On the formation of massive stars

Abstract

We present a model for the formation of massive (M≳10 M⊙) stars through accretion‐induced collisions in the cores of embedded dense stellar clusters. This model circumvents the problem of accreting on to a star whose luminosity is sufficient to reverse the infall of gas. Instead, the central core of the cluster accretes from the surrounding gas, thereby decreasing its radius until collisions between individual components become sufficient. These components are, in general, intermediate‐mass stars that have formed through accretion on to low‐mass protostars. Once a sufficiently massive star has formed to expel the remaining gas, the cluster expands in accordance with this loss of mass, halting further collisions. This process implies a critical stellar density for the formation of massive stars, and a high rate of binaries formed by tidal capture.

The Formation of Massive Stars

“…Such stars have radiation pressures that can act sufficiently strongly on the dust to reverse the infall, and thus potentially halt mass accretion, limiting the growth of the massive star. Suggestions put forward to circumvent this problem include disc accretion, dust destruction in the inflow (Keto 2003), beaming of the radiation, Raleigh-Taylor instabilities and stellar mergers (Bonnell et al 1998). Several studies (Yorke & Sonnhalter 2002;Krumholz et al 2009;Kuiper et al 2010) have shown that when increasingly realistic physics is included in models, such as frequency dependent treatment of the radiation, gravitational instabilities in the disc and Rayleigh-Taylor instabilities, the formation of a high-mass star can still occur through disc accretion.…”

“…This is due to the difficulty in obtaining the necessary physical conditions for stellar mergers to occur on timescales of less than a million years (Bonnell et al 1998;Bonnell & Bate 2002;Davies et al 2006). While accretion onto a clusters stellar core can drive the core into collapse and dramatically increase the stellar density as n ∝ m 9…”

Orbital motion of the massive multiple stars in the Orion Trapezium

“…Stahler et al 2000;Yorke & Sonnhalter 2002). A particularly interesting model in this context is the scenario described by Bonnell et al (1998), in which massive stars form through accretioninduced collisions and subsequent merging of protostars in the dense central regions of forming stellar clusters. This model predicts a high frequency of close multiple systems (i.e.…”

Binary Stars in Young Clusters –a Theoretical Perspective

“…One immediate but still preliminary interpretation of these results is that OB stars probably must form in energetic binaries (small P and large q~1), and probably already near the centre of their parent cluster, to explain the observed high-velocity OB run-aways, thus tentatively supporting the formation scenario of Bonnell, Bate & Zinnecker (1998).…”