The Progeny of Stellar Dynamics and Stellar Evolution within an N-body model of NGC 188

We present a direct N-body simulation modeling the evolution of the old (7 Gyr) open cluster NGC 188. This is the first N-body open cluster simulation whose initial binary population is directly defined by observations of a specific open cluster: M35 (150 Myr). We compare the simulated color-magnitude diagram at 7 Gyr to that of NGC 188, and discuss the blue stragglers produced in the simulation. We compare the solar-type main sequence binary period and eccentricity distributions of the simulation to detailed observations of similar binaries in NGC 188. These results demonstrate the importance of detailed observations in guiding N-body open cluster simulations. Finally, we discuss the implications of a few discrepancies between the NGC 188 model and observations and suggest a few methods for bringing N-body open cluster simulations into better agreement with observations.Comment: Contributed talk at IAUS 266 'Star clusters: basic galactic building blocks', R. de Grijs and J.R.D. Lepine, eds. 6 pages, 4 figure

A Connection between Submillimeter Continuum Flux and Separation in Young Binaries

We have made sensitive 800-micron continuum observations of low-mass, pre-main sequence (PMS) binary stars with projected separations less than 25 AU in Taurus-Auriga to study disks in the young binary environment. We did not detect any of the observed binaries, with typical 3-sigma upper limits of about 30 mJy. Combining our observations with previous 1300-micron observations of PMS Taurus binaries by Beckwith et al. (1990) and others, we find that the submillimeter fluxes from binaries with projected separations between 1 AU and 50 AU are significantly lower than fluxes from binaries with projected separations > 50 AU. The submillimeter fluxes from the wider binaries are consistent with those of PMS single stars. This may indicate lower disk surface densities and masses in the close binaries. Alternatively, dynamical clearing of gaps by close binaries is marginally sufficient to lower their submillimeter fluxes to the observed levels, even without reduction of surface densities elsewhere in the disks.Comment: 12 pages, uuencoded compressed postscript with figures; Wisconsin Astrophysics 526; to appear in ApJ Letter