NOAO >   Observing Info >   Approved Programs >   2005A-0192

Small NOAO Logo

Proposal Information for 2005A-0192


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



NOAO >   Observing Info >   Approved Programs >   2005A-0192

noaoprop-help@noao.edu

Small NOAO Logo