TESS lightcurves of gamma-Cas stars

TL;DR

This study analyzes TESS lightcurves of gamma-Cas stars, revealing their complex variability patterns and similarities to typical Be stars, with no unique optical photometric signatures.

Contribution

First detailed TESS lightcurve analysis of gamma-Cas stars showing their variability features and lack of distinctive optical signatures.

Findings

Lightcurves show broad frequency groups and narrow peaks.

Signals are mostly at low frequencies, with few above 5/d.

Variability patterns change over time without outbursts.

Abstract

gamma-Cas stars constitute a subgroup of Be stars showing unusually hard and bright X-ray emission. In search for additional peculiarities, we analyzed the TESS lightcurves of 15 gamma-Cas analogs. Their periodograms display broad frequency groups and/or narrow isolated peaks, often superimposed over red noise. The detected signals appear at low frequencies, with few cases of significant signals beyond 5/d (and all of them are faint). The signal amplitudes, and sometimes the frequency content, change with time, even in the absence of outburst events. On the basis of their optical photometric variability, gamma-Cas stars reveal no distinctive behaviour and thus appear similar to Be stars in general.