Probing clumpy stellar winds with a neutron star
Abstract
Context: INTEGRAL, the European Space Agency's γ-ray observatory, tripled the number of super-giant high-mass X-ray binaries (sgHMXB) known in the Galaxy by revealing absorbed and fast transient (SFXT) systems.
Aims: In these sources, quantitative constraints on the wind clumping of the massive stars could be obtained from the study of the hard X-ray variability of the compact accreting object.
Methods: Hard X-ray flares and quiescent emission of SFXT systems have been characterized and used to derive wind clump parameters.
Results: A large fraction of the hard X-ray emission is emitted in the form of flares with a typical duration of 3 ks, frequency of 7 days and luminosity of 1036 erg/s. Such flares are most probably emitted by the interaction of a compact object orbiting at 10 Rast with wind clumps (1022-23 g) representing a large fraction of the stellar mass-loss rate. The density ratio between the clumps and the inter-clump medium is 102-4 in SFXT systems.
Conclusions: The parameters of the clumps and of the inter-clump medium, derived from the SFXT flaring behavior, are in good agreement with macro-clumping scenario and line driven instability simulations. SFXT have probably a larger orbital radius than classical sgHMXB.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- December 2007
- DOI:
- 10.1051/0004-6361:20078353
- arXiv:
- arXiv:0710.2542
- Bibcode:
- 2007A&A...476..335W
- Keywords:
-
- gamma rays: observations;
- X-rays: binaries;
- pulsars: general;
- stars: winds;
- outflows;
- supergiants;
- Astrophysics
- E-Print:
- 8 pages