Zwicky Transient Facility and Globular Clusters: Calibration of the gr-Band Absolute Magnitudes for the Yellow Post-Asymptotic-Giant-Branch Stars

TL;DR

This paper calibrates the absolute magnitudes of yellow PAGB stars in the g- and r-bands using Zwicky Transient Facility data, enabling their use as distance indicators for Population II stars in large sky surveys.

Contribution

First absolute calibration of yellow PAGB stars' magnitudes in g- and r-bands using globular cluster data and time-series observations.

Findings

Linear regression fits g-band magnitudes better.

Calibrated magnitudes can serve as Population II distance indicators.

Two calibration methods provided: mean and linear regression.

Abstract

We present the first absolute calibration for the yellow post-asymptotic-giant-branch (PAGB) stars in the g- and r-band based on time-series observations from the Zwicky Transient Facility. These absolute magnitudes were calibrated using four yellow PAGB stars (one non-varying star and three Type II Cepheids) located in the globular clusters. We provide two calibrations of the gr-band absolute magnitudes for the yellow PAGB stars, by using an arithmetic mean and a linear regression. We demonstrate that the linear regression provides a better fit to the g-band absolute magnitudes for the yellow PAGB stars. These calibrated gr-band absolute magnitudes have a potential to be used as population II distance indicators in the era of time-domain synoptic sky surveys.