The puzzle of the CNO abundances of α cygni variables resolved by the ledoux criterion

Cyril Georgy, Hideyuki Saio, Georges Meynet

Research output: Contribution to journalArticlepeer-review

31 Citations (Scopus)


Recent stellar evolution computations show that the blue supergiant (BSG) stars could come from two distinct populations: a first group arising from massive stars that just left the main sequence and are crossing the Hertzsprung-Russell diagram (HRD) towards the red supergiant (RSG) branch, and a second group coming from stars that have lost considerable amount of mass during the RSG stage and are crossing the HRD for a second time towards the blue region. Due to very different luminosity-to-mass ratio, only stars from the second group are expected to have excited pulsations observable at the surface. In a previous work, we have shown that our models were able to reproduce the pulsational properties of BSGs. However, these models failed to reproduce the surface chemical composition of stars evolving back from an RSG phase. In this Letter, we show how the use of the Ledoux criterion instead of the Schwarzschild one for convection allows us to significantly improve the agreement with the observed chemical composition, while keeping the agreement with the pulsation periods. This gives some support to the Ledoux criterion.

Original languageEnglish
Article numberslt165
Pages (from-to)L6-L10
JournalMonthly Notices of the Royal Astronomical Society: Letters
Issue number1
Publication statusPublished - 2014 Mar


  • Stars: abundances
  • Stars: early-type
  • Stars: evolution
  • Stars: mass-loss
  • Stars: oscillations
  • Stars: rotation

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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