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

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