The Circumstellar Envelope of VX Sagittarii

Abstract

Radio maser emission from OH, H2O and SiO masers provides a means of studying the circumstellar envelopes of long period variable stars. The OH 1612 MHz maser emission arises in the cool outer layers of the envelopes at distances >101 6cm from the photosphere and is pumped by infrared photons (Elitzur 1982). The maser lines of the OH molecule at 1665/7 MHz and of H2O and SiO molecules are valuable probes of the warm inner regions of the envelopes. Only a few sources have been mapped in these lines and physical conditions in the inner regions of circumstellar envelopes are not well understood. For the luminous M-type supergiant star VX Sgr, we have made MERLIN observations of the OH maser emission at 1612 MHz (LHC) and 1665/7 MHz (RHC) and the H2O maser emission at 22 GHz (LHC). These have been combined with published data on the SiO masers (Lane 1984) to give a detailed description of the circumstellar envelope.KeywordsExpansion VelocityMaser EmissionStellar VelocityCircumstellar EnvelopeInfrared PhotonThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.