The Physical Properties of the SVS 13 Protobinary System: Two
  Circumstellar Disks and a Spiraling Circumbinary Disk in the Making
  We present VLA and ALMA observations of the close (0.3" = 90 au separation)
protobinary system SVS 13. We detect two small circumstellar disks (radii
$\sim$12 and $\sim$9 au in dust, and $\sim$30 au in gas) with masses of
$\sim$0.004-0.009 $M_{sun}$ for VLA 4A (the western component) and
$\sim$0.009-0.030 $M_{sun}$ for VLA 4B (the eastern component). A circumbinary
disk with prominent spiral arms extending $\sim$500 au and a mass of
$\sim$0.052 $M_{sun}$ appears to be in the earliest stages of formation. The
dust emission is more compact and with a very high optical depth toward VLA 4B,
while toward VLA 4A the dust column density is lower, allowing the detection of
stronger molecular transitions. We infer rotational temperatures of $\sim$140
K, on scales of $\sim$30 au, across the whole source, and a rich chemistry.
Molecular transitions typical of hot corinos are detected toward both
protostars, being stronger toward VLA 4A, with several ethylene glycol
transitions detected only toward this source. There are clear velocity
gradients, that we interpret in terms of infall plus rotation of the
circumbinary disk, and purely rotation of the circumstellar disk of VLA 4A. We
measured orbital proper motions and determined a total stellar mass of 1
$M_{sun}$. From the molecular kinematics we infer the geometry and orientation
of the system, and stellar masses of $\sim$0.26 $M_{sun}$ for VLA 4A and
$\sim$0.60 $M_{sun}$ for VLA 4B.
