Bibcode
Bernard, Edouard J.
Bibliographical reference
STELLAR PULSATION: CHALLENGES FOR THEORY AND OBSERVATION: Proceedings of the International Conference. AIP Conference Proceedings, Volume 1170, pp. 213-215 (2009).
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9
2009
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Description
We present results of the search for variable stars in a sample of Local
Group isolated dwarf galaxies, namely LGS3, IC1613, Cetus, and Tucana,
based on very deep HST/ACS data. About 900 variables and candidates have
been found in total. Among the confirmed variables, we identified about
700 RR Lyrae stars, 60 Cepheids, and 50 eclipsing binaries from their
light-curve morphology and location in the color-magnitude diagrams. We
find that the properties of these variables reflect details of the star
formation history of the galaxies. In particular, our in depth study of
the RR Lyrae population of the dSph Tucana reveals interesting details
about the early evolution of this galaxy, and the origin of its stellar
population gradients. We find that the fainter RR Lyrae stars, also
having a shorter period, are more centrally concentrated than the more
luminous, longer period RR Lyrae variables. Through comparison with the
predictions of theoretical models of stellar evolution and stellar
pulsation, we interpret the fainter RR Lyrae stars as a more metal-rich
subsample, suggesting that a metallicity gradient must have appeared
very early on in the history of this galaxy. We also compare the
location of the Cepheids found in the galaxies of our sample in the
period-luminosity diagram with the Magellanic Clouds Cepheids of the
OGLE collaboration, and find that the Cepheids in the gas-rich dwarf
galaxies are classical Cepheids, while Cetus and Tucana harbor only
anomalous Cepheids.