... Understanding of accretion disks, accretion flows, X-ray induced winds, compact obect evolution are all in a primitive state. ...
NASA Website
Theory and Modelling Research in the LHEA - Research Topics. Low Mass X-ray Binaries -- Accretion Disk Corona Radiative Transfer � Synthetic X-ray Spectra ...
The spectral evolution of accretion disks in X-ray binaries containing black holes is studied, based
NASA Technical Reports Server (NTRS)
Accretion Disk Coronae were first suggested to explain the incomplete eclipses and shallow profiles observed from some Low Mass X-ray Binaries (White and ...
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. P...
National Technical Information Service (NTIS)
Spectra of accretion disks in active galactic nuclei & X-ray binaries ... and clean probe of accretion disks and black hole physics in most generic AGN! ...
Jun 19, 2006 ... Long Term Intensity Variations in X-ray Binaries ... has led to a number of new insights into accretion onto magnetized neutron stars. ...
neutron stars would have important implications for nuclear and particle physics. While many of these objects are in binary systems ( X-ray binaries ), where ...
The time variability of the x ray binary pulsars is discussed. It is found that the observed power spectral density of the aperiodic time variability of the x ray pulsar can be approximated by a power law spectrum which changes its slope at the coherent p...
A model of the X-ray radiation emitted from the accretion column of a compact object in AM Herculis binaries, using Monte Carlo methods is presented. The accretion column in the model has cylindrical symmetry. Above a shocked region in the column there is...
The relation between the spin period (Ps) and the orbital period (Po) in high-mass X-ray binaries is investigated. Be/X-ray binaries and SG/X-ray binaries occupy different areas in the Corbet diagram. The supergiant fast X-ray transients, IGR J18483-0311 and IGR ...
NASA Astrophysics Data System (ADS)
Unstable thermonuclear ignition of accreted fuel on neu- tron stars (NSs) in low -mass X-ray binaries (LMXBs) is triggered once a critical column density is ...
the accretion disk of the binary system and inconsistent with narrow beaming. ... luminosities are time-averaged estimates, which is critical for variable ...
BATSE Bright Source Monitor (Pulsed Sources). Frequency & Flux Histories ... 20 transient accreting X-ray binaries since the beginning of the CGRO mission, ...
. The times of eclipse can be advanced or delayed by 0.03 or more in orbital phase. X-RAY BINARY MS 1603; accepted 2008 May 27 ABSTRACT We present CCD photometry of the low-mass X-ray binary UW Coronae Borealis 1603.6+2600, UW CrB) -- X-rays: binaries 1. INTRODUCTION The ...
E-print Network
Bright pulsating X-ray sources (X-ray pulsars, AM Her stars,...) have been identified as strongly magnetized compact objects accreting matter from a binary companion. We give here a summary of some of the work which has been recently done to try to unders...
This article reviews the physics of advection-dominated accretion flows (ADAFs) and describes applications to several black hole X-ray binaries and galactic nulcei. The possibility of using ADAFs to explore the event horizons of black holes is highlighted.
We will describe a Thomson X-ray polarimeter developed for a small satellite mission. The instrument works in the 5-30 keV band and will be suitable for X-ray polarisation measurement in about 50 hard X-ray sources. The accretion powered X-ray pulsars, black hole X-ray ...
During the past three years a study has been made of a class of variable x-ray sources in our Galaxy which radiate up to a million times more powerfully than the Sun. The energy supply which powers these luminous sources of x rays is considered. It is argued that this arises from matter transferred from one star to a compact ...
Energy Citations Database
There has been, recently, a revival of the stability problem of accretion disks. Much of this renewed interest is due to recent observational data on transient soft X-ray novae, which are low-mass X-ray binaries. It is widely believed that nonsteady mass ...
Accretion disks are invoked to explain a host of astrophysical phenomena, from protostellar objects to AGN. And yet the mechanism allowing accretion disks to operate are completely unknown. This proposal seeks to observe the ``smoking gun'' signature of magnetically-driven viscosity in accretion disks. Magnetically-induced viscosity is ...
Spectroscopic and photometric observations of LMC X-2 reveal the source to be an X-ray binary with a relatively long orbital period, probably 12.5 days. It appears to be a partially eclipsing system. It is one of a small subclass of low-mass X-ray binaries with longer orbital periods and higher X-ray luminosity ...
Results of simultaneous X-ray, optical, and IR observations of X-ray binaries are discussed. Observations of A 0535 + 26 were made in a cooperative program including the Astron satellite, the Central Astronomical Observatory at Pulkovo, the Astronomical Observatory of Leningrad University, the Crimean Astrophysical Observatory, the Japanese satellites ...
We propose to use the RXTE to obtain a phase-dependent well-sampled hard X-ray light curve of the massive interacting binary system Beta Lyrae. Our minimal SUZAKU HXD-PIN phase dependent observations show significant variability and hints that a very hard X-ray hot spot may be present in the accreting disk. Our ...
