The wind and the magnetospheric accretion onto the T Tauri star S Coronae Australis at sub-au resolution

Abstract

To investigate the inner regions of protoplanetary disks, we performed near-infrared interferometric observations of the classical TTauri binary system S CrA. We present the first VLTI-GRAVITY high spectral resolution ($R\sim$4000) observations of a classical TTauri binary, S CrA (composed of S CrA N and S CrA S and separated by $\sim$1.4"), combining the four 8-m telescopes in dual-field mode. Our observations in the near-infrared K-band continuum reveal a disk around each binary component, with similar half-flux radii of about 0.1 au at d$\sim$130 pc, inclinations ($i=$28$\pm$3${}^o$\ and $i=$22$\pm$6${}^o$), and position angles (PA=0${}^o\pm$6${}^o$ and PA=-2${}^o\pm$12${}^o$), suggesting that they formed from the fragmentation of a common disk. The S CrA N spectrum shows bright HeI and Br${\hat{I}}^3$ line emission exhibiting inverse P-Cygni profiles, typically associated with infalling gas. The continuum-compensated Br${\hat{I}}^3$ line visibilities of S CrA N show the presence of a compact Br${\hat{I}}^3$ emitting region the radius of which is about $\sim$0.06 au, which is twice as big as the truncation radius. This component is mostly tracing a wind. Moreover, a slight radius change between the blue- and red-shifted Br${\hat{I}}^3$ line components is marginally detected. The presence of an inverse P-Cygni profile in the HeI and Br${\hat{I}}^3$ lines, along with the tentative detection of a slightly larger size of the blue-shifted Br${\hat{I}}^3$ line component, hint at the simultaneous presence of a wind and magnetospheric accretion in S CrA N.

Accepted by A&A