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Title:
Status Report on a Search for F stars with Hidden Hot Subdwarf Companions
Authors:
Wade, Richard A.; Clausen, D. R.; Stark, M. A.; Griffith, C. V.
Affiliation:
AA(Penn State Univ), AB(Penn State Univ), AC(Univ. Michigan/Flint), AD(Penn State Univ)
Publication:
American Astronomical Society, AAS Meeting #218, id.122.08; Bulletin of the American Astronomical Society, Vol. 43, 2011
Publication Date:
05/2011
Origin:
AAS
Abstract Copyright:
(c) 2011: American Astronomical Society
Bibliographic Code:
2011AAS...21812208W

Abstract

Observations to date preferentially find Galactic hot subdwarf (sdB/sdO) stars in binaries when the subdwarfs are paired with relatively faint companions (G/K/M dwarfs, white dwarfs). This selection bias may distort our perspective of the evolutionary channels that form hot subdwarfs in the galactic disk. A predicted and possibly more numerous population of binaries features a lower-mass, lower-luminosity, longer-lived hot subdwarf hiding in the glare from its brighter companion: the subdwarf + A/early F binaries. Such systems may arise when mass transfer is initiated in the Hertzsprung gap.

A survey is underway at Penn State to identify hot subdwarfs paired with early F stars, determine their properties, and establish their space density. The project makes use of ground and space archival data to identify these systems (from their UV excesses) and new spectroscopic observations to refine the sample and determine their orbital periods and other properties. Successful characterization of this group of close binaries should help to challenge, calibrate, or refine models of binary star evolution that are used in population synthesis studies. The motivation, methodology, and status of this search for hidden hot subdwarfs will be presented.

This study makes use of NASA archival data from 2MASS and GALEX. Support from NASA grant NNX09AC83G and NSF grant AST-0908642 is gratefully acknowledged. Observations carried out at KPNO and Hobby-Eberly Telescope.

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