EDP Sciences
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Volume 396, Number 3, December IV 2002
Page(s) 911 - 916
Section Formation, structure and evolution of stars
DOI http://dx.doi.org/10.1051/0004-6361:20021456

A&A 396, 911-916 (2002)
DOI: 10.1051/0004-6361:20021456

Line profile variations in the $\delta$ Scuti star FG Virginis: A high number of axisymmetric modes

L. Mantegazza and E. Poretti

INAF - Osservatorio Astronomico di Brera, Via E. Bianchi 46 23807 Merate, Italy
(Received 26 August 2002 / Accepted 26 September 2002)

Five consecutive nights of high resolution spectroscopic observations of the $\delta$ Scuti star FG Vir allowed us to analyze the radial velocity and line profile variations induced by non-radial multi-mode pulsations. Ten modes were detected. All of them have a photometric counterpart (Breger et al. 1998). Preliminary identifications have been performed by means of the simultaneous fit of line-profile and light variations. Most of these modes have an axisymmetric character ( m=0), one is retrograde (9.20 cd -1, m=1) and one is prograde with a relatively high order (21.55 cd -1, $\ell=3$, m=-1). The more accurate results regard the dominant mode (12.72 cd -1) which is axisymmetric with $\ell=1$. In this case we were able to obtain reliable estimates of its physical characteristics. The analysis of our data tends to support the idea that the stellar rotation axis probably has a rather low inclination (about $15^\circ$): this is probably the reason for the high number of observed axisymmetric modes. Hence, since the measured $v\sin i$ is 20.7 km s -1, we deduce that the rotation velocity should be around 80 km s -1 and the rotational period about 1.5 d.

Key words: stars: individual: FG Vir -- stars: oscillations -- stars: variables: $\delta$ Sct -- techniques: spectroscopic

Offprint request: L. Mantegazza, luciano@merate.mi.astro.it

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