NOAO >   Observing Info >   Approved Programs >   2004B-0153

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Proposal Information for 2004B-0153


PI: Chip Kobulnicky, U. Wyoming, chipk@uwyo.edu
Address: Physics Department, Laramie, WY 82070, USA

CoI: Dan Kiminki, U Wyoming
CoI: Chris Fryer, Los Alamos National Lab

Title: Discovering Massive Binaries in Cygnus OB2

Abstract: We are working to resolve a long-standing discrepancy regarding the mass distribution of close companions around massive stars by measuring the binary fraction and the much-disputed exponent, (alpha)_MR, of the binary mass ratio distribution for OB stars. These fundamental parameters are needed by the theoretical community for accurate population synthesis models since massive binary systems are the theoretical progenitors to high-energy phenomena like X-ray binaries and some classes of supernovae and (gamma)-ray bursts. We are asking for 3 bright/grey nights with WIYN+Hydra to continue a velocity-resolved spectroscopic campaign on 150 OB stars in Cygnus OB2, one of the youngest and most populous in the Galaxy. These data are necessary to fill in the short time baselines for our long-term radial-velocity monitoring of association members begun in 1999-2003 at the Keck, Lick, and WIYN observatories until the Wyoming telescope is equiped to carry on the study. Interesting by-products of this program will be the runaway OB fraction and internal association kinematics.


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