Astronomy and Astrophysics, volume 300, 732-745 (1995/8-3)
The ROSAT XRT Sky Survey of X-ray sources in globular clusters.
VERBUNT F., BUNK W., HASINGER G. and JOHNSTON H.M.
Abstract (from CDS):
We present data obtained on globular clusters during the Rosat XRT + PSPC Sky Survey. Sources were detected in the 0.5-2.5keV range in 11 globular clusters. In Ter 6 a previously unknown sources was detected by Rosat ; the source H1825-331 was confirmed to be in the cluster NGC 6652; the persistent flux of the known burst source in Ter 5 was also detected for the first time. The sources in Ter 5 and NGC 6652 are transients, seen by Rosat in their bright state. Improved positions are obtained for the sources in NGC 6652, Ter 5, and Ter 6. From our analysis of the area surrounding ω Cen, we suggest that only one of the five sources detected by Einstein is related to the globular cluster. One source was detected in the 0.07-0.5keV band only, in NGC 5272. A fit of a blackbody to the spectrum of the source in NGC 5272 gives a temperature of ∼45eV, and a bolometric luminosity of ∼1.3x1035erg/s. Upper limits of sources in clusters for which only HEAO-1 observations were available have been improved by factors ten to hundred, and indicate that most clusters do not contain sources with luminosities Lx(0.5-2.5keV)>3x1032erg/s.
globular clusters: general - individual: Ter 6 , NGC 6652 - X-rays: stars