Chandra observation of the globular cluster M15: X-2 is the source of the current activity
ATel #5490; David Pooley (Sam Houston State Univ. & Eureka Scientific, Inc.), Jeroen Homan (MIT)
on 21 Oct 2013; 00:08 UT
Credential Certification: dave pooley (dave@shsu.edu)
Subjects: X-ray, Globular Cluster
Referred to by ATel #: 15586
We observed the globular cluster M15 with Chandra/HRC-S to identify the source of the recent X-ray outburst (ATel #5327, #5396). The observation began on 2013-Oct-07 at 00:57:46 (UT) and had an exposure time of 15.1 ks.
The data show that M15 X-2 is the source of the recent activity, similar to what was seen in 2011 (ATel #3356, #3363, #3393). We measure a count rate of 28.1 c/s in a 1.5" radius extraction region centered on X-2. Assuming a power-law photon index of Gamma=1.7, a column density of n_H = 1.2e21 cm^-2, and a distance of 10.3 kpc, this corresponds to an unabsorbed 0.5-10 keV luminosity of Lx = 9.9e36 erg/s. This is substantially higher than what is seen in some archival observations but similar to its luminosity during the 2011 activity (ATel #3393).
The only other bright source in our observation is AC 211, for which we measure a count rate of 3.8 c/s, corresponding to a 0.5-10 keV luminosity of Lx = 1.3e36 erg/s, similar to its level measured in archival Chandra observations.
We thank Harvey Tananbaum and the entire Chandra staff for their help in executing this observation.