The Tarantula massive binary monitoring VII. The nature of the eccentric O+BH binary candidate VFTS 812
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arXiv
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| Auteurs principaux: | , , , , , , , , , , , |
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| Format: | Preprint |
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2026
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| _version_ | 1866911452210659328 |
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| author | Deshmukh, K. Sana, H. Verhamme, O. Willcox, R. Marchant, P. Shenar, T. Backs, F. Janssens, S. Ludwig, B. Mahy, L. Sundqvist, J. O. Villaseñor, J. I. |
| author_facet | Deshmukh, K. Sana, H. Verhamme, O. Willcox, R. Marchant, P. Shenar, T. Backs, F. Janssens, S. Ludwig, B. Mahy, L. Sundqvist, J. O. Villaseñor, J. I. |
| contents | Massive O-type stars ($M\gtrsim15\,M_\odot$) with an X-ray quiet black hole (BH) companion represent a crucial stage in massive binary evolution leading to binary BH mergers. The population of such binaries remains elusive, with $\lesssim5$ candidate or confirmed systems. The Tarantula nebula harbors thousands of massive stars, 2-3 % of which are expected to have BH companions. It is therefore an ideal place to hunt for such systems. Here we analyse 30 epochs of VLT/FLAMES IFU high-resolution observations of the H$δ$ region, as well as archival FLAMES spectroscopy, of VFTS 812, a 17-day single-lined spectroscopic binary with an O4V primary and a minimum secondary mass of $5.1\,M_\odot$. Following careful removal of the nebular contamination, spectral disentangling on the new data did not reveal any signature of the hidden companion. We derive $T_\mathrm{eff}=49^{+3}_{-4}$ kK, $\log L/L_\odot=5.7\pm0.1$ and $v_\mathrm{rot,max}{\rm \,sin\,}i=110^{+25}_{-35}$ km/s for the O4V component, yielding a (single star) evolutionary mass of $53^{+6}_{-5}$ $M_\odot$ and an age in the range of 0-1.6 Myr. Using injection tests of various luminous artificial companions in our data, we exhaustively rule out the presence of any luminous signature from a main sequence star more massive than $6\,M_\odot$. We discuss the possible nature of the companion, suggesting that the rejuvenated O star + BH companion is the most suitable scenario to consistently explain the location, (rejuvenated) young age, eccentricity and lack of companion signature. While this establishes VFTS 812 as a strong candidate O+BH system, follow-up observations are deemed necessary for robust confirmation and to search for accretion signatures on the O4V star. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2602_03650 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | The Tarantula massive binary monitoring VII. The nature of the eccentric O+BH binary candidate VFTS 812 Deshmukh, K. Sana, H. Verhamme, O. Willcox, R. Marchant, P. Shenar, T. Backs, F. Janssens, S. Ludwig, B. Mahy, L. Sundqvist, J. O. Villaseñor, J. I. Solar and Stellar Astrophysics Massive O-type stars ($M\gtrsim15\,M_\odot$) with an X-ray quiet black hole (BH) companion represent a crucial stage in massive binary evolution leading to binary BH mergers. The population of such binaries remains elusive, with $\lesssim5$ candidate or confirmed systems. The Tarantula nebula harbors thousands of massive stars, 2-3 % of which are expected to have BH companions. It is therefore an ideal place to hunt for such systems. Here we analyse 30 epochs of VLT/FLAMES IFU high-resolution observations of the H$δ$ region, as well as archival FLAMES spectroscopy, of VFTS 812, a 17-day single-lined spectroscopic binary with an O4V primary and a minimum secondary mass of $5.1\,M_\odot$. Following careful removal of the nebular contamination, spectral disentangling on the new data did not reveal any signature of the hidden companion. We derive $T_\mathrm{eff}=49^{+3}_{-4}$ kK, $\log L/L_\odot=5.7\pm0.1$ and $v_\mathrm{rot,max}{\rm \,sin\,}i=110^{+25}_{-35}$ km/s for the O4V component, yielding a (single star) evolutionary mass of $53^{+6}_{-5}$ $M_\odot$ and an age in the range of 0-1.6 Myr. Using injection tests of various luminous artificial companions in our data, we exhaustively rule out the presence of any luminous signature from a main sequence star more massive than $6\,M_\odot$. We discuss the possible nature of the companion, suggesting that the rejuvenated O star + BH companion is the most suitable scenario to consistently explain the location, (rejuvenated) young age, eccentricity and lack of companion signature. While this establishes VFTS 812 as a strong candidate O+BH system, follow-up observations are deemed necessary for robust confirmation and to search for accretion signatures on the O4V star. |
| title | The Tarantula massive binary monitoring VII. The nature of the eccentric O+BH binary candidate VFTS 812 |
| topic | Solar and Stellar Astrophysics |
| url | https://arxiv.org/abs/2602.03650 |