Long-term photometric monitoring with the Mercator telescope. Frequencies and multicolour amplitudes of $\gamma$ Doradus stars

TL;DR

This study used long-term photometric data from the Mercator telescope to identify and analyze frequencies and amplitudes of Gamma Doradus stars, enhancing understanding of their gravity modes through multicolour observations.

Contribution

It provides the first extensive multicolour amplitude database for Gamma Doradus stars and confirms new candidates, improving mode identification for asteroseismology.

Findings

Frequencies and amplitudes for 21 Gamma Doradus stars are reported.

HD 74504 is identified as a new Gamma Doradus star.

Combined data from multiple sources improved frequency accuracy.

Abstract

Gamma Doradus stars are excellent targets for asteroseismology since the gravity modes present in these stars probe the deep stellar interiors. Mode identification will improve the knowledge of these stars considerably. A selected group of Gamma Doradus stars and some candidates were observed with the Mercator telescope to find and/or confirm the periodicities in the light variations and to derive reliable amplitude ratios in different pass bands. A frequency analysis was performed on all new data obtained in the Geneva photometric system. In order to have more reliable and accurate frequencies, the new data were combined with similar data from the literature and with Hipparcos observations. A set of frequencies that minimized the the residuals in a harmonic fit was searched for while allowing means and amplitudes to vary from one observation set to another. Frequencies and amplitudes in the photometric passbands of the Geneva system are given for 21 Gamma Doradus stars. We report the discovery of HD 74504 as a newly found Gamma Doradus star. Our study provides the first extensive multicolour database for the understanding of gravity modes in F-type stars.