Sleuthing Companions to Red Supergiants

Ultraviolet and optical spectroscopy reveals the effects of the
close-in (2.3R_star) companion (Siwarha)  to the supergiant, Betelgeuse
(Alpha Orionis). This companion is believed to be responsible for the
Long Secondary Period (LSP) of the star. Optical circumstellar
absorption increases in strength and expands in phase with the companion.
In addition, the dynamics of the chromosphere change, as the companion
increases the chromospheric outflow velocity. These characteristics
suggest that the companion produces a gravitationally focussed tail
or wake resulting from  stellar wind material from the primary.
Other supergiants exhibit Long Secondary Periods as well.  We present
first results from a program with
the TRES spectrograph at the  Whipple Observatory in Arizona, to monitor
circumstellar features in 6 red supergiants  to assess the ubiquity and
to characterise the circumstellar effects of a companion.