The Nature of Variability in M Supergiants: The Forgotten Type C Semiregulars
The characteristics of SRC variables are summarized from a comprehensive survey of the Galactic population based on new and archival spectroscopic (Moncrieff, Ph.D. Thesis, Saint Mary’s University, 2011) and spectrophotometric (White and Wing, Astrophys. J. 222:209–219, 1978) observations, and brightness estimates from Harvard plates and AAVSO visual archives, with attention on Berkeley 87 member BC Cyg. New spectroscopic observations of BC Cyg phased using a 692d.8 period, found by a new analysis tied to times of light maximum, are consistent with radial pulsation, similar to that in Cepheids. Results for other SRCs are more ambiguous, with starspot activity or supergranulation cycles constituting a complication for small-amplitude stars displaying longer term trends.
KeywordsLight Curve Light Maximum Radial Velocity Variation Classical Cepheid Systematic Offset
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