Astronomy & Astrophysics

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Issue		A&A Volume 373, Number 1, July I 2001
Page(s)		190 - 198
Section		Formation, structure and evolution of stars
DOI		10.1051/0004-6361:20010585

A&A 373, 190-198 (2001)
DOI: 10.1051/0004-6361:20010585

Formation of massive stars by growing accretion rate

R. Behrend and A. Maeder

Geneva Observatory, 1290 Sauverny, Switzerland
e-mail: andre.maeder@obs.unige.ch

(Received 3 April 2001 / Accepted 12 April 2001 )

Abstract
We perform calculations of pre-main sequence evolution of stars from 1 to $85 M_{\odot}$ with growing accretion rates $\dot{M}$ . The values of $\dot{M}$ are taken equal to a constant fraction $\tilde{f}$ of the rates of the mass outflows observed by Churchwell (1998) and Henning (2000). The evolution of the various stellar parameters is given, as well as the evolution of the disc luminosity; electronic tables are provided as a supplement to the articles. Typically, the duration of the accretion phase of massive stars is $\simeq$ $3 \times 10^5 \mathrm{yr}$ and there is less than $10\%$ difference in the time necessary to form a 8 or $80 M_{\odot}$ star. If in a young cluster all the proto-stellar cores start to accrete at the same time, we then have a relation M(t) between the masses of the new stars and the time t of their appearance. Since we also know the distribution of stellar masses at the end of star formation (IMF), we can derive the star formation history N(t). Interestingly enough, the current IMF implies two peaks of star formation: low mass stars form first and high mass star form later.

Key words: stars: formation -- stars: evolution -- stars: pre-main sequence -- stars: statistics -- accretion, accretion discs -- Hertzsprung-Russel (HR) and C -- M diagrams

Offprint request: R. Behrend, raoul.behrend@obs.unige.ch

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