The convective surface of the red supergiant Antares
VLTI/PIONIER interferometry in the near infrared⋆
1 Institut de Radioastronomie Millimétrique, 300 rue de la Piscine, 38406 Saint Martin d’Hères, France
2 Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Lagrange, 34229 Nice, France
3 Unidad Mixta Internacional Franco-Chilena de Astronomía (UMI 3386), CNRS/INSU, France
4 LESIA, Observatoire de Paris, PSL Research University, CNRS UMR 8109, Sorbonne Universités, UPMC, Université Paris Diderot, Sorbonne Paris Cité, 5 place Jules Janssen, 92195 Meudon, France
5 National Optical Astronomy Observatories, 950 North Cherry Avenue, Tucson, AZ 85719, USA
6 UJF-Grenoble 1/CNRS-INSU, Institut de Planétologie et d’Astrophysique de Grenoble (IPAG), UMR 5274, 38400 Grenoble, France
7 Departamento de Astronomía, Universidad de Chile, Camino El Observatorio 1515, Las Condes, Santiago, Chile
Received: 31 October 2016
Accepted: 15 May 2017
Context. Convection is a candidate to explain the trigger of red supergiant star (RSG) mass loss. Owing to the small size of the convective cells on the photosphere, few of the characteristics of RSGs are known.
Aims. Using near infrared interferometry, we intend to resolve the photosphere of RSGs and to bring new constraints on their modeling.
Methods. We observed the nearby RSG Antares using the four-telescope instrument VLTI/PIONIER. We collected data on the three available configurations of the 1.8 m telescopes in the H band.
Results. We obtained unprecedented angular resolution on the disk of a star (6% of the star angular diameter) that limits the mean size of convective cells and offers new constraints on numerical simulations. Using an analytical model with a distribution of bright spots we determine their effect on the visibility signal.
Conclusions. We determine that the interferometric signal on Antares is compatible with convective cells of various sizes from 45% to 5% of the angular diameter. We also conclude that convective cells can strongly affect the angular diameter and limb-darkening measurements. In particular, the apparent angular diameter becomes dependent on the sampled position angles.
Key words: stars: individual: Antares / stars: imaging / supergiants / stars: mass-loss / infrared: stars / techniques: interferometric
© ESO, 2017