SPECTRAL TYPE AND RADIAL VELOCITY VARIATIONS IN THREE SRC VARIABLES

Анотація

SRC variables are M supergiants, precursors
to Type II supernovae, that vary in brightness
with moderately regular periods of order 100–1000
days. Although identified as pulsating stars that obey
their own period-luminosity relation, few have been
examined in enough detail to follow the temperature
and spectral changes that they undergo during their
long cycles. The present study examines such changes
for several SRC variables revealed by CCD spectra
obtained at the Dominion Astrophysical Observatory
(DAO) during 2005–2009, as well as by archival spectra
from the DAO (and elsewhere) for some stars from
the 1960s to 1980s, and Cambridge radial velocity
spectrometer measures for Betelgeuse. Described here
is our classification procedure and information on
the spectral type and radial velocity changes in three
of the stars. The results provide insights into the
pulsation mechanism in M supergiants.