Rare isotopes from the proton drip line to the neutron drip line are produced on the surface and crust of accreting neutron stars. Understanding their properties is essential to address the open questions raised by a variety of new observations of X-ray binaries, in particular X-ray bursters and transients. This paper provides an ...
Recent observations of partial X-ray eclipses from 4U1822-37 have shown that the central X-ray source in this system is diffused by a large Compton-thick accretion disk corona (ADC). Another binary, 4U2129-47, also displays a partial eclipse and contains ...
We report INTEGRAL observations of X-ray binaries containing a black hole, e.g. GX 339-4, Cyg X-1, IGR J17464-3213 and other X-ray novae. The different spectral states and spectral transitions of these sources are of our major interest. Their broad band spectrum generally exhibits two main components: a soft emission from a cool ...
In the past years, a clear picture of the evolution of outbursts of black-hole X-ray binaries has emerged. While the X-ray properties can be classified into our distinct states, based on spectral and timing properties, the observations in the radio band have shown strong links between accretion and ejection properties. Here I briefly ...
The LOBSTER-ISS is a proposed imaging all sky monitor for the 1 - 5 keV X-ray band. It will monitor much of the sky on a 90 minute (orbital) timescale. I will briefly discuss how observations with LOBSTER will address several important science questions related to accreting X-ray binaries.
The nearby barred spiral galaxy NGC 1313 contains three ultraluminous X-ray sources (two accreting binaries and the unusual ultraluminous Type IIn supernova SN 1978K) as well as other bright persistent and transient X-ray sources. Here we will discuss our radio (Australia Telescope Compact Array and Australian Long ...
Five AM Herculis binary systems show an optical QPO that is known to be associated with magentically channeled polar cap accretion. Hard X-ray QPOs are predicted by the time-depndent hydrodynamic models. We propose to search selected AM Her systems for polar cap X-ray QPOs using the XTE PCA. Because of its large ...
An initial study of the evolution of a neutron star in a close-binary orbit of high eccentricity discloses a special class of systems that will never achieve a state of pure, steady accretion: the neutron star will continually oscillate between an accreting state and a propeller state. This may be what is happening in the rapid-spin ...
The high-mass eclipsing X-ray binary system SMC X-1/Sk 160 will be observed for one complete binary orbit (3.892 days) to provide a detailed far ultraviolet spectroscopic record of this important system. The spectra will be used to 1) characterize the phase-dependent X-ray ionization of the stellar wind and its ...
There exists a group of persistently faint galactic X-ray sources that, based on characteristics such as location in the galaxy, high Lx/Lopt, association with X-ray bursts, absence of X-ray pulsations and similar characteristics are thought to be low-mass X-ray binaries, but about which very little is known. We propose to observe a ...
The polarization of X radiation from an accretion disk in a binary X-ray source is investigated. Calculations are discussed which indicate that radiation from an accretion disk is linearly polarized as a result of Thomson scattering, that the hard X-ray electric vector lies in the orbital plane ...
In the recent years, the discovery of a new class of Galactic transients with fast and bright flaring X-ray activity, the supergiant fast X-ray transients, has completely changed our view and comprehension of massive X-ray binaries. These objects display X-ray outbursts which are difficult to ...
... Presumably, ULXs are X-ray binaries with possible maximum stellar-size black holes; ~40 M� black holes theoretically possible (Fryer 1999)
We describe preliminary results of a global model of the radiatively-driven photoionized wind and accretion flow of the high-mass X-ray binary Vela X-1. The full model combines FLASH hydrodynamic calculations, XSTAR photoionization calculations, HULLAC at...
Accreting neutron stars provide the bulk of high luminosity X-ray sources. Decade long studies of low-mass X-ray binaries have provided a wealth of information about the various nature of X-ray emissions and proposed emission sites include the neutron star surface, an immediate boundary layer, the inner disk ...
We have investigated the influence of X-ray irradiation on the vertical structure of the outer accretion disk in low-mass X-ray binaries by performing a self-consistent calculation of the vertical structure and X-ray radiation transfer in the disk. Penetrating deep into the disk, the field of scattered X-ray ...
Understanding black hole systems in their canonical hard state is a major goal of high energy astrophysics. This state features a hard X-ray spectrum, a high level of timing noise, and emission from a jet at radio, infrared, and perhaps higher frequencies. Observations can constrain the theoretical models by answering two questions: Does the inner edge of the ...
We have developed a stellar wind model for OB supergiants to investigate the effects of accretion from a clumpy wind on the luminosity and variability properties of high-mass X-ray binaries. Assuming that the clumps are confined by ram pressure of the ambient gas and exploring different distributions for their mass and radii, we ...
Models are presented for the 6-7 keV iron line emission from low-mass X-ray binaries. A simplified model for an accretion disk corona is used to examine the dependence of the observable line properties, line width and mean energy, on the radial distance of the emission region from the X-ray source, and on the fraction of the X-rays ...
