557 GHz Observations of Water Vapor Outflows from VY CMa and W Hydrae

Abstract

We report the first detection of thermal water vapor emission in the 557 GHz, $1_{10}-1_{01}$ ground state transition of ortho-H${}_2$O toward VY Canis Majoris. In observations obtained with the Submillimeter Wave Astronomy Satellite (SWAS), we measured a flux of $\sim 450$Jy, in a spectrally resolved line centered on a velocity $v_{LSR}=25$km s${}^{-1}$ with a full width half maximum of $\sim 35$ km s${}^{-1}$, somewhat dependent on the assumed line shape. We analyze the line shape in the context of three different radial outflow models for which we provide analytical expressions. We also detected a weaker 557 GHz emission line from W Hydrae. We find that these and other H${}_2$O emission line strengths scale as suggested by Zubko and Elitzur (2000).

Astrophysical Journal Letters, accepted