Discovery of a warm, dusty giant planet around HIP 65426

G. Chauvin, S. Desidera, A. M. Lagrange, A. Vigan, R. Gratton, M. Langlois, M. Bonnefoy, J. L. Beuzit, M. Feldt, D. Mouillet, M. Meyer, A. Cheetham, B. Biller, A. Boccaletti, V. D'Orazi, R. Galicher, J. Hagelberg, A. L. Maire, D. Mesa, J. OlofssonM. Samland, T. O.B. Schmidt, E. Sissa, M. Bonavita, B. Charnay, M. Cudel, S. Daemgen, P. Delorme, P. Janin-Potiron, M. Janson, M. Keppler, H. Le Coroller, R. Ligi, G. D. Marleau, S. Messina, P. Mollière, C. Mordasini, A. Müller, S. Peretti, C. Perrot, L. Rodet, D. Rouan, A. Zurlo, C. Dominik, T. Henning, F. Menard, H. M. Schmid, M. Turatto, S. Udry, F. Vakili, L. Abe, J. Antichi, A. Baruffolo, P. Baudoz, J. Baudrand, P. Blanchard, A. Bazzon, T. Buey, M. Carbillet, M. Carle, J. Charton, E. Cascone, R. Claudi, A. Costille, A. Deboulbe, V. De Caprio, K. Dohlen, D. Fantinel, P. Feautrier, T. Fusco, P. Gigan, E. Giro, D. Gisler, L. Gluck, N. Hubin, E. Hugot, M. Jaquet, M. Kasper, F. Madec, Y. Magnard, P. Martinez, D. Maurel, D. Le Mignant, O. Möller-Nilsson, M. Llored, T. Moulin, A. Origné, A. Pavlov, D. Perret, C. Petit, J. Pragt, P. Puget, P. Rabou, J. Ramos, R. Rigal, S. Rochat, R. Roelfsema, G. Rousset, A. Roux, B. Salasnich, J. F. Sauvage, A. Sevin, C. Soenke, E. Stadler, M. Suarez, L. Weber, F. Wildi, S. Antoniucci, J. C. Augereau, J. L. Baudino, W. Brandner, N. Engler, J. Girard, C. Gry, Q. Kral, T. Kopytova, E. Lagadec, J. Milli, C. Moutou, J. Schlieder, J. Szulágyi, C. Thalmann, Z. Wahhaj

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Abstract

Aims. The SHINE program is a high-contrast near-infrared survey of 600 young, nearby stars aimed at searching for and characterizing new planetary systems using VLT/SPHERE's unprecedented high-contrast and high-angular-resolution imaging capabilities. It is also intended to place statistical constraints on the rate, mass and orbital distributions of the giant planet population at large orbits as a function of the stellar host mass and age to test planet-formation theories. 

Methods. We used the IRDIS dual-band imager and the IFS integral field spectrograph of SPHERE to acquire high-contrast coronagraphic differential near-infrared images and spectra of the young A2 star HIP 65426. It is a member of the ~17 Myr old Lower Centaurus-Crux association. 

Results. At a separation of 830 mas (92 au projected) from the star, we detect a faint red companion. Multi-epoch observations confirm that it shares common proper motion with HIP 65426. Spectro-photometric measurements extracted with IFS and IRDIS between 0.95 and 2.2 μm indicate a warm, dusty atmosphere characteristic of young low-surface-gravity L5-L7 dwarfs. Hot-start evolutionary models predict a luminosity consistent with a 6-12 MJup, Teff = 1300-1600 K and R = 1.5 ± 0.1 RJup giant planet. Finally, the comparison with Exo-REM and PHOENIX BT-Settl synthetic atmosphere models gives consistent effective temperatures but with slightly higher surface gravity solutions of log (g) = 4.0-5.0 with smaller radii (1.0-1.3 RJup). 

Conclusions. Given its physical and spectral properties, HIP 65426 b occupies a rather unique placement in terms of age, mass, and spectral-type among the currently known imaged planets. It represents a particularly interesting case to study the presence of clouds as a function of particle size, composition, and location in the atmosphere, to search for signatures of non-equilibrium chemistry, and finally to test the theory of planet formation and evolution.

Original languageEnglish
Article numberL9
Number of pages9
JournalAstronomy & Astrophysics
Volume605
DOIs
Publication statusPublished - 1 Sep 2017
Externally publishedYes

Keywords

  • Instrumentation: adaptive optics
  • Instrumentation: high angular resolution
  • Methods: observational
  • Planets and satellites: atmospheres
  • Planets and satellites: formation

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