The discovery of new γ Doradus stars from the HIPPARCOS mission

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 γ Doradus stars. We have used a multivariate classification scheme and report the discovery of 14 new γ 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 γ 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 gmodes. In view of the lack of a pulsation mechanism for these objects, we determine their position in the HR diagram with respect to the δ Scuti stars.