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Swift observations of a new outburst of the SFXT IGR J08408-4503

ATel #5190; P. Romano (INAF-IASF Palermo), A. Y. Lien (NASA/GSFC/ORAU), P. A. Evans (LU), S. D. Barthelmy (GSFC), D. N. Burrows (PSU), P. Esposito (INAF-IASFMI), N. Gehrels (GSFC), J. A. Kennea (PSU), H. A. Krimm (CRESST/GSFC/USRA), D. Malesani (DARK/NBI), V. Mangano (PSU), S. Vercellone (INAF-IASF Palermo)
on 3 Jul 2013; 14:13 UT
Credential Certification: Pat Romano (romano@ifc.inaf.it)

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

The Swift Burst Alert Telescope (BAT) triggered on a new outburst from the Supergiant Fast X-ray Transient (SFXT) IGR J08408-4503 on 2013 July 2 at 08:10:45 UT (image trigger=00559642). Swift immediately slewed to the BAT position, and the narrow field instruments started observing about 130 s after the trigger.

Using the BAT data set from T-239 to T+963 s from the recent telemetry downlink, we report that the time-averaged spectrum from T-79.0 to T+497.0 s is best fit by a power law with an exponential cutoff. This fit gives a photon index 0.8+/-1.2, and Epeak of 23 keV. The total fluence in the 15-150 keV band is (2.1+/-0.3)E-06 erg/cm2. All the quoted errors are at the 90% confidence level.

The XRT began observing the field 135 seconds after the BAT trigger. The light curve shows several flares and reached 20 counts/s. The mean XRT/WT spectrum (T+135 to 554 s, 418 s exposure) can be fitted with an absorbed power-law with a photon index of 0.5+/-0.1 and an absorbing column density of NH=(4 +/- 1)E21 cm-2. The mean observed (unabsorbed) flux is about 1.4E-9 (1.5E-9) erg/cm2/s (0.3-10 keV). The mean XRT/PC spectrum (T+ 556 to 1965 s, 1.4 ks exposure) can be fitted with an absorbed power-law with a photon index of 0.6+/-0.2 and an absorbing column density of NH=(5 +/- 2)E21 cm-2. The mean observed (unabsorbed) flux is about 2.6E-10 (2.8E-10) erg/cm2/s (0.3-10 keV).

Previously, Swift observed flares from this source on 2006 October 4 (Gotz et al. 2007,ApJ,655,L101; Romano et al. 2009,MNRAS,392,45), 2008 July 05 (Romano et al. 2009,MNRAS,392,45), 2008 September 21 (Sidoli et al. 2009,MNRAS,397,1528), 2009 August 28 (Barthelmy et al. 2009, ATel #2178), 2010 March 28 (Romano et al. 2010, ATel #2520), and 2011 August 25 (Mangano et al. 2011, ATel #3586). 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/IGRJ08408-4503 .

Scaled Map Transient Analysis for IGR J08408-4503