The Messenger Astronomical Science

Constraining Convection in Evolved Stars with the VLTI

Authors
  • Paladini, Claudia [European Southern Observatory (ESO)]
  • Baron, Fabien [Department of Physics and Astronomy, Georgia State University, USA]
  • Jorissen, Alain [Institut d’Astronomie et d’Astrophysique, Université libre de Bruxelles, Belgium]
  • Le Bouquin, Jean-Baptiste [Université Grenoble Alpes, CNRS, IPAG, France]
  • Freytag, Bernd [Department of Physics and Astronomy, Uppsala University, Sweden]
  • van Eck, Sophie [Institut d’Astronomie et d’Astrophysique, Université libre de Bruxelles, Belgium]
  • Wittkowski, Markus [European Southern Observatory (ESO)]
  • Hron, Josef [Department of Astrophysics, University of Vienna, Austria]
  • Chiavassa, Andrea [Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Lagrange, Nice, France]
  • Berger, Jean-Philippe [Université Grenoble Alpes, CNRS, IPAG, France]
  • Siopis, Christos [Institut d’Astronomie et d’Astrophysique, Université libre de Bruxelles, Belgium]
  • Mayer, Andreas [Department of Astrophysics, University of Vienna, Austria]
  • Sadowski, Gilles [Institut d’Astronomie et d’Astrophysique, Université libre de Bruxelles, Belgium]
  • Kravchenko, Kateryna [Institut d’Astronomie et d’Astrophysique, Université libre de Bruxelles, Belgium]
  • Shetye, Shreeya [Institut d’Astronomie et d’Astrophysique, Université libre de Bruxelles, Belgium]
  • Kerschbaum, Franz [Department of Astrophysics, University of Vienna, Austria]
  • Kluska, Jacques [Institute of Astronomy, KU Leuven, Belgium]
  • Ramstedt, Sofia [Department of Physics and Astronomy, Uppsala University, Sweden]

Section
Astronomical Science
Abstract

We used the Precision Integrated-Optics Near-infrared Imaging ExpeRiment (PIONIER) at the Very Large Telescope Interferometer (VLTI) to image the stellar surface of the S-type Asymptotic Giant Branch (AGB) star π1 Gruis. The angular resolution of two milliarcseconds allowed us to observe the surface of this giant star in unprecedented detail. At the observed wavelength the stellar disc appears circular and dust-free. Moreover, the disc is characterised by a few bubbles of a convective nature. We determine the contrast, and the characteristic horizontal length-scale of the convective granules. The latter is determined, for the first time, directly from the image, without involving the usual geometric modelling that has been used in the literature. The measurements fall along empirical scaling relations between stellar parameters and convective sizes, which are determined on the basis of three-dimensional stellar convection models. Our results open up a new era for the characterisation of stellar convection in stars other than the Sun.


Dates
Created: 2018-06-01/2018-06-30
Length
3 pages

Cite this article:

C. Paladini, F. Baron, A. Jorissen, J. Le Bouquin, B. Freytag, S. van Eck, M. Wittkowski, J. Hron, A. Chiavassa, J. Berger, C. Siopis, A. Mayer, G. Sadowski, K. Kravchenko, S. Shetye, F. Kerschbaum, J. Kluska, S. Ramstedt; Constraining Convection in Evolved Stars with the VLTI. The Messenger 172 (June 2018): 24–26. https://doi.org/10.18727/0722-6691/5077