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Astron. Astrophys. 335, 549-560 (1998)

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Oscillation mode identifications and models for the [FORMULA] Scuti star FG Virginis

M. Viskum 1, H. Kjeldsen 1, 2, T.R. Bedding 3, T.H. Dall 1, I.K. Baldry 3, H. Bruntt 1 and S. Frandsen 1

1 Institute of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C, Denmark
2 Theoretical Astrophysics Center, Danmarks Grundforskningsfond, Aarhus University, DK-8000 Aarhus C, Denmark
3 Chatterton Astronomy Department, School of Physics, University of Sydney, 2006, Australia

Received 30 January 1998 / Accepted 22 April 1998


We present new spectroscopic and photometric time series observations of the [FORMULA] 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 [FORMULA] values to the eight strongest oscillation modes. In particular, we identify two radial modes ([FORMULA]) and find that the main pulsation mode (147 µHz) has [FORMULA]. One of the radial modes (at 140µHz) 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 [FORMULA] Scuti star model and derive a density [FORMULA]. We then obtain a distance of [FORMULA] 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.

Key words: ffi Scuti – stars: oscillations – stars: individual: HD106384=FG Vir

Send offprint requests to: M. Viskum

© European Southern Observatory (ESO) 1998

Online publication: June 18, 1998