Astronomy and Astrophysics
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.
Planets and satellites: detection, Planets and satellites: formation, Techniques: interferometric
© 2020. ESO
Nowak, M.; Lacour, S.; Lagrange, A. M.; Rubini, P.; Wang, J.; Stolker, T.; Abuter, R.; Amorim, A.; Asensio-Torres, R.; Bauböck, M.; Benisty, M.; Berger, J. P.; Beust, H.; Blunt, S.; Boccaletti, A.; Bonnefoy, M.; Bonnet, H.; Brandner, W.; Cantalloube, F.; Charnay, B.; Choquet, E.; Christiaens, V.; Clénet, Y.; Coudé Du Foresto, V.; Cridland, A.; De Zeeuw, P. T.; Dembet, R.; Dexter, J.; Drescher, A.; Duvert, G.; Eckart, A.; Eisenhauer, F.; Ward-Duong, Kimberly; and al, et, "Direct Confirmation of the Radial-Velocity Planet β Pictoris c" (2020). Astronomy: Faculty Publications, Smith College, Northampton, MA.