1998BaltA...7..211B

The Whole Earth Telescope XCOV13 campaign, which was carried out from a temporary command center in Vienna, included two main-sequence pulsators: the δ Scuti star 4 CVn and the new γ Dor variable, HD 108100. The astronomical results for these stars are summarized. The paper also discusses the progress as well as further potential of δ Scuti stars for asteroseismology. Extensive multi-site campaigns of individual δ Scuti stars show that 24 or more pulsation modes with l values of 0, 1 and 2 can be detected photometrically. Spectroscopically, also about 30 modes have been detected, and these can be identified with modes of l values up to 20. Since each technique favors the detection of specific types of modes, hundreds or thousands of modes must be excited in δ Scuti stars. We examine the quantities which can be matched between observations and theoretical models specifically computed for each star. Recent progress in the mode identification of multiple pulsation modes is illustrated by presenting an application of the phase shift method for the two stars, FG Vir and 4 CVn, recently measured by DSN (Delta Scuti Network) and WET. The XCOV13 results on 4 CVn can be used to illustrate why less extensive studies of δ Scuti could lead to erroneous conclusions of unstable pulsation modes.