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Astron. Astrophys. 327, 1077-1086


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A spectroscopic study of the $\delta$ Scuti star $\rho$ Puppis*

P. Mathias1, D. Gillet2, C. Aerts3,**, and M.G. Breitfellner4

1Observatoire de la Côte d'Azur, Département Fresnel, U.M.R. 6528, BP 4229, F-06304 Nice Cedex 04, France
2Observatoire de Haute-Provence, CNRS, F-04870 Saint-Michel l'Observatoire, France
3Instituut voor Sterrenkunde, Katholieke Universiteit Leuven, Celestijnenlaan 200B, B-3001 Heverlee, Belgium
4ISO Science Operations, ESA/VILSPA Satellite Tracking Station, PO Box 50727, E-28080 Madrid, Spain

Received 18 March 1997 / Accepted 21 July 1997

Abstract

We present a spectroscopic analysis of the $\delta$ Scuti star $\rho$ Pup on the basis of high resolution data spread over 4 consecutive nights. Despite the clearly sinusoidal shape of the radial-velocity curves, cycle-to-cycle variations are observed. A frequency analysis points towards the already known frequency $\nu_0=7.098168 $c.d-1 assigned to a radial mode and towards two possible secondary non-radial oscillations at $\nu_{1} = 7.8$ c.d-1 and $\nu_{2} = 6.3$ c.d-1 of much smaller amplitude.

Using the moment method we confirm that the main oscillation is a radial mode. The second mode is found to be axisymmetric, but because of its small amplitude and our relatively small data set, no more detailed information on its pulsation parameters could be derived. The third frequency, if real, corresponds to a non-axisymmetric mode.

The running wave effect may be present between the Fe I and H$\alpha$ lines, the latter being late by about 0.5 % of the pulsation period. No evidence is found in our observed profiles (Ca I, Fe I, H$\alpha$) for a shock wave mechanism as previously suggested by Dravins et al. (1977). New observations are required to confirm the presence of a period-dependent shock wave which should be of weak intensity.

Key words: stars: oscillations - stars: variables: $\delta$ Scuti - stars: individual: $\rho$ Pup

*Based on observations obtained at the European Southern Observatory, Chile
**Postdoctoral Fellow, Fund for Scientific Research, Flanders, Belgium


© European Southern Observatory (ESO) 1997

Online publication: October 20, 1997
Last change: April 6, 1998
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