Discovery of a rapidly pulsating subdwarf B star candidate in omega Cen

TL;DR

This paper reports the discovery of the first variable extreme horizontal branch star in the globular cluster omega Cen, exhibiting rapid pulsations consistent with subdwarf B pulsators, expanding understanding of stellar variability in such environments.

Contribution

It presents the first detection of a rapidly pulsating subdwarf B star candidate within a globular cluster, based on observed pulsation and color analysis.

Findings

Detected a star with 114 s pulsation period and 32 mmag amplitude.

Estimated effective temperature of 31,500 K, within the instability strip.

Strengthens the case for a new class of pulsating stars in globular clusters.

Abstract

We report the discovery of the first variable extreme horizontal branch star in a globular cluster (omega Cen). The oscillation uncovered has a period of 114 s and an amplitude of 32 mmags. A comparison between horizontal branch models and observed optical colours indicates an effective temperature of 31,500+-6,300 K for this star, placing it within the instability strip for rapidly oscillating B subdwarfs. The time scale and amplitude of the pulsation detected are also in line with what is expected for this type of variable, thus strengthening the case for the discovery of a new subdwarf B pulsator.