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Centro de Astrofísica da Universidade do Porto

Hard X-ray flares in IGR J08408-4503 unveil clumpy stellar winds

J.-C. Leyder, R. Walter, M. Lazos, N. Massetti, N. Produit

Abstract
Context: .A 1000-s flare from a new hard X-ray transient, IGR J08408-4503, was observed by INTEGRAL on May 15, 2006 during the real-time routine monitoring of IBIS/ISGRI images performed at the INTEGRAL Science Data Centre. The flare, detected during a single one-hour long pointing, peaked at 250 mCrab in the 20-40 keV energy range.
Aims: .Multi-wavelength observations, combining high-energy and optical data, were used to unveil the nature of IGR J08408-4503.
was performed, and the detailed analysis of another major Methods: .A search in all INTEGRAL public data for other bursts from IGR J08408-4503flare is presented. The results of two Swift Target of Opportunity observations are also described. Finally, a study of the likely optical counterpart, HD 74194, is provided.
Results: .IGR J08408-4503 is very likely a supergiant fast X-ray transient (SFXT) system. The system parameters indicate that the X-ray flares are probably related to the accretion of wind clumps on a compact object orbiting about 1013 cm from the supergiant HD 74194. The clump mass loss rate is of the order of 10-6 Mȯ yr-1.
Conclusions: .Hard X-ray flares from SFXTs allow to probe the stellar winds of massive stars, and could possibly be associated with wind perturbations due to line-driven instabilities.

Astronomy and Astrophysics
Volume 465, Page L35
April 2007

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