend into the soft X-ray bandpass. Part of the soft X-ray excess seen in these objects must be intrinsic emission from the disc unless the vertical structure is very different to that predicted. None the less, this is not the whole story even for the extreme NLS1 as the shape of the soft excess is much broader than predicted by a bare disc spectrum, indicating some Compton upscattering by warm, optically thick material. We associate this with the disc itself, so it must ultimately be powered by mass accretion. We build an energetically self-consistent model assuming that the emission thermalizes to a (colour temperature corrected) blackbody only at large radii. At smaller radii the gravitational energy is split between powering optically thick Comptonized disc emission (forming the soft X-ray excess) and an optically thin corona above the disc (forming the tail to higher energies). We show examples of this model fit to the extreme NLS1 RE J1034+396, and to the much lower Eddington fraction broad-line Seyfert 1 PG 1048+231. We use these to guide our fits and interpretations of three template spectra made from co-adding multiple sources to track out a sequence of active galactic nucleus (AGN) spectra as a function of L/LEdd. Both the individual objects and template spectra show the surprising result that the Compton upscattered soft X-ray excess decreases in importance with increasing L/LEdd. The strongest soft excesses are associated with low mass accretion rate AGN rather than being tied to some change in disc structure around Eddington. We argue that this suggests a true break in accretion flow properties between stellar and supermassive black holes. The new model is publicly available within the XSPEC spectral fitting package.

Done, Chris; Davis, S. W.; Jin, C.; Blaes, O.; Ward, M.

2012-03-01

361

Removing Spectral Diagnostics of Galactic and Stellar X-Ray Emission from Charged Exchange Recombination  

NASA Technical Reports Server (NTRS)

Our research uses the electron beam ion trap (EBIT) at the Lawrence Livermore National Laboratory to study X-ray emission from the charge exchange (CX) of highly charged ions with neutral gases. The resulting data help to fill a void in existing experimental and theoretical understanding of this atomic physics process, and are needed to explain all or part of the observed X-ray emission from the soft X-ray background, stellar winds, the Galactic Center and Galactic Ridge, supernova ejecta, and photoionized nebulae. Appreciation of the astrophysical relevance of our work continues to grow with the publication of roughly a dozen papers in the past four years describing Chandra and XMM observations of geocoronal and heliospheric CX emission, the temporal variation of such emission and correlation with X-ray emission enhancements observed by ROSAT, the theoretical spatial distribution of that emission, and CX emission around other stars. A similar number of papers were also published during that time describing CX emission from planets and comets. We expect that the launch of ASTRSE2, with its second-generation XRS microcalo- (with 6-eV resolution), will reveal even more clearly the contributions of CX to astrophysical emission. In our EBIT work we collected CX spectra from such ions as H-like and He-like Ne, Ar, and Fe. Our early measurements were made with a high-purity Ge detector, but during the second year we began operation of the first-generation XRS microcalorimeter (a twin of the XRS on ASTRO-E) and greatly improved the resolution of our measurements from roughly 150 eV (FWHM) with the Ge detectors to 10 eV with the XRS. We found that saturation of the XRS counting apparatus, which we described in our proposal as a potential concern, is not a problem for studying CX. During the course of our research, we expanded the number of injection gases permitted by the LLNL safety team, purchased and eventually operated an atomic H source, and clearly demonstrated the feasibility of our longer-range plan. For example, we successfully injected He into EBIT (not a small feat because of the difficulty of maintaining a good vacuum with He and avoiding electrical breakdown) to collect a H-like oxygen CX spectrum. The highest energy CX spectrum recorded with the XRS to date is that of the Ar K-shell emission. These measurements provided the first observation of the relative intensity ratios of resolved He-like singlet and triplet n=2->1 lines. We also carried out measurements of He-like Ne as a function of collision energy (i.e., ion temperature). Significant differences in the resulting x-ray spectra were noted. In all cases, the intensity of high-n H-like Lyman lines is significantly higher than current theoretical CX models predict.

Wargelin, Brad

2004-01-01

362

The Multi-Instrument, Comprehensive Differential Emission Measure (DEM) of the Solar Corona During Flares and Quiescent Periods  

NASA Astrophysics Data System (ADS)

Thermal plasma in the solar corona, while often modeled as isothermal for ease of analysis, is in fact decidedly multi-thermal, ranging from ~1-2 MK in the quiescent corona to ~30-50 MK in intensely flaring loops. It has proven difficult to obtain a well-constrained differential emission measure (DEM) from a single instrument, as the wavelength ranges of individual instruments, even those with broadband coverage, provide sensitivity to only a limited range of plasma temperatures. Recently, we developed a new technique using combined extreme ultraviolet (EUV) and soft and hard X-ray (SXR, HXR) data from the EUV Variability Experiment (EVE) onboard the Solar Dynamics Observatory (SDO) and the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI), respectively, to obtain a self-consistent DEM that is strongly constrained across the full range of coronal plasma temperatures (<2 to >50 MK). An accurate, precise determination of the plasma temperature distribution enables not only studies of plasma heating and thermal plasma evolution, but can also provide strong constraints on the non-thermal accelerated electron population, including the low-energy cutoff which is typically determined only as a loose upper limit.We present EVE+RHESSI DEM results from selected intense (X-class) flares from solar cycle 24, including determining the non-thermal low-energy cutoff and examining how this evolves with the temperature distribution. We also apply this technique to combine EUV data from EVE with SXR data from the GOES X-ray Sensor (XRS) and the X123, a new SXR spectrometer flown on two recent SDO/EVE calibration sounding rockets, to examine the DEM during quiescent (non-flaring) times with varying activity levels; the X-ray data provide crucial constraints on the high-temperate extent of the DEM and any potential non-thermal emission. We compare these results with those from a parallel technique to derive DEMs from imaging data from the Atmospheric Imaging Assembly (AIA) onboard SDO, and we discuss the implications for plasma heating, both during flares and in the quiescent corona. This research is supported by NASA contracts NAS5-98033 and NAS5-02140, and NASA Heliophysics Guest Investigator Grant NNX12AH48G.

