Red noise and pulsations in evolved massive stars

TL;DR

This study analyzes high-cadence space photometry of evolved massive stars, revealing pervasive red noise and pulsations, with a significant increase in known pulsating Wolf-Rayet stars, enhancing understanding of their variability.

Contribution

It provides the first comprehensive analysis of variability in a clean sample of evolved massive stars, doubling the known pulsating Wolf-Rayet stars and characterizing their noise and pulsation properties.

Findings

Red noise detected in all stars, similar to OB-stars.

Coherent pulsations found in 20% of Wolf-Rayet stars.

Most pulsations occur at 3-14 per day, indicating pulsational activity.

Abstract

We examine high-cadence space photometry taken by the Transiting Exoplanet Survey Satellite (TESS) of a sample of evolved massive stars (26 Wolf-Rayet stars and 8 Luminous Blue Variables or candidate LBVs). To avoid confusion problems, only stars without bright Gaia neighbours and without evidence of bound companions are considered. This leads to a clean sample, whose variability properties should truly reflect the properties of the WR and LBV classes. Red noise is detected in all cases and its fitting reveals characteristics very similar to those found for OB-stars. Coherent variability is also detected for 20% of the WR sample. Most detections occur at moderately high frequency (3--14/d), hence are most probably linked to pulsational activity. This work doubles the number of WRs known to exhibit high-frequency signals.