Issue |
A&A
Volume 695, March 2025
|
|
---|---|---|
Article Number | A164 | |
Number of page(s) | 8 | |
Section | Catalogs and data | |
DOI | https://doi.org/10.1051/0004-6361/202453137 | |
Published online | 18 March 2025 |
Variable stars in Galactic globular clusters
II. Population II Cepheids
1
Institute of Physics, Laboratory of Astrophysics, École Polytechnique Fédérale de Lausanne (EPFL),
1290
Versoix, Switzerland
2
Konkoly Observatory, HUN-REN Research Centre for Astronomy and Earth Sciences,
Konkoly-Thege Miklós út 15–17,
1121
Budapest, Hungary
3
CSFK, MTA Centre of Excellence, Budapest,
Konkoly-Thege Miklós út 15–17,
1121
Budapest, Hungary
★ Corresponding authors; mauricio.cruzreyes@epfl.ch; richard.anderson@epfl.ch
Received:
23
November
2024
Accepted:
9
February
2025
We identified a sample of 88 bona fide Population II Cepheids (henceforth referred to as Cepheids) and 44 candidates in Galactic globular clusters (GCs). Seventy-eight of the Cepheids in the sample align within 2 σ of the period-luminosity relation for Milky Way Type II Cepheids (T2CEPs). Nine align with the period-luminosity relation for fundamental-mode anomalous Cepheids (ACEPs), and only one (BL Boötis) follows the relation for first-overtone ACEPs, as determined from observations of ACEPs in the Large Magellanic Cloud. For sources in common between our catalog and the OGLE catalog, the classification agrees in 94% of cases. In comparison, for sources shared between the Gaia Specific Object Study (SOS) and OGLE, the agreement is 74%. In the dense environments of GCs, our analysis shows that the completeness of the Gaia catalogs for Cepheids is 64% for the SOS and 74% for the classifier of variable stars. We determined the red and blue edges of the instability strip for T2CEPs using linear MESA-RSP models. We find that the best-fit models, with M = 0.6 M⊙ and Z = 0.0003, are able to fit 90% of the stars in our sample. This percentage is the same for helium abundances Y = 0.220 and 0.245. Higher values of Y lower this percentage, and the same effect is observed with lower values of Z. In the future, combining the sample of T2CEPs with the precise parallaxes obtained from GCs will strengthen the geometric calibration of a distance ladder based on Population II stars. This will be useful for determining distances within the Milky Way and for cross-checking distances to Local Group galaxies determined through other methods.
Key words: catalogs / stars: Population II / stars: variables: Cepheids
© The Authors 2025
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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