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Paper: The Period–Luminosity Relation of Mira Variables in NGC 6388 and NGC 6441
Volume: 378, Why Galaxies Care About AGB Stars: Their Importance as Actors and Probes
Page: 86
Authors: Matsunaga, N.; the IRSF/SIRIUS team
Abstract: We report a result from our repeated near-infrared observations of Mira variables in the globular clusters NGC 6388 and 6441. These two clusters are considered peculiar clusters with blue horizontal branch stars and RR Lyr variables which are not expected for their relatively high metallicities. We derive their distance moduli by fitting the Mira variables in the period-luminosity relation. They are the first distance estimates for these clusters to be observationally obtained in a way that is independent of the horizontal branch stars. The distances obtained reveal that the absolute magnitudes of the peculiar RR Lyr variables are similar to those of the metal-poor ones with [Fe/H] = −2 dex. It is suggested that the constraint we found should be reproduced by any theories to explain the horizontal morphology of these peculiar clusters.
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