Transit detection of the long-period volatile-rich super-Earth ν2 Lupi d with CHEOPS

Laetitia Delrez (1) , David Ehrenreich (2) , Yann Alibert (3) , Andrea Bonfanti , Luca Borsato , Luca Fossati (4) , Matthew Hooton , Sergio Hoyer (5) , Francisco Pozuelos , Sébastien Salmon (6) , Sophia Sulis , Thomas Wilson , Vardan Adibekyan , Vincent Bourrier , Alexis Brandeker , Sébastien Charnoz , Adrien Deline , Pascal Guterman , Jonas Haldemann , Nathan Hara , Mahmoudreza Oshagh , Sergio Sousa , Valérie van Grootel , Roi Alonso , Guillem Anglada-Escudé , Tamás Bárczy , David Barrado , Susana Barros , Wolfgang Baumjohann , Mathias Beck , Anja Bekkelien , Willy Benz , Xavier Bonfils (7) , Nicolas Billot , Christopher Broeg , Juan Cabrera , Andrew Collier Cameron , Melvyn Davies , Magali Deleuil , Jean-Baptiste Delisle , Olivier Demangeon , Brice-Olivier Demory , Anders Erikson , Andrea Fortier , Malcolm Fridlund , David Futyan , Davide Gandolfi , Antonio Garcia Muñoz , Michaël Gillon , Manuel Guedel , Kevin Heng , László Kiss , Jacques Laskar (8) , Alain Lecavelier Des Etangs , Monika Lendl , Christophe Lovis , Pierre Maxted , Valerio Nascimbeni , Göran Olofsson , Hugh Osborn , Isabella Pagano , Enric Pallé , Giampaolo Piotto , Don Pollacco , Didier Queloz , Heike Rauer , Roberto Ragazzoni , Ignasi Ribas , Nuno Santos , Gaetano Scandariato , Damien Ségransan , Attila Simon , Alexis Smith , Manfred Steller , Gyula Szabó , Nicolas Thomas , Stéphane Udry , Nicholas Walton

1 Cavendish Laboratory
2 ObsGE - Observatoire Astronomique de l'Université de Genève
3 LAOB - Laboratoire d'astrophysique de l'observatoire de Besançon (UMR 6091)
4 IWF - Space Research Institute of Austrian Academy of Sciences
5 LAM - Laboratoire d'Astrophysique de Marseille
6 UTBM - Université de Technologie de Belfort-Montbeliard
7 IPAG - Institut de Planétologie et d'Astrophysique de Grenoble
8 IMCCE - Institut de Mécanique Céleste et de Calcul des Ephémérides

Exoplanets transiting bright nearby stars are key objects for advancing our knowledge of planetary formation and evolution. The wealth of photons from the host star gives detailed access to the atmospheric, interior and orbital properties of the planetary companions. ν2 Lupi (HD 136352) is a naked-eye (V = 5.78) Sun-like star that was discovered to host three low-mass planets with orbital periods of 11.6, 27.6 and 107.6 d via radial-velocity monitoring1. The two inner planets (b and c) were recently found to transit2, prompting a photometric follow-up by the brand new Characterising Exoplanets Satellite (CHEOPS). Here, we report that the outer planet d is also transiting, and measure its radius and mass to be 2.56 ± 0.09 R⊕ and 8.82 ± 0.94 M⊕, respectively. With its bright Sun-like star, long period and mild irradiation (~5.7 times the irradiation of Earth), ν2 Lupi d unlocks a completely new region in the parameter space of exoplanets amenable to detailed characterization. We refine the properties of all three planets: planet b probably has a rocky mostly dry composition, while planets c and d seem to have retained small hydrogen-helium envelopes and a possibly large water fraction. This diversity of planetary compositions makes the ν2 Lupi system an excellent laboratory for testing formation and evolution models of low-mass planets.

Keywords: Astrophysics - Earth and Planetary Astrophysics

Domains: Astrophysics [astro-ph]

Laetitia Delrez, David Ehrenreich, Yann Alibert, Andrea Bonfanti, Luca Borsato, et al.. Transit detection of the long-period volatile-rich super-Earth ν2 Lupi d with CHEOPS. Nature Astronomy, 2021, 5, pp.775-787. ⟨10.1038/s41550-021-01381-5⟩. ⟨insu-03458402⟩