An Unexpected Discovery in the Rich Open Cluster NGC 6819 Using XMM-Newton
Abstract
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.
Keywords
Cite
@article{arxiv.1111.6589,
title = {An Unexpected Discovery in the Rich Open Cluster NGC 6819 Using XMM-Newton},
author = {Natalie M. Gosnell and David Pooley and Aaron M. Geller and Jason Kalirai and Robert D. Mathieu and Peter Frinchaboy and Enrico Ramirez-Ruiz},
journal= {arXiv preprint arXiv:1111.6589},
year = {2015}
}
Comments
14 pages, 11 figures, accepted for publication in the Astrophysical Journal