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N. R. Evans (Harvard-Smithsonian CfA), K. C. Carpenter (NASA's GSFC), R. Robinson (Johns Hopkins University), F. Kienzle (Geneva Observatory), A. Dekas (Harvard College)
We have obtained an HST STIS ultraviolet high dispersion Echelle mode spectrum of the double mode classical Cepheid Y Car. The velocity measured for the hot companion from this spectrum is very divergent from reasonable predictions for binary motion, implying that the companion is itself a short period binary. The measured velocity changed by 7 km sec-1 during the 4 days between two segments of the observation confirming this interpretation. We summarize ``binary" Cepheids which are in fact members of triple systems and find 50% are triples. This fraction may be overestimated since binary companions increase the orbital motion of the Cepheids and make them more likely to be detected and studied.
Financial assistance was provided by HST grant HST-GO-09146.01-A and from the Chandra X-ray Center NASA Contract NAS8-39073.
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Bulletin of the American Astronomical Society, 35 #3
© 2003. The American Astronomical Soceity.