Stellar wind in state transitions of high-mass X-ray binaries

Čechura, Jan; Hadrava, Petr

doi:10.1051/0004-6361/201424636

Cited by 23 publications

(23 citation statements)

References 24 publications

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“…In this all-or-nothing approach, it can only be guessed which critical ionization parameter is realistic because the dominant ions are unknown and sharply depend on the stellar properties and chemical composition. Even in this case, the sudden quenching assumed by Manousakis & Walter (2015b) or the even steady decrease of the acceleration assumed byČechura & Hadrava (2015) has been shown to be a far too simplified approximation (Sander et al 2018). Instead, El Mellah et al (2019a relied on the 1D line acceleration profile computed by Sander et al (2018) for the donor star in Vela X-1, but assumed that the nonisotropic 3D features induced by the orbital motion in their simulations had no significant effect on this profile, but were purely a function of the distance to the donor star.…”

Section: Taxonomy Of Wind Modelsmentioning

confidence: 94%

“…Similarly, the 2D and 3D simulations ran byČechura & Hadrava (2015), which are primarily tailored to the properties of Cygnus X-1, another wind-fed high-mass X-ray binary, Blondin et al (1990), Manousakis et al (2012), Walter (2015a,b), andEl Mellah et al (2019a) did not handle the effect of the X-rays on wind acceleration in the same way. Because of their multidimensional aspect, none of these simulations can afford to treat radiative transfer in a way as realistic as the studies above.…”

Section: Taxonomy Of Wind Modelsmentioning

confidence: 99%

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Revisiting the archetypical wind accretor Vela X-1 in depth

Kretschmar

Mellah

Martínez-Núñez

et al. 2021

A&A

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Context. The Vela X-1 system is one of the best-studied X-ray binaries because it was detected early, has persistent X-ray emission, and a rich phenomenology at many wavelengths. The system is frequently quoted as the archetype of wind-accreting high-mass X-ray binaries, and its parameters are referred to as typical examples. Specific values for these parameters have frequently been used in subsequent studies, however, without full consideration of alternatives in the literature, even more so when results from one field of astronomy (e.g., stellar wind parameters) are used in another (e.g., X-ray astronomy). The issues and considerations discussed here for this specific, very well-known example will apply to various other X-ray binaries and to the study of their physics. Aims. We provide a robust compilation and synthesis of the accumulated knowledge about Vela X-1 as a solid baseline for future studies, adding new information where available. Because this overview is targeted at a broader readership, we include more background information on the physics of the system and on methods than is usually done. We also attempt to identify specific avenues of future research that could help to clarify open questions or determine certain parameters better than is currently possible. Methods. We explore the vast literature for Vela X-1 and on modeling efforts based on this system or close analogs. We describe the evolution of our knowledge of the system over the decades and provide overview information on the essential parameters. We also add information derived from public data or catalogs to the data taken from the literature, especially data from the Gaia EDR3 release. Results. We derive an updated distance to Vela X-1 and update the spectral classification for HD 77518. At least around periastron, the supergiant star may be very close to filling its Roche lobe. Constraints on the clumpiness of the stellar wind from the supergiant star have improved, but discrepancies persist. The orbit is in general very well determined, but a slight difference exists between the latest ephemerides. The orbital inclination remains the least certain factor and contributes significantly to the uncertainty in the neutron star mass. Estimates for the stellar wind terminal velocity and acceleration law have evolved strongly toward lower velocities over the years. Recent results with wind velocities at the orbital distance in the range of or lower than the orbital velocity of the neutron star support the idea of transient wind-captured disks around the neutron star magnetosphere, for which observational and theoretical indications have emerged. Hydrodynamic models and observations are consistent with an accretion wake trailing the neutron star. Conclusions. With its extremely rich multiwavelength observational data and wealth of related theoretical studies, Vela X-1 is an excellent laboratory for exploring the physics of accreting X-ray binaries, especially in high-mass systems. Nevertheless, much room remains to improve the accumulated knowledge. On the observational side, well-coordinated multiwavelength observations and observing campaigns addressing the intrinsic variability are required. New opportunities will arise through new instrumentation, from optical and near-infrared interferometry to the upcoming X-ray calorimeters and X-ray polarimeters. Improved models of the stellar wind and flow of matter should account for the non-negligible effect of the orbital eccentricity and the nonspherical shape of HD 77581. There is a need for realistic multidimensional models of radiative transfer in the UV and X-rays in order to better understand the wind acceleration and effect of ionization, but these models remain very challenging. Improved magnetohydrodynamic models covering a wide range of scales are required to improve our understanding of the plasma-magnetosphere coupling, and they are thus a key factor for understanding the variability of the X-ray flux and the torques applied to the neutron star. A full characterization of the X-ray emission from the accretion column remains another so far unsolved challenge.

