Giant outburst from the supergiant fast X-ray transient IGR J17544-2619: accretion from a transient disc?

Journal
Date Issued
2015
Author(s)
•
Bozzo, E.
•
•
Esposito, P.
•
•
Tiengo, A.
•
•
Ducci, L.
•
Ferrigno, C.
•
Kennea, J. A.
DOI
Description
We wholeheartedly thank the Swift team duty scientists and science planners for their courteous efficiency, and S. D. Barthelmy, D. N. Burrows, and N. Gehrels. We thank S. E. Motta, L. Stella, A. Beardmore, M. Capalbi, and S. Vercellone for useful discussions. We also thank our referee for swift comments that helped improve the paper. P.R. and S.C. acknowledge contract ASI-INAF I/004/11/0. P.E. acknowledges a Fulbright Research Scholar grant administered by the US–Italy Fulbright Commission and is grateful to the Harvard–Smithsonian Center for Astrophysics for hosting him during his Fulbright exchange. L.D. thanks Deutsches Zentrum für Luft und Raumfahrt (Grant FKZ 50 OG 1301).
Abstract
Supergiant fast X-ray transients (SFXTs) are high mass X-ray binaries associated with OB supergiant companions and characterized by an X-ray flaring behaviour whose dynamical range reaches 5 orders of magnitude on time scales of a few hundred to thousands of seconds. Current investigations concentrate on finding possible mechanisms to inhibit accretion in SFXTs and to explain their unusually low average X-ray luminosity. We present the Swift observations of an exceptionally bright outburst displayed by the SFXT IGR J17544-2619 on 2014 October 10 when the source achieved a peak luminosity of 3 × 10. This extends the total source dynamic range to the largest (by a factor of 10) recorded so far from an SFXT. Tentative evidence for pulsations at a period of 11.6 s is also reported. We show that these observations challenge, for the first time, the maximum theoretical luminosity achievable by an SFXT and propose that this giant outburst was due to the formation of a transient accretion disc around the compact object. Tables 1 and 2, and Fig. 2 are available in electronic form at http://www.aanda.org
Volume
576
Start page
L4
Uri
Url
Issn Identifier
0004-6361
Ads BibCode
2015A&A...576L...4R
Rights
open.access
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