Caspi, Amir; McTiernan, James; Warren, Harry; Woods, Thomas N.

2014-06-01

363

High-pressure X-ray diffraction and X-ray emission studies on iron-bearing silicate perovskite under high pressures  

SciTech Connect

Iron-bearing silicate perovskite is believed to be the most abundant mineral of the Earth's lower mantle. Recent studies have shown that Fe{sup 2+} exists predominantly in the intermediate-spin state with a total spin number of 1 in silicate perovskite in the lower part of the lower mantle. Here we have measured the spin states of iron and the pressure-volume relation in silicate perovskite [(Mg{sub 0.6},Fe{sub 0.4})SiO{sub 3}] at pressure conditions relevant to the lowermost mantle using in situ X-ray emission and X-ray diffraction in a diamond cell. Our results showed that the intermediate-spin Fe{sup 2+} is stable in the silicate perovskite up to {approx} 125 GPa but starts to transition to the low-spin state at approximately 135 GPa. Concurrent X-ray diffraction measurements showed a decrease of approximately 1% in the unit cell volume in the silicate perovskite [(Mg{sub 0.6},Fe{sub 0.4})SiO{sub 3}], which is attributed to the intermediate-spin to the low-spin transition. The transition pressure coincides with the pressure conditions of the lowermost mantle, raising the possibility of the existence of the silicate perovskite phase with the low-spin Fe{sup 2+} across the transition from the post-perovskite to the perovskite phases in the bottom of the D{double_prime} layer.

Lin, Jung-Fu; Speciale, Sergio; Prakapenka, Vitali B.; Dera, Przemek; Lavina, Babara; Watson, Heather C. (NIU); (UC); (Texas); (GFZ)

2010-06-22

364

Interaction of high intensity laser with non-uniform clusters and enhanced X-ray emission  

SciTech Connect

Laser irradiated clusters with non-uniform density variation are shown to broaden surface plasmon resonance very significantly. As the clusters get heated and expand hydro-dynamically, the Bremsstrahlung X-ray emission yield passes through a maximum in time. The maximum yield decreases with increase in non-uniformity in the electron density inside the clusters. At higher laser intensity, the nonlinearity in laser cluster interaction may arise even prior to electron heating, via the relativistic mass variation and the nonlinear restoration force on electrons. For clusters with radius less than one tenth of the laser wavelength, the restoration force nonlinearity dominates.

Liu, C. S. [Department of Physics, University of Maryland, College Park, Maryland 20742 (United States); Tripathi, V. K.; Kumar, Manoj, E-mail: manojailum@gmail.com [Department of Physics, Indian Institute of Technology Delhi, New Delhi 110016 (India)

2014-10-15

365

GPU-accelerated reconstruction methods for Proton Induced X-Ray Emission Tomography  

NASA Astrophysics Data System (ADS)

A combination of simultaneous Proton Induced X-Ray Emission Tomography (PIXE-T), Scanning Transmission Ion Microscopy Tomography (STIM-T) and Rutherford Backscattering Spectrometry (RBS) can produce 3D quantitative elemental maps with a resolution on the micron scale. This combination is being developed at the Instituto Tecnológico e Nuclear-Instituto Superior Técnico (ITN-IST) nuclear microprobe facility. To reconstruct complex datasets, iterative procedures are usually applied. GPU-accelerated PIXE-T/STIM-T simulation software has been developed and used in conjunction with an iterative reconstruction software DISRA and an MLEM algorithm to reconstruct data produced by simulating a PIXE-T experiment of a phantom.

Beasley, D. G.; Marques, A. C.; Alves, L. C.; da Silva, R. C.

2014-02-01

366

Analytical Applications Of Particle-Induced X-Ray Emission (PIXE)  

NASA Astrophysics Data System (ADS)

In this paper a complex study of the capabilities of Particle-Induced X-ray Emission (PIXE) technique for the determination of major, minor and trace constituents of metallurgical, biological and environmental samples has been done. The elements identified in the metallurgical samples (steels) using PIXE were: K, Ca, V, Cr, Mn, Fe, Co, Cu, Ni, Zn, W, Ga, As, Pb, Mo, Rb, In, Rh, Zr, Pd, Nb, Sn and Sb. In the investigated biological and environmental samples (vegetals leaves, soil and mosses) PIXE analysis allowed determination of: S, Cl, K, Ca, Ti, Mn, Fe, Ni, Cu, Zn, As, Hg and Pb.

Popescu, I. V.; Ene, A.; Stihi, C.; Bancuta, A.; Dima, G.; Badica, T.; Ghisa, V.

2007-04-01

367

Intra-tumor distribution of metallofullerene using micro-particle induced X-ray emission (PIXE).  

