Analyses of "Peculiar" W Virginis Stars in the Milky Way (Abstract)

Volume 39 number 1 (2011)

Doug Welch

100 Melville Street, Dundas, ON L9H 2A3, Canada; welch@physics.mcmaster.ca

Grant Foster

146C Mechanic Street, Westbrook ME 04092; twistor9@gmail.com

Abstract

(Abstract only) We describe the analysis of light curve data for several candidate “peculiar W Virginis” stars in the field population of the Milky Way. Soszynski et al. (2008, 2010) have reported results for the Type 2 Cepheid population from OGLE-III. One of their important findings was a division of the W Vir variables into “regular” and “peculiar” subtypes. The latter are characterized by higher luminosities and a different light curve morphology. Furthermore, the fact that approximately 25% of the sample of “peculiar” W Vir stars were found to be in eclipsing systems suggested that all such stars were in binaries. The orbital periods of the eclipsing or ellipsoidal variations were found to be 10–20 times the pulsation period. Pulsation periods for “peculiar” W Vir stars were found to be between 4 and 10 days in the LMC and between 4.4 and 17.7 days in the SMC, although a claim that such behavior was present in longer-period RV Tau stars was also made. Identifying Milky Way counterparts to “peculiar” W Vir stars would have many potential benefits. The most obvious one is proximity, which allows radial velocity and spectral analysis with intermediate-size telescopes. The number of known or suspected W Vir stars in the Milky Way is large and growing. It would be surprising if there had been no evidence for such behavior in Milky Way stars to date—even if a subclass had not been identified—and indeed it is the case that several stars with similar propertied have been identified. In this paper, we report the time-series analyses of Milky Way “peculiar” W Vir candidates from AAVSO, ASAS-3, MACHO, and SuperWASP photometry in addition to noting binary orbit parameters for the candidates, when known.