Pulsational behaviour of the Delta Scuti star X Caeli

Simultaneous photometric B, V (14 consecutive nights; 100 hours of observations, 1634 V data points) and high resolution spectroscopic observations (4 consecutive nights; 27 hours, 101 spectrograms) have been performed on the Delta Scuti star X Caeli at La Silla Observatory on November 1992. The photometric data allow to detect 14 pulsation terms separated into two frequency groups: 5.8-7.7 c/d and 11.2-15 c/d. Most of the terms of the second group have frequencies corresponding to the second Fourier harmonics or to the non-linear coupling terms of the components of the first group. The comparison with our previous 1989 observations show that while the amplitude of the strongest term (v = 7.39 c/d) is very stable, a few other terms have changed their amplitudes. From the study of the line profiles and their variations we derive v sin i ~= 70 km/s, i ~= 65 - 90 degrees, and that the dominant mode is a prograde mode with m=-1 and l=1 or 2. The other modes are probably nonradial p modes with l=2 +- 1. There is no evidence of the presence of high-degree sectorial modes with l=m. The stellar spectral lines have a narrow absorption core which is probably due to the presence of a circumstellar shell.