Swift observations of IGR J17544-2619
ATel #1971; H. A. Krimm (CRESST/GSFC/USRA), P. Romano (INAF-IASF Palermo), L. Sidoli (INAF-INAF Milano)
on 16 Mar 2009; 21:48 UT
Credential Certification: Hans A. Krimm (Hans.Krimm@nasa.gov)
Subjects: X-ray, Binary, Transient
The Swift/Burst Alert Telescope (BAT) hard X-ray transient monitor detected an
outburst from the Supergiant Fast X-ray Transient (SFXT) IGR 17544-2619.
The outburst was first seen in a 1024-second exposure starting at 2009-03-15
and continued into the next Swift pointing starting at 2009-03-16 01:27:36 UT
The rates in these exposures were, respectively, 0.026 Â± 0.005 ct/s/cm^2
and 0.032 Â± 0.005 ct/s/cm^2 (140 mCrab).
The source then faded below detectability
before re-brightening twice more on 2009-03-16: to 95 mCrab in a 1152-second
exposure beginning 06:16:40 UT
and then to 85 mCrab in a 384-second exposure beginning 09:25:52.
All BAT rates are measured in the 15-50 keV band.
Swift/XRT data are available from our regular monitoring (Sidoli et al 2008,
ApJ, 687, 1230).
On 2009-03-14 (01:11:35 to 01:28:56 UT, about 46 hours before the BAT
a 1ks exposure yielded a 3-sigma upper limit at 1.5 X 10^-2 ct/s.
A second observation, obtained as a Target of Opportunity, on 2009-03-16
17:17:37 UT (2.1ks net exposure, about 16 hours after the outburst), yields a
upper limit at 1.3 X 10^-2 ct/s.
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