Hagai B. Perets, Kaitlin M. Kratter
Physical collisions and close approaches between stars play an important role in the formation of exotic stellar systems. Standard theories suggest that collisions are are, occurring only via random encounters between stars in dense clusters. We present a different formation pathway, the triple evolution dynamical instability (TEDI), in which mass loss in an evolving triple star system causes orbital instability. The subsequent chaotic orbital evolution of the stars triggers close encounters, collisions, exchanges between the stellar components, and the dynamical formation of eccentric compact binaries like Sirius. We demonstrate that the rate of stellar collisions due to the TEDI is ~10^(-4) yr^(-1) per Milky-Way Galaxy, which is ~30 times higher than the collision rate due to random encounters in globular clusters. Moreover, we find that the dominant type of stellar collisions is qualitatively different; most collisions involve asymptotic giant branch stars, rather than main sequence, or slightly evolved stars, which dominate collisions in globular clusters. The TEDI mechanism should lead us to revise our understanding of collisions and the formation of compact, eccentric binaries in the field.
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http://arxiv.org/abs/1203.2914
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