The IRC + 10216 circumstellar envelope. I - Models for the dust and gas

Abstract

Very high resolution infrared spectra of the CO fundamental and first overtone lines have been recorded revealing details of the gas flow from the IRC +10216 photosphere to radii greater than 100 R<SUB>*</SUB>. To aid in the interpretation of these data, the authors have constructed a detailed empirical model of the density, temperature, and velocity profiles of the gas. Continuum radiative transfer in the dust has been calculated, to account for both photometric information and spatially resolved interferometric data. Beginning with a satisfactory model of the continuum spectrum, the transfer of radiation in the absorption lines has been computed, based on a non-LTE comoving frame solution in spherical geometry. The model reproduces most characteristics of the molecular line profiles. The derived mass-loss rate is 2×10<SUP>-5</SUP>M_sun;yr<SUP>-1</SUP>.