Submillimeter Narrow Emission Lines From the Inner Envelope of Irc+10216

A spectral-line survey of IRC+10216 in the 345 GHz band has been undertaken with the Submillimeter Array. Although not yet completed, it has already yielded a fairly large sample of narrow molecular emission lines with line widths indicating expansion velocities of ∼ 4 km s −1 , less than three times the well known value of the terminal expansion velocity (14.5 km s −1 ) of the outer envelope. Five of these narrow lines have now been identified as rotational transitions in vibrationally excited states of previously detected molecules: the v = 1, J = 17–16, and J = 19–18 lines of Si 34 S and 29 SiS and the v = 2, J = 7–6 line of CS. Maps of these lines show that the emission is confined to a region within ∼ 60 AU of the star, indicating that the narrow-line emission is probing the region of dust formation where the stellar wind is still being accelerated.