A stripped helium star in the potential black hole binary LB-1
- Context The recently claimed discovery of a massive (M-BH = 68(-13)(+11) M-circle dot) black hole in the Galactic solar neighborhood has led to controversial discussions because it severely challenges our current view of stellar evolution. Aims A crucial aspect for the determination of the mass of the unseen black hole is the precise nature of its visible companion, the B-type star LSV +22 25. Because stars of different mass can exhibit B-type spectra during the course of their evolution, it is essential to obtain a comprehensive picture of the star to unravel its nature and, thus, its mass. Methods To this end, we study the spectral energy distribution of LSV +22 25 and perform a quantitative spectroscopic analysis that includes the determination of chemical abundances for He, C, N, O, Ne, Mg, Al, Si, S, Ar, and Fe. Results Our analysis clearly shows that LSV +22 25 is not an ordinary main sequence B-type star. The derived abundance pattern exhibits heavy imprints of the CNO bi-cycle of hydrogen burning, that is, HeContext The recently claimed discovery of a massive (M-BH = 68(-13)(+11) M-circle dot) black hole in the Galactic solar neighborhood has led to controversial discussions because it severely challenges our current view of stellar evolution. Aims A crucial aspect for the determination of the mass of the unseen black hole is the precise nature of its visible companion, the B-type star LSV +22 25. Because stars of different mass can exhibit B-type spectra during the course of their evolution, it is essential to obtain a comprehensive picture of the star to unravel its nature and, thus, its mass. Methods To this end, we study the spectral energy distribution of LSV +22 25 and perform a quantitative spectroscopic analysis that includes the determination of chemical abundances for He, C, N, O, Ne, Mg, Al, Si, S, Ar, and Fe. Results Our analysis clearly shows that LSV +22 25 is not an ordinary main sequence B-type star. The derived abundance pattern exhibits heavy imprints of the CNO bi-cycle of hydrogen burning, that is, He and N are strongly enriched at the expense of C and O. Moreover, the elements Mg, Al, Si, S, Ar, and Fe are systematically underabundant when compared to normal main-sequence B-type stars. We suggest that LSV +22 25 is a stripped helium star and discuss two possible formation scenarios. Combining our photometric and spectroscopic results with the Gaia parallax, we infer a stellar mass of 1.1 +/- 0.5 M-circle dot. Based on the binary system's mass function, this yields a minimum mass of 2-3 M-circle dot for the compact companion, which implies that it may not necessarily be a black hole but a massive neutron- or main sequence star. Conclusions The star LSV +22 25 has become famous for possibly having a very massive black hole companion. However, a closer look reveals that the star itself is a very intriguing object. Further investigations are necessary for complete characterization of this object.…
Verfasserangaben: | Andreas IrrgangORCiD, Stephan GeierORCiDGND, Simon KreuzerORCiDGND, Ingrid Domingos PelisoliORCiD, Ulrich HeberORCiDGND |
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DOI: | https://doi.org/10.1051/0004-6361/201937343 |
ISSN: | 0004-6361 |
ISSN: | 1432-0746 |
Titel des übergeordneten Werks (Englisch): | Astronomy and astrophysics : an international weekly journal |
Verlag: | EDP Sciences |
Verlagsort: | Les Ulis |
Publikationstyp: | Wissenschaftlicher Artikel |
Sprache: | Englisch |
Datum der Erstveröffentlichung: | 01.01.2020 |
Erscheinungsjahr: | 2020 |
Datum der Freischaltung: | 24.03.2023 |
Freies Schlagwort / Tag: | pulsars: individual: LS V+22 25; stars: abundances; stars: chemically peculiar; stars: early-type |
Band: | 633 |
Aufsatznummer: | L5 |
Seitenanzahl: | 9 |
Fördernde Institution: | National Aeronautics and Space AdministrationNational Aeronautics &; Space Administration (NASA); National Science FoundationNational Science; Foundation (NSF) |
Organisationseinheiten: | Mathematisch-Naturwissenschaftliche Fakultät / Institut für Physik und Astronomie |
DDC-Klassifikation: | 5 Naturwissenschaften und Mathematik / 52 Astronomie / 520 Astronomie und zugeordnete Wissenschaften |
Peer Review: | Referiert |
Publikationsweg: | Open Access / Bronze Open-Access |