# A Multi-Wavelength Analysis of Dust and Gas in the SR 24S Transition Disk

## TL;DR

This study uses high-resolution ALMA observations at multiple wavelengths to analyze the dust and gas structures in the SR 24S transition disk, revealing a narrow ring, asymmetric features, and gas concentrations inside the cavity, with implications for planet formation.

## Contribution

It provides the first multi-wavelength, high-resolution analysis of the SR 24S disk, highlighting dust trapping, asymmetries, and gas distribution, and compares it with the non-detected SR 24N companion.

## Key findings

- Ring-like dust emission is narrower at longer wavelengths.
- Gas peaks at the center of the dust cavity.
- SR 24N has a very low dust disk mass, suggesting possible planet formation or inhibited dust growth.

## Abstract

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.