Chandra X-ray observations of the globular cluster M28 and optical HST identification of the X-ray sources
Abstract
We present here the results of Chandra X-Ray Observatory observations of NGC 6626 (M 28), and a first search for optical counterparts by using archival HST data. 46 sources have been detected within the field-of-view of Chandra, 12 of which lie within 1 core radius from the cluster center. We measured for the first time the unconfused X-Ray spectrum of the ms pulsar B1821-24 and present spectral identification for other 5 bright unidentified sources. The brightest one shows spectral parameters suggesting that it is a transiently accreting neutron star in a low-mass X-ray binary in quiescent phase. The apparently extended core emission seen by ROSAT is due to superposition of multiple source for which the X-ray luminosity function is determined. Using Chandra derived position, we also present a preliminary report on the search for the optical counterparts of these sources by using archival HST data.
- Publication:
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Memorie della Societa Astronomica Italiana
- Pub Date:
- 2004
- Bibcode:
- 2004MmSAI..75...50T
- Keywords:
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- X-Ray sources;
- millisecond pulsar;
- globular clusters: M 28