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Swift observes a new outburst from the SFXT AX J1841.0-0536

ATel #4276; P. Romano (INAF-IASF Palermo), H. Krimm (CRESST/GSFC/USRA), B. Sbarufatti (INAF-OAB/PSU), T. Sakamoto (GSFC/UMBC), D. N. Burrows (PSU), S. D. Barthelmy (GSFC), M. M. Chester (PSU), J. A. Kennea (PSU), P. Esposito (INAF-IASFMI), P. A. Evans (U Leicester), N. Gehrels (GSFC), V. Mangano (INAF-IASFPA), D. M. Palmer (LANL), S. Vercellone (INAF-IASFPA)
on 25 Jul 2012; 14:51 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Pat Romano (romano@ifc.inaf.it)

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

The Swift Burst Alert Telescope (BAT) triggered on a new outburst from the Supergiant Fast X-ray Transient (SFXT) AX J1841.0-0536 on 2012 July 24 at 00:40:14 (image trigger=528411). Swift immediately slewed to the target.

Using the BAT data set from T-239 to T+963 s from the full telemetry downlink, we report that the time-averaged spectrum from T+0 to T+320 s is best fit by a simple power-law model with a photon index of 2.60 +/- 0.39. The fluence in the 15-150 keV band is (8.0 +/- 1.8)E-07 erg/cm2. All the quoted errors are at the 90% confidence level. The BAT light curve from the event data does not show any significant features. The outburst in hard X rays began at approximately 24 July 2012 at 00:49 UT and continued until roughly 05:09 UT.

The Swift/XRT light curve reached about 6 counts/s. The XRT/PC spectrum (T+444 to T+4173 s, integration time of 474 s) can be fitted with an absorbed power law, with a photon index of 0.5(-0.4,+0.4), and an absorbing column density of NH=(2.5,-0.9,+1.3) E+22 cm-2, consistent with the Galactic value (1.59E22 cm-2; Kalberla et al. 2005). The mean flux is ~5E-10 erg/cm2/s (0.3-10 keV, unabsorbed).

Previously, Swift observed flares from this source on 2010 June 05 (Romano et al. 2011, MNRAS, 412, L30), 2011 June 24 (Mangano et al. 2011, ATel #3453), and on 2012 June 14 (Romano et al 2012, Atel #4176). 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/IGRJ18410-0535/.

Scaled Map Transient Analysis