Pulsating Stellar Atmospheres

We review the basic concepts, the present state of theoretical models, and the future prospects for theory and observations of pulsating stellar atmospheres. Our emphasis is on radially pulsating cool stars, which dynamic atmospheres provide a general example for the differences with standard static model atmospheres.Comment: 9 pages, 2 figs, LaTex, in Proc. of IAU Symp 189, "Fundamental Stellar Properties...", eds. T. R. Bedding, A. J. Booth and J. Davis, Kluwer, p.253, 199

Analysis of Four A-F Supergiants in M31 from Keck HIRES Spectroscopy

The first stellar abundances in M31 are presented, based on Keck I HIRES spectroscopy and model atmospheres analyses of three A-F supergiants, 41-2368, 41-3712, and A-207. We also present the preliminary analysis of a fourth star, 41-3654. We find that the stellar oxygen abundances are in good agreement with those determined from nebular studies, even though the stars do {\it not} show a clear radial gradient in oxygen. The uncertainties in the stellar abundances are smaller than the range in the nebular results, making these stars ideal objects for further studies of the distribution of oxygen in M31. We show that the stars can be used to study the abundance distributions of other elements as well, including iron-group and heavier elements. The A-F supergiants also provide direct information on the metallicity and reddening of nearby Cepheid stars. We have examined the metallicity and reddening assumptions used for Cepheids within 1' of our targets and noted the differences from values used in the literature.Comment: Accepted for publication in the ApJ, October 2000 (23 pages, 4 tables, 11 figures

A survey of line profile variations in non-emission line B0–B5 III–V stars

Some investigators have attributed the photometric and spectral line profile variations (lpv) that are common among the B stars to nonradial pulsation while others have attempted to explain them by rotation of photospheric or circumstellar structures with respect to our line of sight. One of the problems in resolving this debate has been our lack of knowledge of how these variations depend on fundamental stellar characteristics. Surveys of lpv have covered the Be and a few Bn stars (D. Penrod, unpublished), the O stars (Fullerton 1990), and B8-B9.5 main sequence stars (Baade 1989), but noone has carried out a systematic search for lpv among the near main sequence, non-emission line early- and mid-B stars. This paper describes preliminary results from such a survey.</jats:p

Multiperiodicity in light variations of 53 Persei: results from optical photometry in 1990 October–1991 January

The B type star 53 Persei was discovered in 1977 by Smith (1977) as the prototype of a separate group of B-type variables showing light and line profile variability. The physical cause of the variability was thought to be nonradial pulsation (NRP) (see, e.g. Smith et al. 1984). However, the NRP model for this star has been questioned by Balona (1986) who suggested the rotational modulation (RM) model to explain the variability. In order to resolve the long lasting debate about 53 Persei, a campaign was initiated to organize coordinated optical photometry and spectroscopy from the ground, and Far-UV photometry from Voyager in 1991 January. This paper presents the results of period analysis on the groundbased UBV data. In another paper, Smith &amp; Huang (1994) report the new identification of pulsation modes using Voyager Far-UV photometry combined with the results from optical observations. Some preliminary results from APT uvby observations taken at a single site are also cited for comparison.</jats:p