Volume 614, June 2018
|Number of page(s)||11|
|Published online||06 June 2018|
The convective photosphere of the red supergiant CE Tauri
Institute of Astronomy, KU Leuven,
Celestijnenlaan 200D B2401,
2 Institut de Radioastronomie Millimétrique, 300 rue de la Piscine, 38406 Saint-Martin-d’Hères, France
3 Department of Physics and Astronomy, Georgia State University, PO Box 5060 Atlanta, GA 30302-5060, USA
4 Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Lagrange, CS 34229, Nice, France
5 Université de Montpellier, CNRS, LUPM, Place E. Bataillon, 34090 Montpellier, France
Accepted: 3 February 2018
Context. Red supergiant stars are one of the latest stages in the evolution of massive stars. Their photospheric convection may play an important role in the launching mechanism of their mass loss; however, its characteristics and dynamics are still poorly constrained.
Aims. By observing red supergiant stars with near infrared interferometry at different epochs, we expect to reveal the evolution of bright convective features on their stellar surface.
Methods. We observed the M2Iab-Ib red supergiant star CE Tau with the VLTI/PIONIER instrument in the H band at two different epochs separated by one month.
Results. We derive the angular diameter of the star and basic stellar parameters, and reconstruct two reliable images of its H-band photosphere. The contrast of the convective pattern of the reconstructed images is 5 ± 1% and 6 ± 1% for our two epochs of observation.
Conclusions. The stellar photosphere shows few changes between the two epochs. The contrast of the convective pattern is below the average contrast variations obtained on 30 randomly chosen snapshots of the best matching 3D radiative hydrodynamics simulation: 23 ± 1% for the original simulation images and 16 ± 1% for the maps degraded to the reconstruction resolution. We offer two hypotheses to explain this observation. CE Tau may be experiencing a quiet convective activity episode or it could be a consequence of its warmer effective temperature (hence its smaller radius) compared to the simulation.
Key words: stars: individual: CE Tau / stars: imaging / supergiants / stars: mass-loss / infrared: stars / techniques: interferometric
Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO programs 298.D-5005(A) and 298.D-5005(B).
Reconstructed images as FITS files and basic stellar parameters are available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (18.104.22.168) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/614/A12
Animated gif of the two epochs is available at https://www.aanda.org
© ESO 2018
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