A Stacking Analysis of Star Clusters in M51: The Search for X-Ray Binaries
Abstract
We have used multiwavelength data from the Chandra X-Ray Observatory and the Hubble Space Telescope to investigate the faint population of XRBs in the grand-design spiral galaxy M51. A stacking analysis of the X-ray data at the positions of optically-identified star clusters was completed to probe low-luminosity X-ray sources. No cluster type had a significant detection in any X-ray energy band. An average globular cluster had the largest upper limit, 3.36 × 10^{35} erg s^{-1}, in the full-band (0.3-8 keV) while on average all clusters have the lowest upper limit, ≈ 9 × 10^{33} erg s^{-1} in the hard-band (2-8 keV). We conclude that the X-ray data is not deep enough to identify faint sources with a stacking analysis.
- Publication:
-
X-ray Binaries. Celebrating 50 Years Since the Discovery of Sco X-1
- Pub Date:
- July 2012
- Bibcode:
- 2012xrb..confE..62V