Period-luminosity relationship for SX Phoenicis stars in Galactic globular clusters

TL;DR

This study analyzes the period-luminosity relationship of SX Phoenicis stars in Galactic globular clusters by compiling a large dataset and using double-mode pulsators to address mode identification challenges.

Contribution

It introduces a method to study the period-luminosity relation using confirmed double-mode pulsators to overcome mode identification issues.

Findings

Compiled a catalog of ~250 SX Phoenicis stars in globular clusters.

Proposed using double-mode radial pulsators to define the period-luminosity relation.

Highlighted difficulties due to mode mixture and identification challenges.

Abstract

We compiled a list of about 250 SX Phoenicis stars known in Galactic globular clusters in order to study period-luminosity relation for this type of variable. The absolute magnitudes of these stars are derived using metallicity-luminosity calibration for RR Lyrae stars. The mixture of different radial and non-radial modes present in SX Phoenicis stars and the lack of unique method of mode identification cause the difficulties in defining strict period-luminosity relation. As a solution we propose to use confirmed double-mode radial pulsators.