Power Density Spectral analysis as a Method of Compact Object Determination in X-ray Binary Systems

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.

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Accretion onto Relativistic Objects

Symposium - International Astronomical Union ◽

10.1017/s0074180900236346 ◽

1974 ◽

Vol 64 ◽

pp. 194-212

Author(s):

M. J. Rees

Keyword(s):

Black Holes ◽

Interstellar Medium ◽

Neutron Stars ◽

Binary Systems ◽

Compact Object ◽

Stellar Mass ◽

Supermassive Black Holes ◽

Compact Objects ◽

X Ray ◽

Intergalactic Space

The physics of spherically symmetrical accretion onto a compact object is briefly reviewed. Neither neutron stars nor stellar-mass black holes are likely to be readily detectable if they are isolated and accreting from the interstellar medium. Supermassive black holes in intergalactic space may however be detectable. The effects of accretion onto compact objects in binary systems are then discussed, with reference to the phenomena observed in variable X-ray sources.

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Models of ultraluminous X-ray transient sources

Astronomy and Astrophysics ◽

10.1051/0004-6361/202038857 ◽

2020 ◽

Vol 643 ◽

pp. A171

Author(s):

J.-M. Hameury ◽

J.-P. Lasota

Keyword(s):

Decay Time ◽

Binary Systems ◽

Compact Object ◽

Accretion Disc ◽

Accretion Discs ◽

X Ray ◽

Analytical Approximations ◽

Accretion Rates ◽

Transient Sources ◽

Peak Luminosity

Context. It is now widely accepted that most ultraluminous X-ray sources (ULXs) are binary systems whose large (above 1039 erg s−1) apparent luminosities are explained by super-Eddington accretion onto a stellar-mass compact object. Many of the ULXs, especially those containing magnetized neutron stars, are highly variable; some exhibit transient behaviour. Large luminosities might imply large accretion discs that could be therefore prone to the thermal–viscous instability known to drive outbursts of dwarf novae and low-mass X-ray binary transient sources. Aims. The aim of this paper is to extend and generalize the X-ray transient disc-instability model to the case of large (outer radius larger than 1012 cm) accretion discs and apply it to the description of systems with super-Eddington accretion rates at outburst and, in some cases, super-Eddington mass transfer rates. Methods. We have used our disc-instability-model code to calculate the time evolution of the accretion disc and the outburst properties. Results. We show that, provided that self-irradiation of the accretion disc is efficient even when the accretion rate exceeds the Eddington value, possibly due to scattering back of the X-ray flux emitted by the central parts of the disc on the outer portions of the disc, heating fronts can reach the disc’s outer edge generating high accretion rates. We also provide analytical approximations for the observable properties of the outbursts. We have successfully reproduced the observed properties of galactic transients with large discs, such as V404 Cyg, as well as some ULXs such as M51 XT-1. Our model can reproduce the peak luminosity and decay time of ESO 243-39 HLX-1 outbursts if the accretor is a neutron star. Conclusions. Observational tests of our predicted relations between the outburst duration and decay time with peak luminosity would be most welcome.

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Color–color diagrams as tools for assessment of the variable absorption in high mass X-ray binaries

Astronomy and Astrophysics ◽

10.1051/0004-6361/202039183 ◽

2020 ◽

Vol 643 ◽

pp. A109

Author(s):

V. Grinberg ◽

M. A. Nowak ◽

N. Hell

Keyword(s):

Stellar Wind ◽

Binary Systems ◽

Compact Object ◽

Spectral Shape ◽

High Mass ◽

Line Of Sight ◽

Current Generation ◽

X Ray ◽

Partial Covering ◽

X Ray Binaries

High mass X-ray binaries hold the promise of allowing us to understand the structure of the winds of their supermassive companion stars by using the emission from the compact object as a backlight to evaluate the variable absorption in the structured stellar wind. The wind along the line of sight can change on timescales as short as minutes and below. However, such short timescales are not available for the direct measurement of absorption through X-ray spectroscopy with the current generation of X-ray telescopes. In this paper, we demonstrate the usability of color–color diagrams for assessing the variable absorption in wind accreting high mass X-ray binary systems. We employ partial covering models to describe the spectral shape of high mass X-ray binaries and assess the implication of different absorbers and their variability on the shape of color–color tracks. We show that in taking into account, the ionization of the absorber, and in particular accounting for the variation of ionization with absorption depth, is crucial to describe the observed behavior well.

