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SUMMARY:Ellipsoidal and Eccentric Red Giant Binaries - Christine Nicholls 
 (Mt Stromlo Observatory)
DTSTART:20100630T121500Z
DTEND:20100630T124500Z
UID:TALK24740@talks.cam.ac.uk
CONTACT:Dr Jonathan Gair
DESCRIPTION:Variable red giants occupy several sequences in the period--lu
 minosity plane. In this talk I will focus on sequence E. Sequence E stars 
 are distorted red giant binaries\, known as ellipsoidal variables\, lying 
 mostly on the RGB. Their ellipsoidal nature was hypothesised from the ligh
 t curve shape only\; we present velocity curves that confirm this theory. 
 We also use the observed fraction of red giants which are sequence E stars
  to predict the fraction of PN that have close binary post-common envelope
  central stars. Approximately ten percent of sequence E stars are in eccen
 tric orbits\, although binary evolution theory predicts their orbits shoul
 d have been quickly circularised by tidal forces once becoming red giants.
  We present preliminary results in our search for the mechanism that maint
 ains eccentricity in these binaries.
LOCATION:Sackler Lecture Theatre\, IoA
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