A semi-analytical treatment to wind accretion in neutron star supergiant high-mass X-ray binaries – I. Eccentric orbits

ABSTRACT We present in this paper a first step toward a semi-analytical treatment of the accretion process in wind-fed neutron star (NS) supergiant X-ray binaries with eccentric orbits. We consider the case of a spherically symmetric wind for the supergiant star and a simplified model for the accretion on to the compact object. A self-consistent calculation of the photoionization of the stellar wind by the X-rays from the accreting NS is included. This effect is convolved with the modulation of the mass accretion rate induced by the eccentric orbit to obtain the expected X-ray luminosity of a system along the orbit. As part of our results, we first show that the bi-modality of low- and high-X-ray luminosity solutions for supergiant X-ray binaries reported in previous papers is likely to result from the effect of the NS approaching first and then moving away from the companion (without coexisting simultaneously). We propose that episodes of strong wind photoionization can give rise to off-states of the sources. Our calculations are applied to the case of a few classical supergiant X-ray binary systems with known eccentricities (Vela X-1, 4U 1907+09, GX 301-2) and to the case of the only supergiant fast X-ray transient with a confirmed eccentric orbit, IGR J08408-4503. The results are compared with observational findings on these sources. We also discuss the next steps needed to expand the calculations toward a more comprehensive treatment in future publications.

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Mass transfer on a nuclear timescale in models of supergiant and ultra-luminous X-ray binaries

Astronomy and Astrophysics ◽

10.1051/0004-6361/201935453 ◽

2019 ◽

Vol 628 ◽

pp. A19 ◽

Cited By ~ 6

Author(s):

M. Quast ◽

N. Langer ◽

T. M. Tauris

Keyword(s):

Mass Transfer ◽

Black Hole ◽

Neutron Star ◽

Roche Lobe ◽

High Mass ◽

X Rays ◽

X Ray ◽

Mass Ratios ◽

X Ray Binaries ◽

Eddington Limit

Context. The origin and number of the Galactic supergiant X-ray binaries is currently not well understood. They consist of an evolved massive star and a neutron star or black-hole companion. X-rays are thought to be generated from the accretion of wind material donated by the supergiant, while mass transfer due to Roche-lobe overflow is mostly disregarded because the high mass ratios of these systems are thought to render this process unstable. Aims. We investigate how the proximity of supergiant donor stars to the Eddington limit, and their advanced evolutionary stage, may influence the evolution of massive and ultra-luminous X-ray binaries with supergiant donor stars (SGXBs and ULXs). Methods. We constructed models of massive stars with different internal hydrogen and helium gradients (H/He gradients) and different hydrogen-rich envelope masses, and exposed them to slow mass-loss to probe the response of the stellar radius. In addition, we computed the corresponding Roche-lobe overflow mass-transfer evolution with our detailed binary stellar evolution code, approximating the compact objects as point masses. Results. We find that a H/He gradient in the layers beneath the surface, as it is likely present in the well-studied donor stars of observed SGBXs, can enable mass transfer in SGXBs on a nuclear timescale with a black-hole or a neutron star accretor, even for mass ratios in excess of 20. In our binary evolution models, the donor stars rapidly decrease their thermal equilibrium radius and can therefore cope with the inevitably strong orbital contraction imposed by the high mass ratio. We find that the orbital period derivatives of our models agree well with empirical values. We argue that the SGXB phase may be preceded by a common-envelope evolution. The envelope inflation near the Eddington limit means that this mechanism more likely occurs at high metallicity. Conclusion. Our results open a new perspective for understanding that SGBXs are numerous in our Galaxy and are almost completely absent in the Small Magellanic Cloud. Our results may also offer a way to find more ULX systems, to detect mass transfer on nuclear timescales in ULX systems even with neutron star accretors, and shed new light on the origin of the strong B-field in these neutron stars.

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Stellar Winds in Massive X-ray Binaries

Proceedings of the International Astronomical Union ◽

10.1017/s1743921317002411 ◽

2016 ◽

Vol 12 (S329) ◽

pp. 355-358

Author(s):

Peter Kretschmar ◽

Silvia Martínez-Núñez ◽

Enrico Bozzo ◽

Lidia M. Oskinova ◽

Joachim Puls ◽

...