Context. Low mass X-ray binaries are found to have very low frequency breaks in their power density spectra. The power density spectra below these breaks are nearly in white noise structure and at higher frequencies approximately follow the P? ? ?-1.3 law. Aims: To determine whether high mass X-ray binary power ...
The hydrodynamics of axisymmetric accretion flow in stellar wind-fed X-ray sources is investigated, including momentum deposition by radiation, as well as radiative heating and cooling by Compton and bremsstrahlung processes. The results of two-dimensional numerical simulations for mass accretion rates ranging from 0.02 to 0.4 of the ...
The interest in X/ ?-ray Astronomy has grown enormously in the last decades thanks to the ability to send X-ray space missions above the Earth�s atmosphere. There are more than half a million X-ray sources detected and over a hundred missions (past and currently operational) devoted to the study of cosmic ...
The illumination of companion stars in very low mass X-ray binaries by various kinds of radiation from the neighborhood of the neutron star after accretion has terminated or during accretion is considered. If a neutron star's spun-up period approaches 0.001 s, pulsar kHz radiation can quench ...
We propose to study a complete X-ray sample in the luminosity of 0.5-5 x 10^35 erg/s in the Galactic bulge, containing 10 unidentified sources detected in the ROSAT All Sky Survey. Our goal is to obtain, for the first time, a clear picture about X-ray populations in the bulge with detailed X-ray spectroscopic studies of these sources. ...
Narayan and Heyl (2002) have developed a theoretical framework to convert suitable upper limits on type I X-ray bursts from accreting black hole candidates (BHCs) into evidence for an event horizon. However, no appropriate observational limit exists in th...
Narayan and Heyl have developed a theoretical framework to convert suitable upper limits on type I X-ray bursts from accreting black hole candidates (BHCs) into evidence for an event horizon. However, no appropriate observational limit exists in the liter...
In late 2008, the quasi-persistent neutron star X-ray transient and eclipsing binary EXO 0748-676 started a transition from outburst to quiescence, after it had been actively accreting for more than 24 years. In a previous work, we discussed Chandra and S...
We present a detailed spectral and timing analysis of the High Mass X-ray Binary (HMXB) 4U 1909+07 with INTEGRAL and RXTE. 4U 1909+07 is a persistent accreting X-ray pulsar with a period of approximately 605 s. The period changes erratically consistent wi...
We have analyzed Rossi X-Ray Timing Explorer pointed observations of the outbursts of black hole and neutron star soft X-ray transients in which an initial low/hard state, or ``island'' state, followed by a transition to a softer state was observed. In three sources-the black hole transient XTE J1550-564, the neutron star transient Aquila X-1, and the ...
The contribution of UV spectroscopy to the understanding of massive X-ray binaries, is reviewed. Results are given in the context of normal stars and binaries. The IUE results have enabled a greater understanding of the effects of accretion disks and X-ray heating in the systems, and provide absolute fluxes and ...
There are 9 dwarf novae (DN) among the 43 cataclysmic variables (accreting white dwarfs in close binary systems) that were detected during the HEAO-1 all-sky X-ray survey (1977-1979). On the other hand, there are roughly one hundred dwarf novae that are closer and/or optically brighter and yet they were not detected as hard ...
Fletcher & Martens have successfully modeled solar hard X-ray sources observed at the top and footpoints of flaring magnetic loops with a Fokker-Planck type particle transport code. I show here that there are invariances in the Fokker-Planck equations that make these results applicable to environments with vastly different physical parameters, such as hard ...
I show that the assumption that the acceleration and collimation mechanisms of jets are the same in all the classes of astrophysical objects which are observed to produce jets, can lead to interesting conclusions. Jets have now been observed in: active galactic nuclei, young stellar objects, massive x-ray binaries, low mass x-ray ...
Matter accretion onto compact stars has been considered as a likely process of x-ray emission from stellar x-ray sources. The accreting matter forms a circumstellar envelope that absorbs a part of x rays emitted from the central star. The ionization equilibrium due to the ...
The Energetic X-ray Imaging Survey Telescope (EXIST) is a proposed NASA mission for scanning the entire sky in intermediate and hard X-rays. The EXIST mission includes a wide field of view High Energy Telescope (HET) covering the 5-600 keV energy range, and an infrared telescope. The HET has the capability to measure the energy dependent ...
The present radio proposal is part of a multi-wavelength campaign focused on the study of the accretion/ejection process in the neutron star X-ray binary system 4U 1728-34. Our intention is to study the behaviour of the inner part of the accretion disc as inferred from the X-ray observations of the Fe emission line ...
The accreting millisecond pulsar SAX J1808.4-3658 may be a transition object between accreting X-ray binaries and millisecond radio pulsars. We have constrained the thermal radiation from its surface through XMM-Newton X-ray observations, providing strong evidence for neutrino cooling processes ...
