RT Journal Article
T1 The first heavy-metal hot subdwarf composite binary SB 744
A1 Németh, P.
A1 Vos, J.
A1 Molina González, Francisco
A1 Bastian, A.
AB Aims. A radial velocity follow-up of the long-period sdOB+G1V type spectroscopic binary SB 744 revealed strong lines of fluorineand lead in the optical spectrum of the sdOB star and subsolar metallicity in the G1V companion. With high quality observationsand Gaia astrometric data we aim at measuring the chemical composition and Galactic kinematics of the system to put it in contextwith known populations of hot subdwarfs. Such binary systems have high potential, as they give insights into the late stages of binaryevolution as well as into the mysterious formation of stripped core helium burning stars.Methods. We have analyzed the optical spectra with homogeneous atmospheric models to derive surface parameters of the binarymembers from a direct wavelength space decomposition and independently measured the atmospheric properties of the cool com-panion. The two independent methods reached consistent results, which, amended with constraints from spectral energy distributionsprovided a subdwarf mass. The Gaia astrometry allowed us to derive the Galactic kinematics of the system.Results. SB 744 turned out to be an old, Population II system, that has gone through dramatic events. The hot subdwarf star belongsto the heavy-metal subclass of sdOB stars and we report super-solar abundances of lead, based on Pb iii/iv lines. The He abundanceof the hot subdwarf is the lowest among the known heavy-metal sdOB stars. The presence of fluorine implies that SB 744 was once ahierarchical triple system and the inner binary has merged in the near past. As an alternative scenario, single-star evolution through latecore helium flash and atmospheric mixing can also produce the observed fluorine abundances. The atmospheric metal over-abundancescurrently observed are perhaps the results of a combination of mixing processes during formation and radiative support.
PB EDP Sciences
SN 0004-6361
SN 1432-0746 (electrónico)
YR 2021
FD 2021
LK http://hdl.handle.net/10272/20340
UL http://hdl.handle.net/10272/20340
LA eng
NO Németh, P., Vos, J., Molina, F., & Bastian, A. (2021). The first heavy-metal hot subdwarf composite binary SB 744. In Astronomy & Astrophysics (Vol. 653, p. A3). EDP Sciences. https://doi.org/10.1051/0004-6361/202141442
DS Repositorio Institucional de la Universidad de Huelva
RD 30 may 2026