2001ApJ...549L.125B

A survey with the Heinrich Hertz Submillimeter Telescope of HCN emission from mass-losing carbon stars has revealed masers in the J=3-2 and 4-3 transitions of the (01^1c0) vibrational bending mode. These lines have not previously been known to show maser action. Five stars–R Scl, V384 Per, R Lep, Y CVn, and V Cyg–out of 12 observed were detected as masers. Allowing for evidence of variability, this detection rate suggests that these HCN lines are masers at least some of the time in the majority of mass-losing carbon stars. The line widths and velocities imply that the maser action occurs in gas close to the star, where the circumstellar envelope is just being accelerated outward.