The wind and the magnetospheric accretion onto the T Tauri star S Coronae Australis at sub-au resolution
1 Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
2 Dublin Institute for Advanced Studies, 31 Fitzwilliam Place, D02 XF86 Dublin, Ireland
3 University Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France
4 I. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, 50937 Köln, Germany
5 Universidade do Porto – Faculdade de Engenharia, Rua Dr. Roberto Frias, 4200-465 Porto, Portugal
6 CENTRA, Instituto Superior Tecnico, Av. Rovisco Pais, 1049-001 Lisboa, Portugal
7 European Southern Observatory, Karl-Schwarzschild-Straße 2, 85748 Garching, Germany
8 Max Planck Institute for Extraterrestrial Physics, Giessenbachstrasse, 85741 Garching bei München, Germany
9 LESIA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universités, UPMC University Paris 06, University Paris Diderot, Sorbonne Paris Cité, 75005 Paris, France
10 European Southern Observatory, Casilla 19001, Santiago 19, Chile
11 Max-Planck-Institute for Radio Astronomy, Auf dem Hügel 69, 53121 Bonn, Germany
12 Department of Physics, Le Conte Hall, University of California, Berkeley, CA 94720, USA
13 Unidad Mixta Internacional Franco-Chilena de Astronomía (CNRS UMI 3386), Departamento de Astronomía, Universidad de Chile, Camino El Observatorio 1515, Las Condes, 1058 Santiago, Chile
14 Sterrewacht Leiden, Leiden University, Postbus 9513, 2300 RA Leiden, The Netherlands
Received: 27 April 2017
Accepted: 5 September 2017
Aims. To investigate the inner regions of protoplanetary discs, we performed near-infrared interferometric observations of the classical T Tauri binary system S CrA.
Methods. We present the first VLTI-GRAVITY high spectral resolution (R ~ 4000) observations of a classical T Tauri binary, S CrA (composed of S CrA N and S CrA S and separated by ~1.̋4), combining the four 8m telescopes in dual-field mode.
Results. Our observations in the near-infrared K-band continuum reveal a disc around each binary component, with similar half-flux radii of about 0.1 au at d ~ 130 pc, inclinations (i = 28 ± 3° and i = 22 ± 6°), and position angles (PA = 0°± 6° and PA = –2°± 12°), suggesting that they formed from the fragmentation of a common disc. The S CrA N spectrum shows bright He i and Brγ line emission exhibiting inverse P Cygni profiles, typically associated with infalling gas. The continuum-compensated Brγ line visibilities of S CrA N show the presence of a compact Brγ emitting region whose radius is about ~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 Brγ line components is marginally detected.
Conclusions. The presence of an inverse P Cygni profile in the He i and Brγ lines, along with the tentative detection of a slightly larger size of the blue-shifted Brγ line component, hint at the simultaneous presence of a wind and magnetospheric accretion in S CrA N.
Key words: stars: formation / circumstellar matter / ISM: jets and outflows / ISM: individual objects: S CrA / infrared: ISM / techniques: interferometric
GRAVITY is developed in a collaboration by the Max Planck Institute for Extraterrestrial Physics, LESIA of Paris Observatory and IPAG of Université Grenoble Alpes/CNRS, the Max Planck Institute for Astronomy, the University of Cologne, the Centro Multidisciplinar de Astrofisica Lisbon and Porto, and the European Southern Observatory.
© ESO, 2017