PubMed

To clarify the intra tumor distribution of gadlinium containing fullerene (Gd@C82), micro particle induced X-ray emission (Micro-PIXE) analysis were performed. The tumor bearing BALB/c mice were injected Gd@C82 and subcutaneous tumors were taken from 48h after the intravenous injection. Using the Micro-PIXE method, we could visualize Gd intra tumor distribution. Therefore our results indicate the possibility that Micro-PIXE is useful technique for imaging the bioditribution of Gd, and Gd@C82 is potentially useful Gd carrier for NCT. PMID:24491681

Yamamoto, Yohei; Yamamoto, Tetsuya; Horiguchi, Yukichi; Shirakawa, Makoto; Satoh, Takahiro; Koka, Masashi; Nagasaki, Yukio; Nakai, Kei; Matsumura, Akira

2014-06-01

368

A magnetizing system for dichroism measurements in soft x-ray emission excited by synchrotron radiation  

SciTech Connect

We present the design and performance of a magnetic circuit suitable for magnetizing solid samples in the measurements of soft x-ray emission dichroism excited by synchrotron radiation. The system allows a variety of samples to be magnetized and satisfies the rather stringent geometrical constraints due to the need for minimizing the effect of photon self-absorption by the sample. The magnetic circuit is ultrahigh vacuum compatible, can reach about 2800 G, and allows fine adjustment of sample position. {copyright} {ital 1996 American Institute of Physics.}

Dallera, C.; Ghiringhelli, G.; Braicovich, L. [INFM and Dipartimento di Fisica del Politecnico Milano, Piazza Leonardo da Vinci 32, 20133 Milano (Italy)] [INFM and Dipartimento di Fisica del Politecnico Milano, Piazza Leonardo da Vinci 32, 20133 Milano (Italy)

1996-02-01

369

The Sun as an X-Ray Star. II. Using theYohkoh/Soft X-Ray Telescope-derived Solar Emission Measure versus Temperature to Interpret Stellar X-Ray Observations  

NASA Astrophysics Data System (ADS)

This paper is the second of a project dedicated to using solar Yohkoh/SXT data as a guide and a template to interpret data on stellar coronae. In the light of the large differences in scope and approach between solar and stellar studies, we have developed a method to translate Yohkoh/SXT data of the whole solar corona into stellar-like data, i.e., to put them in the same format and context as the stellar ones. First from the Yohkoh/SXT images we derive the whole-Sun X-ray emission measure versus temperature [EM(T)], in the range 105.5-108 K, during the specific observation. Then, we synthesize the solar X-ray spectrum; finally, we fold the spectrum through the instrumental response of nonsolar X-ray observatories, for instance, ROSAT/PSPC and ASCA/SIS. Finally, we analyze such solar coronal data in the same band and with the same methods used for stellar observations, allowing a direct and homogeneous comparison with them. In this paper we present in detail our method and, as an example of results, we show and discuss EM(T) and stellar-like spectra for three phases of the solar cycle: maximum, intermediate phase, and minimum. The total amount and the distribution of the emission measure change dramatically during the cycle, in particular at temperatures above 106 K. We also show the EM(T) of the whole solar corona during a large flare. The ROSAT/PSPC- and ASCA/SIS-like X-ray spectra of the Sun as a star that we obtain are discussed in the context of stellar coronal physics. The Sun's coronal total luminosity in the ROSAT/PSPC band ranges from ~2.7×1026 ergs s-1 (at minimum) to ~4.7×1027 ergs s-1 (at maximum). We discuss future developments and possible applications of our method.

Peres, G.; Orlando, S.; Reale, F.; Rosner, R.; Hudson, H.

2000-01-01

370

Anatomy of the AGN in NGC 5548: the X-ray narrow emission lines  

NASA Astrophysics Data System (ADS)

After a very successful multi-satellite campaign on Mrk 509 in 2009, we conducted a similar campaign on the AGN NGC 5548 in 2013. During the latter the source appeared unusually strongly absorbed in the soft X-rays, and signatures of strong outflows were also present in the UV. While a talk giving an overview of the campaign (PI: J. Kaastra) is also proposed at this conference, we will focus here on the data obtained from the XMM-RGS, resulting in a stacked spectrum of 660 ks. Narrow emission lines, including He-like triplets of Oxygen, Nitrogen and Neon, and radiative recombination (RRC) features dominate this spectrum due to the low soft X-ray continuum flux. All emission features are consistent with having constant flux over our campaign. The O VII triplet has been one focus of our analysis, especially due to unexpected differences of ˜300 km s^{-1} among the measured outflow velocities of its individual lines. The RRCs allow us to directly calculate a temperature of the emitting gas of a few eV (˜10^{4}K), favouring photoionised conditions. We have modelled the emission lines and features using the photoionisation code Cloudy, to attempt to construct a self-consistent picture of the physical environment of the AGN.

Whewell, M.; Branduardi-Raymont, G.; Kaastra, J.; Mehdipour, M.; Bianchi, S.; NGC 5548 Collaboration

2014-07-01

371

Photosphere Emission in the X-Ray Flares of Swift Gamma-Ray Bursts and Implications for the Fireball Properties  

NASA Astrophysics Data System (ADS)

X-ray flares of gamma-ray bursts (GRBs) are usually observed in the soft X-ray range and the spectral coverage is limited. In this paper, we present an analysis of 32 GRB X-ray flares that are simultaneously observed by both Burst Alert Telescope and X-Ray Telescope on board the Swift mission, so that a joint spectral analysis with a wider spectral coverage is possible. Our results show that the joint spectra of 19 flares are fitted with the absorbed single power law or the Band function models. More interestingly, the joint spectra of the other 13 X-ray flares are fitted with the absorbed single power-law model plus a blackbody component. Phenomenally, the observed spectra of these 13 flares are analogous to several GRBs with a thermal component, but only with a much lower temperature of kT = 1 ~ 3 keV. Assuming that the thermal emission is the photosphere emission of the GRB fireball, we derive the fireball properties of the 13 flares that have redshift measurements, such as the bulk Lorentz factor ?ph of the outflow. The derived ?ph range from 50 to 150 and a relation of ?ph to the thermal emission luminosity is found. It is consistent with the ?0 - L iso relations that are derived for the prompt gamma-ray emission. We discuss the physical implications of these results within the content of jet composition and the radiation mechanism of GRBs and X-ray flares.

