The ACS LCID Project. VIII. The short-period Cepheids of Leo A
Edouard J. Bernard, Matteo Monelli, Carme Gallart, Giuliana, Fiorentino, Santi Cassisi, Antonio Aparicio, Andrew A. Cole, Igor Drozdovsky,, Sebastian L. Hidalgo, Evan D. Skillman, Peter B. Stetson, Eline Tolstoy

TL;DR
This study identifies and classifies variable stars, including Cepheids and RR Lyrae, in Leo A using Hubble data, providing insights into their properties, distances, and metallicity effects in a low-metallicity galaxy.
Contribution
First detailed survey of variable stars in Leo A, revealing their types, periods, and implications for distance measurement and metallicity effects.
Findings
Detected 166 variables, including 156 Cepheids and 10 RR Lyrae stars.
Most Cepheids have periods shorter than 1.5 days due to low metallicity.
Distance estimates from different methods are consistent, highlighting metallicity effects.
Abstract
We present the results of a new search for variable stars in the Local Group dwarf galaxy Leo A, based on deep photometry from the Advanced Camera for Surveys onboard the Hubble Space Telescope. We detected 166 bona fide variables in our field, of which about 60 percent are new discoveries, and 33 candidate variables. Of the confirmed variables, we found 156 Cepheids, but only 10 RR Lyrae stars despite nearly 100 percent completeness at the magnitude of the horizontal branch. The RR Lyrae stars include 7 fundamental and 3 first-overtone pulsators, with mean periods of 0.636 and 0.366 day, respectively. From their position on the period-luminosity (PL) diagram and light-curve morphology, we classify 91, 58, and 4 Cepheids as fundamental, first-overtone, and second-overtone mode Classical Cepheids (CC), respectively, and two as population II Cepheids. However, due to the low metallicity…
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