Conditions for accretion disc formation and observability of wind-accreting X-ray binaries

Hirai, Ryosuke; Mandel, Ilya

doi:10.1017/pasa.2021.53

Cited by 33 publications

(23 citation statements)

References 86 publications

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“…Furthermore, a correlation between BH spins and X-ray detectability may arise if scenarios for spinning up the BH or its progenitor stellar core are more efficient at small orbital periods and BH-XRBs in tight orbits are more detectable (Qin et al 2019). For example, Hirai & Mandel (2021) argued that HMXB systems are observable only if the companion main-sequence star is close to filling its Roche lobe, which may in turn imply that the system is less likely to survive a common envelope and become a merging BBH system (Neijssel et al 2021). Further detailed modeling of the evolutionary histories of HMXBs, LMXBs, and BBHs will shed insight into the astrophysical and observational effects that distinguish these populations (C. Liotine et al 2021, in preparation;J.…”

Section: Discussionmentioning

confidence: 99%

Apples and Oranges: Comparing Black Holes in X-Ray Binaries and Gravitational-wave Sources

Fishbach

Kalogera

2022

ApJL

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The component black holes (BHs) observed in gravitational-wave (GW) binary black hole (BBH) events tend to be more massive and slower spinning than those observed in black hole X-ray binaries (BH-XRBs). Without modeling their evolutionary histories, we investigate whether these apparent tensions in the BH populations can be explained by GW observational selection effects alone. We find that this is indeed the case for the discrepancy between BH masses in BBHs and the observed high-mass X-ray binaries (HMXBs), when we account for statistical uncertainty from the small sample size of just three HMXBs. On the other hand, the BHs in observed low-mass X-ray binaries (LMXBs) are significantly lighter than the astrophysical BBH population, but this may just be due to a correlation between component masses in a binary system. Given their light stellar companions, we expect light BHs in LMXBs. The observed spins in HMXBs and LMXBs, however, are in tension with the inferred BBH spin distribution at the >99.9% level. We discuss possible scenarios behind the significantly larger spins in observed BH-XRBs. One possibility is that a small subpopulation (conservatively <30%) of BBHs have rapidly spinning primary components, indicating that they may have followed a similar evolutionary pathway to the observed HMXBs. In LMXBs, it has been suggested that BHs can spin up by accretion. If LMXB natal spins follow the BBH spin distribution, we find LMXBs must gain an average dimensionless spin of 0.47 − 0.11 + 0.10 , but if their natal spins follow the observed HMXB spins, the average spin-up must be <0.03.

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Section: Discussionmentioning

confidence: 99%

Apples and Oranges: Comparing Black Holes in X-Ray Binaries and Gravitational-wave Sources

Fishbach

Kalogera

2022

ApJL

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“…In our samples, even for systems with higher v ∞ , the wind velocities at the NS positions are typically v w ≈ 500 km s −1 , and still show very slow wind. However, in some tight binaries, the tidal effects could reduce stellar wind velocity towards the accretor (Hirai & Mandel 2021).…”

Section: Investigating Wind Parameters In Sg Hmxb Systemsmentioning

confidence: 99%

Determination of wind-fed model parameters of neutron stars in high-mass X-ray binaries

Taani

Karino

Song

et al. 2022

Publ. Astron. Soc. Aust.

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We have studied several neutron star high-mass X-ray binaries (HMXBs) with super-giant (SG) companions using a wind-fed binary model associated with the magnetic field. By using the concept of torque balance, the magnetic field parameter determines the mass accretion rate. This would help us to consider the relationship between wind velocity and mass-loss rate. These parameters significantly improve our understanding of the accretion mechanism. The wind velocity is critical in determining the X-ray features. This can be used to identify the ejection process and the stochastic variations in their accretion regimes. However, even in systems with a long orbital period, an accretion disk can be created when the wind velocity is slow. This will allow the HMXB of both types, SG and Be, to be better characterised by deriving accurate properties from these binaries. In addition, we have performed segmentation in the parameter space of donors intended for several SG-HMXB listed in our sample set. The parameter space can be categorised into five regimes, depending on the possibility of disk formation associated with accretion from the stellar wind. This can give a quantitative clarification of the observed variability and the properties of these objects. For most of the systems, we show that the derived system parameters are consistent with the assumption that the system is emitting X-rays through direct accretion. However, there are some sources (LMC X-4, Cen X-3 and OAO1657-415) that are not in the direct accretion regime, although they share similar donor parameters. This may indicate that these systems are transitioning from a normal wind accretion phase to partial RLOF regimes.

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“…However, such X-ray emission only arises in tight binary systems or when the secondary star starts filling its Roche lobe, hence where substantial accretion can occur (e.g. Shapiro et al 1976;Sen et al 2021;Hirai & Mandel 2021). In wider binaries or binaries with largely unevolved stellar companions, it is natural to expect a stellar-mass BH in a quiescent stage, that is without X-ray emission.…”

Section: Introductionmentioning

confidence: 99%

Identifying quiescent compact objects in massive Galactic single-lined spectroscopic binaries

Mahy

Sana

Shenar

et al. 2022

A&A

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Context. The quest to detect dormant stellar-mass black holes (BHs) in massive binaries (i.e. OB+BH systems) is challenging; only a few candidates have been claimed to date, all of which must still be confirmed. Aims. To search for these rare objects, we study 32 Galactic O-type stars that were reported as single-lined spectroscopic binaries (SB1s) in the literature. In our sample we include Cyg X-1, which is known to host an accreting stellar-mass BH, and HD 74194, a supergiant fast X-ray transient, in order to validate our methodology. The final goal is to characterise the nature of the unseen companions to determine if they are main-sequence (MS) stars, stripped helium stars, triples, or compact objects such as neutron stars (NSs) or stellar-mass BHs. Methods. After measuring radial velocities and deriving orbital solutions for all the systems in our sample, we performed spectral disentangling to extract putative signatures of faint secondary companions from the composite spectra. We derived stellar parameters for the visible stars and estimated the mass ranges of the secondary stars using the binary mass function. Variability observed in the photometric TESS light curves was also searched for indications of the presence of putative companions, degenerate or not. Results. In 17 of the 32 systems reported as SB1s, we extract secondary signatures, down to mass ratios of ∼ 0.15. For the 17 newly detected double-lined spectroscopic binaries (SB2s), we derive physical properties of the individual components and discuss why they have not been detected as such before. Among the remaining systems, we identify nine systems with possible NS or low-mass MS companions. For Cyg X-1 and HD 130298, we are not able to extract any signatures for the companions, and the minimum masses of their companions are estimated to be about 7 M . Our simulations show that secondaries with such a mass should be detectable from our dataset, no matter their nature: MS stars, stripped helium stars or even triples. While this is expected for Cyg X-1, confirming our methodology, our simulations also strongly suggest that HD 130298 could be another candidate to host a stellar-mass BH. Conclusions. The quest to detect dormant stellar-mass BHs in massive binaries is far from over, and many more systems need to be scrutinised. Our analysis allows us to detect good candidates, but confirming the BH nature of their companions will require further dedicated monitorings, sophisticated analysis techniques, and multi-wavelength observations.

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Conditions for accretion disc formation and observability of wind-accreting X-ray binaries

Cited by 33 publications

References 86 publications

Apples and Oranges: Comparing Black Holes in X-Ray Binaries and Gravitational-wave Sources

Apples and Oranges: Comparing Black Holes in X-Ray Binaries and Gravitational-wave Sources

Determination of wind-fed model parameters of neutron stars in high-mass X-ray binaries

Identifying quiescent compact objects in massive Galactic single-lined spectroscopic binaries

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