A comet dust model for the beta Pictoris disk

摘要: The 10m silicate emission feature and the contin- uum from near infrared to millimeter of dust in disk Pictoris may be derived by assuming that is continually replenished comets orbiting close star. basic, initial shed taken fluffy aggregates interstellar core-organic refractory mantle grains (with an additional ice outer regionofthedisk).Theheatingofthedustisprimarilyprovided organic absorption stellar radia- tion. temperature some particles star sufcient crystallize initially amorphous silicates. are then distributed throughout tion pressure. steady state distribution consists a mixture crystalline ag- gregates (without/with mantles) with variable ratios or- ganic mass. whole which extends inward 1AU outward 2200AU divided into three components primarily responsible respectively, for emission, mid-infrared far infrared/millimeter emission. As starting point, grain size distributionisassumedtobelikethatobservedforcometHalley while inner regions small isrelativelyenhancedwhichmaybeattributedtotheevaporation and/or fragmentation large particles. best reproduce observations highly porous, porosity around 0.95 or as high 0.975. radial such provides excellent match (plus 11.2m) spectral well excess continuum flux over wide range wavelengths. These models result total mass 2 10 27 g only 5 {1 0 4 hot enough give specic mineralogy silicates has been discussed.