2007A&A...465L..35L

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 20-40keV energy range. Multi-wavelength observations, combining high-energy and optical data, were used to unveil the nature of IGR J08408-4503. A search in all INTEGRAL public data for other bursts from IGR J08408-4503 was performed, and the detailed analysis of another major flare 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. 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 10¹³cm from the supergiant HD 74194. The clump mass loss rate is of the order of 10^–6M_☉/yr. 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.