Nuclear-powered oscillations during Type-I X-ray bursts have so far revealed the spin of about twenty accreting millisecond pulsars in low-mass X-ray binaries. We study the properties of such burst oscillations by means of numerical computations of hot spots on the neutron star surface. We use adaptive mesh ...
I will present an overview of the Galactic population of X-ray binaries and related systems, including cataclysmic variables. The advent of new instrumentation with unprecedented capabilities�spatial resolution, time resolution, sensitivity at higher energies�has advanced our understanding of accretion-powered X-ray sources over ...
Progress made over the last decade in the understanding of the binary X-ray pulsars is reviewed. The
We explore thermal X-ray iron line emission from the galactic X-ray binary GX 339-4 in the off state, using the models of the advection-dominated accretion flow (ADAF) without or with outflows. The equivalent widths of hydrogen-like and helium-like thermal iron lines are calculated with different model parameters ...
The x rays emitted by the close binary system ..beta.. Per evidently represent the radiation of a ''hot spot'' on the surface of the Algol A component. This spot is formed by accretion onto Algol A of gas shed by the other component, Algol B. Unlike familiar ...
We show that X-ray Binaries undergo optical state changes within X-ray quiescence. All states show emission from the accretion flow, but in what we call the "passive" state, we show that it is possible to separate stellar flux from flux due to the accretion flow. We thereby gain a better understanding of both ...
X-ray emission from accreting binary systems (X-ray binaries) uniquely probe the binary phase of stellar evolution and the formation of compact objects such as neutron stars and black holes. A detailed understanding of X-ray binary systems is needed to ...
We report on a Chandra Director's Discretionary Time observation of the globular cluster Terzan 5, carried out �7 weeks after the cessation of the 2010 outburst of the newly discovered transiently accreting 11-Hz X-ray pulsar. We detect a thermal spectrum that can be fitted with a neutron star atmosphere model with a temperature for an observer at ...
The observations of the binary X-ray source Circinus X-1 discussed in this thesis provide samples of a range of spectral and temporal behavior whose variety is thought to reflect a broad continuum of accretion conditions in an eccentric binary system. The data support an identification of three or more ...
Hard X-ray emission associated with white dwarfs (WDs) can be used to diagnose the presence of late-type binary companions, mass accretion from companions, or physical processes with unknown origins. Since our previous systematic searches for hard X-ray emission associated with WDs, the Galactic WD catalog has been ...
We report the detection of 15 X-ray bursts with RXTE and Swift observations of the peculiar X-ray binary Circinus X-1 (Cir X-1) during its 2010 May X-ray re-brightening. These are the first X-ray bursts observed from the source after the initial discovery by Tennant and collaborators, 25 years ...
Basic observational data on CH Cyg are presented and an empirical model explaining the data is developed. The star CH Cyg is a binary comprising a semiregular M6 III giant and a white dwarf, around which a transient accretion disk is formed during sufficiently high maxima of the semiregular star. The prediction is made that soft X-rays ...
Systematic multi-wavelength studies of neutron stars (NSs) have shown a jet and disk-jet coupling phenomenology which resembles, although with some important differences, that observed in black holes; ultra-relativistic transient ejection, steady compact jets, accretion-ejection cycles are indeed observed in NSs. I will review our observational knowledge of jet in NS ...
The spectral evolution of accretion disks in X-ray binaries containing black holes is studied, based on the disk instability model. The thermal transition of the outer portions of the disk controls the mass flow rate into the inner portions of the disk, thus modulating the soft X-ray flux which is thought to arise from the inner disk. ...
FUTau belongs to a rare class of young, wide brown dwarf binaries. We have resolved the system in a Chandra X-ray observation and detected only the primary, FUTauA. Hard X-ray emission, presumably from a corona, is present but, unexpectedly, we also detect a strong and unusually soft component from FUTauA. Its ...
through it. In the X-ray band is where we see most of the accretion power coming from these sources population, a stellar population, would make high mass binaries. If you look at the population sources in X-rays you really see that they have different characteristics. Which X-ray sources interest you the most
Accretion from a disk onto a collapsed, relativistic star--a neutron star or black hole--is the mechanism widely believed to be responsible for the emission from compact X-ray binaries. Because of the extreme spatial resolution required, is not yet possib...
Pulsars inside binary systems can accrete matter that arrives up to the pulsar surface provided that its period is long enough. During the accretion process, matter has to be accelerated to the rotational velocity of the pulsar magnetosphere at the distance where the balance between the pressure of matter and the magnetic field is ...
Anomalous X-ray pulsars (AXPs) are a class of rare X-ray emitting pulsars whose energy source has been perplexing for some 20 years. Unlike other X-ray emitting pulsars, AXPs cannot be powered by rotational energy or by accretion of matter from a binary companion star, hence the designation ...
PubMed
Over the past decade our understanding of accreting neutron stars has been revolutionized. Observations with NASA's Rossi X-ray Timing Explorer (RXTE) have resulted in the discovery of fast, coherent X-ray intensity oscillations (hereafter, ``burst oscillations'') during thermonuclear X-ray bursts from 13 low mass ...
