Discovery of a warm, dusty giant planet around HIP 65426
Moutou, C.; Rouan, D.; Augereau, J. -C.; Schmidt, T. O. B.; Henning, T.; Fantinel, D.; Girard, J.; Dominik, C.; Brandner, W.; Messina, S.; Turatto, M.; D'Orazi, V.; Udry, S.; Milli, J.; Wahhaj, Z.; Vakili, F.; Fusco, T.; Costille, A.; Menard, F.; Zurlo, A.; Boccaletti, A.; Janson, M.; Keppler, M.; Kral, Q.; Langlois, M.; Ligi, R.; Maire, A. -L.; Meyer, M.; Sauvage, J. -F.; Szulágyi, J.; Baruffolo, A.; Baudoz, P.; Le Mignant, D.; Maurel, D.; Ramos, J.; Weber, L.; Lagrange, A. -M.; Claudi, R.; Desidera, S.; Rodet, L.; Delorme, P.; Bonnefoy, M.; Baudino, J. -L.; Bonavita, M.; Cheetham, A.; Hagelberg, J.; Mesa, D.; Perrot, C.; Charnay, B.; Gratton, R.; Olofsson, J.; Vigan, A.; Chauvin, G.; Galicher, R.; Samland, M.; Thalmann, C.; Beuzit, J. -L.; Mouillet, D.; Peretti, S.; Sissa, E.; Abe, L.; Feldt, M.; Madec, F.; Perret, D.; Petit, C.; Rabou, P.; Soenke, C.; Möller-Nilsson, O.; Müller, A.; Antoniucci, S.; Gry, C.; Baudrand, J.; Lagadec, E.; Mordasini, C.; Pavlov, A.; Hubin, N.; Rochat, S.; Stadler, E.; Roux, A.; Martinez, P.; Biller, B.; Engler, N.; Le Coroller, H.; Wildi, F.; Buey, T.; Giro, E.; Kasper, M.; Cascone, E.; Mollière, P.; Roelfsema, R.; Pragt, J.; Gisler, D.; Carle, M.; Feautrier, P.; Gluck, L.; Daemgen, S.; Janin-Potiron, P.; Kopytova, T.; Antichi, J.; Bazzon, A.; Blanchard, P.; Carbillet, M.; Charton, J.; De Caprio, V.; Dohlen, K.; Gigan, P.; Hugot, E.; Jaquet, M.; Llored, M.; Magnard, Y.; Moulin, T.; Origné, A.; Puget, P.; Rousset, G.; Salasnich, B.; Sevin, A.; Suarez, M.; Schlieder, J.; Cudel, M.; Marleau, G. D.; Schmid, H. -M.; Deboulbe, A.; Rigal, R.
France, Chile, Italy, Germany, Switzerland, United States, United Kingdom, Sweden, Netherlands, Russia
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.