X-ray emission from BH+O star binaries expected to descend from the observed galactic WR+O binaries

Sen, K.; Xu, Xiao-Tian; Langer, N.; Mellah, I. El; Schürmann, Christoph; Quast, M.

doi:10.1051/0004-6361/202141214

Cited by 26 publications

(23 citation statements)

References 121 publications

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“…Another possible selection effect that could explain the high spins in the observed BH-XRB sample relative to the BBH spin distribution is a correlation between BH-XRB detectability and BH spin. Sen et al (2021) argued that rapidly spinning BHs in BH-XRBs are more likely to form accretion disks that lead to longer and brighter X-ray emission. 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).…”

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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“…Such a disk is expected to radiate energy mostly in X-rays (Frank et al 2002). To estimate whether an accretion disk can form, and the corresponding Xray luminosity, we follow the work of Sen et al (2021). We take the maximum possible unseen companion mass as the mass of the BH, which increases the likelihood of accretion disk formation.…”

Section: Wind Accreting Black Holesmentioning

confidence: 99%

“…In fact, Cyg X-1 is known to contain a maximally spinning BH of 21.2 M (Miller-Jones et al 2021). Assuming that to be the case, the method of Sen et al (2021) does predict an accretion disk radiating about 700 L , a factor of a few smaller than the observed average of ∼2600 L (Orosz et al 2011). Due to the absence of bright X-rays from HD 94024, a 4 M Kerr BH companion can be excluded.…”

Section: Wind Accreting Black Holesmentioning

confidence: 99%

“…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%

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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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“…Such binaries represent an intermediate evolutionary phase that appears in the majority of evolutionary sequences leading to the formation of BH+BH mergers (Belczynski et al 2002;Giacobbo & Mapelli 2018;Kruckow et al 2018;Marchant et al 2019). As such, OB+BH binaries provide crucial constraints on binary evolution, supernova physics, and the presence of BH kicks (e.g., Fryer et al 2012;Vanbeveren et al 2020;Sen et al 2021). Langer et al (2020) predicted that about 2 to 3% of massive stars should host a BH companion, implying that hundreds of such binaries are lurking in Galactic and extragalactic OB-star catalogues.…”

Section: Introductionmentioning

confidence: 99%

The Tarantula Massive Binary Monitoring

Shenar

Sana

Mahy

et al. 2022

A&A

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Context. Massive binaries hosting a black hole (OB+BH) represent a critical phase in the production of BH mergers in the context of binary evolution. In spite of this, such systems have so far largely avoided detection. Single-lined spectroscopic (SB1) O-type binaries are ideal objects to search for elusive BH companions. Moreover, SB1 binaries hosting two main sequence stars probe a regime of more extreme mass ratios and longer periods compared to double-lined binaries (SB2), and are thus valuable for establishing the natal mass ratio distribution of massive stars. Aims. We characterise the hidden companions in 51 SB1 O-type and evolved B-type binaries identified in the Large Magellanic Cloud (LMC) in the framework of the VLT-FLAMES Tarantula Survey (VFTS) and its follow-up, the Tarantula Massive Binary Monitoring (TMBM). The binaries cover periods between few days to years (0 < log P < 3 [d]). Goals are to hunt for BHs and sample the low-mass end of the mass-ratio distribution. Methods. To uncover the hidden companions, we implement the shift-and-add grid disentangling algorithm on 32 epochs of spectroscopy acquired in the framework of TMBM with the FLAMES spectrograph, allowing us to detect companions contributing as little as ≈ 1 − 2% to the visual flux. We further analyse OGLE photometric data for the presence of eclipses or ellipsoidal variations. Results. Out of the 51 SB1 systems, 43 (84%) are found to have non-degenerate stellar companions, of which 28 are confident detections, and 15 are less certain (SB1: or SB2:). Of these 43 targets, one is found to be a triple (VFTS 64), and two are found to be quadruples (VFTS 120, 702). Our sample includes a total of eight eclipsing binaries. The remaining 8 targets (16%) retain an SB1 classification. We model the mass-ratio distribution as f (q) ∝ q κ , and derive κ through a Bayesian approach. We use massratio constraints from previously known SB2 binaries, newly uncovered SB2 binaries, and SB1 binaries, while accounting for binary detection bias. We find κ = 0.2 ± 0.2 for the entire sample and κ = −0.2 ± 0.2 when excluding binaries with periods shorter than 10 d. In contrast, κ = 1.2 ± 0.5 is retrieved for tight binaries (P < 10 d), proposed here to be a consequence of binary interaction. Aside from the unambiguous O+BH binary VFTS 243, analysed in detail in a separate paper, we identify two additional OB+BH candidates: VFTS 514 and 779. Conclusions. Our study firmly establishes a virtually flat natal mass-ratio distribution (κ = 0) for O-type stars at LMC metallicity, covering the entire mass-ratio range (0.05 < q < 1) and periods in the range 0 < log P < 3 [d]. The nature of the OB+BH candidates should be verified through future monitoring, but the frequency of OB+BH candidates is generally in line with recent predictions at LMC metallicity.

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X-ray emission from BH+O star binaries expected to descend from the observed galactic WR+O binaries

Cited by 26 publications

References 121 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

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

The Tarantula Massive Binary Monitoring

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