Peng, Fang-Kun; Liang, En-Wei; Wang, Xiang-Yu; Hou, Shu-Jin; Xi, Shao-Qiang; Lu, Rui-Jing; Zhang, Jin; Zhang, Bing

2014-11-01

372

X-ray emission from an Ap star /Phi Herculis/ and a late B star /Pi Ceti/  

NASA Technical Reports Server (NTRS)

Using the HEAO 1 soft X-ray sky survey, a search was conducted for X-ray emission from 18 stars in the spectral range B5-A7. The detection of 0.25 keV X-ray sources consistent with the positions of Pi Ceti, a normal B7 V star, and Phi Herculis, a classic Ap star was reported. The detection of these stars argues for large mass motions in the upper layers of stars in this spectral range, and argues against radiative diffusion as the source of abundance anomalies in Ap stars.

Cash, W.; Snow, T. P., Jr.; Charles, P.

1979-01-01

373

X-RAY EMISSION FROM THE SOMBRERO GALAXY: A GALACTIC-SCALE OUTFLOW  

SciTech Connect

Based on new and archival Chandra observations of the Sombrero galaxy (M 104 = NGC 4594), we study the X-ray emission from its nucleus and the extended X-ray emission in and around its massive stellar bulge. We find that the 0.3-8 keV luminosity of the nucleus appears constant at {approx}2.4 x 10{sup 40} erg s{sup -1}, or {approx}10{sup -7} of its Eddington luminosity, on three epochs between 1999 December and 2008 April, but drops by a factor of two in the 2008 November observation. The 2-6 keV unresolved emission from the bulge region closely follows the K-band starlight and most likely arises from unresolved stellar sources. At lower energies, however, the unresolved emission reaches a galactocentric radius of at least 23 kpc, significantly beyond the extent of the starlight, clearly indicating the presence of diffuse hot gas. We isolate the emission of the gas by properly accounting for the emission from unresolved stellar sources, predominantly cataclysmic variables and coronally active binaries, whose quasi-universal X-ray emissivity was recently established. We find a gas temperature of {approx}0.6 keV with little variation across the field of view, except for a lower temperature of {approx}0.3 keV along the stellar disk. The metal abundance is not well constrained due to the limited counting statistics, but is consistent with metal enrichment by Type Ia supernovae (SNe Ia). We measure a total intrinsic 0.3-2 keV luminosity of {approx}2 x 10{sup 39} erg s{sup -1}, which corresponds to only 1% of the available energy input by SNe Ia in the bulge, but is comparable to the prediction by the latest galaxy formation models for disk galaxies as massive as Sombrero. However, such numerical models do not fully account for internal feedback processes, such as nuclear feedback and stellar feedback, against accretion from the intergalactic medium. On the other hand, we find no evidence for either the nucleus or the very modest star-forming activities in the disk to be a dominant heating source for the diffuse gas. We also show that neither the expected energy released by SNe Ia nor the expected mass returned by evolved stars is recovered by observations. We argue that in Sombrero a galactic-scale subsonic outflow of hot gas continuously removes much of the 'missing' energy and mass input from the bulge region. The observed density and temperature distributions of such an outflow, however, continue to pose challenges to theoretical studies.

Li Zhiyuan; Jones, Christine; Forman, William R.; Kraft, Ralph P.; Lal, Dharam V.; Di Stefano, Rosanne [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Spitler, Lee R. [Centre for Astrophysics and Supercomputing, Swinburne University, Hawthorn, VIC 3122 (Australia); Tang, Shikui; Wang, Q. Daniel [Department of Astronomy, University of Massachusetts, 710 North Pleasant Street, Amherst, MA 01003 (United States); Gilfanov, Marat [Max-Planck-Institut fuer Astrophysik, Karl-Schwarzschild-Str 1, 85741 Garching bei Muenchen (Germany); Revnivtsev, Mikhail, E-mail: zyli@cfa.harvard.edu [Excellence Cluster Universe, Technische Universitaet Muenchen, Boltzmannstr.2, 85748 Garching (Germany)

2011-04-01

374

Charge Exchange Studies for Solar System X-ray Emission Modeling  

NASA Astrophysics Data System (ADS)

As most of the gas in the Universe is not in thermal equilibrium, accurate modeling and interpretation of observations requires understanding of a variety of collisional processes. When ions and neutrals are present, charge exchange is one such process. While it can be important for the ionization balance, it can also affect ion emission spectra, such as in the case of the solar wind charge exchange (SWCX) mechanism. While charge exchange cross sections can be measured and/or calculated, the enhancements in the spectral line resolution and sensitivity from current X-ray observatories (Chandra, XMM-Newton, Suzaku), and planned missions (e.g., IXO and Astro-H) place severe demands on the collisional data. As a consequence, the construction of reliable charge exchange datasets for atmospheric and astrophysical modeling faces a number of challenges: i) Due to the quantity of required data at the quantum-state-resolved level, theory must provide the bulk of the results with experiment serving as benchmarks. ii) The accuracy of the scattering calculations is directly dependent on the reliability and availability of the quantum structure/chemical data. iii) Database construction requires consistent and appropriate funding which is typically lacking. We review these issues in the context of our on-going collaborative work on charge exchange calculations and measurements for SWCX modeling. Cross sections, diagnostic line ratios, and x-ray yields will be presented for collisions of C^5+, N^6+, O^6+, O^7+ with H and their role in X-ray emission from Earth's geocorona, the exosphere of Mars, Jupiter, comets, the heliosphere, and astrospheres will be discussed. This work was partially supported by NASA grants NNX09AV46G, NNG09WF24I, and NNH07ZDA001N.

