Journal Article

Asymptotic giant branch stars in the Leo I dwarf spheroidal galaxy

John W. Menzies, Patricia A. Whitelock, Michael W. Feast and Noriyuki Matsunaga

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 406, issue 1, pages 86-94
Published in print July 2010 | ISSN: 0035-8711
Published online July 2010 | e-ISSN: 1365-2966 | DOI:
Asymptotic giant branch stars in the Leo I dwarf spheroidal galaxy

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26 asymptotic giant branch (AGB) variables are identified in the Local Group galaxy Leo I. These include seven Mira and five semiregular variables for which periods, amplitudes and mean magnitudes are determined. The large range of periods for the Miras, 158 < P < 523 d, suggests an AGB spanning a significant age range. The youngest must be around 1.6 Gyr while the oldest could be 10 Gyr or more. Two of these old Miras are found in the outer regions of Leo I (over 490 arcsec from the centre) where stars on the extended AGB are rare. They could provide an interesting test of third dredge-up and mass-loss in old stars with low metallicity, and are worth further detailed investigation. At least two stars, one a Mira and the other an irregular variable, are undergoing obscuration events due to dust ejection.

An application of the Mira period–luminosity relation to these stars yields a distance modulus for Leo I of (mM)0= 21.80 ± 0.11 mag (internal), ± 0.12 (total) (on a scale that puts the Large Magellanic Cloud at 18.39 mag) in good agreement with other determinations.

Keywords: stars: AGB and post-AGB; stars: variables: general; galaxies: dwarf; galaxies: individual: Leo I; Local Group; galaxies: stellar content

Journal Article.  4816 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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