Natalie M. Gosnell, David Pooley, Aaron M. Geller, Jason Kalirai, Robert D. Mathieu, Peter Frinchaboy, Enrico Ramirez-Ruiz
We present the first study of the X-ray population of the intermediate-age
rich open cluster NGC 6819 using the XMM-Newton Observatory. In the past
decade, Chandra X-ray observations have shown a relationship between the X-ray
population of globular clusters and their internal dynamics and encounter
frequency. We investigate the role dynamics possibly play in the formation of
X-ray sources in NGC 6819, and compare our results with known properties of
field and globular cluster X-ray populations. We implement a multi wavelength
approach to studying the X-ray sources, utilizing X-ray and UV data from XMM
observations along with the wealth of photometry and radial-velocity data from
the WIYN Open Cluster Study (WOCS) and the CFHT Open Cluster Survey. Within the
cluster half-light radius we detect 12 X-ray sources down to a luminosity of
10^30 erg/s for cluster members. The sources include a candidate quiescent
low-mass X-ray binary (qLMXB), a candidate cataclysmic variable, and two active
binary systems. The presence of a qLMXB in an open cluster is previously
unexpected given the known relationships between luminous X-ray sources and
encounter frequency in globular clusters, and most likely has a dynamical
origin.
View original:
http://arxiv.org/abs/1111.6589
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