New short period stellar pulsators at large Galactocentric distances

TL;DR

This paper reports the discovery of 31 distant short-period pulsating stars, likely SX Phe or delta Scuti types, using the Rapid Temporal Survey, providing insights into their distribution and properties in the Galaxy.

Contribution

First identification of a large sample of distant short-period pulsators, expanding knowledge of their distribution and characteristics in the Galactic halo.

Findings

Most stars are over 3 kpc away, some beyond 20 kpc.

Several stars are located more than 10 kpc from the Galactic plane.

Spectral analysis indicates they are SX Phe or delta Scuti stars.

Abstract

We report the discovery of 31 blue, short period, pulsators made using data taken as part of the Rapid Temporal Survey (RATS). We find they have periods between 51-83 mins and full-amplitudes between 0.05-0.65 mag. Using the period-luminosity relationship for short period pulsating stars we determine their distance. Assuming they are pulsating in either the fundamental or first over-tone radial mode the majority are located at a distance greater than 3kpc, with several being more than 20 kpc distant. Most stars are at least 1 kpc from the Galactic plane, with three being more than 10 kpc. One is located in the direction of the Galactic anti-center and has Galactocentric distance of ~30 kpc and is ~20 kpc below the plane: they are therefore potential tracers of Galactic structure. We have obtained low-resolution spectra for a small number our targets and find they have temperatures between 7200--7900K and a metal content less than Solar. The colours of the pulsators and the spectral fits to those stars for which we have spectra indicate that they are either SX Phe or delta Scuti stars. We estimate the number of SX Phe stars in our Galaxy and find significantly fewer per unit mass than reported in massive globular clusters or dwarf spheroidal galaxies.