Probing the Stellar Wind of the Wolf–Rayet Star in IC 10 X-1

We present a statistical analysis of the He ii 4686 emission line in the spectra of the black hole and Wolf-Rayet (WR) star of the high-mass X-ray binary IC10 X-1. This line is visibly skewed, and the third moment (skewness) varies with the binary’s orbital phase. We describe a new method of extracting such weak/faint features lying barely above a noisy continuum. Using the moments of these features, we have been able to decompose these skewed lines into two symmetric Gaussian profiles as a function of the orbital phase. The astrophysical implications of this decomposition are significant due to the complex nature of wind-accretion stream interactions in such binary systems. Previous studies have already shown a 0.25 phase lag in the radial velocity curve of the star and the X-ray eclipse, which indicates that the He ii emitters might be in the stellar wind, hence not tracing the star’s orbital motion. Results from this work further suggest the existence of two separate emitting regions, one in the stellar wind in the shadow of the WR star, and another in the accretion stream that impacts the black hole’s outer accretion disk; and the observed skewed He ii lines can be reproduced by superposition of the two corresponding time-dependent Gaussian emission profiles.

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Accreting black holes skewing and bending the optical emission from massive Wolf–Rayet companions – a case study of IC10 X-1

Bhattacharya

Christodoulou

Chené

et al. 2023

Monthly Notices of the Royal Astronomical Society

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On the Short-period Eclipsing High-mass X-Ray Binary in NGC 4214

Lin,

Soria,

Swartz

2023

ApJ

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We present the results of our study of the luminous (L X ≈ 1039 erg s−1) X-ray binary CXOU J121538.2+361921 in NGC 4214, the high-mass X-ray binary with the shortest known orbital period. Using Chandra data, we confirm the ≈13,000 s (3.6 hr) eclipse period, and an eclipse duration of ≈2000 s. From this, we estimate a mass ratio M 2/M 1 ≳ 3 and a stellar density ρ ≈ 6 g cm−3, which implies that the donor must be a Wolf–Rayet or a stripped helium star. The eclipse egress is consistently much slower than the ingress. This can be explained by denser gas located either in front of the compact object (as expected for a bow shock) or trailing the donor star (as expected for a shadow wind, launched from the shaded side of the donor). There is no change in X-ray spectral shape with changing flux during the egress, which suggests either variable partial covering of the X-ray source by opaque clumps or, more likely, a gray opacity dominated by electron scattering in a highly ionized medium. We identify the optical counterpart from Hubble images. Photometry blueward of ∼5500 Å indicates a bright (M B ≈ −3.6 ± 0.3 mag, for a range of plausible extinctions), hot (T ≈ 90,000 ± 30,000 K) emitter, consistent with the Wolf–Rayet scenario. There is also a bright (M I ≈ −5.2 mag), cool (T ≈ 2700 ± 300 K) component consistent with an irradiated circumbinary disk or with a chance projection of an unrelated asymptotic giant branch star along the same line of sight.

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IC 10 X-1: A Double Black Hole Progenitor Probably Formed through Stable Mass Transfer

Wang,

Shao,

et al. 2024

ApJ

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IC 10 X-1 is one of the close X-ray binaries containing a Wolf–Rayet donor, which can provide an evolutionary link between high-mass X-ray binaries and gravitational wave sources. It is still unclear about the precise nature of the accreting compact object in IC 10 X-1, although it looks more like a black hole (BH) than a neutron star. In this work, we use a binary population synthesis method to simulate the formation of IC 10 X-1–like binaries by assuming different common-envelope ejection efficiencies. This work represents a big step forward over previous studies since we adopt new criteria for mass-transfer stability. These criteria allow the formation of IC 10 X-1–like systems without experiencing common envelope evolution. Based on our calculations, we propose that the compact object in IC 10 X-1 is a BH with a mass of ∼10–30 M ⊙ and the progenitor evolution of this binary probably just experienced stable mass transfer.

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Probing the Stellar Wind of the Wolf–Rayet Star in IC 10 X-1

Cited by 3 publications

References 45 publications

Accreting black holes skewing and bending the optical emission from massive Wolf–Rayet companions – a case study of IC10 X-1

Accreting black holes skewing and bending the optical emission from massive Wolf–Rayet companions – a case study of IC10 X-1

On the Short-period Eclipsing High-mass X-Ray Binary in NGC 4214

IC 10 X-1: A Double Black Hole Progenitor Probably Formed through Stable Mass Transfer

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