Toward a Census of Variable Stars in Northern Local Group Dwarf Irregular Galaxies

Abstract

Dwarf galaxies in the local group provide a unique astrophysical laboratory. In particular, they allow us to probe pulsating (and other) variable stars in low-metallicity environments with abundances below that of the SMC. Our observing program, described in detail by C. Gössl's contribution, yields a large number of intrinsically bright variable stars that can serve as probes of the stellar population and star formation history of these galaxies. Most prominent are pulsation variables like Miras (LPVs) and $δ$ Cep stars, but we also find other types of variable stars, e.g. RV Tauri stars, irregular red variables etc. We present a preliminary census for the three galaxies DDO 216, Leo A and GR8.