NOAO >   Observing Info >   Approved Programs >   2007A-0052

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Proposal Information for 2007A-0052


PI: Chip Kobulnicky, University of Wyoming, chipk@uwyo.edu
Address: Physics Department, 1000 E University, Laramie, WY 82070, USA

CoI: Kiminki, University of WYoming
CoI: Chris Fryer, Los Alamos National Laboratory

Title: Defining the Distribution of Orbital Separations Among Massive Binaries

Abstract: Close massive binary systems are the progenitors of energetic phenomena such as X-ray binaries and some classes of supernovae and (gamma)-ray bursts. Population synthesis models which predict the galactic and cosmic frequency of these events require reliable estimates of the \it mass ratio distribution and the \it orbital separation distribution among massive binaries. We have measured the first of these key parameters using spectroscopic velocity data for 140 OB stars in Cygnus OB2 over the period 1999-2006. We find the that the distribution of mass ratios, P(q) where q\equiv m_2/m_1, is peaked toward high mass companions and is described by P(q)\propto q^(alpha) with (alpha)>=0. We request 5 nights with WIYN+Hydra to help finish measuring the distribution of orbital separations by obtaining secure periods for the velocity variable systems, especially the short-period systems which have eluded definitive measurement due to aliasing.


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NOAO >   Observing Info >   Approved Programs >   2007A-0052

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