Whispering in the dark: Faint X-ray emission from black holes with OB star companions
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| Autores principales: | , , , , , |
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| Formato: | Preprint |
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2024
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| _version_ | 1866912080941023232 |
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| author | Sen, Koushik Mellah, Ileyk El Langer, Norbert Xu, Xiao-Tian Quast, Martin Pauli, Daniel |
| author_facet | Sen, Koushik Mellah, Ileyk El Langer, Norbert Xu, Xiao-Tian Quast, Martin Pauli, Daniel |
| contents | Context. Recent astrometric and spectroscopic surveys of OB stars have revealed a few stellar-mass black holes (BHs) with orbital periods as low as 10 days. No X-ray counterpart has been detected, due to the absence of a radiatively efficient accretion disk around the BH. Yet, dissipative processes in the hot, dilute and strongly magnetized plasma around the BH (so-called BH corona) can still lead to non-thermal X-ray emission (e.g. synchrotron).
Aims. We determine the X-ray luminosity distribution from BH+OB star binaries up to orbital periods of a few thousand days.
Methods. We use detailed binary evolution models computed with MESA for initial primary masses of 10-90 $M_{\odot}$ and orbital periods from 1-3000 d. The X-ray luminosity is computed for a broad range of radiative efficiencies.
Results. We show that particle acceleration through magnetic reconnection can heat the BH corona. A substantial fraction of the gravitational potential energy from the accreted plasma is converted into non-thermal X-ray emission. Our population synthesis analysis predicts at least 28 (up to 72) BH+OB star binaries in the Large Magellanic Cloud (LMC) to produce X-ray luminosity above 10$^{31}$ erg$\,$s$^{-1}$, observable through focused Chandra observations. We identify a population of SB1 systems in the LMC and HD96670 in the Milky Way comprising O stars with unseen companions of masses above 2.3 $M_{\odot}$ that aligns well with our predictions. The predicted luminosities of the OB companions to these X-ray-emitting BHs are 10$^{4.5-5.5}$ $L_{\odot}$.
Conclusions. These results make the case for long-time exposure in X-rays of the stellar-mass BH candidates identified around OB stars. It will constrain the underlying population of X-ray-faint BHs, the evolution from single to double degenerate binaries, and the progenitors of gravitational wave mergers. (Abridged) |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2406_08596 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Whispering in the dark: Faint X-ray emission from black holes with OB star companions Sen, Koushik Mellah, Ileyk El Langer, Norbert Xu, Xiao-Tian Quast, Martin Pauli, Daniel High Energy Astrophysical Phenomena Solar and Stellar Astrophysics Context. Recent astrometric and spectroscopic surveys of OB stars have revealed a few stellar-mass black holes (BHs) with orbital periods as low as 10 days. No X-ray counterpart has been detected, due to the absence of a radiatively efficient accretion disk around the BH. Yet, dissipative processes in the hot, dilute and strongly magnetized plasma around the BH (so-called BH corona) can still lead to non-thermal X-ray emission (e.g. synchrotron). Aims. We determine the X-ray luminosity distribution from BH+OB star binaries up to orbital periods of a few thousand days. Methods. We use detailed binary evolution models computed with MESA for initial primary masses of 10-90 $M_{\odot}$ and orbital periods from 1-3000 d. The X-ray luminosity is computed for a broad range of radiative efficiencies. Results. We show that particle acceleration through magnetic reconnection can heat the BH corona. A substantial fraction of the gravitational potential energy from the accreted plasma is converted into non-thermal X-ray emission. Our population synthesis analysis predicts at least 28 (up to 72) BH+OB star binaries in the Large Magellanic Cloud (LMC) to produce X-ray luminosity above 10$^{31}$ erg$\,$s$^{-1}$, observable through focused Chandra observations. We identify a population of SB1 systems in the LMC and HD96670 in the Milky Way comprising O stars with unseen companions of masses above 2.3 $M_{\odot}$ that aligns well with our predictions. The predicted luminosities of the OB companions to these X-ray-emitting BHs are 10$^{4.5-5.5}$ $L_{\odot}$. Conclusions. These results make the case for long-time exposure in X-rays of the stellar-mass BH candidates identified around OB stars. It will constrain the underlying population of X-ray-faint BHs, the evolution from single to double degenerate binaries, and the progenitors of gravitational wave mergers. (Abridged) |
| title | Whispering in the dark: Faint X-ray emission from black holes with OB star companions |
| topic | High Energy Astrophysical Phenomena Solar and Stellar Astrophysics |
| url | https://arxiv.org/abs/2406.08596 |