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Do neutron stars produce jets?

Canadian Journal of Physics ◽

10.1139/p86-087 ◽

1986 ◽

Vol 64 (4) ◽

pp. 474-478 ◽

Cited By ~ 3

Author(s):

Eric D. Feigelson

Keyword(s):

Neutron Star ◽

Neutron Stars ◽

Supernova Remnants ◽

Binary Systems ◽

Crab Nebula ◽

Compact Object ◽

Radio Pulsars ◽

X Ray ◽

The Crab Nebula ◽

X Ray Binaries

The evidence for jets emanating from neutron stars is reviewed. Isolated radio pulsars do not appear to produce collimated outflows. A few supernova remnants, notably the Crab nebula, exhibit jetlike protrusions at their outer boundaries. These are probably "blowouts" of the plasma in the remnant rather than true jets from a neutron star. However, several cases of degenerate stars in X-ray binary systems do make jets. SS433 has twin precessing jets moving outward at v ~ 0.26c, and Sco X-1 has radio lobes with v ~ 0.0001c. Cyg X-3 appears to eject synchrotron plasmoids at high velocities. Other X-ray binaries associated with variable radio sources are discussed; some are interesting candidates for collimated outflow. G109.1-1.0 is an X-ray binary in a supernova remnant that may have radio or X-ray jets. It is not clear in all these cases, however, that the compact object is a neutron star and not a black hole or white dwarf.A tentative conclusion is reached that isolated neutron stars do not produce jets, but degenerate stars in accreting binary systems can. This suggests that the presence of an accretion disk, rather than the characteristics of an isolated pulsar's dipole magnetosphere, is critical in making collimated outflows.

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Stellar winds in high-mass X-ray binaries

Symposium - International Astronomical Union ◽

10.1017/s0074180900202131 ◽

1995 ◽

Vol 163 ◽

pp. 271-279

Author(s):

Lex Kaper

Keyword(s):

Stellar Wind ◽

Large Scale ◽

Binary Systems ◽

Compact Object ◽

High Mass ◽

X Rays ◽

Ionization Zone ◽

X Ray ◽

Massive Binary Systems ◽

X Ray Binaries

High-mass X-ray binaries (HMXBs) represent an important stage in the evolution of massive binary systems. The compact object (in most cases an X-ray pulsar) not only provides information on the orbital and stellar parameters, but also probes the stellar wind of the massive companion, an OB supergiant or Be star. The X-ray luminosity directly depends on the density and the velocity of the wind at the orbit of the X-ray source. Important constraints on the stellar-wind structure can be set by studying the orbital modulation of UV P-Cygni profiles. In this paper different aspects of the interactive wind-accretion process are highlighted, such as the highly variable X-ray luminosity, the influence of the X-rays on the radiative acceleration of the wind inside the ionization zone, and the large-scale structures that trail the X-ray source in its orbit.

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Inventory of black hole binaries

Symposium - International Astronomical Union ◽

10.1017/s0074180900212448 ◽

2003 ◽

Vol 212 ◽

pp. 365-371 ◽

Cited By ~ 6

Author(s):

Jerome A. Orosz

Keyword(s):

Black Holes ◽

Black Hole ◽

Binary Systems ◽

Compact Object ◽

X Rays ◽

Optical Studies ◽

Dynamical Mass ◽

X Ray ◽

Black Hole Binaries ◽

X Ray Binaries

A small group of X-ray binaries currently provides the best evidence for the existence of stellar-mass black holes. These objects are interacting binary systems where the X-rays arise from accretion of material onto a compact object (i.e., an object with a radius of less than a few hundred km). In some favourable cases, optical studies of the companion star lead to dynamical mass estimates for both components. In 17 cases, the mass of the compact object in an X-ray binary has been shown to exceed the maximum mass of a stable neutron star (about 3 M⊙), which leads to the conclusion that these objects are black holes. In this contribution I will review the basic properties of these black hole binaries.

