SiO maser emission and the intrinsic properties of Mira variables

Abstract

Observations of SiO maser emission from 161 Mira variables distributed over a wide range of intrinsic parameters like spectral type, bolometric magnitude, and amplitude of pulsation are reported. The observations were made at 86.243 GHz, using the 10.4 m millimeter-wave telescope of the Raman Research Institute at Bangalore, India. The maser emission is found to be restricted to Miras having mean spectral types between M6 and M10. The IR period-luminosity relation for Mira variables is employed to calculate their distances and hence estimate their maser luminosities from the observed fluxes. The maser luminosity is found to be correlated with the bolometric magnitude of the Mira variable. On an H-R diagram, the masing Mira variables are shown to lie in a region distinct from that for the nonmasing ones.