The Variable Stars of the Draco Dwarf Spheroidal Galaxy - Revisited

TL;DR

This study provides an extensive CCD survey of variable stars in the Draco dwarf galaxy, including detailed photometry and metallicity analysis, reaffirming its Oosterhoff intermediate classification and expanding knowledge of its variable star population.

Contribution

It offers the largest areal coverage of Draco variable stars to date, with new data on their properties, metallicities, and classifications, including double-mode RR Lyrae stars and anomalous Cepheids.

Findings

Identified 270 RR Lyrae stars and 9 anomalous Cepheids in Draco.

Reconfirmed the Oosterhoff intermediate nature of Draco's RR Lyrae population.

Derived mean metallicity of <[Fe/H]> = -2.19 for ab-type RR Lyrae stars.

Abstract

We present a CCD survey of variable stars in the Draco dwarf spheroidal galaxy. This survey, which has the largest areal coverage since the original variable star survey by Baade & Swope, includes photometry for 270 RR Lyrae stars, 9 anomalous Cepheids, 2 eclipsing binaries, and 12 slow, irregular red variables, as well as 30 background QSOs. Twenty-six probable double-mode RR Lyrae stars were identified. Observed parameters, including mean V and I magnitudes, V amplitudes, and periods, have been derived. Photometric metallicities of the ab-type RR Lyrae stars were calculated according to the method of Jurcsik & Kovacs, yielding a mean metallicity of <[Fe/H]> = -2.19 +/- 0.03. The well known Oosterhoff intermediate nature of the RR Lyrae stars in Draco is reconfirmed, although the double-mode RR Lyrae stars with one exception have properties similar to those found in Oosterhoff type II globular clusters. The period-luminosity relation of the anomalous Cepheids is rediscussed with the addition of the new Draco anomalous Cepheids.