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The detection of binary companions to subdwarf B stars C.S.Jeffery

Summary: The detection of binary companions to subdwarf B stars
Armagh Observatory, College Hill, Armagh BT61 9DG, Northern
Isaac Newton Group, La Palma
Abstract. We have instigated a spectroscopic survey to make unam­
biguous detections of cool companions to subdwarf B stars and to refine
measurements of the sdB binary frequency. From an initial sample of
40 sdB stars, we have made a strong detection of the infrared triplet of
singly­ionized calcium in seven cases, including Feige 87. Three of these
were not previously recognised to be composite objects. These are the
first spectroscopic detections of cool sdB companions. The technique is an
effective means of identifying binaries and offers the potential for making
direct measurements of orbits, mass ratios and masses of sdB stars.
1. Introduction
The second Boulder­Munich workshop was devoted principally to studies of lu­
minous hot stars. Whilst OB stars dominate the light from young stellar popula­
tions, hot subdwarfs dominate the ultraviolet flux from old populations such as
galactic globular clusters and giant elliptical galaxies. It is also likely that some


Source: Armagh Observatory


Collections: Physics