The peculiar O9.5V star BD+53°2790, the massive counterpart to the X-ray binary system 4U 2206+54

Blay, P.; Reglero, Víctor
Referencia bibliográfica

Société Royale des Sciences de Liège, Bulletin, vol. 80, p. 634-638 (Proceedings of the 39th Liège Astrophysical Colloquium, held in Liège 12-16 July 2010, edited by G. Rauw, M. De Becker, Y. Nazé, J.-M. Vreux, P. Williams)

Fecha de publicación:
1
2011
Número de autores
2
Número de autores del IAC
0
Número de citas
1
Número de citas referidas
1
Descripción
The X-ray binary system 4U 2206+54 hides many mysteries. Among them, the surprising behavior of both of its co components: the O9.5 dwarf star BD+53°2790 and a slowly rotating neutron star. BD+53°2790 misled the astronomers, exhibiting characteristics reminiscent of Be stars. However, a deeper spectral analysis and more intense monitoring revealed that the real picture was a bit more complicated: a) Although it shows evidence of a circumstellar envelope, its observable properties differ from those typical of envelopes in Be stars. b) Comparison with spectral standards and models indicates a possible over-abundance in He. This would open the possibility to link the behavior of BD+53°2790 to the He-rich class of stars. c) UV spectra show an abnormally slow and dense wind for an O9.5V star. d) Spectral classification in the IR wavelength region suggest a more likely supergiant nature of the source, in contradiction with the optical classification. e) The presence of an intense magnetic field is under investigation. BD+53°2790 stands as a perfect laboratory for testing stellar structure, as well as wind and evolutionary theories. The observable properties of this source in a wide range of spectral bands are discussed, and some interpretations outlined.