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SUMMARY:Planetesimal dynamics and growth in tight binary star systems - Ke
 dron Silsbee (Princeton)
DTSTART:20170606T120000Z
DTEND:20170606T130000Z
UID:TALK72864@talks.cam.ac.uk
CONTACT:Jean Teyssandier
DESCRIPTION:The existence of planets in 20-AU separation binary systems pr
 esents an interesting puzzle.  It is thought that cores of giant planets f
 orm via agglomeration of planetesimals in mutual collisions.  However\, in
  tight binary systems\, one would naïvely expect the collision velocities
  between planetesimals to be so high that collisions would destroy even 10
 0 km bodies.  Planetesimals are perturbed by gravity from the companion st
 ar\, and gravity and gas drag from an eccentric gas disk.  Because the gas
  drag acts more strongly on smaller planetesimals\, orbital eccentricity d
 epends on planetesimal size. Consequently\, planetesimal collision velocit
 ies depend on the sizes of the collision partners.  The inclusion of disk 
 gravity gives rise to a damaging secular resonance typically at a few AU\,
  however it can also create locations of low relative eccentricity between
  planetesimals of different sizes.\n\nWe run a multi-annulus coagulation/f
 ragmentation simulation to determine the minimum size of initial planetesi
 mal necessary for growth to large sizes in collisions.  The minimum initia
 l planetesimal size necessary for growth depends greatly on the disk mass\
 , eccentricity and the degree of apsidal alignment with the binary.  We fi
 nd that in a wide variety of situations\, it is a reasonable approximation
  that growth occurs as long as there are no collisions capable of complete
 ly destroying a planetesimal\, but erosion by moderately damaging collisio
 ns can also prevent growth from occurring.  
LOCATION:MR14\,  Centre for Mathematical Sciences\, Wilberforce Road\, Cam
 bridge
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