Stellar and circumstellar evolution of long period variable stars

Abstract

In a rst paper, HIPPARCOS astrometric and kinematic data were used to calibrate both infraredKand IRAS luminosities at the same time as kinematic parameters of Long Period Variable stars (LPVs). Individualestimated absolute magnitudes and a probabilistic assignation to galactic populations were deduced from thesecalibrations for each LPV of our sample. Here we propose a scenario of simultaneous stellar and circumstellarevolution according to the galactic populations. The transitory states of S and Tc stars allow us to con rm thelocation of the rst dredge-up atMbol=−3:5. There is also evidence suggesting that a previous enrichment ins-elements from a more evolved companion may accelerate the evolution along the AGB. The possible evolutionto OH LPVs is included in this scenario, and any of these stars may have a mass at the limit of the capability fora C enrichment up to C=O>1. A list of bright massive LPVs with peculiar envelope and luminosity properties isproposed as Hot Bottom Burning candidates. The He-shell flash star, R Cen, is found to be exceptionally brightand could become, before leaving the AGB, a C-rich LPV brighter than the usual luminosity limit of carbon stars.