The 22 GHz water maser of RX Bootis

Abstract

The SRb-type semiregular variable star RX Bootis was studied as part of an ongoing monitoring program of the maser emission of selected late-type stars. Maps of the star are presented and discussed. The observations are consistent with the assumption that before 1983 RX Boo could sustain H2O maser emission at larger radial distances than later on. At this larger distance, the gradient of the outflow velocity is smaller, allowing radial beaming to become prominent, leading to the well-known double-peaked profile. After 1983 the maser region was completely confined to the accelerating part of the shell, giving preferential rise of the tangentially beaming components. The maser profile is then contaminated by features close to the stellar velocity. (AIAA)