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


Abstract in English

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 ($Rsim$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$), and position angles (PA=0$^opm$6$^o$ and PA=-2$^opm$12$^o$), suggesting that they formed from the fragmentation of a common disk. The S CrA N spectrum shows bright HeI and Br$gamma$ line emission exhibiting inverse P-Cygni profiles, typically associated with infalling gas. The continuum-compensated Br$gamma$ line visibilities of S CrA N show the presence of a compact Br$gamma$ emitting region the radius of which is about $sim$0.06 au, which is twice as big as the truncation radius. This component is mostly tracing a wind. Moreover, a slight radius change between the blue- and red-shifted Br$gamma$ line components is marginally detected. The presence of an inverse P-Cygni profile in the HeI and Br$gamma$ lines, along with the tentative detection of a slightly larger size of the blue-shifted Br$gamma$ line component, hint at the simultaneous presence of a wind and magnetospheric accretion in S CrA N.

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