High-resolution observations of the symbiotic system R Aqr. Direct
  imaging of the gravitational effects of the secondary on the stellar wind
  We have observed the symbiotic stellar system R Aqr, aiming to describe the
gravitational interaction between the white dwarf (WD) and the wind from the
Mira star, the key phenomenon driving the symbiotic activity and the formation
of nebulae in such systems. We present high-resolution ALMA maps of the 12CO
and 13CO J=3-2 lines, the 0.9 mm continuum distribution, and some
high-excitation molecular lines in R Aqr. The maps, which have resolutions
ranging between 40 milliarcsecond (mas) and less than 20 mas, probe the
circumstellar regions at suborbital scales as the distance between the stars is
~ 40 mas. Our observations show the gravitational effects of the secondary on
the stellar wind. The AGB star was identified in our maps from the continuum
and molecular line data, and we estimated the probable position of the
secondary from a new estimation of the orbital parameters. The (preliminary)
comparison of our maps with theoretical predictions is surprisingly
satisfactory and the main expected gravitational effects are directly mapped
for the first time. We find a strong focusing in the equatorial plane of the
resulting wind, which shows two plumes in opposite directions that have
different velocities and very probably correspond to the expected double spiral
due to the interaction. Our continuum maps show the very inner regions of the
nascent bipolar jets, at scales of some AU. Continuum maps obtained with the
highest resolution show the presence of a clump that very probably corresponds
to the emission of the ionized surroundings of the WD and of a bridge of
material joining both stars, which is likely material flowing from the AGB
primary to the accretion disk around the WD secondary.