Exosat observations are used to compare the spectral properties of the persistent emission from a number of X-ray burst sources, high-luminosity low-mass X-ray binaries (LMXRB) and galactic black hole candidates with various models for X-ray emission from an accretion disk surrounding a compact object in a binary ...
Re-analysis of a Swift/XRT ToO observation of IGR J01572-7259 in the Magellanic Bridge (=IGR J015712-7259, c.f. Coe et al., 2008, ATel #1882) has enabled us to establish the first soft X-ray spectrum for this 11.6-s X-ray pulsar and suspected high-mass X-ray binary. Observation-ID 00031313001 was taken on ...
We report the detection of optical bursts during a low-amplitude, flat-topped eruption of the soft X-ray transient Aql X-1. The bursts had amplitudes between 0.17 and 0.35 mag and were variable in duration, some lasting longer than 78 s. On one night they recurred quasi-periodically at a mean interval of 1.01 hr. Regularly repeating optical bursts of this kind have not ...
The evolution of X-ray astronomy up to the launching of the Einstein observatory is presented. The evaluation proceeded through the following major steps: (1) discovery of an extrasolar X-ray source, Sco X-1, orders of magnitude stronger than astronomers believed might exist (2) identification of a strong X-ray source with the Crab Nebula (3) ...
We present three numerical models of accretion from radiation driven stellar winds onto compact objects in massive X-ray binary systems. The wind is given a velocity profile consistent with a radiatively driven wind, and a 'negative mass' gravitational potential is derived from this profile to represent the wind ...
We have obtained the first broadband X-ray spectra of the nearby compact elliptical galaxy M32 by using the ASCA satellite. The extracted spectra and X-ray luminosity are consistent with the properties of the hard spectral component measured in giant elliptical galaxies believed to originate from X-ray binaries. Two ASCA observations ...
In this paper, we investigate the relationship between the maximal luminosity of X-ray outburst and the orbital period in transient low mass X-ray binaries (or soft X-ray transients) observed by the Rossi X-ray Timing Explorer (RXTE) in the past decade. We find that the maximal luminosity (3-200 keV) in Eddington ...
The well-studied X-ray/optical/radio supernova remnant (SNR) DDB 1-15 (CXOM31 J004327.8+411829; r3-63) in M31 has been investigated with archival XMM-Newton and Chandra observations. The timing data from XMM-Newton reveal a power density spectrum (PDS) characteristic of accreting compact objects in X-ray binaries (XRBs). The PDS shows ...
The advent of the grating spectrometers onboard Chandra and XMM-Newton opened up a new era in plasma diagnostics of compact binaries. High resolution spectroscopy using these spectrometers is of particular use in investigating accretion plasmas in cataclysmic variables (CVs) because they show a wealth of emission lines owing to their optically thin thermal ...
Gamma-ray loud X-ray binaries are binary systems that show non-thermal broadband emission from radio to gamma rays. If the system comprises a massive star and a young non-accreting pulsar, their winds will collide producing broadband non-thermal emission, most likely originated in the shocked pulsar wind. Thermal ...
We present optical spectra in the range 4600-8600� for three low-mass X-ray binaries which have been suggested to belong to the class of ultra-compact X-ray binaries based on their X-ray spectra. Our spectra show no evidence for hydrogen or helium emission lines, as are seen in classical ...
We report results on three low-mass X-ray binaries (LMXB) in the LMC, obtained with EXOSAT, IUE and ground-based (ESO) telescopes: LMC X-2 which appears to be �Sco X-1�-like, LHG 83 and LHG 87. The latter are two weaker sources first detected in the course of the HEAO-B LMC survey. They have faint optical counterparts of which LHG 87 was only recently ...
We have studied X-ray spectral state transitions that can be seen in the long-term monitoring light curves of bright X-ray binaries from the All-Sky Monitor (ASM) onboard the Rossi X-ray Timing Explorer (RXTE) and the Burst Alert Telescope (BAT) onboard Swift during a period of five years from 2005 to 2010. We have ...
Millisecond pulsars are believed to descend from low-mass X-ray binaries. Observable parameters of binary millisecond pulsars, e.g. mass of the pulsar, mass of the companion, spin period of the pulsar, orbital period, orbital eccentricity, etc., are used to probe the past accretion history of the millisecond ...
Disk accretion onto a magnetized spinning neutron star or a white dwarf will not be possible if the radius of the magnetosphere exceeds the corotation radius. A dead disk serving as a reservoir of material will then form around the star. Such a disk could retard the spin of the star; it might produce a transient x-ray source of a flare in a dwarf ...
Galactic accreting compact objects, such as stellar-mass black holes and neutron stars, can give us a unique perspective into the behavior of matter in extreme conditions. However, the exact nature of accretion onto these objects is not yet well understood. X-ray studies provide us with a means to observe the innermost regions around ...
