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Title: Swift monitoring of supergiant fast X-ray transients: The out-of-outburst behaviour and the flares from IGR J17544-2916 and XTE J1739-302
Authors: Sidoli, L
Romano, P
Cusumano, G
Mangano, V
Vercellone, S
Paizis, A
Pellizzoni, A
Kennea, JA
Burrows, DN
Krimm, HA
Gehrels, N
Guidorzi, C
Evans, PA
First Published: 8-Jul-2009
Presented at: 7th INTEGRAL Workshop (Integral08), Copenhagan, Denmark
Publisher: Sissa Medialab srl Partita IVA
Citation: Proceedings of Science, 2008, Vol. 067
Abstract: Supergiant Fast X-ray Transients (SFXTs) are a sub-class of High Mass X-ray Binaries (HMXBs) associated with OB supergiant companions and displaying transient X-ray activity. This behaviour is quite surprising since HMXBs hosting supergiants were known to be persistent sources, until the INTEGRAL discoveries obtained by means of the monitoring of the Galactic plane. We have been performing a monitoring campaign with Swift of four SFXTs with the main aim of characterizing both the long-term behaviour of these transients and the properties during bright outbursts. Here we discuss the properties of the X-ray emission observed outside the outbursts as well as the flares observed from two SFXTs: IGR J17544-2916 and XTE J1739-302. Contrarily to what previously thought, Swift allowed us to discover that SFXTs spend most of the time in accretion at a low level, even outside the bright outbursts, with an accretion luminosity of 1033-1034 erg s-1, and that the quiescent level ∼1032 erg s-1, is a much rarer state.
DOI Link: 10.22323/1.067.0084
eISSN: 1824-8039
Version: Publisher Version
Status: Peer-reviewed
Type: Journal Article
Rights: Copyright © the authors, 2009. This is an open-access article distributed under the terms of the Creative Commons Attribution-ShareAlike License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited, and that any contributions are distributed under the same license as the original.
Appears in Collections:Published Articles, Dept. of Physics and Astronomy

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