Wu, Yong; Nolte, J.; Stancil, P.; Schultz, D.; Hui, Y.; Lieberman, H.; Buenker, R.; Shelton, R.; Draganic, I.; Havener, C.

2011-05-01

375

Spectral Modeling of the Charge-exchange X-Ray Emission from M82  

NASA Astrophysics Data System (ADS)

It has been proposed that the charge-exchange (CX) process at the interface between hot and cool interstellar gases could contribute significantly to the observed soft X-ray emission in star-forming galaxies. We analyze the XMM-Newton/reflection grating spectrometer (RGS) spectrum of M82 using a newly developed CX model combined with a single-temperature thermal plasma to characterize the volume-filling hot gas. The CX process is largely responsible for not only the strongly enhanced forbidden lines of the K? triplets of various He-like ions but also good fractions of the Ly? transitions of C VI (~87%), O VIII, and N VII (gsim50%) as well. In total about a quarter of the X-ray flux in the RGS 6-30 Å band originates in the CX. We infer an ion incident rate of 3 × 1051 s-1 undergoing CX at the hot and cool gas interface and an effective area of the interface of ~2 × 1045 cm2 that is one order of magnitude larger than the cross section of the global biconic outflow. With the CX contribution accounted for, the best-fit temperature of the hot gas is 0.6 keV, and the metal abundances are approximately solar. We further show that the same CX/thermal plasma model also gives an excellent description of the EPIC-pn spectrum of the outflow Cap, projected at 11.6 kpc away from the galactic disk of M82. This analysis demonstrates that the CX is potentially an important contributor to the X-ray emission from starburst galaxies and also an invaluable tool to probe the interface astrophysics.

Zhang, Shuinai; Wang, Q. Daniel; Ji, Li; Smith, Randall K.; Foster, Adam R.; Zhou, Xin

2014-10-01

376

The X-ray emission lines in GRB afterglows: the evidence for the two-component jet model  

E-print Network

Recently, X-ray emission lines have been observed in X-ray afterglows of several $\\gamma$-ray bursts. It is a major breakthrough for understanding the nature of the progenitors. It is proposed that the X-ray emission lines can be well explained by the Geometry-Dominated models, but in these models the illuminating angle is much larger than that of the collimated jet of the $\\gamma$-ray bursts(GRBs). For GRB 011211, we obtain the illuminating angle is about $\\theta\\sim45^{\\circ}$, while the angle of GRB jet is only $3.6^{\\circ}$, so we propose that the outflow of the GRBs with emission lines should have two distinct components. The wide component illuminates the reprocessing material, and produces the emission lines, while the narrow one produces the $\\gamma$-ray bursts. The observations show that the energy for producing the emission lines is higher than that of the GRBs. In this case, when the wide component dominates the afterglows, a bump will appear in the GRBs afterglows. For GRB 011211, the emergence time of the bump is less than 0.05 days after the GRB, it is obviously too early for the observation to catch it. With the presence of the X-ray emission lines there should also be a bright emission component between the UV and the soft X-rays. These features can be tested by the $Swift$ satellite in the near future.

W. H. Gao; D. M. Wei

2005-09-06

377

SPOT THE DIFFERENCES: THE X-RAY SPECTRUM OF SU AUR COMPARED TO TW HYA , M. Audard2  

E-print Network

1 SPOT THE DIFFERENCES: THE X-RAY SPECTRUM OF SU AUR COMPARED TO TW HYA K. Smith1 , M. Audard2 , M Aur. The quiescent X- ray emission is dominated by a 20­40 MK plasma, which contrasts strongly: activity ­ Stars: indi- vidual: SU Aur ­ Stars: pre-main-sequence 1. Introduction The classical T Tauri

Audard, Marc

378

A search for iron emission lines in the Chandra X-ray spectra of neutron star low-mass X-ray binaries  

E-print Network

While iron emission lines are well studied in black hole systems, both in X-ray binaries and Active Galactic Nuclei, there has been less of a focus on these lines in neutron star low-mass X-ray binaries (LMXBs). However, recent observations with Suzaku and XMM-Newton have revealed broad asymmetric iron line profiles in 4 neutron star LMXBs, confirming an inner disk origin for these lines in neutron star systems. Here, we present a search for iron lines in 6 neutron star LMXBs. For each object we have simultaneous Chandra and RXTE observations at 2 separate epochs, allowing for both a high resolution spectrum, as well as broadband spectral coverage. Out of the six objects in the survey, we only find significant iron lines in two of the objects, GX 17+2 and GX 349+2. However, we cannot rule out that there are weak, broad lines present in the other sources. The equivalent width of the line in GX 17+2 is consistent between the 2 epochs, while in GX 349+2 the line equivalent width increases by a factor of ~3 between epochs as the source flux decreases by a factor of 1.3. This suggests that the disk is highly ionized, and the line is dominated by recombination emission. We find that there appears to be no specific locations in the long-term hardness-intensity diagrams where iron emission lines are formed, though more sources and further observations are required.

