Armagh Observatory Preprint Series No. 299

The detection of binary companions to subdwarf B stars

Authors: C.S.Jeffery, D.L.Pollacco

Journal: 1998, The 2nd Boulder-Munich Workshop

Abstract. We have instigated a spectroscopic survey to make unambiguous 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 singly-ionized 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.

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