Swift observes an outburst from the supergiant fast X-ray transient XTE J1739-30
ATel #4366; P. Romano (INAF-IASFPA), S. D. Barthelmy (GSFC), T. Sakamoto (AGU), D. N. Burrows (PSU), J. A. Kennea (PSU), H. Krimm (CRESST/GSFC/USRA), P. Esposito (INAF-IASFMI), P. A. Evans (U. Leicester), V. Mangano (INAF-IASFPA), D. M. Palmer (LANL), S. Vercellone (INAF-IASFPA), N. Gehrels (GSFC)
on 10 Sep 2012; 15:05 UT
Credential Certification: Pat Romano (romano@ifc.inaf.it)
Subjects: X-ray, Gamma Ray, Binary, Neutron Star, Transient
Referred to by ATel #: 14964
Swift observed a new outburst from the SFXT XTE J1739-302.
The Swift/BAT triggered on it on 2012 September 09 at 23:34:14 UT
(a 320-s image trigger, 533120, sub-threshold Interesting Source
BAT trigger criteria). Swift immediately slewed to the target.
Using the BAT data set from T-239 to T+723 s from recent telemetry
downlinks, we can report that the mask-weighted light curve shows the
event starting at ~T+0 (possibly sooner at ~T-60 s) and lasting out past
T+300 s when Swift slewed and the source went out of the BAT FoV.
The time-averaged spectrum from T_0 to T+309 s is best fit by a simple
power-law model. The photon index of the time-averaged spectrum is
2.36 +/- 0.58.
The fluence in the 15-150 keV band is (4.5+/-1.6)E-7 erg/cm2.
All the quoted errors are at the 90% confidence level.
The XRT began observing the field at 23:40:36.6 UT, 382.3 seconds after
the BAT trigger. The light curve reached about 10 count/s.
The mean XRT/WT spectrum (from T+386 to 465 s, 79 s) can be fit by an
absorbed power-law model with a photon index of 0.89 (+0.38, -0.36)
and an absorbing column density of NH=1.45 (+0.67, -0.54) E22 cm-2,
consistent with the Galactic value (1.19E22 cm-2; Kalberla et al. 2005).
The average 0.3-10 keV observed (unabsorbed) flux is
6E-10 (7E-10) erg/cm2/s.
Previously, Swift observed flares from this source on
2007 June 18, 2008 Apr 8 (Sidoli et al. 2009, ApJ, 690, 120),
2008 Aug 13 (Sidoli et al. 2009, MNRAS, 397, 1528),
2009 March 10 (Romano et al. 2011, MNRAS, 410, 1825),
and on 2011 February 22 (Farinelli et al. 2012, MNRAS, 424, 2854).
The historical light curve from the BAT hard X-ray transient monitor
(Krimm et al, 2006, ATel #904; 15-50 keV) can be found at http://swift.gsfc.nasa.gov/docs/swift/results/transients/weak/IGRJ17391-3021/
Scaled Map Transient Analysis