E. M. Cackett; J. M. Miller; J. Homan; M. van der Klis; W. H. G. Lewin; M. Mendez; J. Raymond; D. Steeghs; R. Wijnands

2008-09-18

379

The Origin of T Tauri X-Ray Emission: New Insights from the Chandra Orion Ultradeep Project  

Microsoft Academic Search

The Chandra Orion Ultradeep Project (COUP) provides the most comprehensive data set ever acquired on the X-ray emission of pre-main-sequence stars. In this paper, we study the nearly 600 X-ray sources that can be reliably identified with optically well-characterized T Tauri stars (TTSs) in the Orion Nebula Cluster. With a detection limit of LX,min~1027.3 ergs s-1 for lightly absorbed sources,

Thomas Preibisch; Yong-Cheol Kim; Fabio Favata; Eric D. Feigelson; Ettore Flaccomio; Konstantin Getman; Giusi Micela; Salvatore Sciortino; Keivan Stassun; Beate Stelzer; Hans Zinnecker

2005-01-01

380

The X-ray emission from Nova V382 Velorum I. The hard component observed with BeppoSAX  

E-print Network

The X-ray emission from Nova V382 Velorum ­ I. The hard component observed with BeppoSAX M. Orio,1SAX observations of Nova Velorum 1999 (V382 Vel), carried out in a broad X-ray band covering 0:1­300 keV only 15 d after the discovery and again after 6 months. The nova was detected at day 15 with the Beppo

Greiner, Jochen

381

Hard X-ray emission from laser-produced plasmas of U and Pb recorded by a transmission crystal spectrometer  

Microsoft Academic Search

Hard X-ray spectra from laser-produced plasmas were recorded by a transmission crystal survey spectrometer covering the 12–60keV energy range with a resolving power of E\\/?E?100. This emission is of interest for the development of hard X-ray backlighters and hot electron diagnostics. Foils of U and Pb were irradiated at the OMEGA laser facility by 24 beams (12 on each side),

J. F. Seely; R. Doron; A. Bar-Shalom; L. T. Hudson; C. Stoeckl

2003-01-01

382

The Effect of Porosity on X-ray Emission Line Profiles from Hot-Star Winds  

E-print Network

We investigate the degree to which the nearly symmetric form of X-ray emission lines seen in Chandra spectra of early-type supergiant stars could be explained by a possibly porous nature of their spatially structured stellar winds. Such porosity could effectively reduce the bound-free absorption of X-rays emitted by embedded wind shocks, and thus allow a more similar transmission of red- vs. blue-shifted emission from the back vs. front hemispheres. For a medium consisting of clumps of size l and volume filling factor f, in which the `porosity length' h=l/f increases with local radius as h = h' r, we find that a substantial reduction in wind absorption requires a quite large porosity scale factor h' > 1, implying large porosity lengths h > r. The associated wind structure must thus have either a relatively large scale l~ r, or a small volume filling factor f ~ l/r porosity lengths, leaving again the prospect of instead having to invoke a substantial (ca. factor 5) downward revision in assumed mass-loss rates.

Stanley P. Owocki; David H. Cohen

2006-02-02

383

Elemental analysis of renal slices by proton-induced X-ray emission.  

PubMed Central

We optimized proton-induced X-ray emission (PIXE) for tissue analysis in a toxicity-disposition study. We used cultured rabbit renal slices as the biological system to demonstrate the use of PIXE analysis. The renal slices were exposed to HgCl2, CdCl2, K2Cr2O7, or NaAsO2 alone or in a mixture. The PIXE analysis provides information on concentrations of elements above atomic number 11, and it is the only analytical technique that can determine 20-30 elements nondestructively in a single, small sample (approximately 5 mg) with detection limits of 1-5 ppm (dry weight). The renal slices are thin targets that yield X-ray emission spectra with low backgrounds and high elemental sensitivities. The nondestructive nature of PIXE and the ability to simultaneously measure uptake of multiple metals and endogenous elements are unique to this methodology. Images p302-a Figure 1. Figure 2. Figure 3. Figure 4. Figure 5. Figure 6. A Figure 6. B Figure 6. C Figure 6. D Figure 7. A Figure 7. B Figure 7. C Figure 7. D p307-a PMID:8275986

Lowe, T; Chen, Q; Fernando, Q; Keith, R; Gandolfi, A J

1993-01-01

384

Application of PIXE, RBS and high energy proton microbeams to the elemental analysis of coal and coal waste. [Proton and x-ray induced x-ray emission and Rutherford backscattering  

Microsoft Academic Search

Proton and x-ray induced x-ray emission have proved to be sensitive and convenient methods to measure major trace element concentrations in bulk quantities of coal and coal waste materials. These techniques are complementary in their sensitivities as a function of atomic number, and both require little sample preparation. The PIXE measurements were made with the proton beam in air in

H. W. Kraner; A. L. Hanson; K. W. Jones; S. A. Oakley; I. W. Duedall; P. M. J. Woodhead

1980-01-01

385

Physical constraints on X-ray absorption and emission regions of NGC 4151  

NASA Astrophysics Data System (ADS)

I present the results of spectral analysis and modeling of nine Chandra and XMM-Newton X-ray observations of NGC 4151, spanning the period 2000-2007. The complex and highly variable spectrum is characterized by attenuation of the intrinsic power-law continuum by nested absorption components, which contribute both broadband curvature in the 1-5 keV continuum, and individual line absorption. Significant and variable narrow line emission and radiative recombination continua dominate energies below ~1.5 keV. The modeling process made extensive use of absorption tables produced by a newly-available Cloudy- XSPEC interface. Observed spectral evolution could not be explained entirely by simple changes in absorber ionization states in response to variations in the level of incident continuum, but required additional variations in absorber column densities. This fact implies transverse motion of the absorbers across the line of sight. The transverse velocity, coupled with observed absorber outflow determined from line energies, suggest a possible helical motion for the absorbers. Scattered incident continuum flux was also indicated. Model results predict that the absorbers may also serve as substantial emitters of observed soft X-ray narrow line emission. However, additional emission components, not represented by absorbers, were required. Narrow emission line modeling of a single observation required three separate components, two of which may be represented by model absorbers. A strong Fe Ka fluorescent line was present in all observations, with highly-variable equivalent width. While photoionization model results predicted contributions to Fe Ka line flux by all absorbers, the absorber contributions to emission were minor. High-energy feature analysis revealed the presence of an additional, highly-ionized absorber in at least one observation.

