An Inner Disk in the Large Gap of the Transition Disk SR 24S

We report new Atacama Large Millimeter/submillimeter Array (ALMA) Band 3 observations at 2.75 mm of the transition disk around SR 24S, with an angular resolution of similar to 0 ''.11 x 0 '' 09. and a peak signal-to-noise ratio of similar to 24. We detect an inner disk and a mostly symmetric ring-like structure that peaks at similar to 0 ''.32, which is similar to 37 au at a distance of similar to 114.4 pc. The full width at half maximum of this ring is similar to 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 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 the dead zone can be excluded as leading mechanisms for the cavity formation in the 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 less than or similar to 5 M(Jup )and alpha similar to 10(-4)-10(-3), respectively.