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Swift observes an outburst from the Supergiant Fast X-ray Transient IGR J16479-4514

ATel #1920; P. Romano (INAF-IASF Palermo), L. Sidoli (INAF-IASF Milano), V. Mangano (INAF-IASF Palermo), J. A. Kennea (PSU), V. La Parola, G. Cusumano, S. Vercellone (INAF-IASF Palermo), K. P. Page (U. Leicester), D. N. Burrows (PSU), N. Gehrels (GSFC)
on 29 Jan 2009; 17:01 UT
Distributed as an Instant Email Notice Request For Observations
Credential Certification: Pat Romano (romano@ifc.inaf.it)

Subjects: X-ray, Gamma Ray, Request for Observations, Binary, Transient

Referred to by ATel #: 1929

The Swift/BAT caught a new outburst from the Supergiant Fast X-ray Transient IGR J16479-4514 on January 29 at 06:33:07 UT. The Swift/BAT light curve shows a broad peak with maximum around the trigger time. The time-averaged spectrum from T-419 to T+964 s is best fit by a simple power-law model with a photon index of 2.5+/-0.3 (90% c.l.). The 15-150 keV flux is 2E-9 ergs/cm2/s.

Swift slewed to the target, so that the XRT started observing the field at 06:46:46.9 UT, 819.3s after the BAT trigger. The initial WT data (823 to 863 s since the trigger) light curve shows a count rate of 2 to 4 count/s (0.3-10 keV). The following PC data light curve (864-7529 s) shows that the source has declined from 4 to about 0.5 count/s. The PC spectrum, fitted with an absorbed powerlaw model, yields a photon index of 1.00 (-0.25,+0.27) and an absorbing column density of 4.79(-0.88,+1.03)E+22 cm-2. The observed (unabsorbed) 0.3-10 keV flux is 0.9E-10 (1.4E-10) erg/cm2/s.

These results are consistent with the ones derived for the previous outburst which occurred on March 19, 2008 (i.e. 315 days ago), recorded by Swift (ATel#1435; Romano et al. 2008, ApJ, 680, L137).

Further Swift observations are ongoing.