Armentrout, Bryan Keith

2009-06-01

386

The luminous X-ray hotspot in 4C74.26: synchrotron or inverse-Compton emission?  

NASA Astrophysics Data System (ADS)

We report the discovery of an X-ray counterpart to the southern radio hotspot of the largest-known radio quasar 4C74.26 (whose redshift is z = 0.104). Both XMM-Newton and Chandra images reveal the same significant (10arcsec i.e. 19kpc) offset between the X-ray hotspot and the radio hotspot imaged with MERLIN. The peak of the X-ray emission may be either due to synchrotron emission or due to inverse-Compton emission. If synchrotron emission, the hotspot represents the site of particle acceleration and the offset arises from either the jet exhibiting Scheuer's `dentist's drill' effect or a fast spine having less momentum than the sheath surrounding it, which creates the radio hotspot. If the emission arises from the inverse-Compton process, it must be inverse-Compton scattering of the cosmic microwave background in a decelerating relativistic flow, implying that the jet is relativistic (? >= 2) out to a distance of at least 800kpc. Our analysis, including optical data from the Liverpool Telescope, rules out a background active galactic nucleus for the X-ray emission and confirms its nature as a hotspot, making it the most-X-ray-luminous hotspot detected at low redshift.

Erlund, M. C.; Fabian, A. C.; Blundell, Katherine M.; Moss, C.; Ballantyne, D. R.

2007-08-01

387

The XMM-Newton X-Ray Emission of the Supernova Remnant N 120 in the Large Magellanic Cloud  

NASA Astrophysics Data System (ADS)

We present new XMM-Newton observations of the supernova remnant (SNR) N 120 in the Large Magellanic Cloud, and numerical simulations on the evolution of this SNR which we compare with the X-ray observations. The SNR N 120, together with several H II regions, forms a large nebular complex (also called N 120) whose shape resembles a semicircular ring. From the XMM-Newton data, we generate images and spectra of this remnant in the energy band between 0.2 and 2.0 keV. The images show that the X-ray emission is brighter toward the east (i.e., toward the rim of the large nebular complex). The EPIC/MOS1 and MOS2 data reveal a thermal spectrum in soft X-rays. Two-dimensional axisymmetric numerical simulations with the Yguazú-a code were carried out assuming that the remnant is expanding into an inhomogeneous interstellar medium with an exponential density gradient and showing that thermal conduction effects are negligible. Simulated X-ray emission maps were obtained from the numerical simulations in order to compare them with the observations. We find good agreement between the XMM-Newton data, previous optical kinematic data, and the numerical simulations; the simulations reproduce the observed X-ray luminosity and surface brightness distribution. We have also detected more extended diffuse X-ray emission that is possibly due to the N 120 large H II complex or superbubble.

Reyes-Iturbide, Jorge; Rosado, Margarita; Velázquez, Pablo F.

2008-11-01

388

Unfolding core asymmetries with x-ray emission images in symmetry diagnostic experiments.  

PubMed

A novel inversion technique is proposed to unfold core asymmetries at the source with x-ray emission images, which were obtained from imploded surrogate capsules in symmetry diagnostic experiments. The axisymmetrical core emission can be expanded as a Fourier series, with Legendre polynomials and spherical Bessel functions as bases concerned with polar angle and radius, respectively. A least-squares estimator is employed to obtain the unknown coefficients from its two-dimensional image data. The unfolded Legendre coefficients can be further used to test modeling of drive asymmetries in hohlraums. This technique is also demonstrated with a proof-of-principle experiment performed on the Shenguang II laser facility [L. Zunqi et al., Chin. J. Lasers B10, 6 (2001)]. PMID:18513065

Huang, T X; Ding, Y K; Zheng, Z J; Miao, W Y; Cao, Z R; Jiang, S E; Liu, S Y; Liu, Z L

2008-05-01

389

Spectrometer for X-ray emission experiments at FERMI free-electron-laser.  

PubMed

A portable and compact photon spectrometer to be used for photon in-photon out experiments, in particular x-ray emission spectroscopy, is presented. The instrument operates in the 25-800 eV energy range to cover the full emissions of the FEL1 and FEL2 stages of FERMI. The optical design consists of two interchangeable spherical varied-lined-spaced gratings and a CCD detector. Different input sections can be accommodated, with/without an entrance slit and with/without an additional relay mirror, that allow to mount the spectrometer in different end-stations and at variable distances from the target area both at synchrotron and at free-electron-laser beamlines. The characterization on the Gas Phase beamline at ELETTRA Synchrotron (Italy) is presented. PMID:25362376

Poletto, L; Frassetto, F; Miotti, P; Di Cicco, A; Finetti, P; Grazioli, C; Iesari, F; Kivimäki, A; Stagira, S; Coreno, M

2014-10-01

390

Spectrometer for X-ray emission experiments at FERMI free-electron-laser  

NASA Astrophysics Data System (ADS)

A portable and compact photon spectrometer to be used for photon in-photon out experiments, in particular x-ray emission spectroscopy, is presented. The instrument operates in the 25-800 eV energy range to cover the full emissions of the FEL1 and FEL2 stages of FERMI. The optical design consists of two interchangeable spherical varied-lined-spaced gratings and a CCD detector. Different input sections can be accommodated, with/without an entrance slit and with/without an additional relay mirror, that allow to mount the spectrometer in different end-stations and at variable distances from the target area both at synchrotron and at free-electron-laser beamlines. The characterization on the Gas Phase beamline at ELETTRA Synchrotron (Italy) is presented.

