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New Outburst of the Magnetar 1E 1048.1-5937

ATel #9316; R. F. Archibald (McGill), S. P. Tendulkar (McGill), P. Scholz (McGill), and V. M. Kaspi (McGill)
on 4 Aug 2016; 12:26 UT
Credential Certification: Robert Archibald (rarchiba@physics.mcgill.ca)

Subjects: X-ray, Soft Gamma-ray Repeater, Pulsar

Referred to by ATel #: 11241

We report an increase in the X-ray flux from the magnetar 1E 1048.1-5937 in our most recent Swift X-ray Telescope (XRT) monitoring observations from 23-29 July-2016 (MJD 57592-57598). We measure an 0.5-10 keV flux of (30+/-5)x10^-12 erg/s/cm^2, which represents a factor of 5+/-1 increase relative to that during the last monitoring observation of (6.5+/-1.5)x10^-12 erg/s/cm^2 on 18-19 July 2016 (MJD 57587 - 57588). In addition, the 0.5-10 keV pulse profile shows a (3-sigma) deviation from the quiescent profile, with a modest secondary peak appearing. We detect no significant bursts in any of these observations. Comparing the spectra from the XRT observations taken on 18-19 July 2016 (obs ids 00032923243, 00032923244, 00032923245) to the outburst observations (obs id 00032923248, 00032923249, 00032923250), the spectra are well-fit by an absorbed blackbody, where the blackbody temperature has increased from 0.60(3) keV to 0.74(4) keV. Photoelectric absorption was modeled using tbabs, the measured column density, nH is 5.1(9)E21 /cm^2 (with 'wilm' abundances and 'vern' cross-sections). This new outburst epoch is approximately consistent with that which the previously reported (Archibald et al. 2015) quasi-periodicity would predict. Observations at other wavelengths are encouraged.