The GRAVITY young stellar object survey. XIV. Investigating the magnetospheric accretion-ejection processes in S CrA N

Context. The dust- and gas-rich protoplanetary disks around young stellar systems play a key role in star and planet formation. While considerable progress has recently been made in probing these disks on large scales of a few tens of astronomical units (au), the central au requires further investigation. Aims. We aim to unveil the physical processes at play in the innermost regions of the strongly accreting T Tauri Star S CrA N by means of near-infrared interferometric observations. As recent spectropolarimetric observations suggest that S CrA N might undergo intense ejection processes, we focus on the accretion–ejection phenomena and on the star–disk interaction region. Methods. We obtained interferometric observations with VLTI/GRAVITY in the K -band during two consecutive nights in August 2022. The analysis of the continuum emission, coupled with the differential analysis across the Br γ line, allows us to constrain the morphology of the dust and the gas distribution in the innermost regions of S CrA N and to investigate their temporal variability. These observations are compared to magnetospheric accretion–ejection models of T Tauri stars and to previous observations in order to elucidate the physical processes operating in these regions. Results. The K -band continuum emission is well reproduced with an azimuthally modulated dusty ring with a half-light radius of 0.24 au (∼20 R * ), an inclination of ∼30°, and a position angle of ∼150°. As the star alone cannot explain such a large sublimation front, we propose that magnetospheric accretion is an important dust-heating mechanism leading to this continuum emission. The Br γ -emitting region (0.05–0.06 au; 5–7 R * ) is found to be more compact than the continuum, to be similar in size or larger than the magnetospheric truncation radius. The on-sky displacements across the Br γ spectral channels are aligned along a position angle offset by 45° from the disk, and extend up to 2 R * . This is in agreement with radiative transfer models combining magnetospheric accretion and disk winds. These on-sky displacements remain unchanged from one night to another, while the line flux decreases by 13%, suggesting a dominant contribution of wind to the origin of the Br γ line. Conclusions. Our observations support the scenario where the Br γ line originates from a combination of (variable) accretion–ejection processes in the inner disk region.