# Rotational modulation in TESS B stars

## TL;DR

This study analyzes light curves of B stars from TESS and Kepler to identify rotational modulation, revealing that many B stars exhibit surface features causing brightness variations, with implications for stellar surface phenomena.

## Contribution

The paper provides the first comprehensive classification of rotational variability in B stars using TESS and Kepler data, confirming the prevalence of surface features causing brightness modulation.

## Key findings

- Approximately 40% of B stars show rotational modulation.
- Observed projected rotational velocities are lower than estimated equatorial velocities.
- Many B stars likely have surface features not caused by abundance patches.

## Abstract

Light curves and periodograms of 160 B stars observed by the TESS space mission and 29 main-sequence B stars from Kepler and K2 were used to classify the variability type. There are 114 main-sequence B stars in the TESS sample, of which 45 are classified as possible rotational variables. This confirms previous findings that a large fraction (about 40 percent) of A and B stars may exhibit rotational modulation. Gaia DR2 parallaxes were used to estimate luminosities, from which the radii and equatorial rotational velocities can be deduced. It is shown that observed values of the projected rotational velocities are lower than the estimated equatorial velocities for nearly all the stars, as they should be if rotation is the cause of the light variation. We conclude that a large fraction of main-sequence B stars appear to contain surface features which cannot likely be attributed to abundance patches.