An Inner Disk in the Large Gap of the Transition Disk SR 24S
  We report new Atacama Large Millimeter/sub-millimeter Array (ALMA) Band 3
observations at 2.75 mm of the TD around SR 24S with an angular resolution of
$\sim$0.11''$\times$ 0.09'' and a peak signal-to-noise ratio of $\sim24$. We
detect an inner disk and a mostly symmetric ring-like structure that peaks at
$\sim$0.32'', that is $\sim$37 au at a distance of $\sim$114.4 pc. The full
width at half maximum of this ring is $\sim$28 au. We analyze the observed
structures by fitting the dust continuum visibilities using different models
for the intensity profile, and compare with previous ALMA observations of the
same disk at 0.45 mm and 1.30 mm. We qualitatively compare the results of these
fits with theoretical predictions of different scenarios for the formation of a
cavity or large gap. The comparison of the dust continuum structure between
different ALMA bands indicates that photoevaporation and dead zone can be
excluded as leading mechanisms for the cavity formation in SR 24S disk, leaving
the planet scenario (single or multiple planets) as the most plausible
mechanism. We compared the 2.75 mm emission with published (sub-)centimeter
data and find that the inner disk is likely tracing dust thermal emission. This
implies that any companion in the system should allow dust to move inwards
throughout the gap and replenish the inner disk. In the case of one single
planet, this puts strong constraints on the mass of the potential planet inside
the cavity and the disk viscosity of about $\lesssim$5 $M_{\rm{Jup}}$ and
$\alpha\sim10^{-4}-10^{-3}$, respectively.
