A Homogenized Catalogue of Variable Stars in the Globular Cluster M22: Membership, Physical Parameters, and Distance
Abstract
We present a photometric analysis of the variable stars in the field of the globular cluster M22 (NGC 6656), using time-series photometry from the literature and from OGLE and Gaia-DR3 data. From a sample of 666 variable stars in the field, we identify 94 as cluster members, including 10 RRab, 17 RRc, 2 Type II Cepheids, 15 SX Phe, 15 SR stars and 22 eclipsing binaries. Fourteen of these members are not included in the Catalogue of Variable Stars in Globular Clusters. Through the Fourier decomposition of the RR Lyrae light curves, we derived [Fe/H] = −1.73 ± 0.17 dex and d = 3.27 ± 0.14 kpc. Among the RRc stars, V15 shows an additional frequency with a frequency ratio f0.61/f1O = 0.6152, consistent with the RR0.61 phenomenon. Using P-L relations for member SX Phe stars, we obtained d = 3.31 ± 0.17 kpc, consistent with the RR Lyrae distance. We constructed a CMD comprising only cluster members, which allows us to confirm the evolutionary status of the cluster's RR Lyrae stars. None of the fitted isochrones satisfactorily reproduces the CMD morphology, which is consistent with the presence of multiple stellar populations in M22.
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BibTeX
@misc{yepez2026homogenized,
title = {{A Homogenized Catalogue of Variable Stars in the Globular Cluster M22: Membership, Physical Parameters, and Distance}},
author = {M. A. Yepez and B. Moreno-Amaro and M. Ornelas-Castañeda and A. Arellano Ferro and D. Deras},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.11850},
eprint = {2609.11850},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.11850},
}
RIS
TY - UNPB
TI - A Homogenized Catalogue of Variable Stars in the Globular Cluster M22: Membership, Physical Parameters, and Distance
AU - M. A. Yepez
AU - B. Moreno-Amaro
AU - M. Ornelas-Castañeda
AU - A. Arellano Ferro
AU - D. Deras
PY - 2026
DA - 2026/09/10
PB - arXiv
DO - 10.48550/arxiv.2609.11850
UR - https://arxiv.org/abs/2609.11850
AB - We present a photometric analysis of the variable stars in the field of the globular cluster M22 (NGC 6656), using time-series photometry from the literature and from OGLE and Gaia-DR3 data. From a sample of 666 variable stars in the field, we identify 94 as cluster members, including 10 RRab, 17 RRc, 2 Type II Cepheids, 15 SX Phe, 15 SR stars and 22 eclipsing binaries. Fourteen of these members are not included in the Catalogue of Variable Stars in Globular Clusters. Through the Fourier decomposition of the RR Lyrae light curves, we derived [Fe/H] = −1.73 ± 0.17 dex and d = 3.27 ± 0.14 kpc. Among the RRc stars, V15 shows an additional frequency with a frequency ratio f_0.61/f_1O = 0.6152, consistent with the RR_0.61 phenomenon. Using P-L relations for member SX Phe stars, we obtained d = 3.31 ± 0.17 kpc, consistent with the RR Lyrae distance. We constructed a CMD comprising only cluster members, which allows us to confirm the evolutionary status of the cluster's RR Lyrae stars. None of the fitted isochrones satisfactorily reproduces the CMD morphology, which is consistent with the presence of multiple stellar populations in M22.
ER -