Armagh Observatory Preprint Series No. 302

The detection of binary companions to subdwarf B stars

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

Journal: 1998, MNRAS 298, 179-184

Abstract. Intermediate dispersion spectroscopy of a sample of 40 hot subdwarf B stars between 5500 and 9000Angstroms has been obtained. The sample includes a large fraction of targets which have been studied photometrically. Seven targets show strong lines arising from the infrared Caii triplet, the unequivocal signature of a cool companion. The positiveCaii identifications include known photometric binaries and new targets; all are associated with a photometric red excess. Assuming a canonical value for the subdwarf luminosity, all of the detected companions are overluminous compared with the main sequence. The detection procedure indicates an improved and more secure method for the measurement of the binary frequency of hot subdwarfs.

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