The discovery of new gamma Doradus stars from the HIPPARCOS mission

Abstract

We present a classification of 39 new variable stars with spectral type between A2 and F8 discovered by Hipparcos with the aim to find new gamma Doradus stars. We have used a multivariate classification scheme and report the discovery of 14 new gamma Doradus variables among this unbiased sample. Our results point out the biased nature towards hot temperatures of earlier, ground-based surveys of these variables. The coolest star among our sample has an effective temperature only slightly hotter than 6 000 K. For most of the 14 new gamma Doradus stars, we are able to detect more than one period in the Hipparcos light curve. The multiperiodicity points towards the presence of high-order g-modes. In view of the lack of a pulsation mechanism for these objects, we determine their position in the HR diagram with respect to the delta Scuti stars.