A Shock Wave Model for the Processing of Silicates in Circumstellar Disks

PARISI, M. G.; STERZIK, M.

PUCON, CHILE

Simposio; XI IAU Regional Latin American Meeting of Astronomy; 2005

IAU

Shock waves seems to be the mechanism able to explain the existence of crystalline silicates found in chondrites, long-period comets and disks around YSOs (Scott & Krot 2005, ApJ, 623, 571). We propose a new energy source of gas dynamics shocks based on gravitational perturbations excited by a companion object, i.e., a giant planet or a companion star. We carry out a parameterization of the wave dynamics and of the dust heating in the shock front that predicts the melting of silicates in a bound orbital range determined by the orbital semiaxis of the companion object. We obtain that the gravitational perturbations of the companion would generate shock waves able to process dust particles at ? 0.5-5 AU depending on the central star and disk physical parameters as well as on the companion orbital semiaxis. The recent detection of crystalline silicates in young binary systems (e.g. Meeus et al. 2003, A&A, 409, L25) might be understood within this scenario. For the Solar Nebula, we obtain that dust processing could have taken place by Jupiter-driven waves at a minimum distance of ? 1-2 AU. Our main result is that density waves excited by a companion object are an efficient mechanism to account for the in situ crystallization and melting of silicates at a large distance from the central star in contrast with the well known difficulty that the observed crystalline dust in YSOs appears to be much colder than the minimum temperature required for crystallization to take place.