Galactic accreting compact objects, such as stellar-mass black holes and neutron stars can give us a unique perspective into the behavior of matter in extreme conditions. However, the exact nature of accretion onto these objects is not yet well understood. X-ray studies provide us with a means to observe the innermost regions around ...
We present here the high-resolution X-ray spectrum of the accreting binary X-ray pulsar GX 1+4, obtained with the High Energy Transmission Grating (HETG) instrument of the Chandra X-Ray Observatory. This was supplemented by a simultaneous observation with the Proportional Counter Array (PCA) of ...
We propose to use the IRAC and MIPS camera arrays on Spitzer to establish the mid-infrared spectral energy distribution and search for evidence for jet emission contributions at Spitzer wavelengths for three Z sources: GX 349+2, GX 17+2, and Cyg X-2. These neutron star X-ray binaries are the brightest X-ray sources in the Galaxy and ...
The X-ray binary XTE J1817-330 was discovered in outburst on 26 January 2006 with RXTE/ASM. One year later, another X-ray transient discovered in 1996, XTE J1856+053, was detected by RXTE during a new outburst on 28 February 2007. We triggered XMM-Newton target of opportunity observationson these two objects to constrain their parameters and search for a ...
One of the most intriguing challenges in high-energy astrophysics has been understanding the dynamics of accretion flow onto compact objects. X-ray binaries exhibit many different patterns of accretion flow, manifested as "X- ray states". Various states show dramatically ...
We present the results of the long-term hard X-ray monitoring of the high-mass X-ray binary 2S 0114+65 with INTEGRAL/IBIS from 2003 to 2008. 2S 0114+65 is a variable hard X-ray source with X-ray luminosities of 1035-4 � 1036 erg s-1 from 20 to 100 keV due to accretion rate changes in ...
Most stars in the solar neighborhood are either double or multiple systems. They provide a unique opportunity to measure stellar masses and radii and to study many interesting and important phenomena. The best candidates for black holes are compact massive components of two x-ray binaries: Cygnus X-1 and LMC X-3. The binary radio ...
We present X-ray light curves for the cataclysmic variable EX Hydrae obtained with the Chandra High Energy Transmission Grating Spectrometer and the Extreme Ultraviolet Explorer Deep Survey photometer. We confirm earlier results on the shape and amplitude of the binary light curve and discuss a new feature: the phase of the minimum in the ...
DOE Information Bridge
We study the accretion/ejection processes (i.e. disc/jet coupling) in the neutron star X-ray binary Aquila X-1 via a multi-wavelength approach. We use in the radio band the publicly available VLA archive containing observations of the object between 1986-2005, in the X-ray band the archival RXTE data (PCA and HEXTE) between 1997-2008, ...
Jun 26, 2003 ... A special class of binary stars is the X-ray binaries, so-called because they emit X-rays. X-ray binaries are made up of a normal star and a ...
ESO Very Large Telescope observations revealed on a high confidence level the presence of a variable magnetic field in the optical component (O-supergiant) and in the outer parts of the accreting structure around BH. This result creates observational basis for models of magnetic disc accretion on BH in X-ray binaries, quasars and other ...
Accreting neutron stars can produce jets only if they are weakly magnetized (B ~ 108 G). On the other hand, neutron stars are compact objects born with strong surface magnetic fields (B ~ 1012 G). In this work we study the conditions for jet formation in a binary system formed by a neutron star and a massive donor star once the magnetic field has decayed ...
The goal of this investigation is to further our understanding of the dynamics of secreting neutron stars and black holes in the hope of using these systems as probes of the physics of strong gravitational fetus. The main focus of this work has been a multi-year program of simultaneous millisecond X-ray timing and spectral observations carried out with the Rossi ...
We will present Chandra observations of 4 giant elliptical galaxies:NGC1399,NGC1404,NGC4472 and NGC4636. We have determined the spectrum with position deriving temperature and abundance profiles, cooling times and mass accretion rates. We place strong upper limits on the presence of a central point source strongly bounding accretion onto the central ...
We calculate the accretion disc temperature profiles, disc luminosities and boundary layer luminosities for rapidly rotating neutron stars considering the full effect of general relativity. We compare the theoretical values of these quantities with their values inferred from EXOSAT data for four low mass X-ray binary sources: XB ...
We suggest a possible explanation for the high frequency quasi-periodic oscillations (QPOs) in black hole (BH) low-mass X-ray binaries. By solving the perturbation general relativistic magnetohydrodynamic equations, we find two stable modes of the Alfven wave in the accretion disks with toroidal magnetic fields. We suggest that these ...
We calculate the emission from relativistic flows in black hole systems using a fully general relativistic radiative transfer formulation, with flow structures obtained by general relativistic magneto-hydrodynamic simulations. We consider thermal free-free emission and thermal synchrotron emission. Bright filament-like features protrude (visually) from the accretion disk ...
