2011ApJ...739L...5C

We report on a pilot imaging line survey (36.0-37.0 GHz, with ∼1 km/s spectral channels) with the Expanded Very Large Array for two asymptotic giant branch stars, RW LMi (= CIT6, which has a carbon-rich circumstellar envelope, CSE) and IK Tau (=NML Tau, with an oxygen-rich CSE). Radio continuum emission consistent with photospheric emission was detected from both stars. From RW LMi we imaged the HC₃ N (J = 4{x2192}3) emission. The images show several partial rings of emission; these multiple shells trace the evolution of the CSE from 400 to 1200 years. SiS (J = 2{x2192}1) emission was detected from both RW LMi and IK Tau. For both stars the SiS emission is centrally condensed with the peak line emission coincident with the stellar radio continuum emission. In addition, we have detected weak HC₇ N (J = 32{x2192}31) emission from RW LMi.