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A Chandra observation of the neutron-star transient IGR J18245-2452 in M28

ATel #5045; Jeroen Homan (MIT), David Pooley (Sam Houston State University)
on 4 May 2013; 15:44 UT
Credential Certification: Jeroen Homan (jeroen@space.mit.edu)

Subjects: X-ray, Globular Cluster, Neutron Star, Transient

Referred to by ATel #: 5069, 5086

We observed the globular cluster M28 with Chandra/ACIS-S to identify the recently discovered neutron-star X-ray transient IGR J18245-2452 (ATel #4925, #4927). The 14.8 ks observation started on 2013 April 28 at 19:37 UT. The high-energy transmission gratings were inserted to avoid possible pile-up effects. An inspection of the resulting image reveals only one X-ray source in the 0.5 ATCA error circle (ATel #4981), source 23 from Becker et al. (2003 ApJ, 594, 798). A fit with an absorbed power-law yields a 0.5-8 keV luminosity of ~3.3e33 erg/s (assuming a distance of 5.5 kpc and Nh of 1.8e21 atoms/cm^2; power-law index 1.52+/-0.12), which is significantly higher than the 6.5e31 erg/s reported for source 23 by Becker et al. (2003).

We thank Harvey Tananbaum and the entire Chandra staff for their help in executing this observation.