Keyword(s):

Compact Object ◽

High Mass ◽

Stellar Winds ◽

X Rays ◽

X Ray ◽

Current State ◽

Wide Range ◽

Strong Winds ◽

The One ◽

X Ray Binaries

AbstractStrong winds from massive stars are a topic of interest to a wide range of astrophysical fields. In High-Mass X-ray Binaries the presence of an accreting compact object on the one side allows to infer wind parameters from studies of the varying properties of the emitted X-rays; but on the other side the accretor’s gravity and ionizing radiation can strongly influence the wind flow. Based on a collaborative effort of astronomers both from the stellar wind and the X-ray community, this presentation attempts to review our current state of knowledge and indicate avenues for future progress.

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Modelling decretion discs in Be/X-ray binaries

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz1757 ◽

2019 ◽

Cited By ~ 4

Author(s):

R O Brown ◽

M J Coe ◽

W C G Ho ◽

A T Okazaki

Keyword(s):

Neutron Star ◽

Orbital Period ◽

Major Axis ◽

High Mass ◽

Model Parameters ◽

Be Stars ◽

Semi Major Axis ◽

X Ray ◽

Smoothed Particle ◽

X Ray Binaries

Abstract As the largest population of high mass X-ray binaries, Be/X-ray binaries provide an excellent laboratory to investigate the extreme physics of neutron stars. It is generally accepted that Be stars possess a circumstellar disc, providing an additional source of accretion to the stellar winds present around young hot stars. Interaction between the neutron star and the disc is often the dominant accretion mechanism. A large amount of work has gone into modelling the properties of these circumstellar discs, allowing for the explanation of a number of observable phenomena. In this paper, smoothed particle hydroynamics simulations are performed whilst varying the model parameters (orbital period, eccentricity, the mass ejection rate of the Be star and the viscosity and orientation of the disc). The relationships between the model parameters and the disc’s characteristics (base gas density, the accretion rate of the neutron star and the disc’s size) are presented. The observational evidence for a dependency of the size of the Be star’s circumstellar disc on the orbital period (and semi-major axis) is supported by the simulations.

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Effect of Compact Objects Near Be Stars

International Astronomical Union Colloquium ◽

10.1017/s0252921100116720 ◽

1987 ◽

Vol 92 ◽

pp. 516-518

Author(s):

Krishna M.V. Apparao ◽

S.P. Tarafdar

Keyword(s):

Black Holes ◽

Neutron Star ◽

Rotation Period ◽

Compact Object ◽

Compact Objects ◽

X Rays ◽

Be Stars ◽

Eccentric Orbit ◽

X Ray ◽

Be Star

Several Be stars are identified with bright X-ray sources. (Rappaport and Van den Heuvel, 1982). The bright X-ray emission and observed periodicities indicate the existence of compact objects (white dwarfs, neutron stars or black holes) near the Be stars. A prime example is the brightest X-ray source A0538-66 in LMC, which contains a neutron star with a rotation period of 59 ms. Apparao (1985) explained the X-ray emission, which occurs in periodic flares, by considering an inclined eccentric orbit for the neutron star around the assumed Be-star. The neutron star when it enters a gas ring (around the Be-star) accreting matter giving out X-rays.The X-ray emission from the compact objects, when the gas ring from the Be-star envelopes the objects, has interesting consequences. The X-ray emission produces an ionized region (compact object Stromgren sphere or COSS) in the gas surrounding the compact object (CO).

