Zwicky Transient Facility and Globular Clusters: The Period-Luminosity and Period-Wesenheit Relations for Type II Cepheids
Abstract
We present the first gri-band period-luminosity (PL) and period-Wesenheit (PW) relations for 37 Type II Cepheids (TIICs) located in 18 globular clusters based on photometric data from the Zwicky Transient Facility. We also updated BVIJHK-band absolute magnitudes for 58 TIICs in 24 globular clusters using the latest homogeneous distances to the globular clusters. The slopes of g/r/i- and B/V/I-band PL relations are found to be statistically consistent when using the same sample of distance and reddening. We employed the calibration of ri-band PL/PW relations in globular clusters to estimate a distance to M31 based on a sample of ~270 TIICs from the PAndromeda project. The distance modulus to M31, obtained using calibrated ri-band PW relation, agrees well with the recent determination based on classical Cepheids. However, distance moduli derived using the calibrated r- and i-band PL relations are systematically smaller by ~0.2 mag, suggesting there are possible additional systematic errors on the PL relations. Finally, we also derive the period-color (PC) relations and for the first time the period-Q-index (PQ) relations, where the Q-index is reddening free, for our sample of TIICs. The PC relations based on (r - i) and near-infrared colors and the PQ relations are found to be relatively independent of the pulsation periods.
- Publication:
-
The Astronomical Journal
- Pub Date:
- October 2022
- DOI:
- 10.3847/1538-3881/ac87a4
- arXiv:
- arXiv:2208.03404
- Bibcode:
- 2022AJ....164..154N
- Keywords:
-
- Type II Cepheid variable stars;
- Globular star clusters;
- Distance indicators;
- Sky surveys;
- Wide-field telescopes;
- 2124;
- 656;
- 394;
- 1464;
- 1800;
- Astrophysics - Solar and Stellar Astrophysics;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 14 pages, 8 Figures and 5 Tables, AJ accepted