Rossi X-Ray Timing Explorer (RXTE) All-Sky Monitor observations of the X-ray source 4U 2206+54, previously proposed to be a Be star system, show the X-ray flux to be modulated with a period of approximately 9.6 days. If the modulation is due to orbital variability, then this would be one of the shortest orbital periods known for a Be star X-ray source. ...
A binary X-ray source, an extended extragalactic X-ray source and several nearby stars were surveyed
Hard X-ray observations of the binary system AM Her were coincident with soft X-ray and ground-based
Using X-ray monitoring observations with the All-Sky Monitor on board the Rossi X-Ray Timing Explorer and the Burst Alert Telescope on board the Swift, we are able to study the spectral state transitions occurred in about 20 bright persistent and transient black hole and neutron star binaries. We have confirmed that there is a ...
We have obtained high-resolution (approximately 1") deep x-ray images of the globular cluster 47Tucanae (NGC 104) with the Chandra X-ray Observatory to study the population of compact binaries in the high stellar density core. A 70-kilosecond exposure of the cluster reveals a centrally concentrated population of faint (Lx approximately ...
A steady-state model of the accretion disk around a white dwarf, including the boundary layer and the hot spot, has been constructed. Calculated distributions of radiation are compared with soft X-ray, ultraviolet, visual, and infrared observations of SS Cyg during outburst as well as with ultraviolet measurements of V 603 Aql and RR Pic. The results ...
We provide a brief review of the physical processes behind the radiative driving of the winds of OB stars and the Bondi-Hoyle-Lyttleton capture and accretion of a fraction of the stellar wind by a compact object, typically a neutron star, in detached high-mass X-ray binaries (HMXBs). In addition, we describe a program to develop global ...
We propose to capitalise on the extensive set of scientific and calibration observations of the remarkable globular cluster 47 Tuc. The chief goals are: 1 to address key questions about the binaries found in this massive cluster, including studies of cataclysmic variables CVs, low-mass X-ray binaries LMXBs, millisecond pulsars MSPs and ...
In this paper we discuss the spin equilibrium of accreting neutron stars in low-mass X-ray binaries (LMXBs). We demonstrate that, when combined with a naive spin-up torque, the observed data lead to inferred magnetic fields which are at variance with those of Galactic millisecond radio pulsars. This indicates the need for either ...
A solid theoretical understanding of how inflowing, accreting plasma around black holes and other compact objects gives rise to outflowing winds and jets is still lacking, despite decades of observations. The fact that similar processes and morphologies are observed in both X-ray binaries and active galactic nuclei has led to ...
Accretion in astrophysical objects and the energetic phenomena it triggers are discussed in reviews and reports of recent theoretical and observational investigations. Topics examined include fly's-eye observations of ultrahigh-energy (UHE) gamma rays, recent results from the IMB detector, the theoretical implications of UHE detections of binary ...
2S 0918-549 is a low-mass X-ray binary (LMXB) with a low optical to X-ray flux ratio. Probably it is an ultracompact binary with an orbital period shorter than 60 min. Such binaries cannot harbor hydrogen rich donor stars. As with other (sometimes confirmed) ultracompact LMXBs, 2S 0918-549 is observed to have a ...
In recent years, much effort has been devoted to unravelling the connection between the accretion flow and the jets in accreting compact objects. In the present work, we report new constraints on these issues, through the long-term study of the radio and X-ray behaviour of the black hole candidate H1743-322. This source is known to be one of the 'outliers' ...
UV emission in many X-ray binaries is dominated by X-raysreprocessed in the accretion disk. For pulsars illumination ofthe accretion disk by a rotating beam of X-rays should resultin pulsed UV emission lines with Doppler shifts correspondingto projected gas velocities. Simultaneous high time resolutionUV and X-ray ...
The primary goal of this proposal was to increase our understanding of the accretion dynamics and emission mechanisms in neutron-star low-mass x-ray binaries via accurate measurements of their broad-band x-ray spectrum with particular emphasis on the hard x-ray emission. We obtained an ...
Radio pulsars with millisecond spin periods are thought to have been spun up by the transfer of matter and angular momentum from a low-mass companion star during an x-ray-emitting phase. The spin periods of the neutron stars in several such low-mass x-ray binary (LMXB) systems have been shown to be in the millisecond regime, but no radio pulsations have ...
We have carried out a deep X-ray and optical survey with Chandra and HST of low-extinction regions in the Galactic bulge. Here we present the results of a search for low-luminosity (LX lsim 1034 erg s-1) accreting binaries among the Chandra sources in the region closest to the Galactic center, at an angular offset of 1fdg4, that we ...
Results are presented for 10 evolutionary sequences of close binary systems of extreme mass ratio. Angular momentum loss associated with material outflow from the system, a consequence of the ineffectiveness of tidal torques, as well as gravitational radiation is included in the calculations. We find that a previously described mass transfer instability is extremely sensitive ...
