The HI 21-cm Line as a Probe of Stellar Mass-Loss and Evolution

Massachusetts Institute Of Technology, Cambridge MA

Investigators

Abstract

This award will support an observational study of neutral hydrogen (HI) in the envelopes of a type of highly-evolved low- to intermediate-mass star known as an asymptotic giant branch (AGB) star. Such stars have very large outer envelopes and are losing mass into the interstellar medium; they also are copious producers of dust. The mechanism and rates of mass loss in such stars are poorly known, and this study will measure radio emission and absorption in the circumstellar hydrogen to probe the conditions and kinematics in the gas. The project aims for an improved knowledge of the total mass and extent of circumstellar envelopes, of the duration and geometry of mass loss, and of the formation of planetary nebulae. The project is expected to provide improved understanding of the physical conditions in the outer layers of evolved stars. It will also provide research opportunities for undergraduates, and the results from this study will be incorporated into public lectures and podcasts.