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Paper: Theory of Formation of Massive Stars via Accretion
Volume: 267, Hot Star Workshop III: the Earliest Stages of Massive Star Birth
Page: 165
Authors: Yorke, H. W.
Abstract: Radiative effects strongly hinder the formation of massive stars via accretion. A necessary condition for accretion growth of a hydrostatic object up to high masses M > 20 Msun (rather than coalescence of optically thick objects) is the formation of and accretion through a circumstellar disk. These disks will be photoevaporated on a timescale of 105 yr, similar to the accretion timescale, and be observed as UCHII's. Collapse simulations with grey radiation transfer display significantly different results from corresponding frequency-dependent simulations. A single example of a 60 Msun molecular core with resulting stellar masses of Mfinalgrey = 20.7 Msun and Mfinalnu = 33.6 Msun is briefly discussed. In order to include the effects of accretion in modifying the central source's luminosity evolution, a semi-analytical scheme for augmenting existing evolutionary tracks of pre-main sequence protostars is introduced and discussed. It is shown that the ``birthline'', i.e. the equilibrium position of fully convective, deuterium-burning stars in the HR diagram with cosmic deuterium abundance, is - strictly speaking - unattainable via accretion for stars more massive than 1 Msun.
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