Three Principles of Multiplicity in Stellar Dynamics

TYPEAstrophysics Seminar
Speaker:Nathan Leigh
Organizer:Hagai Perets
Time:14:30 - 15:30
Location:Lidow 620
Abstract:Within the last few years, observational surveys have revealed that high-order multiple-star systems (e.g. triples, quadruples, etc.) are common in our Galaxy. In this talk, we consider the dynamical significance of this transformation in our understanding of stellar multiplicity. To this end, we present and justify three principles of multiplicity for stellar dynamical interactions. These can be succinctly stated as follows: (1) The average cross-section for dynamical encounters increases with increasing multiplicity; (2) The probability of a direct physical collision occurring between two stars during a dynamical encounter increases with increasing multiplicity; (3) The energetics of dynamical encounters increase with increasing multiplicity.

The key consequence that arises from these principles is that, for surprisingly low number fractions, dynamical interactions involving high-order multiples can occur more often than encounters involving either single or binary stars, particularly in sparse low-mass open clusters. Consequently, high-order multiples could be more important than previously realized for a number of astrophysical phenomena, including the formation and destruction of compact binaries and various types of stellar exotica typically found in dense globular clusters, such as blue straggler stars, low-mass x-ray binaries, millisecond pulsars, and cataclysmic variables.