OSCILLATION MODE-IDENTIFICATIONS AND MODELS FOR THE DELTA-SCUTI STAR FG VIRGINIS

We present new spectroscopic and photometric time series observations of the delta Scuti star FG Vir.We detect the oscillations via changes in the equivalent widths of hydrogen and metal absorption lines. From the ratios between spectroscopic and photometric amplitudes, we assign l values to the eight strongest oscillation modes. In particular, we identify two radial modes (l = 0) and find that the main pulsation mod e (147 mu Hz) has l = 1. One of the radial modes (at 140 mu Hz) is the fundamental, implying that two modes with lower frequencies are g-mod es. For the radial modes, we compare frequencies with those calculated from a scaled delta Scuti star model and derive a density 0.1645 +/- 0.0005 rho(.). We then obtain a distance of 84 +/- 3 pc, in excellent agreement with the Hipparcos value. Finally, we suggest that a 3.5-day variability in all observables (equivalent widths and intensity) is c aused by stellar rotation.