Swift observations of a new outburst of the SFXT IGR J17544-2619

ATel #5179; P. Romano (INAF-IASFPA), P. A. Evans (U Leicester), J. A. Kennea (PSU), J. R. Cummings (GSFC/UMBC), D. N. Burrows (PSU), S. D. Barthelmy (GSFC), V. D'Elia (ASDC), N. Gehrels (GSFC), H. Krimm (CRESST/GSFC/USRA), A. Y. Lien (NASA/GSFC/ORAU), D. Malesani (DARK/NBI), S. R. Oates (UCL-MSSL), K. L. Page (U Leicester), P. Esposito (INAF-IASFMI), S. Vercellone (INAF-IASFPA)
on 29 Jun 2013; 14:11 UT
Credential Certification: Pat Romano (romano@ifc.inaf.it)

Tweet

The Swift Burst Alert Telescope (BAT) triggered on 2013 June 28 at 07:26:21 UT (subthreshold, image trigger=559221) on what appeared to be a noise spike (D'Elia et al., GCN Circ. 14946). Swift immediately slewed to the BAT position, and the narrow field instruments started observing about 131.7 s after the trigger. Subsequent XRT observations detected a new outburst in progress from Supergiant Fast X-ray Transient (SFXT) IGR J17544-2619, which was located over 6 arcminutes from the BAT on-board position, but within the XRT field of view. No other bright X-ray sources were found in the XRT field of view, which covered the entire BAT error circle.

Using the BAT data set from T-119 to T+183 s from the telemetry downlink, we report that the time-averaged spectrum from T+0 to T+64 s is best fit by a simple power-law model with a photon index of 3.0 +/- 0.8. The fluence in the 15-150 keV band is (2.1 +/- 0.7)E-07 erg/cm2. All the quoted errors are at the 90% confidence level.

The Swift/XRT light curve reached a count rate of about 80 counts/s. The XRT/PC spectrum (T+147 to T+648 s, integration 501 s) can be fitted with an absorbed power law, with a photon index of 1.0+/-0.2, and an absorbing column density of NH=(1.3+/-0.3)E+22 cm-2. The mean observed (unabsorbed) flux is about 5.2E-9 (6.5E-9) erg/cm2/s (0.3-10 keV).

Previously, Swift observed bright flares from this source on 2007 November 8 (Krimm et al. 2007, Atel #1265), 2008 March 31 (Sidoli et al. 2009, ApJ, 690, 120), 2008 September 4 (Sidoli et al. 2009, MNRAS, 397, 1528), 2009 March 15 (Krimm et al. 2009, Atel #1971), 2009 June 6 (Romano et al. 2011, MNRAS, 410, 1825), 2010 March 4 (Romano et al. 2011, MNRAS, 412, L30), 2011 March 24 (Farinelli et al. 2012, MNRAS, 424, 2854), 2012 April 12 (Romano et. al 2012, ATel #4040), and 2012 July 24 (Romano et al. 2012, ATel #4275). 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/IGRJ17544-2619 .

Scaled Map Transient Analysis for IGR J17544-2619