The circumstellar environment of IRAS 16293-2422 - ISO-LWS and SCUBA observations

We present far-infrared (FIR) continuum observations of the deeply embedded source IRAS 16293-2422 performed with the Long Wavelength Spectrometer (LWS) on-board the Infrared Space Observatory (ISO). We also report 450 and 850 mum mapping observations done with the Submillimetre Common-User Bolometer Array (SCUBA) at the James Clerk Maxwell Telescope (JCMT). We combined these observations with IRAS and other JCMT data available in the literature to construct a complete spectral energy distribution (SED) of the source. A spherically symmetric dusty envelope model was used to reproduce the SED and to characterize the circumstellar matter around the object. We call attention to the fact that when using models such as the one presented here, one needs spatial information about the object to distinguish between different possible fits to the SED. A comparison between the intensity profiles at 450 and 850 mum obtained from the SCUBA observations and the profiles predicted by the model allowed us to constrain the size of the envelope and its density distribution. The SED and the 850 mum intensity profile of the source are consistent with a centrally peaked power law dust density distribution of the form p(r) proportional to r(-p) with p = 1.5-2, with a radius R-env = 3000-3250 AU, defining a very compact circumstellar envelope. We estimate a bolometric luminosity L-bol = 36 L., an envelope mass M-env = 3.4 M. and a submillimetre to bolometric luminosity ratio L-submm/L-bol = 1.9%, confirming that the source shows a submillimetre excess characteristic of Class 0 sources.