The Nature of the Low-luminosity Globular Cluster X-ray
Sources
D. Pooley(MIT), W. H. G. Lewin (MIT), L. Homer (Washington), B. Gaensler (MIT), S. Anderson (Washington), B. Margon (STScI), F. Verbunt (Utrecht), J. Miller (MIT), D. Fox (Caltech), V. Kaspi (McGill), M. van der Klis (Amsterdam)
Abstract
We present results of our Chandra observation of the globular
cluster NGC 6752. We detected 19 sources within the half-mass radius
of the cluster, down to a luminosity of 1030 erg s-1. After
performing small astrometric corrections based on X-ray/radio
coincidences, we searched the 0.6 arcsec radius Chandra error
circles for HST counterparts and found nine. Five counterparts
are bright in both H
and UV emission and are very likely
cataclysmic variables (CVs). Two candidate CVs (based on H
brightness) were previously known in this cluster. The other four
counterparts are also bright in UV emission (two of these show some
H
excess as well) and are probably CVs or maybe quiescent
low-mass X-ray binaries. Of the remaining 10 sources, we expect five
will be the known millisecond radio pulsars (MSPs), the radio
positions of which are not yet known. The majority of the other five
sources are likely background objects not associated with the cluster;
we expect four such sources based on the number of sources detected
outside the cluster in our observation.
CATEGORY: WHITE DWARF BINARIES AND CATACLYSMIC VARIABLES