Direct confirmation of the radial-velocity planet β Pictoris c

M. Nowak, S. Lacour, A. M. Lagrange, P. Rubini, J. Wang, T. Stolker, R. Abuter, A. Amorim, R. Asensio-Torres, M. Bauböck, M. Benisty, J. P. Berger, H. Beust, S. Blunt, A. Boccaletti, M. Bonnefoy, H. Bonnet, W. Brandner, F. Cantalloube, B. CharnayE. Choquet, V. Christiaens, Y. Clénet, V. Coudé Du Foresto, A. Cridland, P. T. De Zeeuw, R. Dembet, J. Dexter, A. Drescher, G. Duvert, A. Eckart, F. Eisenhauer, F. Gao, P. Garcia, R. Garcia Lopez, T. Gardner, E. Gendron, R. Genzel, S. Gillessen, J. Girard, A. Grandjean, X. Haubois, G. Heißel, T. Henning, S. Hinkley, S. Hippler, M. Horrobin, M. Houllé, Z. Hubert, A. Jiménez-Rosales, L. Jocou, J. Kammerer, P. Kervella, M. Keppler, L. Kreidberg, M. Kulikauskas, V. Lapeyrère, J. B. Le Bouquin, P. Léna, A. Mérand, A. L. Maire, P. Mollière, J. D. Monnier, D. Mouillet, A. Müller, E. Nasedkin, T. Ott, G. Otten, T. Paumard, C. Paladini, K. Perraut, G. Perrin, L. Pueyo, O. Pfuhl, J. Rameau, L. Rodet, G. Rodríguez-Coira, G. Rousset, S. Scheithauer, J. Shangguan, J. Stadler, O. Straub, C. Straubmeier, E. Sturm, L. J. Tacconi, E. F. Van Dishoeck, A. Vigan, F. Vincent, S. D. Von Fellenberg, K. Ward-Duong, F. Widmann, E. Wieprecht, E. Wiezorrek, J. Woillez, The GRAVITY Collaboration

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Abstract

Context. Methods used to detect giant exoplanets can be broadly divided into two categories: indirect and direct. Indirect methods are more sensitive to planets with a small orbital period, whereas direct detection is more sensitive to planets orbiting at a large distance from their host star. This dichotomy makes it difficult to combine the two techniques on a single target at once. 

Aims. Simultaneous measurements made by direct and indirect techniques offer the possibility of determining the mass and luminosity of planets and a method of testing formation models. Here, we aim to show how long-baseline interferometric observations guided by radial-velocity can be used in such a way. 

Methods. We observed the recently-discovered giant planet β Pictoris c with GRAVITY, mounted on the Very Large Telescope Interferometer. 

Results. This study constitutes the first direct confirmation of a planet discovered through radial velocity. We find that the planet has a temperature of T = 1250 ± 50 K and a dynamical mass of M = 8.2 ± 0.8 MJup. At 18.5 ± 2.5 Myr, this puts β Pic c close to a 'hot start' track, which is usually associated with formation via disk instability. Conversely, the planet orbits at a distance of 2.7 au, which is too close for disk instability to occur. The low apparent magnitude (MK = 14.3 ± 0.1) favours a core accretion scenario. 

Conclusions. We suggest that this apparent contradiction is a sign of hot core accretion, for example, due to the mass of the planetary core or the existence of a high temperature accretion shock during formation.

Original languageEnglish
Article numberL2
Number of pages8
JournalAstronomy & Astrophysics
Volume642
Issue numberOctober 2020
DOIs
Publication statusPublished - 1 Oct 2020

Keywords

  • Planets and satellites: detection
  • Planets and satellites: formation
  • Techniques: interferometric

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