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Early neutron star evolution in high-mass X-ray binaries

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa675 ◽

2020 ◽

Vol 494 (1) ◽

pp. 44-49 ◽

Cited By ~ 2

Author(s):

Wynn C G Ho ◽

M J P Wijngaarden ◽

Nils Andersson ◽

Thomas M Tauris ◽

F Haberl

Keyword(s):

Magnetic Field ◽

Neutron Star ◽

Thermal Emission ◽

Equilibrium Phase ◽

High Mass ◽

X Ray ◽

Spin Period ◽

Long Duration ◽

X Ray Binaries ◽

The Magnetic Field

ABSTRACT The application of standard accretion theory to observations of X-ray binaries provides valuable insights into neutron star (NS) properties, such as their spin period and magnetic field. However, most studies concentrate on relatively old systems, where the NS is in its late propeller, accretor, or nearly spin equilibrium phase. Here, we use an analytic model from standard accretion theory to illustrate the evolution of high-mass X-ray binaries (HMXBs) early in their life. We show that a young NS is unlikely to be an accretor because of the long duration of ejector and propeller phases. We apply the model to the recently discovered ∼4000 yr old HMXB XMMU J051342.6−672412 and find that the system’s NS, with a tentative spin period of 4.4 s, cannot be in the accretor phase and has a magnetic field B > a few × 1013 G, which is comparable to the magnetic field of many older HMXBs and is much higher than the spin equilibrium inferred value of a few × 1011 G. The observed X-ray luminosity could be the result of thermal emission from a young cooling magnetic NS or a small amount of accretion that can occur in the propeller phase.

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On the origin of Supergiant Fast X-ray Transients

Proceedings of the International Astronomical Union ◽

10.1017/s1743921318008426 ◽

2018 ◽

Vol 14 (S346) ◽

pp. 193-196

Author(s):

Swetlana Hubrig ◽

Lara Sidoli ◽

Konstantin A. Postnov ◽

Markus Schöller ◽

Alexander F. Kholtygin ◽

...

Keyword(s):

Magnetic Field ◽

Neutron Star ◽

Stellar Wind ◽

Longitudinal Magnetic Field ◽

High Mass ◽

Large Telescope ◽

X Ray ◽

Very Large Telescope ◽

Low X ◽

X Ray Binaries

Abstract. A fraction of high-mass X-ray binaries are supergiant fast X-ray transients. These systems have on average low X-ray luminosities, but display short flares during which their X-ray luminosity rises by a few orders of magnitude. The leading model for the physics governing this X-ray behaviour suggests that the winds of the donor OB supergiants are magnetized. In agreement with this model, the first spectropolarimetric observations of the SFXT IGR J11215-5952 using the FORS 2 instrument at the Very Large Telescope indicate the presence of a kG longitudinal magnetic field. Based on these results, it seems possible that the key difference between supergiant fast X-ray transients and other high-mass X-ray binaries are the properties of the supergiant’s stellar wind and the physics of the wind’s interaction with the neutron star magnetosphere.

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Probing the stellar wind geometry in Vela X-1 with infrared interferometry

Proceedings of the International Astronomical Union ◽

10.1017/s174392131201959x ◽

2012 ◽

Vol 8 (S290) ◽

pp. 197-198

Author(s):

Élodie Choquet ◽

Pierre Kervella ◽

Jean-Baptiste Le Bouquin ◽

Antoine Mérand ◽

Xavier Haubois ◽

...

Keyword(s):

Neutron Star ◽

High Mass ◽

Resolution Limit ◽

X Ray ◽

Upper Limit ◽

Accretion Process ◽

Massive Neutron Star ◽

Infrared Interferometry ◽

X Ray Binaries ◽

K Band

AbstractHigh-mass X-ray Binaries (HMXBs) are keys to study stellar remnants that are otherwise extremely faint and difficult to observe when isolated. Vela X-1 is a well-known eclipsing HMXB composed of a very massive neutron star orbiting a B0.5I supergiant with a period of 9 days. The supergiant wind is the main feeding material for the accreting neutron star, and its properties are of prime interest to understand the physics at stakes in the accretion process.In order to characterize the geometry and physical properties of the dense wind at a scale of a few stellar radii, we obtained infrared interferometric observations of Vela X-1 in 2010 using the VLTI/AMBER instrument in the K band (2.2 μm), and in 2012 using the VLTI/PIONIER instrument in the H band (1.6 μm).Although the apparent disk of the supergiant and the orbital separation of the two objects are beyond the present resolution limit of the VLTI, the K-band observations partially resolve the wind envelope on the two longest baselines. We were able to measure the radius of 265±82 R⊙ for the circumstellar wind at a temperature of 1300 K, assuming a distance of 1.9 kpc. The H-band observations do not resolve the system, and we were able to set an upper limit of 112 R⊙ for the envelope radius at a temperature of 1800 K.

