First Images of R Aquarii and its Asymmetric H$_{2}$O Shell

TL;DR

This paper presents near-infrared and radio imaging of R Aquarii, revealing a complex, clumpy water shell and turbulent outer envelope with jet-like features, advancing understanding of its circumstellar environment.

Contribution

It introduces a multi-wavelength imaging approach and models that reveal the non-uniform, clumpy water shell and turbulent features around R Aquarii.

Findings

Water shell is highly non-uniform and clumpy.

VLBA observations show turbulence and jet-like features.

Models favor a three-component structure over uniform disk.

Abstract

We report imaging observations of the symbotic long-period Mira variable R Aquarii (R Aqr) at near-infrared and radio wavelengths. The near-infrared observations were made with the IOTA imaging interferometer in three narrow-band filters centered at 1.51, 1.64, and 1.78 $\mu$m, which sample mainly water, continuum, and water features, respectively. Our near-infrared fringe visibility and closure phase data are analyzed using three models. (a) A uniform disk model with wavelength-dependent sizes fails to fit the visibility data, and is inconsistent with the closure phase data. (b) A three- component model, comprising a Mira star, water shell, and an off-axis point source, provide a good fit to all data. (c) A model generated by a constrained image reconstruction analysis provides more insight, suggesting that the water shell is highly non-uniform, i.e., clumpy. The VLBA observations of SiO masers in the outer molecular envelope show evidence of turbulence, with jet-like features containing velocity gradients.