scholarly journals A Strong Variation of Accretion Disc Corona Size with Luminosity in LMXB

2004 ◽  
Vol 194 ◽  
pp. 140-143
Author(s):  
M. J. Church
Keyword(s):  
Thermal Emission ◽  
Compact Object ◽  
Accretion Disc ◽  
Spectral Form ◽  
X Ray ◽  
Radial Extent ◽  
Low Mass ◽  
X Ray Binaries ◽  
Rule Out ◽  
The Continuum

AbstractThe controversy that has existed for many years over the nature of the continuum X-ray emission components in X-ray binaries is reviewed, in which workers have been polarized between the Eastern model with a small central Comptonizing region around the compact object and alternative models. We present measurements of the radial extent of the Comptonizing ADC in low mass X-ray binaries which rule out the Eastern model and show that, the ADC is extended (the Birmingham model). Dip ingress timing shows conclusively that the ADC radial extent varies from 7% of the accretion disc radius in faint sources, to 65% in bright sources. Remarkably, the size depends strongly on the source luminosity suggesting that the ADC is formed by irradiation of the disc by the neutron star and the hot inner disc. These results have fundamental implications for the correct description of Comptonization in X-ray binaries, and the spectral form is derived for the Comptonized emission of an extended ADC led by soft, seed photons from the underlying disc which differs substantially from that of the Eastern model. Measured ADC electron températures provide values of the Compton radius in broad agreement with measured values of the radial extent of the ADC. Finally, we show that the results are inconsistent with the non-thermal emission being produced in a jet, and so provide evidence against the recent suggestion that all LMXB have jets.

scholarly journals A Machine Learning Approach For Classifying Low-mass X-ray Binaries Based On Their Compact Object Nature

2020 ◽  
Author(s):  
R Pattnaik ◽  
K Sharma ◽  
K Alabarta ◽  
D Altamirano ◽  
M Chakraborty ◽  
...  
Keyword(s):  
Machine Learning ◽  
Black Hole ◽  
Neutron Star ◽  
Binary Systems ◽  
Compact Object ◽  
X Ray ◽  
Average Accuracy ◽  
Machine Learning Approach ◽  
Low Mass ◽  
X Ray Binaries

Abstract Low Mass X-ray binaries (LMXBs) are binary systems where one of the components is either a black hole or a neutron star and the other is a less massive star. It is challenging to unambiguously determine whether a LMXB hosts a black hole or a neutron star. In the last few decades, multiple observational works have tried, with different levels of success, to address this problem. In this paper, we explore the use of machine learning to tackle this observational challenge. We train a random forest classifier to identify the type of compact object using the energy spectrum in the energy range 5-25 keV obtained from the Rossi X-ray Timing Explorer archive. We report an average accuracy of 87±13% in classifying the spectra of LMXB sources. We further use the trained model for predicting the classes for LMXB systems with unknown or ambiguous classification. With the ever-increasing volume of astronomical data in the X-ray domain from present and upcoming missions (e.g., SWIFT, XMM-Newton, XARM, ATHENA, NICER), such methods can be extremely useful for faster and robust classification of X-ray sources and can also be deployed as part of the data reduction pipeline.

Evolution of low-mass X-ray binaries: dependence on the mass of the compact object

2012 ◽  
Vol 12 (10) ◽  
pp. 1417-1426 ◽  
Author(s):  
Qian Xu ◽  
Tao Li ◽  
Xiang-Dong Li
Keyword(s):  
Compact Object ◽  
X Ray ◽  
Low Mass ◽  
X Ray Binaries

scholarly journals Alignment and precession of a black hole misaligned with its accretion disc: application to low-mass X-ray binaries

2019 ◽  
Vol 487 (3) ◽  
pp. 3488-3504
Author(s):  
Srimanta Banerjee ◽  
Chandrachur Chakraborty ◽  
Sudip Bhattacharyya
Keyword(s):  
Black Hole ◽  
Accretion Disc ◽  
X Ray ◽  
Low Mass ◽  
X Ray Binaries

scholarly journals Quiescent thermal emission from neutron stars in low-mass X-ray binaries

