Luminosities and mass loss rates of OH/H2O maser stars

The authors discuss the results of a high-sensitivity (⪉1 Jy) search for H2O maser emission from late-type stars. The survey has resulted in the discovery of 21 circumstellar H2O masers, all of which are associated with Mira variables. These data and published data are used to examine the range of H2O maser luminosities. A correlation is found between the H2O luminosity and the stellar mass loss rate, whereby the most luminous H2O masers are associated with Mira variables and supergiant stars which have high mass loss rates. OH and H2O maser luminosities are then compared for late-type stars. It is found that the ratio of H2O to OH luminosities also depends on the mass loss rate and has a range of at least three orders of magnitude, being systematically larger for nearby Mira variables with low mass loss rates.