Poletto, L.; Frassetto, F.; Miotti, P.; Di Cicco, A.; Finetti, P.; Grazioli, C.; Iesari, F.; Kivimäki, A.; Stagira, S.; Coreno, M.

2014-10-01

391

Spectrometer for X-ray emission experiments at FERMI free-electron-laser  

SciTech Connect

A portable and compact photon spectrometer to be used for photon in-photon out experiments, in particular x-ray emission spectroscopy, is presented. The instrument operates in the 25–800 eV energy range to cover the full emissions of the FEL1 and FEL2 stages of FERMI. The optical design consists of two interchangeable spherical varied-lined-spaced gratings and a CCD detector. Different input sections can be accommodated, with/without an entrance slit and with/without an additional relay mirror, that allow to mount the spectrometer in different end-stations and at variable distances from the target area both at synchrotron and at free-electron-laser beamlines. The characterization on the Gas Phase beamline at ELETTRA Synchrotron (Italy) is presented.

Poletto, L., E-mail: poletto@dei.unipd.it; Frassetto, F.; Miotti, P. [CNR - Institute of Photonics and Nanotechnologies (CNR-IFN), via Trasea 7, I-35131 Padova (Italy); Di Cicco, A.; Iesari, F. [Physics Division, School of Science and Technology, Università di Camerino, I-62032 Camerino (Italy); Finetti, P. [ELETTRA - Sincrotrone Trieste, Basovizza Area Science Park, S. S. 14 - km 163,5, I-34149, Basovizza (TS) (Italy); Grazioli, C. [Department of Chemical and Pharmaceutical Sciences, University of Trieste, Via L. Giorgieri 1, I-34127 Trieste (Italy); CNR-Istituto Officina dei Materiali (CNR-IOM), Laboratorio TASC, I-34149 Trieste (Italy); Kivimäki, A. [CNR-Istituto Officina dei Materiali (CNR-IOM), Laboratorio TASC, I-34149 Trieste (Italy); Stagira, S. [Politecnico di Milano – Department of Physics, I-20133 Milano (Italy); Coreno, M. [ELETTRA - Sincrotrone Trieste, Basovizza Area Science Park, S. S. 14 - km 163,5, I-34149, Basovizza (TS) (Italy); CNR – Istituto di Struttura della Materia (CNR-ISM), UOS Basovizza, I-34149 Trieste (Italy)

2014-10-15

392

Influence of ground-state geometry on carbon monoxide x-ray emission spectral profiles  

NASA Astrophysics Data System (ADS)

Photon excitation x-ray spectator emission dynamics of the core excited carbon monoxide molecule has been studied using ab initio multiconfiguration self-consistent field calculations and a modified two-step absorption-followed-by-emission approach. The core excitations of the CO molecule and the core ionizations of the 0953-4075/31/16/006/img1 species have been considered as the precursor steps for producing the same decaying electronic states of CO. The purpose of this study is to illustrate the influence of the absorption process, using target species with different ground electronic state geometries, on the de-excitation spectra. Nuclear dynamical effects of the decaying processes of carbon and oxygen core excited states of CO to the singlet low-lying excited (final) states of 0953-4075/31/16/006/img2 and 0953-4075/31/16/006/img3 have been studied. Vibrational envelopes of the decay spectra of CO are simulated.

Wang, Feng; Larkins, Frank P.

1998-08-01

393

X-RAY EMISSION FROM STRONGLY ASYMMETRIC CIRCUMSTELLAR MATERIAL IN THE REMNANT OF KEPLER'S SUPERNOVA  

SciTech Connect

Kepler's supernova remnant resulted from a thermonuclear explosion, but is interacting with circumstellar material (CSM) lost from the progenitor system. We describe a statistical technique for isolating X-ray emission due to CSM from that due to shocked ejecta. Shocked CSM coincides well in position with 24 {mu}m emission seen by Spitzer. We find most CSM to be distributed along the bright north rim, but substantial concentrations are also found projected against the center of the remnant, roughly along a diameter with position angle {approx}100 Degree-Sign . We interpret this as evidence for a disk distribution of CSM before the supernova, with the line of sight to the observer roughly in the disk plane. We present two-dimensional hydrodynamic simulations of this scenario in qualitative agreement with the observed CSM morphology. Our observations require Kepler to have originated in a close binary system with an asymptotic giant branch star companion.

Burkey, Mary T.; Reynolds, Stephen P.; Borkowski, Kazimierz J.; Blondin, John M., E-mail: reynolds@ncsu.edu [Department of Physics, North Carolina State University, Raleigh NC 27695-8202 (United States)

2013-02-10

394

Coronal X-ray emission of cool stars in relation to chromospheric activity and magnetic cycles.  

NASA Astrophysics Data System (ADS)

We study the relationship between the coronal X-ray emission of single, main-sequence F-K stars and the characteristics of their magnetic cycles. We use X-ray data primarily from the ROSAT all-sky survey (RASS) as well as data acquired by us in the ROSAT pointed program, and the published data of the Mt. Wilson CaII H+K monitoring program. According to their CaII H+K long-term variability characteristics, we divide the stars into three groups: non-variable, regular variable and irregular (chaotic) variable stars. We show that the regular and the irregular stars differ mainly in their Rossby-numbers (Ro): regular stars have almost always Ro<1 whereas the irregular group is characterized by Ro>1 further, the X-ray surface flux distributions differ significantly between these three groups. We discuss to what extent stars exhibiting constant Ca II fluxes can be considered "Maunder minimum" stars, and demonstrate - in a statistical sense - that cyclic chromospheric activity also implies cyclic coronal activity. From a reanalysis of the flux-