NOAO >   Observing Info >   Approved Programs >   2010B-0372

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Proposal Information for 2010B-0372


PI: Richard A. Wade, Pennsylvania State University, wade@astro.psu.edu
Address: Astronomy Department, 525 Davey Lab, University Park, PA 16802, USA

Title: Early F dwarfs with hidden hot subdwarf companions: completing the `winter' sample

Abstract: Theories of binary star evolution predict that an early F dwarf star will sometimes be paired with a hot subdwarf (an ``sdB'' star). This is an essential prediction from theories that successfully account for pairings of sdB stars with white dwarf or lower-mass stars, but only a few F+sdB systems have been studied previously. Their space density in the disk of the Galaxy needs to be determined. The distribution of orbital periods of the F+sdB systems, which depends on the processes of mass transfer/loss and angular momentum loss from the binary, needs to be established. Observations of F+sdB pairs provide a new way to help test and improve binary population synthesis (BPS) models, which are used throughout astrophysics to understand a wide variety of exotic objects and to predict their numbers. Using 2MASS and GALEX archival data, it is possible to identify early F star candidates with UV excesses (F+UVX). The 2.1m telescope with GoldCam spectrograph will be used to classify these color-selected F+UVX candidates on the MK system, reject interloping Algol systems and other objects that mimic F-star colors, and develop a representative sample of F+UVX stars that will be observed synoptically at high spectral resolution to obtain spectroscopic orbits. For a sample of stars that can be observed synoptically throughout the year and be of use to other observers, the entire range of RA needs to be included; this proposal for 2010B complements similar proposals which were awarded time in 2009B and 2010A, to complete the necessary MK classifications and other validation in the fall/winter sky.


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