EDP Sciences
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Volume 380, Number 1, December II 2001
Page(s) 198 - 211
Section Formation, structure and evolution of stars
DOI http://dx.doi.org/10.1051/0004-6361:20011392

A&A 380, 198-211 (2001)
DOI: 10.1051/0004-6361:20011392

Stellar and circumstellar evolution of long period variable stars

M. O. Mennessier1 and X. Luri2

1  Université de Montpellier II and CNRS, G.R.A.A.L., cc072, 34095 Montpellier Cedex 5, France
2  Departament d'Astronomia i Meteorologia, Universitat de Barcelona, Avda. Diagonal 647, 08028 Barcelona, Spain

(Received 4 May 2001 / Accepted 26 September 2001)

In a first paper, HIPPARCOS astrometric and kinematic data were used to calibrate both infrared K and IRAS luminosities at the same time as kinematic parameters of Long Period Variable stars (LPVs). Individual estimated absolute magnitudes and a probabilistic assignation to galactic populations were deduced from these calibrations for each LPV of our sample. Here we propose a scenario of simultaneous stellar and circumstellar evolution according to the galactic populations. The transitory states of S and Tc stars allow us to confirm the location of the first dredge-up at $M_{\rm bol}=-3.5$. There is also evidence suggesting that a previous enrichment in s-elements from a more evolved companion may accelerate the evolution along the AGB. The possible evolution to OH LPVs is included in this scenario, and any of these stars may have a mass at the limit of the capability for a C enrichment up to ${\rm C/O} > 1$. A list of bright massive LPVs with peculiar envelope and luminosity properties is proposed as Hot Bottom Burning candidates. The He-shell flash star, R Cen, is found to be exceptionally bright and could become, before leaving the AGB, a C-rich LPV brighter than the usual luminosity limit of carbon stars.

Key words: stars: variable: general -- stars: evolution -- stars: AGB and post-AGB

Offprint request: M. O. Mennessier, Marie-Odile.Mennessier@graal.univ-montp2.fr

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