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S. Portegies Zwart (University of Amsterdam)
Dense star clusters may experience an early phase of core collapse driven by the most massive stars. A runaway collision process starts when the gravothermal collapse of the cluster core happens before the most massive stars explode in supernovae. During the collapse phase one single star experiences multiple (10-100) collisions, preferentially with other massive (30-50 solar mass) main-sequence stars, which also happen to have segregated to the cluster center.
Star clusters with initial half-mass relaxation times <50Myr and sufficiently deep central potentials are dominated by this process. (Though alien, there are several clusters which fulfill this criterion in the Milky-way Galaxy.) The phase of runaway growth in these clusters lasts until mass loss by stellar evolution arrests core collapse. The massive object can grow to a mass of about 0.1 per cent of the mass of the entire star cluster. This massive star ultimately collapses to a black hole of intermediate mass.
This work is supported by the Royal Dutch Academy of Sciences (KNAW), the Dutch Organization for Scientific Research (NWO), the Netherlands Research School for Astronomy (NOVA) and NASA ATP.
The author(s) of this abstract have provided an email address for comments about the abstract: spz@science.uva.nl
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Bulletin of the American Astronomical Society, 35#5
© 2003. The American Astronomical Soceity.