Population II Cepheids in Galactic GC Virtual Observatory Resource

Authors
  1. Cruz Reyes M.
  2. Anderson I.R.
  3. Das S.
  4. Published by
    CDS
Abstract

We have identified a sample of 88 bona fide population II Cepheids (henceforth: Cepheids) and 44 candidates in Galactic globular clusters (GCs). Seventy-eight of the Cepheids in the sample align within 2{sigma} of the period-luminosity relation for Milky Way Type II Cepheids (T2CEP). Nine align with the period-luminosity relation for fundamental-mode Anomalous Cepheids (ACEPs), and only one (BL Bootis) follows the relation for first-overtone ACEPs determined using 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 Gaia 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 (Specific Object Study) and 74% for the classifier of variable stars. Using linear MESA-RSP models, we determined the red and blue edges of the instability strip for T2CEPs. We found that the models providing the best fit to the observations are able to fit 90% of the stars in our sample. They have the following parameters: M=0.6M_{sun}_, Z=0.0003, and this percentage does not change for two different values of the helium abundance (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.

Keywords
  1. globular-star-clusters
  2. variable-stars
  3. population-ii-stars
Bibliographic source Bibcode
2025A&A...695A.164C
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History

2025-03-18T11:08:29Z
Resource record created
2025-03-18T11:08:29Z
Created
2025-04-01T12:52:45Z
Updated

Contact

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