CO J = 2-1 emission from evolved stars in the Galactic Bulge.
SARGENT B.A., PATEL N.A., MEIXNER M., OTSUKA M., RIEBEL D. and SRINIVASAN S.
Abstract (from CDS):
We observe a sample of eight evolved stars in the Galactic bulge in the CO J = 2-1 line using the Submillimeter Array with angular resolution of 1''-4''. These stars have been detected previously at infrared wavelengths, and several of them have OH maser emission. We detect CO J = 2-1 emission from three of the sources in the sample: OH 359.943 +0.260, [SLO2003] A12, and [SLO2003] A51. We do not detect the remaining five stars in the sample because of heavy contamination from the galactic CO emission. Combining CO data with observations at infrared wavelengths constraining dust mass loss from these stars, we determine the gas-to-dust ratios of the Galactic bulge stars for which CO emission is detected. For OH 359.943 +0.260, we determine a gas mass-loss rate of 7.9 (±2.2)x10–5 M☉/yr and a gas-to-dust ratio of 310 (±89). For [SLO2003] A12, we find a gas mass-loss rate of 5.4 (±2.8)x10–5 M☉/yr and a gas-to-dust ratio of 220 (±110). For [SLO2003] A51, we find a gas mass-loss rate of 3.4 (±3.0)x10–5 M ☉/yr and a gas-to-dust ratio of 160 (±140), reflecting the low quality of our tentative detection of the CO J = 2-1 emission from A51. We find that the CO J = 2-1 detections of OH/IR stars in the Galactic bulge require lower average CO J = 2-1 backgrounds.
circumstellar matter - infrared: stars - radio lines: stars - stars: AGB and post-AGB