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The MAVERIC Survey: Variable Jet-accretion Coupling in Luminous Accreting Neutron Stars in Galactic Globular Clusters

The Astrophysical Journal ◽

10.3847/1538-4357/ac2c6b ◽

2021 ◽

Vol 923 (1) ◽

pp. 88

Author(s):

Teresa Panurach ◽

Jay Strader ◽

Arash Bahramian ◽

Laura Chomiuk ◽

James C. A. Miller-Jones ◽

...

Keyword(s):

Black Holes ◽

Neutron Star ◽

Radio Emission ◽

Neutron Stars ◽

Globular Clusters ◽

Radio Continuum ◽

X Rays ◽

X Ray ◽

Galactic Globular Clusters ◽

X Ray Binaries

Abstract Accreting neutron stars in low-mass X-ray binaries show outflows—and sometimes jets—in the general manner of accreting black holes. However, the quantitative link between the accretion flow (traced by X-rays) and outflows and/or jets (traced by radio emission) is much less well understood for neutron stars than for black holes, other than the general observation that neutron stars are fainter in the radio at a given X-ray luminosity. We use data from the deep MAVERIC radio continuum survey of Galactic globular clusters for a systematic radio and X-ray study of six luminous (L X > 1034 erg s−1) persistent neutron star X-ray binaries in our survey, as well as two other transient systems also captured by our data. We find that these neutron star X-ray binaries show an even larger range in radio luminosity than previously observed. In particular, in quiescence at L X ∼ 3 × 1034 erg s−1, the confirmed neutron star binary GRS 1747–312 in Terzan 6 sits near the upper envelope of the black hole radio/X-ray correlation, and the persistently accreting neutron star systems AC 211 (in M15) and X1850–087 (in NGC 6712) show unusual radio variability and luminous radio emission. We interpret AC 211 as an obscured “Z source” that is accreting at close to the Eddington limit, while the properties of X1850–087 are difficult to explain, and motivate future coordinated radio and X-ray observations. Overall, our results show that neutron stars do not follow a single relation between inflow and outflow, and confirm that their accretion dynamics are more complex than for black holes.

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Evidence from high-mass X-ray binaries that Galactic WR components of WR+O binaries end their life with a supernova explosion

Astronomy and Astrophysics ◽

10.1051/0004-6361/201937253 ◽

2020 ◽

Vol 636 ◽

pp. A99 ◽

Cited By ~ 3

Author(s):

D. Vanbeveren ◽

N. Mennekens ◽

E. P. J. van den Heuvel ◽

J. Van Bever

Keyword(s):

Black Hole ◽

Neutron Star ◽

Supernova Explosion ◽

Solar Neighborhood ◽

High Mass ◽

Population Number ◽

X Ray ◽

Theoretical Population ◽

X Ray Binaries

Context. Theoretical population number studies of binaries with at least one black hole (BH) component obviously depend on whether or not BHs receive a (natal) kick during their formation. Aims. Several observational facts seem to indicate that BHs do indeed receive a kick during their formation. In the present paper, we discuss additional evidence of this. Methods. The progenitors of wind-fed high-mass X-ray binaries (HMXB) with a BH component (BH HMXB) are WR+OB binaries where the Wolf–Rayet (WR) star will finally collapse and form the BH. Starting from the observed population of WR+OB binaries in the solar neighborhood, we predict the population of wind-fed BH HMXBs as a function of the BH-natal kick. Results. The simulations reveal that when WR stars collapse into a BH with a zero or low kick, we should expect 100 or more wind-fed BH HMXBs in the solar neighborhood, whereas only one is observed (Cyg X-1). We consider this as evidence that either WR components in binaries end their life as a neutron star or that they collapse into BHs, both accompanied by a supernova explosion imparting significant (natal) kicks.

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