Relation of Rotation and Pulsation Properties in $γ$ Doradus Stars

Abstract

Connection between stellar rotation and pulsation amplitude has been proposed for several types of pulsating variable stars, but no such relation has been established for gamma Doradus stars from spectroscopic v sin i measurements. A high-amplitude gamma Dor subclass was also suggested recently, which had not been explored by spectroscopic means before. We investigate the connection between rotation and pulsational properties of gamma Dor stars using a homogeneous spectroscopic sample with available TESS light curves. We obtained new stellar spectra with the ACE spectrograph on the 1-m RCC telescope of Konkoly Observatory and measured v sin i for a sample of 124 targets. For target selection, Gaia classifications were combined with TESS photometry. We used Fourier methods to determine the dominant frequencies from all available TESS light curves through sector 98. We also performed rotation- and inclination-dependent mode visibility modelling relying on GYRE Hough functions with TAR visibilities for the interpretation of our results. We find a decreasing upper envelope in both the peak-to-peak amplitude and the dominant-component semi-amplitude as a function of v sin i: high-v sin i stars show only low photometric amplitudes, whereas high-amplitude stars have low v sin i. We also confirm a positive relation between v sin i and the dominant pulsation frequency. The highest observed amplitudes also decrease towards higher dominant frequencies. Visibility modelling indicates that these trends cannot be explained by geometric effects alone, suggesting that the intrinsic pulsation amplitudes of gamma Dor stars physically decrease with increasing equatorial rotational velocity. Furthermore, the strong suppression of zonal dipole mode visibility at high rotation suggests that high-amplitude gamma Dor stars are likely slow rotators or moderate rotators viewed nearly pole-on.