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Astron. Astrophys. 326, 1001-1012 (1997)

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Physics of accretion onto young stars

II. Structure and evolution of accreting stars

Lionel Siess , Manuel Forestini and Claude Bertout

Observatoire de Grenoble, Laboratoire d'Astrophysique, Université Joseph Fourier, B.P.53X, F-38041, Grenoble Cedex, France

Received 10 November 1995 / Accepted 30 May 1997


We present new computations of pre-main sequence evolution for stars that accrete a substantial part of their mass. We compute several models with different mass accretion rates, focusing on the effect of deuterium burning on stellar evolution during the accretion phase. We treat accretion not only as a surface boundary condition but as a global phenomenon that affect also the inner parts of the star, using a formalism developed by Siess & Forestini (1996a). We study the effect of varying the mass distribution of accreted matter into the star, and analyze the influence of different chemical compositions for the accreted matter. We also take into account the possible deposition of accretion energy transported by the accreted matter. We show that accretion can lead to substantial changes in the pre-main sequence evolutionary tracks in the Hertzsprung-Russell diagram (HRD). When accretion stops, the star relaxes to its "standard" track in the HRD, and this, independently of the previous accretion rate.

Key words: accretion – pre-main sequence stars – stellar evolution – Hertzsprung-Russell (HR) diagram

Send offprint requests to: Lionel Siess


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© European Southern Observatory (ESO) 1997

Online publication: April 8, 1998