Swift/XRT monitoring of the supergiant fast X-ray transient IGR J18483−0311 for an entire orbital period

• Published in: Monthly notices of the Royal Astronomical Society 2010-01, Vol.401 (3), p.1564-1569
• Main Authors: Romano, P., Sidoli, L., Ducci, L., Cusumano, G., La Parola, V., Pagani, C., Page, K. L., Kennea, J. A., Burrows, D. N., Gehrels, N., Sguera, V., Bazzano, A.
• Format: Article
• Language: English
• Subjects: Astronomy; Astrophysics; Double stars; Earth, ocean, space; Exact sciences and technology; Pulsars; X-rays; X-rays: binaries; X-rays: individual: IGR J18483−0311
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1111/j.1365-2966.2009.15789.x

IGR J18483−0311 is an X-ray pulsar with transient X-ray activity, belonging to the new class of high-mass X-ray binaries called supergiant fast X-ray transients. This system is one of the two members of this class, together with IGR J11215−5952, where both the orbital (18.52 d) and spin period (21 s) are known. We report on the first complete monitoring of the X-ray activity along an entire orbital period of a supergiant fast X-ray transient. These Swift observations, lasting 28 d, cover more than one entire orbital phase consecutively. They are a unique data set, which allows us to constrain the different mechanisms proposed to explain the nature of this new class of X-ray transients. We applied the new clumpy wind model for blue supergiants developed by Ducci et al. to the observed X-ray light curve. Assuming an eccentricity of e= 0.4, the X-ray emission from this source can be explained in terms of the accretion from a spherically symmetric clumpy wind, composed of clumps with different masses, ranging from 1018 g to 5 × 1021 g.