Astronomy and Astrophysics – Astronomy
Scientific paper
Dec 2004
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2004aj....128.2988s&link_type=abstract
The Astronomical Journal, Volume 128, Issue 6, pp. 2988-2996.
Astronomy and Astrophysics
Astronomy
9
Stars: Variables: Cepheids, Stars: Population Ii
Scientific paper
We have obtained Hα profiles from 175 spectra of 37 Cepheids with periods longer than 8 days. About two-thirds of the stars are likely type II Cepheids. In contrast to the situation among short-period stars, the velocity of Hα relative to the metal-line spectrum is not a useful parameter for distinguishing type I and type II Cepheids. On the other hand, at periods longer than 11 days and shorter than 34 days strong emission is observed in many stars and appears to be a good discriminator of type. On this basis we identify one probable type I Cepheid at a large distance from the Galactic plane. We have found He λ5876 emission in seven Cepheids among the long-period stars discussed here and in one star with a short period, bringing to nine the number of type II Cepheids known to exhibit He emission.
Based in part on observations obtained with the Apache Point Observatory 3.5 m telescope, which is owned and operated by the Astrophysical Research Consortium.
Johnston Dale
Langan Shawn
Lee Kevin M.
Newman Peter R.
Schmidt Edward G.
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