1. Neutron Star Low Mass. X-ray Binaries. (NSLMXBs) seen by. INTEGRAL: high energy behaviour. Neutron Star Low Mass. X-ray Binaries. (NSLMXBs) seen by ...
Sep 4, 1998 ... 5. Timing Properties of High-Mass X-Ray Binaries. ... 5. Timing Properties of High-Mass X-Ray Binaries. 1. Dynamical Timescales for ...
We examine a variety of X-ray and optical data for evidence of evolution in the accretion structure of the dipping, eclipsing, bursting low-mass X-ray binary (LMXB) EXO 0748-676. Our results are divided into three main sections. New ASCA and archival EXOSAT data reveal behavior related to the source brightness state. An anomalous dip ...
The University of Iowa is currently establishing a new space based X-ray astronomy program with a focus on soft X-Ray instrumentation. The program is renovating 1300 square feet into a cutting-edge lab facility with all necessary hardware to successfully design, fabricate, integrate and test suborbital payloads. In addition to the facility buildup, ...
Thanks to its high throughput and good spatial, timing and spectral resolution, the XMM-Newton X-ray space telescope is well suited to perform detailed studies also of faint X-ray sources. Here we report the results we obtained on the persistent Be binaries, a sub-class of the accreting X-ray ...
The Chandra X-ray Observatory has now discovered nearly 10,000 X-ray point sources in the 2� � 0fdg8 region around the Galactic Center. The sources are likely to be a population of accreting binaries in the Galactic Center, but little else is known of their nature. We obtained JHKs imaging of the 17' � 17' ...
We present a tabulation of 46 transient x-ray sources monitored with the All-Sky Monitor (ASM) on the Rossi X-ray Timing Explorer (RXTE). They fall into four broad categories: short (~1 d), intermediate, and long (>500 d) duration of outbursts, and long period binary systems that flare up at periastron (e.g., Be systems). The ...
Three Exosat observations are reported of the low-mass X-ray binary 4U 1705-44 during which X-ray bursts are detected. Seventeen bursts are recorded in the low-intensity state and seven bursts in the medium-intensity state, of which 22 are suitable for a detailed analysis. Correlations between the burst properties and the strength of ...
I point to an interesting similarity in the radio and the soft X-ray light curves between the November 2009 outburst of the X-ray binary Aquila X-1 and some solar flares. The ratio of the soft X-ray and radio luminosities of Aquila X-1 in that outburst is also similar to some weak solar flares, and so is the radio spectrum near 8 GHz. ...
I point to an interesting similarity in the radio and the soft X-ray light curves between the 2009 November outburst of the X-ray binary Aquila X-1 and some solar flares. The ratio of the soft X-ray and radio luminosities of Aquila X-1 in that outburst is also similar to some weak solar flares, as is the radio spectrum near 8 GHz. ...
We report the discovery of several new OB/X-ray accreting binary candidates. These massive systems were found by cross-correlating in position SIMBAD OB star catalogues with the part of the ROSAT all-sky survey located at low galactic latitudes (|b|<=20�) and selecting the early type stars which apparently displayed the most ...
We present an analysis of archival X-ray observations of the Type IIL supernova SN 1979C. We find that its X-ray luminosity is remarkably constant at (6.5 � 0.1) � 1038 erg s-1 over a period of 12 years between 1995 and 2007. The high and steady luminosity is considered as possible evidence for a stellar-mass (�5-10 M?) black hole ...
The discovery of the high-ionization [Ne V] ?3426 � emission line in the spectrum of the blue compact dwarf (BCD) galaxy Tol 1214-277 is reported. The detection of this line implies the presence of intense ionizing X-ray emission with a luminosity Lx in the range 1039-1040 erg s-1. Such a high X-ray luminosity cannot be reproduced by models of massive ...
Holmberg IX X-1 is an archetypal ultraluminous X-ray source (ULX). Here we study the properties of the optical counterpart and of its stellar environment using optical data from SUBARU/Faint Object Camera and Spectrograph, GEMINI/GMOS-N and Hubble Space Telescope (HST)/Advanced Camera for Surveys, as well as simultaneous Chandra X-ray data. The V ~ 22.6 ...
HD 15137 is an intriguing runaway O-type binary system that offers a rare opportunity to explore the mechanism by which it was ejected from the open cluster of its birth. Here, we present recent blue optical spectra of HD 15137 and derive a new orbital solution for the spectroscopic binary and physical parameters of the O star primary. We also present the ...
Context. The burst-only source Swift J1749.4-2807 was discovered in a high X-ray-active state, during an INTEGRAL observations of the Galactic bulge on 2010 April 10. Pulsations at 518 Hz were discovered in the RXTE data, confirming previous suggestions of possible associations between burst-only sources and accreting millisecond X-ray ...
Black holes, neutron stars in binary x ray source systems, and supernova remnants (SNRs) are briefly discussed.
An eclipsing X-ray binary pulsator consistent with the location of A1540-53 was observed. The source
