  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 ~90 au. VLA4A is undergoing an
accretion burst that enriches the chemistry of the surrounding gas. This gives
us an excellent opportunity to probe the chemical and physical conditions as
well as the accretion process. Methods. We observe the (12K-11K) lines of CH3CN
and CH313CN, the DCN (3-2) line, and the C18O (2-1) line toward SVS13A using
NOEMA. Results. We find complex line profiles at disk scales which 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 between 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
high-angular-resolution observations, we find that the binary system (or VLA4A)
might be fed by an infalling streamer from envelope scales (~700 au). If this
is the case, this streamer contributes to the accretion of material onto the
system with a rate of at least 1.4x10-6 Msun 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.
