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Issue A&A
Volume 366, Number 2, February I 2001
Page(s) 547 - 557
Section Formation, structure and evolution of stars
DOI http://dx.doi.org/10.1051/0004-6361:20000196



A&A 366, 547-557 (2001)
DOI: 10.1051/0004-6361:20000196

Simultaneous intensive photometry and high resolution spectroscopy of $\delta$ Scuti stars

V. The high-degree modes in the pulsational content of BV Circini
L. Mantegazza, E. Poretti and F. M. Zerbi

Osservatorio Astronomico di Brera, Via E. Bianchi 46, 23807 Merate, Italy

(Received 6 September 2000 / Accepted 3 November 2000)

Abstract
We discuss here the pulsation properties of the $\delta$ Scuti star BV Circini on the basis of data obtained during a simultaneous photometric and spectroscopic campaign in 1996 and a spectroscopic one in 1998, and taking also advantage of the previous photometric observations by Kurtz (1981). Nine pulsation modes were detected from photometry and thirteen from spectroscopy; five of them are in common to both techniques. The spectroscopic data give ample evidence of dramatic amplitude variations in some modes, in particular the strongest spectroscopic mode in 1998 was not detectable in 1996 data. The two dominant photometric modes (6.33 and 7.89 cd-1) are observed on both seasons. The typing of the modes was performed by means of a simultaneous model fit of line profile and light variations. The 6.33 cd-1 photometric term is probably the fundamental radial mode, while the 7.89 cd-1 is a nonradial mode with $m\neq 0$. There are six high-degree prograde modes with an azimuthal order m ranging from -12 to -14, and also a retrograde mode with $m\sim 7$. These modes combined with the identification of the 6.33 cd-1 mode allowed us to estimate $i\sim 60^{\rm o}$ for the value of the inclination of the rotation axis. An accurate evaluation of the main stellar physical parameters is also proposed as a result of the pulsational analysis.


Key words: methods: data analysis -- techniques: spectroscopic -- techniques: photometric -- stars: individual: BV Cir -- stars: oscillations -- stars: variables: $\delta$ Sct

Offprint request: E. Poretti, poretti@merate.mi.astro.it

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© ESO 2001


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