2015 ◽  
Vol 577 ◽  
pp. A5 ◽  
Author(s):  
A. Turlione ◽  
D. N. Aguilera ◽  
J. A. Pons
Keyword(s):  
Neutron Stars ◽  
Thermal Emission ◽  
X Ray ◽  
Low Mass ◽  
X Ray Binaries

scholarly journals New Constraints on the Nuclear Equation of State from the Thermal Emission of Neutron Stars in Quiescent Low-mass X-Ray Binaries

2019 ◽  
Vol 887 (1) ◽  
pp. 48 ◽  
Author(s):  
Nicolas Baillot d’Etivaux ◽  
Sebastien Guillot ◽  
Jérôme Margueron ◽  
Natalie Webb ◽  
Márcio Catelan ◽  
...  
Keyword(s):  
Equation Of State ◽  
Neutron Stars ◽  
Thermal Emission ◽  
X Ray ◽  
Nuclear Equation Of State ◽  
Low Mass ◽  
X Ray Binaries

scholarly journals Accretion disc atmospheres and winds in low-mass X-ray binaries

2016 ◽  
Vol 337 (4-5) ◽  
pp. 368-374 ◽  
Author(s):  
M. Díaz Trigo ◽  
L. Boirin
Keyword(s):  
Accretion Disc ◽  
X Ray ◽  
Low Mass ◽  
X Ray Binaries

scholarly journals The advection-dominated accretion flow for the anticorrelation between the X-ray photon index and the X-ray luminosity in neutron star low-mass X-ray binaries

2020 ◽  
Vol 496 (3) ◽  
pp. 2704-2714
Author(s):  
Erlin Qiao ◽  
B F Liu
Keyword(s):  
Neutron Star ◽  
Thermal Emission ◽  
X Ray ◽  
Radiative Efficiency ◽  
Accretion Flow ◽  
Self Similar Solution ◽  
Photon Index ◽  
Low Mass ◽  
Self Similar ◽  
X Ray Binaries

ABSTRACT Observationally, an anticorrelation between the X-ray photon index Γ (obtained by fitting the X-ray spectrum between 0.5 and 10 keV with a single power law) and the X-ray luminosity L0.5-10 keV, i.e. a softening of the X-ray spectrum with decreasing L0.5-10 keV, is found in neutron star low-mass X-ray binaries (NS-LMXBs) in the range of $L_{\rm 0.5\!-\!10\,keV}\sim 10^{34}\!-\!10^{36}\ \rm erg\ s^{-1}$. In this paper, we explain the observed anticorrelation between Γ and L0.5–10 keV within the framework of the self-similar solution of the advection-dominated accretion flow (ADAF) around a weakly magnetized NS. The ADAF model intrinsically predicts an anticorrelation between Γ and L0.5–10 keV. In the ADAF model, there is a key parameter, fth, which describes the fraction of the ADAF energy released at the surface of the NS as thermal emission to be scattered in the ADAF. We test the effect of fth on the anticorrelation between Γ and L0.5–10 keV. It is found that the value of fth can significantly affect the anticorrelation between Γ and L0.5–10 keV. Specifically, the anticorrelation between Γ and L0.5–10 keV becomes flatter with decreasing fth as taking fth = 0.1, 0.03, 0.01, 0.005, 0.003, and 0, respectively. By comparing with a sample of non-pulsating NS-LMXBs with well measured Γ and L0.5–10 keV, we find that indeed only a small value of 0.003 ≲ fth ≲ 0.1 is needed to match the observed anticorrelation between Γ and L0.5–10 keV. Finally, we argue that the small value of fth ≲ 0.1 derived in this paper further confirms our previous conclusion that the radiative efficiency of NSs with an ADAF accretion may not be as high as $\epsilon \sim {\dot{M} GM\over R_{*}}/{\dot{M} c^2}\sim 0.2$.

