Infrared and SiO Maser Observations of OH/IR Stars

摘要

The authors have performed quasisimultaneous infrared photometry and observations of the SiO 86 GHz (v=1, J=2-1) and SiO 43 GHz (v=1 and 2, J=1-0) maser emission from a sample of 44 OH/IR stars. In contrast to masers associated with Mira variables, the SiO 86 GHz integrated flux densities in OH/IR stars are weaker than those at 43 GHz, and the SiO 43 GHz (v=2) emission is often stronger than the SiO 43 GHz (v=1) emission. Results show that it is useful to divide the sample into two groups because of the difference in their SiO maser properties: sources with warm, thin envelopes (K - L 4). In the warmer sources the average 43 GHz/86 GHz integrated flux density ratio is of order 2, but in the cooler sources it is significantly larger, more than 10.