Transit detection of the long-period volatile-rich super-Earth $ν^2$ Lupi d with $CHEOPS$
Creators: name: Delrez, Laetitia
name: Ehrenreich, David
name: Alibert, Yann
name: Bonfanti, Andrea
name: Borsato, Luca
name: Fossati, Luca
name: Hooton, Matthew J.
name: Hoyer, Sergio
name: Pozuelos, Francisco J.
name: Salmon, Sébastien
name: Sulis, Sophia
name: Wilson, Thomas G.
name: Adibekyan, Vardan
name: Bourrier, Vincent
name: Brandeker, Alexis
name: Charnoz, Sébastien
name: Deline, Adrien
name: Guterman, Pascal
name: Haldemann, Jonas
name: Hara, Nathan
name: Oshagh, Mahmoudreza
name: Sousa, Sergio G.
name: Van Grootel, Valérie
name: Alonso, Roi
name: Escudé, Guillem Anglada
name: Bárczy, Tamás
name: Barrado, David
name: Barros, Susana C. C.
name: Baumjohann, Wolfgang
name: Beck, Mathias
name: Bekkelien, Anja
name: Benz, Willy
name: Billot, Nicolas
name: Bonfils, Xavier
name: Broeg, Christopher
name: Cabrera, Juan
name: Cameron, Andrew Collier
name: Davies, Melvyn B.
name: Deleuil, Magali
name: Delisle, Jean-Baptiste
name: Demangeon, Olivier D. S.
name: Demory, Brice-Olivier
name: Erikson, Anders
name: Fortier, Andrea
name: Fridlund, Malcolm
name: Futyan, David
name: Gandolfi, Davide
name: Muñoz, Antonio Garcia
name: Gillon, Michaël
name: Guedel, Manuel
name: Heng, Kevin
name: Kiss, László
name: Laskar, Jacques
name: Etangs, Alain Lecavelier des
name: Lendl, Monika
name: Lovis, Christophe
name: Maxted, Pierre F. L.
name: Nascimbeni, Valerio
name: Olofsson, Göran
name: Osborn, Hugh P.
name: Pagano, Isabella
name: Pallé, Enric
name: Piotto, Giampaolo
name: Pollacco, Don
name: Queloz, Didier
name: Rauer, Heike
name: Ragazzoni, Roberto
name: Ribas, Ignasi
name: Santos, Nuno C.
name: Scandariato, Gaetano
name: Ségransan, Damien
name: Simon, Attila E.
name: Smith, Alexis M. S.
name: Steller, Manfred
name: Szabó, Gyula M.
name: Thomas, Nicolas
name: Udry, Stéphane
name: Walton, Nicholas A.
Publisher: name: arXiv
Year: 2021
Subjects: subject: Earth and Planetary Astrophysics (astro-ph.EP)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: 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. $ν^2$ 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 days via radial velocity monitoring (Udry et al. 2019). The two inner planets (b and c) were recently found to transit (Kane et al. 2020), 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 $2.56\pm0.09$ $R_{\oplus}$ and $8.82\pm0.94$ $M_{\oplus}$, respectively. With its bright Sun-like star, long period, and mild irradiation ($\sim$5.7 times the irradiation of Earth), $ν^2$ 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 likely 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 $ν^2$ Lupi system an excellent laboratory for testing formation and evolution models of low-mass planets.
description: Published in Nature Astronomy. 60 pages, 18 Figures, 6 Tables. This is the authors' version of the manuscript. The final authenticated version is available online at https://www.nature.com/articles/s41550-021-01381-5