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Oscillation mode identifications and models for the delta Scuti star FG Virginis

M. Viskum·H. Kjeldsen·T. R. Bedding·T. H. Dall·I. K. Baldry·H. Bruntt·S. Frandsen
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Abstract

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 mode (147 microHz) has l = 1. One of the radial modes (at 140 microHz) is the fundamental, implying that two modes with lower frequencies are g-modes. 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_sol. 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 caused by stellar rotation.

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M. Viskum, H. Kjeldsen, T. R. Bedding, T. H. Dall, I. K. Baldry, H. Bruntt, S. Frandsen. 1998-04-21. Oscillation mode identifications and models for the delta Scuti star FG Virginis. https://arxiv.org/abs/astro-ph/9804218

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