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New Swift observations of the SFXT IGR J11215-5952 in outburst

ATel #3200; P. Romano (INAF-IASFPA), P. Esposito (INAF-OAC), S. Vercellone (INAF-IASFPA), V. Mangano (INAF-IASFPA), D. N. Burrows (PSU), G. Cusumano (INAF-IASFPA), R. Farinelli (INAF-IASFPA, U. Ferrara), J. A. Kennea (PSU), V. La Parola (INAF-IASFPA), N. Gehrels (GSFC)
on 2 Mar 2011; 09:44 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Pat Romano (romano@ifc.inaf.it)

Subjects: X-ray, Binary, Transient, Pulsar

The supergiant fast X-ray transient (SFXT) IGR J11215-5952 (Lubinski et al. 2005, Atel #469) undergoes periodic outbursts separated by about 165 days (Sidoli et al. 2007, A&A 476, 1307), which most likely correspond to the orbital period of the binary system. Based on the ephemeris of Romano et al. (2009, ApJ, 696, 2068), that predicted the peak of the new outburst on 2011 March 1 at about 9.30 UT, we observed the source with Swift.

The Swift/XRT observations started on 2011 March 1 at 12:16:46 (effective exposure 2.4 ks). IGR J11215-5952 was detected with a mean count rate of (1.1+/-0.1)E-01 counts/s (1-10 keV). The average XRT/PC spectrum can be fit with an absorbed powerlaw model with a photon index of Gamma=1.0-0.5+0.6 and an absorbing column density of NH=(2.2-1.0+1.3)E+22 cm-2 (Cash statistics C-stat=542.6; 51% of 1E4 Monte Carlo realizations with statistic < C-stat). The mean observed (unabsorbed) 1-10 keV flux is 1.2E-11 erg/cm2/s (1.5E-11 erg/cm2/s), which translates into a luminosity of about 0.7E35 erg/s (assuming the optical counterpart HD 306414 at a distance of 6.2 kpc, Masetti et al. 2006 A&A, 449, 1139). These findings are consistent with those of previous outbursts (Romano et al. 2007, A&A, 469, L5; Sidoli et al 2007, A&A, 476, 1307; Romano et al. 2009, ApJ, 696, 2068; Atel #2257).

We thank the Swift Team for making these observations possible, in particular the duty scientists and the science planners.

SFXT Project web page