The Swift Supergiant Fast X-ray Transients Project: recent results

P. Romano; S. Vercellone; V. La Parola; G. Cusumano; V. Mangano; P. Esposito; J. A. Kennea; D. N. Burrows; H. A. Krimm; C. Pagani; N. Gehrels

arXiv · 1103.6036

The Swift Supergiant Fast X-ray Transients Project: recent results

P. Romano·S. Vercellone·V. La Parola·G. Cusumano·V. Mangano·P. Esposito·J. A. Kennea·D. N. Burrows·H. A. Krimm·C. Pagani·N. Gehrels

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Abstract

We present an overview of our Supergiant Fast X-ray Transients (SFXT) project, that started in 2007, by highlighting the unique observational contribution Swift is giving to this exciting new field. By means of outburst detection with Swift/BAT and follow-up with Swift/XRT, we demonstrated that while the brightest phase of the outburst only lasts a few hours, further significant activity is observed at lower fluxes for a considerably longer (weeks) time. After intense monitoring with Swift/XRT, we now have a firm estimate of the time SFXTs spend in each phase. The 4 SFXTs we monitored for 1-2 years spend between 3 and 5 % of the time in bright outbursts. The most most probable flux level at which a random observation will find these sources, when detected, is F(2-10 keV) ~ 1-2E-11 erg cm^{-2} s^{-1} (unabsorbed), corresponding to luminosities of a few 10^{33} to a few 10^{34} erg s^{-1}. Finally, the duty-cycle of inactivity ranges between 19 and 55 %.

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P. Romano, S. Vercellone, V. La Parola, G. Cusumano, V. Mangano, P. Esposito, J. A. Kennea, D. N. Burrows, H. A. Krimm, C. Pagani, N. Gehrels. 2011-03-30. The Swift Supergiant Fast X-ray Transients Project: recent results. https://arxiv.org/abs/1103.6036

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