PRODIGE - envelope to disk with NOEMA II. Small-scale temperature structure and streamer feeding the SVS13A protobinary based on CH3CN and DCN

Aims. We present high-sensitivity and high spectral-resolution NOEMA observations of the Class 0/I binary system SVS13A, composed of the low-mass protostars VLA4A and VLA4B, with a separation of similar to 90 au. VLA4A is undergoing an accretion burst that is enriching the chemistry of the surrounding gas, which provides an excellent opportunity to probe the chemical and physical conditions as well as the accretion process. Methods. We observe the (12(K)-11(K)) lines of CH3CN and (CH3CN)-C-13, the DCN (3-2) line, and the (CO)-O-18 (2-1) line toward SVS13A using NOEMA. Results. We find complex line profiles at disk scales that cannot be explained by a single component or pure Keplerian motion. By adopting two velocity components to model the complex line profiles, we find that the temperatures and densities are significantly different among these two components. This suggests that the physical conditions of the emitting gas traced via CH3CN can change dramatically within the circumbinary disk. In addition, combining our observations of DCN (3-2) with previous ALMA observations at high angular resolution, we find that the binary system (or VLA4A) might be fed by an infalling streamer from envelope scales (similar to 700 au). If this is the case, this streamer contributes to the accretion of material onto the system at a rate of at least 1.4 x 10(-6) M(circle dot)yr(-1). Conclusions. We conclude that the CH3CN emission in SVS13A traces hot gas from a complex structure. This complexity might be affected by a streamer that is possibly infalling and funneling material into the central region.

Automated summary

This study presents high-sensitivity and high spectral-resolution observations of the binary system SVS13A using NOEMA. Complex line profiles at disk scales suggest the presence of multiple velocity components and significant variations in physical conditions within the circumbinary disk. Furthermore, the observations indicate the possible existence of an infalling streamer feeding material into the central region. Overall, this research provides valuable insights into the chemistry, physics, and accretion processes of interstellar matter.