Spatial Resolution of the R Aquarii Binary System

Abstract

We report continuum VLA observations at 7 mm that have resolved the stellar components in the R Aqr binary system. R Aqr was simultaneously probed in both a 50 MHz bandpass containing lineless continuum emission associated with the hot companion/accretion disk and a 3.125 MHz bandpass containing the spectral line v = 1, J = 1-0, SiO maser emission associated with the long-period-variable (LPV) envelope. The offset between the two stars is 55 ± 2 mas with a position angle of ~18° ± 2° relative to the LPV, providing the first data point for a subsequent monitoring program to determine precisely the binary orbit that is suspected to be highly elliptical and have a period of ~44 yr. We evaluate these first observations in the context of constraints placed on the orbital geometry of the system and obtain a geometrical distance of ~200 pc to R Aqr. We also report spectral line VLA observations at this same epoch that confirm that the SiO maser spots have a ringlike morphology, as previously reported by other investigators using the VLBA.