A partially stripped massive star in a Be binary at low metallicity: a missing link towards Be X-ray binaries and double neutron star mergers
Standard binary evolutionary models predict a significant population of core helium-burning stars that lost their hydrogen-rich envelope after mass transfer via Roche-lobe overflow. However, there is a scarcity of observations of such stripped stars in the intermediate-mass regime (∼1.5 − 8 <i>...
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| Main Authors: | , , , , , , |
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| Format: | Article (Journal) Editorial |
| Language: | English |
| Published: |
2023
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| In: |
Astronomy and astrophysics
Year: 2023, Volume: 674, Pages: 1-21 |
| ISSN: | 1432-0746 |
| DOI: | 10.1051/0004-6361/202346818 |
| Online Access: | lizenzpflichtig lizenzpflichtig 
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| Author Notes: | V. Ramachandran, J. Klencki, A.A.C. Sander, D. Pauli, T. Shenar, L.M. Oskinova, and W.-R. Hamann |
| Summary: | Standard binary evolutionary models predict a significant population of core helium-burning stars that lost their hydrogen-rich envelope after mass transfer via Roche-lobe overflow. However, there is a scarcity of observations of such stripped stars in the intermediate-mass regime (∼1.5 − 8 <i>M<i/><sub>⊙<sub/>), which are thought to be prominent progenitors of SN Ib/c. Especially at low metallicity, a significant fraction of these stars are expected to be only partially stripped, retaining a significant amount of hydrogen on their surfaces. For the first time, we discovered a partially stripped massive star in a binary with a Be-type companion located in the Small Magellanic Cloud (SMC) using a detailed spectroscopic analysis. The stripped-star nature of the primary is revealed by the extreme CNO abundance pattern and very high luminosity-to-mass ratio, which suggest that the primary is likely shell-hydrogen burning. Our target SMCSGS-FS 69 is the most luminous and most massive system among the known stripped star + Be binaries, with <i>M<i/><sub>stripped<sub/> ∼ 3 <i>M<i/><sub>⊙<sub/> and <i>M<i/><sub>Be<sub/> ∼ 17 <i>M<i/><sub>⊙<sub/>. Binary evolutionary tracks suggest an initial mass of <i>M<i/><sub>ini<sub/> ≳ 12 <i>M<i/><sub>⊙<sub/> for the stripped star and predict it to be in a transition phase towards a hot compact He star, which will eventually produce a stripped-envelope supernova. Our target marks the first representative of an as-yet-missing evolutionary stage in the formation pathway of Be X-ray binaries and double neutron star mergers. |
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| Item Description: | Gesehen am 25.10.2023 |
| Physical Description: | Online Resource |
| ISSN: | 1432-0746 |
| DOI: | 10.1051/0004-6361/202346818 |