TY - JOUR
T1 - A partially stripped massive star in a Be binary at low metallicity
T2 - A missing link towards Be X-ray binaries and double neutron star mergers
AU - Ramachandran, V.
AU - Klencki, J.
AU - Sander, A. A.C.
AU - Pauli, D.
AU - Shenar, T.
AU - Oskinova, L. M.
AU - Hamann, W. R.
N1 - Publisher Copyright:
© The Authors 2023.
PY - 2023/6/1
Y1 - 2023/6/1
N2 - 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 (â ¼1.5â ââ 8â Mâ ), 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 Mstrippedâ â ¼â 3â Mâ and MBeâ â ¼â 17âMâ . Binary evolutionary tracks suggest an initial mass of Miniâ â³â 12â Mâ 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.
AB - 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 (â ¼1.5â ââ 8â Mâ ), 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 Mstrippedâ â ¼â 3â Mâ and MBeâ â ¼â 17âMâ . Binary evolutionary tracks suggest an initial mass of Miniâ â³â 12â Mâ 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.
KW - Be
KW - Binaries: spectroscopic
KW - Stars: early-type
KW - Stars: emission-line
KW - Stars: fundamental parameters
KW - Stars: massive
KW - Stars: neutron
UR - http://www.scopus.com/inward/record.url?scp=85163543603&partnerID=8YFLogxK
U2 - 10.1051/0004-6361/202346818
DO - 10.1051/0004-6361/202346818
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AN - SCOPUS:85163543603
SN - 0004-6361
VL - 674
JO - Astronomy and Astrophysics
JF - Astronomy and Astrophysics
M1 - L12
ER -