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Section: Taxonomy Of Wind Modelsmentioning

confidence: 94%

Section: Taxonomy Of Wind Modelsmentioning

confidence: 99%

Revisiting the archetypical wind accretor Vela X-1 in depth

Kretschmar

Mellah

Martínez-Núñez

et al. 2021

A&A

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“…The X-ray flux from the pulsar is also expected to affect the wind of Wray 977, leading to further distortions in its structure (e.g. Blondin 1994, Cechura & Hadrava 2015.…”

Section: Resolving the Stellar Wind In Bp Cru / Gx 301-2mentioning

confidence: 99%

Optical interferometry of High-Mass X-ray Binaries: Resolving wind, disk and jet outflows at sub-milliarcsecond scale

et al. 2018

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Because of their small angular size < 1 mas, spatial information on High-mass X-ray binaries (HMXB) has typically been inferred from photometry or spectroscopy. Optical interferometry offers the possibility to spatially resolve such systems, but has been traditionally limited to bright targets or low spectral resolution. The VLTI instrument GRAVITY, working in the near-infrared K band, achieves unprecedented precision in differential interferometric quantities at high spectral resolution, allowing to study HMXBs through the lens of optical interferometry for the first time. We present GRAVITY observations on two X-ray binaries: the microquasar SS 433 and the supergiant HMXB BP Cru. The former is the only known steady super-Eddington accretor in the Galaxy and is in a unique stage of binary evolution, with probable ties to at least part of the ULX population. With GRAVITY, we resolve its massive winds and optical baryonic jets for the first time, finding evidence for powerful equatorial outflows and photoionization as the main heating process along the jets. BP Cru harbors an X-ray pulsar accreting from the wind of its early-blue hypergiant companion Wray 977. The GRAVITY observations resolve the inner parts of the stellar wind and allow probing the influence of the orbiting pulsar on the circumstellar environment.

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“…In summary, there is ample evidence that the pulsar is closely interacting with the stellar environment in BP Cru. Recent 3D hydrodynamical simulations to study simultaneously the gravitational and radiation effects of the compact object on the stellar wind of HMXBs support that these interactions should play an important role in such systems (Walder et al 2014;Čechura & Hadrava 2015).…”

Section: The Radiation Influence Of the Pulsarmentioning

confidence: 99%

Submilliarcsecond Optical Interferometry of the High-mass X-Ray Binary BP Cru with VLTI/GRAVITY

Waisberg¹,

Dexter²,

Pfuhl³

et al. 2017

ApJ

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We observe the high-mass X-ray binary (HMXB) BP Cru using interferometry in the near-infrared K band with VLTI/GRAVITY. Continuum visibilities are at most partially resolved, consistent with the predicted size of the hypergiant. Differential visibility amplitude ( V 5% D| |) and phase ( 2 f D~) signatures are observed across the He I 2.059 m m and Brγ lines, the latter seen strongly in emission, unusual for the donor star's spectral type. For a baseline B 100 m, the differential phase rms 0 . 2  corresponds to an astrometric precision of 2 as m . We generalize expressions for image centroid displacements and variances in the marginally resolved limit of interferometry to spectrally resolved data, and use them to derive model-independent properties of the emission such as its asymmetry, extension, and strong wavelength dependence. We propose geometric models based on an extended and distorted wind and/or a high-density gas stream, which has long been predicted to be present in this system. The observations show that optical interferometry is now able to resolve HMXBs at the spatial scale where accretion takes place, and therefore to probe the effects of the gravitational and radiation fields of the compact object on its environment.

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Stellar wind in state transitions of high-mass X-ray binaries

Cited by 23 publications

References 24 publications

Revisiting the archetypical wind accretor Vela X-1 in depth

Revisiting the archetypical wind accretor Vela X-1 in depth

Optical interferometry of High-Mass X-ray Binaries: Resolving wind, disk and jet outflows at sub-milliarcsecond scale

Submilliarcsecond Optical Interferometry of the High-mass X-Ray Binary BP Cru with VLTI/GRAVITY

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