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

ATel #4040; P. Romano (INAF-IASF Palermo), H. A. Krimm (CRESST/GSFC/USRA), D. M. Palmer (LANL)
on 13 Apr 2012; 20:06 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Pat Romano (romano@ifc.inaf.it)

Subjects: X-ray, Gamma Ray, Binary, Neutron Star, Transient

Referred to by ATel #: 4275, 5179, 5388, 6173, 6227, 6566

The source IGR J17544-2619 was detected in the Swift/BAT both as on-board sub-threshold event and in the BAT hard X-ray transient monitor. On-board, the source reached 5.7-sigma significance (just below the 6-sigma trigger threshold) in a 320-sec period beginning 2012-April-12 00:37:19.9 UT, with a flux of 104 +/- 18 mCrab (15-50 keV). In the BAT transient monitor, the source was detected in seven pointings over the period from 2012-04-11 19:59:04 UT to 2012-04-12 06:54:00 UT, with a peak of 0.02 +/- 0.004 ct/s/cm^2 (15-50 keV; ~90 mCrab) in the 1000-sec pointing beginning at 2012-04-12 00:37:28 UT.

A Swift/XRT observation was obtained as a Target of Opportunity, on 2012-04-13 08:29:02 to 08:41:57 UT (765s net exposure, about 32 hours after the outburst) and it yields a 3-sigma upper limit at 2.0x10^-2 ct/s (0.2-10 keV). Further observations are scheduled.

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, 410, 1825), 2010 March 4 (Romano et al 2011, MNRAS, 412, L30), and 2011 March 24 (Romano et al 2011, ATel #3235).

We thank Neil Gehrels and the Swift science operations team for approving and scheduling this rapid Target of Opportunity observation.

Swift BAT hard X-ray transient monitor light curves for IGR 17544-2619