A Multi-Wavelength Analysis of Dust and Gas in the SR 24S Transition
  Disk
  We present new Atacama Large Millimeter/sub-millimeter Array (ALMA) 1.3 mm
continuum observations of the SR 24S transition disk with an angular resolution
$\lesssim0.18"$ (12 au radius). We perform a multi-wavelength investigation by
combining new data with previous ALMA data at 0.45 mm. The visibilities and
images of the continuum emission at the two wavelengths are well characterized
by a ring-like emission. Visibility modeling finds that the ring-like emission
is narrower at longer wavelengths, in good agreement with models of dust
trapping in pressure bumps, although there are complex residuals that suggest
potentially asymmetric structures. The 0.45 mm emission has a shallower profile
inside the central cavity than the 1.3 mm emission. In addition, we find that
the $^{13}$CO and C$^{18}$O (J=2-1) emission peaks at the center of the
continuum cavity. We do not detect either continuum or gas emission from the
northern companion to this system (SR 24N), which is itself a binary system.
The upper limit for the dust disk mass of SR 24N is $\lesssim
0.12\,M_{\bigoplus}$, which gives a disk mass ratio in dust between the two
components of $M_{\mathrm{dust, SR\,24S}}/M_{\mathrm{dust,
SR\,24N}}\gtrsim840$. The current ALMA observations may imply that either
planets have already formed in the SR 24N disk or that dust growth to mm-sizes
is inhibited there and that only warm gas, as seen by ro-vibrational CO
emission inside the truncation radii of the binary, is present.
