The Circumstellar Envelope of Alpha Herculis.

Abstract

system of a Herculis, the M-type supergiant, and its visual companion, a giant G-type spectroscopic binary, are surrounded by a common circumstellar envelope. This envelope produces violet-displaced absorption cores in the zero-volt lines of the M star and stationary zero-volt absorption lines in the spectrum of the G star. The minimum radius of the envelope is 2 X 10 RO; its minimum mass is probably about 1 X 10- ®. It is condensed into clouds that fill only the fraction 10- of the whole spherical volume; within a condensation, the electron density is about 106 . The envelope is expanding at a velocity of 10 km/sec; the matter in it has been ejected by the M star and is being lost to the system at a probable rate of at least 3 X 10-8 ®/year. There is evidence for a comparable rate of mass loss from all other late-type supergiants. This process may be important in the evolution of all massive stars that have exhausted their hydrogen.