SIMBAD references

1996A&A...307..829B - Astronomy and Astrophysics, volume 307, 829-839 (1996/3-3)

About the absence of a proper zero age main sequence for massive stars.


Abstract (from CDS):

The formation of stars up to 120M is computed in the framework of the accretion scenario. For realistic accretion rates derived from the observed line width in various molecular dark clouds, the accretion interlude lasts some 2-2.5Myr, and accounts for an appreciable nuclear evolution during the optically thick MS life. Several new results are found concerning massive stars at the top of the MS: 1) A newly formed massive star with M≥40M at the time it emerges from its parental cloud has already burned a substantial fraction of its central hydrogen content. 2) As a consequence, the formal MS lifetime is substantially reduced. 3) A proper ZAMS does not exist, since at the time it becomes visible, the star has already evolved towards lower Teff. 4) As a result of previous evolution, the size of the convective core for a given central H content is reduced by about 5-10%. 5) We find that for realistic accretion rates applicable to ordinary star forming regions in the Galaxy and Magellanic Clouds, a truncation of the IMF is naturally established around 85-150M where the accretion time becomes comparable to the hydrogen burning time. 6) Since massive stars spend a fraction of their H-burning phase in the parental cocoon, their true number is larger than estimated and the slope of the IMF is flatter.

Abstract Copyright:

Journal keyword(s): stars: evolution - stars: pre-main sequence - Hertzsprung-Russell (HR) diagram

Status at CDS:  

Simbad objects: 6

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