On the masses of the circumstellar dust disks around the YSO's R Mon and R50.

ABSmACT. We have estimated the masses associated with the circunstellar disks associated with the Young Stellar Objects R Mon and and Reipurth 50 from 2 by 3 araninute deep maps at 1.25 and 2.2 `m. The maps have limiting surface brightness of 20.8 and 19.9 magnitude per square arCseC. Under the assumptions: I) the intrinsiC luminosity of the associated bipolar nebulae is s ?ninetric with respect to the central object and ii) the gas to dust ratio is 100, the masses of the circumstellar disks in R Mon and R50 are 50 and 3 respectively as estimated fran the dimensions of the obscuring region and the differential extinction inferred fran the observed fluxes for the two sides of the nebulae. The masses reported here for the disks are satie hat larger than those derived fran molecular column densities at radio wavelengths, probably indicating that the depletion of heavy elements (molecules) into dust grains is higher than in the interstellar medium in general. An important inference is that the mass of the disk apparently cales with the mass of the central object. `td : STARS-CIRCUMSTELLAR SHELLS - INFRARED-PHOTOMETRY