NOAO >   Observing Info >   Approved Programs >   2007B-0099

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Proposal Information for 2007B-0099


PI: Aaron M. Geller, University of Wisconsin - Madison, geller@astro.wisc.edu
Address: Dept. of Astronomy, 475 N. Charter Street, Madison, Wisconsin 53706, USA

CoI: Robert D. Mathieu, University of Wisconsin - Madison
CoI: Ella Braden, University of Wisconsin - Madison
CoI: Soren Meibom, Harvard-Smithsonian CfA
CoI: David W. Latham, Harvard-Smithsonian CfA

Title: A Study Of Anomalous Stars and Binary Populations Within Open Clusters: Tests Of Theoretical Models

Abstract: ``Anomalous'' stars, such as blue stragglers and more recently sub- subgiants, have been an enduring challenge for stellar evolution theory. Recently it has become clear that in star clusters these systems are closely linked to the binary star populations. Furthermore, through advances in N-body modeling, we have come to realize that stellar dynamical processes play a central role in their formation. Indeed, these stars trace the interface between the classical fields of stellar evolution and stellar dynamics. We propose a thesis study to directly probe this interface through high-precision radial-velocity measurements of the anomalous stars and the binary populations in four open clusters. We have selected NGC 188 (7 Gyr), M67 (NGC 2682; 4 Gyr), NGC 6819 (2.4 Gyr), and M35 (NGC 2168; 150 Myr), as these span a wide range in age, are rich enough to provide statistically significant conclusions, and already have an extensive base of kinematic, spectroscopic, and photometric observations from the WIYN Open Cluster Study. Our proposed observations will define the spectroscopic binary populations (fraction, frequency distributions of orbital parameters, mass ratios) for orbital periods approaching the hard-soft boundary. These observations will also provide a comprehensive survey for anomalous stars, including secure establishment of their cluster membership. These data will allow us to perform the first detailed comparison with predictions of open cluster simulations of the binary populations among normal and anomalous stars, and thereby to constrain the evolutionary paths from one to the other.


National Optical Astronomy Observatory, 950 North Cherry Avenue, P.O. Box 26732, Tucson, Arizona 85726, Phone: (520) 318-8000, Fax: (520) 318-8360



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