An Interferometric Spectral-line Survey of IRC+10216 in the 345 GHz Band

TL;DR

This spectral-line survey of IRC+10216 in the 345 GHz band identified over 200 new lines, revealing a population of narrow, vibrationally excited emissions close to the star, and provided insights into the physical conditions of its inner envelope.

Contribution

First comprehensive spectral-line survey of IRC+10216 at 345 GHz, detecting numerous new lines and characterizing vibrationally excited emissions in the star's inner envelope.

Findings

Over 200 new spectral lines detected

Narrow lines with ~4 km/s expansion velocity identified

Vibrationally excited states dominate the emission close to the star

Abstract

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 ~3" were obtained for each line. A substantial new population of narrow lines with an expansion velocity of ~4 km/s (i.e. ~ 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.