A Pilot Imaging Line Survey of RW LMi and IK Tau Using the Expanded Very large Array

TL;DR

This pilot survey using the Expanded Very Large Array studied molecular emissions around two asymptotic giant branch stars, revealing shell structures and molecular distributions that inform stellar evolution and circumstellar envelope dynamics.

Contribution

First imaging line survey of RW LMi and IK Tau at 36-37 GHz, mapping molecular emissions and circumstellar structures with high spectral resolution.

Findings

Detected multiple shells around RW LMi indicating envelope evolution.

Centrally condensed SiS emission coincident with stellar radio continuum.

Weak HC7N emission detected from RW LMi.

Abstract

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) and IK Tau (= NML Tau, with an oxygen-rich circumstellar envelope). Radio continuum emission consistent with photospheric emission was detected from both stars. From RW LMi we imaged the HC3N (J = 4 -> 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 -> 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 HC7N (J = 32 -> 31) emission from RW LMi.