The lack of binaries among hot horizontal branch stars: M80 and NGC5986

Abstract

We present preliminary results of a our search for close (period P < 10 days) binary systems among hot (Teff > 20000 K) horizontal branch stars in globular clusters M80 and NGC5986. We measured radial velocity variations of 11 targets in M80 and 5 in NGC5986, spectroscopically observed at medium resolution (R=4100) during four nights at VLT-FORS2. We found one close binary candidate in M80, showing statistically significative radial velocity variations, and no clear evidence in NGC5986. These results confirm the lack of close binaries among hot horizontal branch stars in globular clusters, as already found in NGC6752, at variance with what observed among hot subdwarfs in the field.

arXiv comment2 pages, 1 figure, to appear in the proceedings of the "Globular Clusters: Guides to Galaxies" conference, March 2006, Concepcion, Chile

References in corpus (5)

• The binary fraction of extreme horizontal branch stars
• Close binary EHB stars from SPY
• The ubiquitous nature of the Horizontal Branch second U-jump: A link with the Blue Hook scenario?
• The lack of close binaries among hot horizontal branch stars in NGC6752
• Why Hot Horizontal Branch Stars Can Appear Redder Than Red Giants