Astrophysics Senior Project Abstracts
Formation of Massive Stellar Objects and Intermediate Mass Black Holes Due to Runaway Collisions in Young Dense Star Clusters
Valerie McVay, 2007
The formation of a very massive star (VMS) by a runaway collision process is investigated in this paper. The possibility of this VMS evolving and becoming an intermediate mass black hole (IMBH) is also speculated. A stellar evolution code, TYCHO, is used to scale star models that are then relaxed and collided using smoothed particle hydrodynamics (SPH). The mass, radius, age, and collision parameters are similar to the stars in the collision sequence K3-37 from Freitag et al. (2006). All stars are main sequence stars with masses ranging from 0.2-117 solar masses, a metalicity Z=0.01, and ages that range from 2.5x105 years to 1.8x106 years. It was found that collisions between stars of unequal mass result in the lower mass star sinking to the center of the larger star. For collisions involving merger products from previous collisions, it was found that the product has a dense core with an extended envelope of gas. The largest collision product created was from collision # 70 of the sequence of 39 collisions. This merger product had a mass of 295 solar masses and an overall mass loss of 14.9%. There is some indication that the mass loss will increase with each collision in the sequence meaning that the runaway collision process may stall and not be capable of forming stars with thousands of solar masses.