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The acs LCID project-VIII. The short-period cepheids of Leo A


Bernard, EJ and Monelli, M and Gallart, C and Fiorentino, G and Cassisi, S and Aparicio, A and Cole, AA and Drozdovsky, I and Hidalgo, SL and Skillman, ED and Stetson, PB and Tolstoy, E, The acs LCID project-VIII. The short-period cepheids of Leo A, Monthly Notices of the Royal Astronomical Society, 432, (4) pp. 3047-3061. ISSN 0035-8711 (2013) [Refereed Article]

Copyright Statement

Copyright 2013 the authors.

DOI: doi:10.1093/mnras/stt655


We present the results of a newsearch 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 per cent are new discoveries and 33 candidate variables. Of the confirmed variables, we found 156 Cepheids, but only 10 RR Lyrae stars despite nearly 100 per cent completeness at the magnitude of the horizontal branch. The RR Lyrae stars include seven fundamental and three first-overtone pulsators, with mean periods of 0.636 and 0.366 d, 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 of Leo A, about 90 per cent of the detected Cepheids have periods shorter than 1.5 d. Comparison with theoretical models indicate that some of the fainter stars classified as CC could be Anomalous Cepheids. We estimate the distance to Leo A using the tip of the red giant branch (TRGB) and various methods based on the photometric and pulsational properties of the Cepheids and RR Lyrae stars. The distances obtained with the TRGB and RR Lyrae stars agree well with each other while that from the Cepheid PL relations is somewhat larger, which may indicate a mild metallicity effect on the luminosity of the short-period Cepheids. Due to its very low metallicity, Leo A thus serves as a valuable calibrator of the metallicity dependences of thevariable star luminosities.

Item Details

Item Type:Refereed Article
Keywords:stars: variables: Cepheids stars: variables: RR Lyrae galaxies: evolution galaxies: individual: Leo A dIrr Local Group galaxies: stellar content
Research Division:Physical Sciences
Research Group:Astronomical sciences
Research Field:Cosmology and extragalactic astronomy
Objective Division:Expanding Knowledge
Objective Group:Expanding knowledge
Objective Field:Expanding knowledge in the physical sciences
UTAS Author:Cole, AA (Professor Andrew Cole)
ID Code:87032
Year Published:2013
Web of Science® Times Cited:28
Deposited By:Mathematics and Physics
Deposited On:2013-11-06
Last Modified:2017-11-06

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