| Texto completo | |
| Autor(es): |
El-Badry, Kareem
;
Conroy, Charlie
;
Quataert, Eliot
;
Rix, Hans-Walter
;
Labadie-Bartz, Jonathan
;
Jayasinghe, Tharindu
;
Thompson, Todd
;
Cargile, Phillip
;
Stassun, Keivan G.
;
Ilyin, Ilya
Número total de Autores: 10
|
| Tipo de documento: | Artigo Científico |
| Fonte: | Monthly Notices of the Royal Astronomical Society; v. 516, n. 3, p. 29-pg., 2022-09-19. |
| Resumo | |
Motivated by recent suggestions that many Be stars form through binary mass transfer, we searched the APOGEE survey for Be stars with bloated, stripped companions. From a well-defined parent sample of 297 Be stars, we identified one mass-transfer binary, HD 15124. The object consists of a main-sequence Be star (M-Be = 5.3 +/- 0.6 M-circle dot) with a low-mass (M-donor = 0.92 +/- 0.22 M-circle dot), subgiant companion on a 5.47-d orbit. The emission lines originate in an accretion disc caused by ongoing mass transfer, not from a decretion disc as in classical Be stars. Both stars have surface abundances bearing imprint of CNO processing in the donor's core: the surface helium fraction is Y-He approximate to 0.6, and the nitrogen-to-carbon ratio is 1000 times the solar value. The system's properties are well-matched by binary evolution models in which mass transfer begins while a 3-5 M-circle dot donor leaves the main sequence, with the originally less massive component becoming the Be star. These models predict that the system will soon become a detached Be + stripped star binary like HR 6819 and LB-1, with the stripped donor eventually contracting to become a core helium-burning sdO/B star. Discovery of one object in this short-lived (similar to 1 Myr) evolutionary phase implies the existence of many more that have already passed through it and are now Be + sdO/B binaries. We infer that (10-60) per cent of Be stars have stripped companions, most of which are similar to 100 x fainter than the Be stars in the optical. Together with the dearth of main-sequence companions to Be stars and recent discovery of numerous Be + sdO/B binaries in the UV, our results imply that binarity plays an important role in the formation of Be stars. (AU) | |
| Processo FAPESP: | 17/23731-1 - Análise e Modelagem de uma Grande Amostra de Estrelas Be Galácticas |
| Beneficiário: | Jonathan Michael Labadie-Bartz |
| Modalidade de apoio: | Bolsas no Brasil - Pós-Doutorado |