| Type |
Conference Paper |
| Names |
Aaron M. Geller, J. R. Hurley, R. D. Mathieu |
| Proceedings Title |
Bulletin of the American Astronomical Society |
| Conference Name |
American Astronomical Society, AAS Meeting #217, #327.02 |
| Volume |
43 |
| Pages |
32702 |
| Date |
January 1, 2011 |
| URL |
http://adsabs.harvard.edu/abs/2011AAS...21732702G |
| Library Catalog |
NASA ADS |
| Abstract |
We recently completed a detailed radial-velocity study of the old (7
Gyr) open cluster NGC 188 in which we identify all solar-type cluster
members, and study the binaries and blue stragglers (BSs) in great
detail. Using these data for guidance, we attempt to recreate the
observed properties of NGC 188 within a sophisticated N-body model.
Specifically, we study how a population of primordial triples impacts
the dynamical evolution of the solar-type main-sequence binary
population as well as the BS production rate and mechanisms. We employ
the observed main-sequence binary population of M35 (180 Myr) to set our
initial binary frequency and distributions of orbital parameters. Thus
we create the first N-body model whose initial binary population is
defined by such detailed observations of a binary population in a young
open cluster. Without any triples, the 7 Gyr main-sequence solar-type
hard-binary population in the simulation matches that of NGC 188 in both
frequency and distributions of orbital parameters. This simulation is
also consistent with the observed spatial density profile and mass of
NGC 188. However, our simulations with binaries alone cannot reproduce
the large number of BSs observed in NGC 188 or their distinctive
eccentricity - period distribution. Adding tertiary companions to the
initial binaries produces an additional population of BSs, primarily
formed through dynamical encounters that lead to direct collisions of
the stars in the inner binary. Importantly, these added BSs have a high
binary frequency similar to what we observe in NGC 188. Comparisons
between our simulations and observations of the NGC 188 BSs place
important constraints on the initial triple population, which in turn
results in detailed predictions for future observations of triples in
young star clusters. We suggest that dynamical encounters with triples
likely played a significant role in creating the observed NGC 188 BSs. |