Discovery of a highly magnetic He-sdO star from a double-degenerate binary merger
Dorsch M, Reindl N, Pelisoli I, Heber U, Geier S, Istrate AG, Justham S (2022)
Publication Type: Journal article
Publication year: 2022
Journal
Book Volume: 658
Article Number: L9
DOI: 10.1051/0004-6361/202142880
Abstract
Helium-rich hot subdwarf stars of spectral type O (He-sdO) are considered prime candidates for stellar merger remnants. Such events should lead to the generation of strong magnetic fields. However, no magnetic He-sdO has yet been unambiguously discovered despite the high magnetic rate (20%) among white dwarf stars, the progeny of hot subdwarfs. Here we present the discovery of a strong magnetic field (B = 353 ± 10 kG) from Zeeman-split hydrogen, helium, and metal lines in the optical X-shooter spectrum of an He-sdO and present the first spectroscopic analysis of any magnetic hot subdwarf. For this we used line-blanketed TLUSTY non-local thermodynamic equilibrium models and assumed a simple homogeneous magnetic field. The derived atmospheric parameters Teff = 44 900 ± 1000 K and log g = 5.93 ± 0.15 are typical for He-sdO stars, while the star is less hydrogen-poor than most He-sdOs at log n(He)/n(H) = + 0.28 ± 0.10. The star is a slow rotator (vrot sin i < 40 km s-1). Its chemical composition is N-rich and C- and O-poor, and the Si and S abundances are close to solar. Combining the atmospheric parameters with Gaia parallax and photometry, the stellar radius and luminosity are found to be typical for He-sdOs and place the star on the helium main sequence in the Hertzsprung-Russell diagram. Its mass of 0.93-0.30+0.44 M⊙, although uncertain, appears to be remarkably high. The strong magnetic field along with the atmospheric parameters and metal abundances provide overwhelming evidence for the double-degenerate merger scenario.
Authors with CRIS profile
Matti Dorsch
Dr.Karl-Remeis-Sternwarte Bamberg, Astronomisches Institut
Ulrich Heber
Professur für Astronomie und Astrophysik
Involved external institutions
Universität Potsdam
Germany (DE)
Radboud University Nijmegen
Netherlands (NL)
Peking University (PKU) / 北京大学
China (CN)
Germany (DE)
Radboud University Nijmegen
Netherlands (NL)
Peking University (PKU) / 北京大学
China (CN)
How to cite
APA:
Dorsch, M., Reindl, N., Pelisoli, I., Heber, U., Geier, S., Istrate, A.G., & Justham, S. (2022). Discovery of a highly magnetic He-sdO star from a double-degenerate binary merger. Astronomy & Astrophysics, 658. https://dx.doi.org/10.1051/0004-6361/202142880
MLA:
Dorsch, Matti, et al. "Discovery of a highly magnetic He-sdO star from a double-degenerate binary merger." Astronomy & Astrophysics 658 (2022).
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