Swift/XRT Observations of Anomalous X-ray Pulsar 4U 0142+61 Following a Burst
ATel #3520; F. P. Gavriil (UMBC/NASA/GSFC), V. M. Kaspi (McGill University), M. A. Livingstone (McGill University), P. Scholz (McGill University), R. Archibald (McGill University)
on 30 Jul 2011; 04:00 UT
Credential Certification: Fotis Gavriil (fotis.gavriil@nasa.gov)
Subjects: X-ray, Neutron Star, Soft Gamma-ray Repeater, Pulsar
We report on Swift/XRT observations of the Anomalous X-ray Pulsar 4U 0142+61 after its most recent burst detected by Swift/BAT (GCN 12209). A preliminary analysis of the Windowed Timing mode data from MJD 55771.47 to 55771.55 shows that the source's persistent 2-10 keV flux (unabsorbed) increased by a factor of ~5.5, and in 3 hrs decayed down to 1.6 times the quiescent level. Similarly, the pulsed flux went from a factor of 10+/-2 to 2.1+/-0.6 above the quiescent level in the same time frame. The source's spectral shape, as modeled by a blackbody with a power-law tail, also exhibited significant variations. The thermal component of the source's emission got much hotter. Its blackbody temperature rose to 1.27+/-0.07 keV -- a factor of 3.2+/-0.2 above the quiescent level. The non-thermal component of the source's emission significantly hardened to a power-law with an index of 2.78+/-0.15 rather than ~3.6 as observed in quiescence. Both the blackbody temperature and the power-law index returned to a few percent of their quiescent values within 3 hours. The morphology of the pulse also changed, going from two distinct peaks to a broad single peak. With the current data it is difficult to determine whether shorter timescale features are superimposed on the broad single peak of the pulse profile. This outburst is similar to the one seen from the source in 2006 (Gavriil et al. 2011, ApJ, 736, 138) where total/pulsed flux enhancements and pulse morphology changes were seen in conjunction with bursts. Observations at other wavelengths are strongly encouraged.
