| Author(s): |
Motch, C.
;
Lopes de Oliveira, R.
;
Negueruela, I.
;
Haberl, F.
;
Janot-Pacheco, E.
;
Stefl, S
;
Owocki, SP
;
Okazaki, AT
Total Authors: 8
|
| Document type: | Journal article |
| Source: | ACTIVE OB-STARS: LABORATORIES FOR STELLAR AND CIRCUMSTELLAR PHYSICS, PROCEEDINGS; v. 361, p. 2-pg., 2007-01-01. |
| Abstract | |
A growing number of early Be stars discovered in X-ray surveys exhibit X-ray luminosities intermediate between those of normal stars and those of most Be/X-ray binaries in quiescence. Their X-ray spectra are also much harder than those of shocked wind OB stars and can be best fitted by a thin thermal plasma with T similar to 10(8) K, added to a cooler and much fainter thermal component. An iron line complex including a fluorescence component is detected in many cases. There is no evidence for coherent pulsations in any of these systems but strong variability on time scales as short as 100s is usually observed. Large oscillations with quasi-periods of the order of one hour or more are detected in the X-ray light curves of several sources, but have so far failed to prove to be strictly periodic. The optical and X-ray properties of these new objects strikingly resemble those of the so far unique and enigmatic Be star gamma Cas and define a new class of X-ray emitters. We discuss the possible origin of the X-ray emission in the light of the models proposed for gamma Cas, magnetic disc-star interaction or accretion onto a compact companion object - neutron star or white dwarf. (AU) | |
| FAPESP's process: | 03/06861-6 - Search for massive binary X-ray sources in the Galactic Plane with the X-ray multi-mirror satellite (XMM-Newton) |
| Grantee: | Raimundo Lopes de Oliveira Filho |
| Support Opportunities: | Scholarships in Brazil - Doctorate |