NOAO > Observing Info > Approved Programs > 2005A-0192
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NOAO > Observing Info > Approved Programs > 2005A-0192 |
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PI: Shawn T Langan, University of Nebraska-Lincoln, nuaur@hotmail.com
Address: Physics Department, 116 Brace Laboratory, Lincoln, NE 68588-0111, U.S.A.
CoI: Edward G. Schmidt, University of Nebraska-Lincoln
Title: Emission Line Profiles in Short Period Type II Cepheids
Abstract:
Although strong hydrogen line emission in long period type II
Cepheids has been known for many years, the discovery of moderately
strong hydrogen emission and weak helium emission in one class of short
period type II Cepheids was a surprise. We propose to obtain higher
resolution spectra for these stars in order to determine whether the
mechanism which produces emission is similar to that in the long period
stars, compare the observations with pulsational models for short period
type II Cepheids, search for metal emission lines as predicted by some
shock wave models, and study the dynamics of the atmospheres.
The high-resolution spectra will provide emission line profiles,
permit a determination of the duration of the emission, allow us to
detect helium emission with certainty and obtain ratios of the hydrogen
to helium emission strength, detect doubling and broadening of
absorption lines, and measure velocity differentials. These various
parameters will be compared with currently existing models and with
those we develop. They will also guide future developments in the
modeling of the dynamics in stellar atmospheres.
National Optical Astronomy Observatory, 950 North Cherry Avenue, P.O. Box 26732, Tucson, Arizona 85726, Phone: (520) 318-8000, Fax: (520) 318-8360
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NOAO > Observing Info > Approved Programs > 2005A-0192 |
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