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Astron. Astrophys. 337, 779-789 (1998)


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The pulsating yellow supergiant V810 Centauri * **

F. Kienzle, G. Burki, M. Burnet and G. Meynet

Observatoire de Genève, Ch. des Maillettes 51, CH-1290 Sauverny, Switzerland

Received 25 May 1998 / Accepted 22 June 1998

Abstract

The F8 Ia supergiant V810 Centauri is part of a long-term high-precision photometric monitoring program on long period variables started twenty years ago. Time series analysis of this unique set of 500 data points, spanning almost fifteen years in the homogeneous Geneva photometric system, is presented. Cluster membership, physical parameters and evolutionary status of the star are reinvestigated. Radial velocity data do not support the cluster membership to Stock 14. Ultraviolet and optical spectrophotometry is combined with optical and infrared photometry to evaluate the physical parameters of the yellow supergiant ([FORMULA] = 5970 K, [FORMULA] = -8.5, R = 420 [FORMULA]) and of its B0 III companion. From theoretical stellar evolutionary tracks, an initial mass of [FORMULA]25 [FORMULA] is estimated for V810 Cen, which is actually at the end of its first redward evolution.

V810 Cen is a multi-periodic small amplitude variable star, whose amplitudes are variable with time. The period of the main mode, [FORMULA]156 d, is in agreement with the Period-Luminosity-Colour relation for supergiants. This mode is most probably the fundamental radial one. According to the theoretical pulsation periods for the radial modes, calculated from a linear non-adiabatic analysis, the period of the observed second mode, [FORMULA]107 d, is much too long to correspond to the first radial overtone . Thus, this second mode could be a non-radial p-mode. Other transient periods are observed, in particular at [FORMULA]187 d. The length of this period suggests a non-radial g-mode. Then, the complex variability of V810 Cen could be due to a mixing of unstable radial and non-radial p- and g-modes.

Key words: stars: individual: V 810 Centauri – stars: supergiants – stars: oscillations – stars: evolution – open clusters and associations: individual: Stock 14

* Based on observations collected at the Swiss 40 cm and 70 cm and at the Danish 1.54 m telescopes, at the European Southern Observatory (La Silla, Chile)
** The photometric data are only available in electronic form at the CDS via anonymous ftp to cdsarc.u.strasbg.fr/pub/cats/J/A+A/337/779 (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/337/779

Send offprint requests to: F. Kienzle
Correspondence to: Francesco.Kienzle@obs.unige.ch

© European Southern Observatory (ESO) 1998

Online publication: August 27, 1998

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