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The XMM-NEWTON VIEW ON NEUTRON STARS AND BLACK HOLES

International Journal of Modern Physics D ◽

10.1142/s0218271804005365 ◽

2004 ◽

Vol 13 (07) ◽

pp. 1229-1237

Author(s):

CHRISTIAN MOTCH

Keyword(s):

Black Holes ◽

Spectral Analysis ◽

Neutron Stars ◽

Binary Systems ◽

Short Review ◽

High Energy ◽

Compact Objects ◽

High Energy Resolution ◽

X Ray ◽

Physical Conditions

The improved sensitivity of the XMM-Newton satellite is quickly expanding our knowledge of X-ray emission mechanisms and physical conditions in and around compact objects. Thanks to the large collecting power and high energy resolution of the EPIC and RGS instruments, detailed X-ray spectral analysis can be performed in the 0.2 to 12 keV energy range. In this short review, I highlight the most significant results obtained by XMM-Newton on neutron stars both isolated and in binary systems and on accreting stellar mass black holes.

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Population of Accreting Neutron Stars in External Galaxies

Symposium - International Astronomical Union ◽

10.1017/s0074180900160681 ◽

1987 ◽

Vol 125 ◽

pp. 149-159

Author(s):

Ginevra Trinchieri

Keyword(s):

Black Hole ◽

Neutron Star ◽

Binary Systems ◽

Compact Object ◽

Milky Way Galaxy ◽

X Ray ◽

Object A ◽

The Galaxy ◽

Bulge Region ◽

External Galaxies

The X-ray observations of the Milky Way galaxy with non-imaging X-ray satellites (e.g. UHURU, HEAO1) has revealed a number of discrete, point -like bright sources clustered around the Galaxy's center (in the bulge region) and on the plane of the Galaxy (see for example Tanambaum and Tucker, 1984). The brightermost ones have been associated with close accreting binary systems, containing an evolved object (a white dwarf, a neutron star or a black hole) and a companion visible star. For sources with X-ray luminosities Lx≦1038 erg s−1, the compact object needs to be a neutron star or a black hole.

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Accretion disc by Roche lobe overflow in the supergiant fast X-ray transient IGR J08408−4503

Astronomy and Astrophysics ◽

10.1051/0004-6361/201936544 ◽

2019 ◽

Vol 631 ◽

pp. A135 ◽

Cited By ~ 4

Author(s):

L. Ducci ◽

P. Romano ◽

L. Ji ◽

A. Santangelo

Keyword(s):

Binary Systems ◽

Dynamic Range ◽

Compact Object ◽

Accretion Disc ◽

Roche Lobe ◽

Optical Observations ◽

Optical Data ◽

X Ray ◽

Orbital Parameters ◽

Large Size

Supergiant fast X-ray transients (SFXTs) are X-ray binary systems with a supergiant companion and likely a neutron star, which show a fast (∼103 s) and high variability with a dynamic range up to 105−6. Given their extreme properties, they are considered among the most valuable laboratories to test accretion models. Recently, the orbital parameters of a member of this class, IGR J08408−4503, were obtained from optical observations. We used this information, together with X-ray observations from previous publications and new results from X-ray and optical data collected by INTEGRAL and presented in this work, to study the accretion mechanisms at work in IGR J08408−4503. We found that the high eccentricity of the compact object orbit and the large size of the donor star imply Roche lobe overflow (RLO) around the periastron. It is also likely that a fraction of the outer layers of the photosphere of the donor star are lost from the Lagrangian point L2 during the periastron passages. On the basis of these findings, we discuss the flaring variability of IGR J08408−4503 assuming the presence of an accretion disc. We point out that IGR J08408−4503 may not be the only SFXT with an accretion disc fueled by RLO. These findings open a new scenario for accretion mechanisms in SFXTs, since most of them have so far been based on the assumption of spherically symmetric accretion.

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