AAS 200th meeting, Albuquerque, NM, June 2002
Session 7. Variable Stars and Relatives
Display, Monday, June 3, 2002, 9:20am-6:30pm, SW Exhibit Hall

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[7.04] A Status Report on Radial Velocities and Metallicities of M31/M33 Cepheids

A. D. Forestell, T. G. Barnes (University of Texas at Austin), T. J. Moffett (Purdue University)

Radial velocities and metallicities of Cepheid variables in other galaxies are of considerable interest. We have begun observations with the 9.2 meter Hobby-Eberly Telescope (HET) at McDonald Observatory to determine these quantities for selected Cepheids in Local Group galaxies M31 and M33. Our targets have been selected from the DIRECT database (http://cfa-www.harvard.edu/~kstanek/DIRECT/). We present the first radial velocities results for one Cepheid in each galaxy: V2203_D31F and V22665_D33B. These Cepheids have magnitudes in the range V = 17.8--19.0 mag. Our R=15,000 spectra cover the wavelength range 4800--6800 Åand were obtained using the lowest resolving power of the fiber-fed High Resolution Spectrograph on the HET. The spectra have peak S/N of order 5--10 in 1200--3000 sec integrations. We achieve an internal precision of approximately ±1 km/s through cross-correlation techniques on the 37 echelle orders. Observations of these and additional Cepheids will continue when the season begins again for M31/M33.

We plan to use these spectra to infer metallicities for the Cepheids in the next step of our analyses.

We thank the DIRECT researchers for their assistance in target selection. The HET is operated by McDonald Observatory on behalf of The University of Texas at Austin, Pennsylvania State University, Stanford University, Ludwig-Maximilians-Universität München, and Georg-August-Universität Göttingen. This work is supported through NSF grants AST-9986817 (TGB) and AST-9987347 (TJM).

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Bulletin of the American Astronomical Society, 34
© 2002. The American Astronomical Soceity.