Astronomy and Astrophysics, volume 290, 796-802 (1994/10-3)
Stellar OH masers toward globular clusters.
FRAIL D.A. and BEASLEY A.J.
Abstract (from CDS):
We have carried out a search for stellar maser emission from evolved stars in globular clusters (GCs) with the NRAO 140-ft Telescope. All known GCs north of declination -42deg were searched in the 1667MHz main line of the hydroxyl radical OH and its 1612MHz satellite line to typical rms sensitivity limits of 69mJy and 66mJy, respectively. A targeted search was also done on IRAS point sources in the vicinity of GCs, selected on the basis of their infrared colors. We detected the stellar maser emission toward 5 GCs, and found another 3 stellar maser sources from a search of the literature. In 6 of these cases we find that their cluster membership is doubtful, based on radial velocity information. A candidate associated with Djorg 1 is thought to be a line of sight coincidence with a previously-unknown stellar maser located in the galactic plane. The remaining candidate IRAS 16296-1305 is identified with the Mira variable V720 Oph, whose membership within NGC 6171 is supported by a near match between the radial velocities of the star and the cluster, the small expansion velocity of the stellar shell, and a lack of proper motion for the star. We suggest reasons for the low detection rates in our survey and give directions for future observations.
stars: AGB and post-AGB - radio lines: stars - masers - globular clusters: general, NGC 6171 - stars: individual: V720 Oph