scholarly journals An ionized accretion disc wind in Hercules X-1

2019 ◽  
Vol 491 (3) ◽  
pp. 3730-3750
Author(s):  
P Kosec ◽  
A C Fabian ◽  
C Pinto ◽  
D J Walton ◽  
S Dyda ◽  
...  
Keyword(s):  
Accretion Rate ◽  
Compact Object ◽  
Accretion Disc ◽  
Strong Correlations ◽  
X Ray ◽  
Outflow Rate ◽  
Mass Outflow ◽  
X Ray Binaries ◽  
Absorption Features ◽  
Reflection Grating

ABSTRACT Hercules X-1 is one of the best-studied highly magnetized neutron star X-ray binaries with a wealth of archival data. We present the discovery of an ionized wind in its X-ray spectrum when the source is in the high state. The wind detection is statistically significant in most of the XMM–Newton observations, with velocities ranging from 200 to 1000 km s−1. Observed features in the iron K band can be explained by both wind absorption and a forest of iron emission lines. However, we also detect nitrogen, oxygen, and neon absorption lines at the same systematic velocity in the high-resolution Reflection Grating Spectrometer grating spectra. The wind must be launched from the accretion disc, and could be the progenitor of the ultraviolet absorption features observed at comparable velocities, but the latter likely originate at significantly larger distances from the compact object. We find strong correlations between the ionization level of the outflowing material and the ionizing luminosity as well as the superorbital phase. If the luminosity is driving the correlation, the wind could be launched by a combination of Compton heating and radiation pressure. If instead the superorbital phase is the driver for the variations, the observations are likely scanning the wind at different heights above the warped accretion disc. If this is the case, we can estimate the wind mass outflow rate, corrected for the limited launching solid angle, to be roughly 70 per cent of the mass accretion rate.

scholarly journals Variability of winds in X-ray binaries

2012 ◽  
Vol 8 (S290) ◽  
pp. 25-28
Author(s):  
M. Díaz Trigo ◽  
L. Boirin ◽  
S. Migliari ◽  
J. Miller-Jones ◽  
A. Parmar ◽  
...  
Keyword(s):  
Black Hole ◽  
Neutron Star ◽  
Column Density ◽  
X Ray ◽  
Low Mass ◽  
X Ray Binaries ◽  
The Continuum

AbstractWe discuss the variability of winds in two low-mass X-ray binaries, GX 13+1 and 4U 1630-47. XMM-Newton observations of these sources show that strong, photoionised winds with column densities well above 1022 cm−2 can be present in both neutron star and black hole LMXBs. Such winds can fade significantly due to changes in the flux or spectral hardness of the continuum. In particular, a decrease of column density and/or an increase of ionisation are measured when the flux increases or the spectrum hardens. We show how variability studies can help us to understand what triggers changes in the wind and discuss the limitations of current instruments for such studies.

scholarly journals Measuring the Masses of Compact Objects in Low-Mass X-Ray Binaries

2004 ◽  
Vol 194 ◽  
pp. 214-214
Author(s):  
Dawn M. Gelino
Keyword(s):  
Black Hole ◽  
Neutron Star ◽  
Compact Object ◽  
Compact Objects ◽  
Orbital Inclination ◽  
X Ray ◽  
Secondary Star ◽  
Low Mass ◽  
The Masses ◽  
X Ray Binaries

Low-mass X-ray binaries (LMXBs) contain compact, black hole (BH) or neutron star (NS) primaries, and cool, low-mass secondary stars. We measure the orbital inclination of the system in quiescence by modeling infrared (IR) ellipsoidal variations from the secondary star in order to determine the compact object mass. I present our results for a few LMXBs, including the first BH that appears to conclusively fall in the 3-5 M⊙ range.

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