X‐Ray Bursts from the Transient Magnetar Candidate XTE J1810−197

We have discovered four X-ray bursts, recorded with the Rossi X-ray TimingExplorer Proportional Counter Array between 2003 September and 2004 April, thatwe show to originate from the transient magnetar candidate XTE J1810-197. Theburst morphologies consist of a short spike or multiple spikes lasting ~1 seach followed by extended tails of emission where the pulsed flux from XTEJ1810-197 is significantly higher. The burst spikes are likely correlated withthe pulse maxima, having a chance probability of a random phase distribution of0.4%. The burst spectra are best fit to a blackbody with temperatures 4-8 keV,considerably harder than the persistent X-ray emission. During the X-ray tailsfollowing these bursts, the temperature rapidly cools as the flux declines,maintaining a constant emitting radius after the initial burst peak. During thebrightest X-ray tail, we detect a narrow emission line at 12.6 keV with anequivalent width of 1.4 keV and a probability of chance occurrence less than 4x 10^-6. The temporal and spectral characteristics of these bursts closelyresemble the bursts seen from 1E 1048.1-5937 and a subset of the burstsdetected from 1E 2259+586, thus establishing XTE J1810-197 as a magnetarcandidate. The bursts detected from these three objects are sufficientlysimilar to one another, yet significantly different from those seen from softgamma repeaters, that they likely represent a new class of bursts from magnetarcandidates exclusive (thus far) to the anomalous X-ray pulsar-like sources.Comment: Accepted for publication in ApJ. 26 pages and 11 figure