AN INTERFEROMETRIC SPECTRAL-LINE SURVEY OF IRC+10216 IN THE 345 GHz BAND

Abstract

We report a spectral-line survey of the extreme carbon star IRC+10216 carried\nout between 293.9 and 354.8 GHz with the Submillimeter Array. A total of 442\nlines were detected, more than 200 for the first time; 149 are unassigned. Maps\nat an angular resolution of ~3" were obtained for each line. A substantial new\npopulation of narrow lines with an expansion velocity of ~4 km/s (i.e. ~ 30% of\nthe terminal velocity) was detected. Most of these are attributed to rotational\ntransitions within vibrationally excited states, emitted from energy levels\nabove the v=0, J=0 ground state with excitation energy of 1000-3000 K. Emission\nfrom these lines appears to be centered on the star with an angular extent of\n<1". We use multiple transitions detected in several molecules to derive\nphysical conditions in this inner envelope of IRC+10216.\n