3-DIMENSIONAL STRUCTURE OF THE CIRCUMSTELLAR ENVELOPE OF CRL-618 BASED ON THE (CO)-C-13 J=1-0 MAPPING OBSERVATIONS

The circumstellar envelope of the carbon-rich star CRL 618 has been ma pped by the (CO)-C-13 J = 1-0 transition with a resolution of about 5' '.0 x 4''.3 with the Nobeyama Millimeter Array. Emission is extended i n size by about 10'', and the distribution is approximately spherical. No strong elongation of (CO)-C-12 features along or perpendicular to the bipolar axis has been observed. Combining with the (CO)-C-12 J = 1 -0 data that were taken before, we have created three-dimensional dens ity and temperature profiles of the CRL 618 circumstellar envelope. Fo r creating the three-dimensional model, it is assumed that the expansi on velocity is constant and the large-velocity-gradient model is appli cable. The former (CO)-C-12 observations show that the envelope of CRL 618 consists of complex features. On the basis of the present (CO)-C- 13 observations, these features are interpreted as the temperature and density irregularities in the outer circumstellar shell. The comparis on of the present results with the model density profile given by opti cal light-scattering maps is made.