Rotational characteristics of five photometrically variable stars

TL;DR

This study investigates whether brightness variations in hot stars are caused by rotational modulation from surface spots, comparing spectroscopic and photometric frequencies, and finds evidence supporting rotational effects in some cases.

Contribution

It demonstrates that surface spot activity may cause rotational modulation in stars hotter than 6500 K, using combined spectroscopic and photometric data.

Findings

Spectroscopic frequency was lower than photometric frequency in all five stars.

Two stars showed complex variability likely due to pulsations.

Surface spots may induce rotational modulation in hot stars above 6500 K.

Abstract

This study explores photometric variability in a sample of hot stars in order to test whether variability arises from rotational modulation due to surface temperature spots. Frequencies determined from the projected rotational velocities were compared with frequencies estimated on the basis of TESS light curves. In all five cases, the spectroscopic frequency was lower than the photometric one preserving possibility that the observed brightness variations can be rotationally induced. In two of our targets, HT Cet and HD 219487, the photometric frequency spectra suggest more complex variability, likely pulsations. Our results suggest that spot activity inducing rotational modulation may exist in stars hotter than 6500 K, highlighting the value of combined spectroscopic and photometric analysis of variations.