Volume 642, October 2020
|Number of page(s)||8|
|Section||Letters to the Editor|
|Published online||02 October 2020|
Letter to the Editor
Direct confirmation of the radial-velocity planet β Pictoris c
Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
2 Kavli Institute for Cosmology, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
3 LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Université de Paris, 5 Place Jules Janssen, 92195 Meudon, France
4 Université Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France
5 Max Planck Institute for Extraterrestrial Physics, Giessenbachstraße 1, 85748 Garching, Germany
6 Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
7 European Southern Observatory, Karl-Schwarzschild-Straße 2, 85748 Garching, Germany
8 European Southern Observatory, Casilla, 19001 Santiago 19, Chile
9 Aix Marseille Univ, CNRS, CNES, LAM, Marseille, France
10 Department of Astronomy, California Institute of Technology, Pasadena, CA 91125, USA
11 Space Telescope Science Institute, Baltimore, MD 21218, USA
12 Astronomy Department, University of Michigan, Ann Arbor, MI 48109, USA
13 School of Physics and Astronomy, Monash University, Clayton, Melbourne, VIC 3800, Australia
14 Center for Astrophysics and Planetary Science, Department of Astronomy, Cornell University, Ithaca, NY 14853, USA
15 Institute of Physics, University of Cologne, Zülpicher Straße 77, 50937 Cologne, Germany
16 Universidade de Lisboa – Faculdade de Ciências, Campo Grande, 1749-016 Lisboa, Portugal
17 CENTRA – Centro de Astrofísica e Gravitação, IST, Universidade de Lisboa, 1049-001 Lisboa, Portugal
18 Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
19 School of Physics, University College Dublin, Belfield, Dublin 4, Ireland
20 Pasadena City College, Pasadena, CA 91106, USA
21 Max Planck Institute for Radio Astronomy, Auf dem Hügel 69, 53121 Bonn, Germany
22 STAR Institute/Université de Liège, Liège, Belgium
23 Center for Astrophysics | Harvard & Smithsonian, Cambridge, MA 02138, USA
24 Pixyl, 5 Av. du Grand Sablon, 38700 La Tronche, France
25 Research School of Astronomy & Astrophysics, Australian National University, Canberra, ACT 2611, Australia
26 University of Exeter, Physics Building, Stocker Road, Exeter EX4 4QL, UK
27 Institute for Particle Physics and Astrophysics, ETH Zurich, Wolfgang-Pauli-Strasse 27, 8093 Zurich, Switzerland
28 Universidade do Porto, Faculdade de Engenharia, Rua Dr. Roberto Frias, 4200-465 Porto, Portugal
29 Five College Astronomy Department, Amherst College, Amherst, MA 01002, USA
Accepted: 26 August 2020
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.
Key words: planets and satellites: detection / planets and satellites: formation / techniques: interferometric
© ESO 2020
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