ON THE NATURE OF THE PROTOTYPE LUMINOUS BLUE VARIABLE AG CARINAE. II. WITNESSING A MASSIVE STAR EVOLVING CLOSE TO THE EDDINGTON AND BISTABILITY LIMITS

@article{Groh2011ONTN,
  title={ON THE NATURE OF THE PROTOTYPE LUMINOUS BLUE VARIABLE AG CARINAE. II. WITNESSING A MASSIVE STAR EVOLVING CLOSE TO THE EDDINGTON AND BISTABILITY LIMITS},
  author={Jose H Groh and D. John Hillier and Augusto Damineli},
  journal={The Astrophysical Journal},
  year={2011},
  volume={736}
}
We show that the significantly different effective temperatures (Teff) achieved by the luminous blue variable AG Carinae during the consecutive visual minima of 1985–1990 (Teff ≃ 22,800 K) and 2000–2001 (Teff ≃ 17,000 K) place the star on different sides of the bistability limit, which occurs in line-driven stellar winds around Teff ∼ 21,000 K. Decisive evidence is provided by huge changes in the optical depth of the Lyman continuum in the inner wind as Teff changes during the S Dor cycle… 

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