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Mon. Not. R. Astron. Soc. 000, 000--000 (0000) Printed 18 February 1998 (MN L A T E X style file v1.4) The detection of binary companions to subdwarf B stars ?
 

Summary: Mon. Not. R. Astron. Soc. 000, 000--000 (0000) Printed 18 February 1998 (MN L A T E X style file v1.4)
The detection of binary companions to subdwarf B stars ?
C. Simon Jeffery 1 and Don L. Pollacco 2
1 Armagh Observatory, College Hill, Armagh BT61 9DG, Northern Ireland
2 Isaac Newton Group, La Palma
Accepted . Received ; .
ABSTRACT
Intermediate dispersion spectroscopy of a sample of 40 hot subdwarf B stars between
5500 š A and 9000 š A has been obtained. The sample includes a large fraction of targets
which have been studied photometrically. Seven targets show strong lines due to the
infrared Ca ii triplet, the unequivocal signature of a cool companion. The positive
Ca ii identifications include known photometric binaries and new targets; all are as­
sociated 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.
Key words: Stars: early­type, subdwarfs, binaries: spectroscopic.
1 INTRODUCTION
Hot subdwarfs are O and B­type stars which may be found,
on an Hertzsprung­Russell diagram, below the upper main

  

Source: Armagh Observatory

 

Collections: Physics