NOAO >   Observing Info >   Approved Programs >   2013A-0288

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Proposal Information for 2013A-0288


PI: Brad N. Barlow, Pennsylvania State University, bbarlow@psu.edu
Address: Astronomy Department, 525 Davey Lab, University Park, PA 16802, USA

CoI: Richard A. Wade, Pennsylvania State University
CoI: Jackson Norris, Pennsylvania State University

Title: Radial Velocities of Hot Subdwarfs in Resolved Pairs

Abstract: Binary population synthesis (BPS) models show that common--envelope and Roche lobe overflow processes can strip a red giant of its envelope and form a hot subdwarf B (sdB) star with a binary companion, but the details of these processes are unclear. Because of these strong interactions, the sdB's companion cannot be used to definitively determine such important sdB parameters as the age, luminosity, metallicity, and distance. We have found a significant number of sdB stars with resolved, visual companions separated by 4-20 arcseconds, too far for the cool companion to have played a significant role in the formation of the sdB. Their published magnitudes and proper motions are consistent with their being true binaries, but radial velocity (RV) measurements are needed to confirm this. We propose spectroscopic observations with the Kitt Peak 4--m telescope to measure the component RVs in each pair and remove chance alignments from our study. For pairs that turn out to be true binaries, we will use the spectra of the cool companion to infer distance and initial metallicity of the sdB. The masses and ages of the companions will constrain the empirical mass distribution of sdB progenitors, which will help improve BPS codes.


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NOAO >   Observing Info >   Approved Programs >   2013A-0288

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