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F. Marzari (Dept. of Physics, Padova.), P. Thebault (Observatoire de Paris.), H. Scholl (Observatoire de Nice), D. Turrini (Dept. of Physics, Padova)
Gamma Cephei is, among the 5 presently known binary stars system harbouring extra solar planets, that with the closest companion. Within the core-accretion model, a critical parameter for planetary formation is the relative velocity between planetesimals. If the proximity and the high eccentricity of the companion star excites large impact speeds, fragmentation dominates over accretion. We will show that only in presence of a high gas density of the protoplanetary nebula, in agreement with the values suggested in Bodenheimer et al. (2000) for in situ formation of 47 UMA, planetesimal accumulation is possible within 3 AU from the star.
We have also modelled the subsequent phase of the planet growth when planetary embryos, that possibly accreted during the planetesimal phase, collide and form a large core of 10 or more terrestrial masses. This phase precedes that of rapid gas accretion that begins when a substantial mass is accumulated into the core. We will show that the system naturally tends to form a giant planet at 1 AU and additional constraints are needed to form a planet at 2 AU.
We have also improved the estimate of the stability region for the observed planet that extends from 2.3 AU for high eccentricity orbits to 3.8 AU for low eccentricity orbits.
The author(s) of this abstract have provided an email address for comments about the abstract: marzari@pd.infn.it
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Bulletin of the American Astronomical Society, 35 #4
© 2003. The American Astronomical Soceity.