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Swift observes a new outburst from the Supergiant Fast X-ray Transient AX J1841.0-0536

ATel #4176; P. Romano (INAF-IASFPA), S. D. Barthelmy (GSFC), J. A. Kennea (PSU), P. Esposito (INAF-IASFMI), P. A. Evans (U Leicester), V. Mangano (INAF-IASFPA), D. M. Palmer (LANL), D. N. Burrows (PSU), M. M. Chester (PSU), H. Krimm (CRESST/GSFC/USRA), T. N. Ukwatta (MSU), S. Vercellone (INAF-IASFPA), N. Gehrels (GSFC)
on 15 Jun 2012; 12:58 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Pat Romano (romano@ifc.inaf.it)

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

Referred to by ATel #: 4276

Swift observed a new outburst from the SFXT AX J1841.0-0536. The Swift/BAT triggered on it on 2012 Jun 14 at 19:11:51 UT (image trigger 524364). Swift performed an immediate slew.

Using the BAT data set from T-239 to T+963 s from recent telemetry downlinks, we report that the mask-weighted light curve shows the source was active when it came into the BAT FoV (at T-100 s) during a preplanned slew. It decreased to a minimum around T+80 s, then increased again reaching a broad maximum from T+350 to T+600 s, then declined slightly. Due to an observing constraint, Swift slewed and the source left the FoV at T+811 s. The time-averaged spectrum from T-91.3 to T+811 s is best fit by a simple power-law model with a photon index of 2.51+/-0.17. The fluence in the 15-150 keV band is (3.0+/-0.3)E-06 erg/cm2. All the quoted errors are at the 90% c.l.

The XRT began observing the field at 19:18:41.5 UT, 409.9 s after the BAT trigger. The XRT/WT (T+416 to T+4210 s, on-source exposure 257 s) and PC (4212 to 6323 s, on-source exposure 2111s) spectra can be fit well together with an absorbed power-law model, which yields a photon index of 0.7+/-0.1 and an absorbing column density of NH=(1.8+/-0.3)E22 cm-2, consistent with the Galactic value (1.59E22 cm-2; Kalberla et al. 2005). The average 2-10 keV observed (unabsorbed) flux in the WT spectrum is 5.8E-10 (6.4E-10) erg/cm2/s; in the PC spectrum it is 4.1E-10 (4.4E-10) erg/cm2/s.

Previously, Swift observed flares from this source on 2010 June 05 (Romano et al. 2011, MNRAS, 412, L30) and 2011 June 24 (Mangano et al. 2011, ATel #3453). 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 for IGR J18410-0535