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arXiv · 0905.2815

Supergiant Fast X-ray Transients in outburst: new Swift observations of XTEJ1739-302, IGRJ17544-2619, and IGRJ08408-4503

L. Sidoli·P. Romano·L. Ducci·A. Paizis·G. Cusumano·V. Mangano·H. A. Krimm·S. Vercellone·D. N. Burrows·J. A. Kennea·N. Gehrels
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Abstract

We report on new X-ray outbursts observed with Swift from three Supergiant Fast X-ray Transients (SFXTs): XTEJ1739-302, IGRJ17544-2619 and IGRJ08408-4503. The former two outbursts were caught during the monitoring campaign we have been performing with the Swift satellite since October 2007: XTEJ1739-302 underwent a new outburst on 2008, August 13, IGRJ17544-2619 on 2008, September 4, while IGRJ08408-4503 on 2008, September 21. While XTEJ1739-302 and IGRJ08408-4503 bright emission triggered the Swift/Burst Alert Telescope, IGRJ17544-2619 did not, thus we could perform a spectral investigation only of the spectrum below 10 keV. The broad band spectra from XTEJ1739-302 and IGRJ08408-4503 were compatible with the X-ray spectral shape displayed during the previous flares. A variable absorbing column density during the flare was observed in XTEJ1739-302 for the first time. The broad band spectrum of IGRJ08408-4503 requires the presence of two distinct photon populations, a cold one (0.3 keV) most likely from a thermal halo around the neutron star and a hotter one (1.4-1.8 keV) from the accreting column. The outburst from XTEJ1739-302 could be monitored with a very good sampling, thus revealing a shape which can be explained with a second wind component in this SFXT, in analogy to what we have suggested in the periodic SFXT IGRJ11215-5952. The outburst recurrence timescale in IGRJ17544-2619 during our monitoring campaign with Swift suggests a long orbital period of ~150 days (in an highly eccentric orbit), compatible with what previously observed with INTEGRAL.

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L. Sidoli, P. Romano, L. Ducci, A. Paizis, G. Cusumano, V. Mangano, H. A. Krimm, S. Vercellone, D. N. Burrows, J. A. Kennea, N. Gehrels. 2009-05-18. Supergiant Fast X-ray Transients in outburst: new Swift observations of XTEJ1739-302, IGRJ17544-2619, and IGRJ08408-4503. https://doi.org/10.1111/j.1365-2966.2009.15049.x

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