VLA Observations of HI in the Circumstellar Envelopes of AGB Stars

Abstract

We present the results of a VLA search for HI emission in the circumstellar envelopes of five nearby AGB stars: RS Cnc, IRC+10216, EP Aqr, R Cas, and R Aqr. We have detected emission coincident in both position and velocity with RS Cnc, implying that the emission arises from its extended envelope. For R Cas, we detected weak emission that peaks at the stellar systemic velocity and overlaps with the location of its circumstellar dust shell and thus is probably related to the star. Toward IRC+10216 and EP Aqr, we detected multiple, arcminute-scale HI emission features at velocities consistent with the circumstellar envelopes, but spatially offset from the stellar positions; in these cases we cannot determine unambiguously if the emission is associated with the stars. In the case of IRC+10216, we were unable to confirm the detection of HI in absorption against the cosmic background previously reported by Le Bertre & Gerard. We detected our fifth target, R Aqr (a symbiotic binary), in the 1.4 GHz continuum.