Hydrogen and Helium Emission in Type II Cepheids: The Long Period Stars

Details Hydrogen and Helium Emission in Type II Cepheids: The Long Period Stars Hydrogen and Helium Emission in Type II Cepheids: The Long Period Stars

Dec 2003

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003aas...20312706s&link_type=abstract

American Astronomical Society Meeting 203, #127.06; Bulletin of the American Astronomical Society, Vol. 35, p.1414

Astronomy and Astrophysics

Astronomy

Scientific paper

We have obtained intermediate-resolution spectra of a large sample of both classical and type II Cepheids in order to compare the behavior of the hydrogen alpha line between the two types of stars and to determine the incidence of helium emission in type II Cepheids. In this paper we will describe the results for 38 stars with periods longer than ten days.
Very strong hydrogen emission is quite common but not ubiquitous among the longer period type II Cepheids. Although earlier work on W Vir showed emission throughout the cycle, it appeared in our spectra only during the time from minimum light to shortly after maximum light. None of the classical Cepheids exhibited emission.
We have searched our spectra for helium emission lines which were earlier reported in the spectrum of W Vir. Emission stronger than a few tenths of an Angstrom in equivalent width occurs in only in only about one-third of our type II Cepheids. The temporal variations of the helium lines will be described.
We are grateful to the staffs of Kitt Peak National Observatory and Apache Point Observatory for help in obtaining the data used here. This work was supported in part by NSF grant AST 00-97353.

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