A pair of Sub-Neptunes transiting the bright K-dwarf TOI-1064 characterised with CHEOPS
Creators: name: Wilson, Thomas G.
name: Goffo, Elisa
name: Alibert, Yann
name: Gandolfi, Davide
name: Bonfanti, Andrea
name: Persson, Carina M.
name: Cameron, Andrew Collier
name: Fridlund, Malcolm
name: Fossati, Luca
name: Korth, Judith
name: Benz, Willy
name: Deline, Adrien
name: Florén, Hans-Gustav
name: Guterman, Pascal
name: Adibekyan, Vardan
name: Hooton, Matthew J.
name: Hoyer, Sergio
name: Leleu, Adrien
name: Mustill, Alexander James
name: Salmon, Sébastien
name: Sousa, Sérgio G.
name: Suarez, Olga
name: Abe, Lyu
name: Agabi, Abdelkrim
name: Alonso, Roi
name: Anglada, Guillem
name: Asquier, Joel
name: Bárczy, Tamas
name: Navascues, David Barrado y
name: Barros, Susana C. C.
name: Baumjohann, Wolfgang
name: Beck, Mathias
name: Beck, Thomas
name: Billot, Nicolas
name: Bonfils, Xavier
name: Brandeker, Alexis
name: Broeg, Christopher
name: Bryant, Edward M.
name: Burleigh, Matthew R.
name: Buttu, Marco
name: Cabrera, Juan
name: Charnoz, Sébastien
name: Ciardi, David R.
name: Cloutier, Ryan
name: Cochran, William D.
name: Collins, Karen A.
name: Colón, Knicole D.
name: Crouzet, Nicolas
name: Csizmadia, Szilard
name: Davies, Melvyn B.
name: Deleuil, Magali
name: Delrez, Laetitia
name: Demangeon, Olivier
name: Demory, Brice-Olivier
name: Dragomir, Diana
name: Dransfield, Georgina
name: Ehrenreich, David
name: Erikson, Anders
name: Fortier, Andrea
name: Gan, Tianjun
name: Gill, Samuel
name: Gillon, Michaël
name: Gnilka, Crystal L.
name: Grieves, Nolan
name: Grziwa, Sascha
name: Güdel, Manuel
name: Guillot, Tristan
name: Haldemann, Jonas
name: Heng, Kevin
name: Horne, Keith
name: Howell, Steve B.
name: Isaak, Kate G.
name: Jenkins, Jon M.
name: Jensen, Eric L. N.
name: Kiss, Laszlo
name: Lacedelli, Gaia
name: Lam, Kristine
name: Laskar, Jacques
name: Latham, David W.
name: Etangs, Alain Lecavelier des
name: Lendl, Monika
name: Lester, Kathryn V.
name: Levine, Alan M.
name: Livingston, John
name: Lovis, Christophe
name: Luque, Rafael
name: Magrin, Demetrio
name: Marie-Sainte, Wenceslas
name: Maxted, Pierre F. L.
name: Mayo, Andrew W.
name: McLean, Brian
name: Mecina, Marko
name: Mékarnia, Djamel
name: Nascimbeni, Valerio
name: Nielsen, Louise D.
name: Olofsson, Göran
name: Osborn, Hugh P.
name: Osborne, Hannah L. M.
name: Ottensamer, Roland
name: Pagano, Isabella
name: Pallé, Enric
name: Peter, Gisbert
name: Piotto, Giampaolo
name: Pollacco, Don
name: Queloz, Didier
name: Ragazzoni, Roberto
name: Rando, Nicola
name: Rauer, Heike
name: Redfield, Seth
name: Ribas, Ignasi
name: Ricker, George R.
name: Rieder, Martin
name: Santos, Nuno C.
name: Scandariato, Gaetano
name: Schmider, François-Xavier
name: Schwarz, Richard P.
name: Scott, Nicholas J.
name: Seager, Sara
name: Ségransan, Damien
name: Serrano, Luisa Maria
name: Simon, Attila E.
name: Smith, Alexis M. S.
name: Steller, Manfred
name: Stockdale, Chris
name: Szabó, Gyula
name: Thomas, Nicolas
name: Ting, Eric B.
name: Triaud, Amaury H. M. J.
name: Udry, Stéphane
name: Van Eylen, Vincent
name: Van Grootel, Valérie
name: Vanderspek, Roland K.
name: Viotto, Valentina
name: Walton, Nicholas
name: Winn, Joshua N.
Publisher: name: arXiv
Year: 2022
Subjects: subject: Earth and Planetary Astrophysics (astro-ph.EP)
subject: Instrumentation and Methods for Astrophysics (astro-ph.IM)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: We report the discovery and characterisation of a pair of sub-Neptunes transiting the bright K-dwarf TOI-1064 (TIC 79748331), initially detected in TESS photometry. To characterise the system, we performed and retrieved CHEOPS, TESS, and ground-based photometry, HARPS high-resolution spectroscopy, and Gemini speckle imaging. We characterise the host star and determine $T_{\rm eff, \star}=4734\pm67$ K, $R_{\star}=0.726\pm0.007$ $R_{\odot}$, and $M_{\star}=0.748\pm0.032$ $M_{\odot}$. We present a novel detrending method based on PSF shape-change modelling and demonstrate its suitability to correct flux variations in CHEOPS data. We confirm the planetary nature of both bodies and find that TOI-1064 b has an orbital period of $P_{\rm b}=6.44387\pm0.00003$ d, a radius of $R_{\rm b}=2.59\pm0.04$ $R_{\oplus}$, and a mass of $M_{\rm b}=13.5_{-1.8}^{+1.7}$ $M_{\oplus}$, whilst TOI-1064 c has an orbital period of $P_{\rm c}=12.22657^{+0.00005}_{-0.00004}$ d, a radius of $R_{\rm c}=2.65\pm0.04$ $R_{\oplus}$, and a 3$σ$ upper mass limit of 8.5 ${\rm M_{\oplus}}$. From the high-precision photometry we obtain radius uncertainties of $\sim$1.6%, allowing us to conduct internal structure and atmospheric escape modelling. TOI-1064 b is one of the densest, well-characterised sub-Neptunes, with a tenuous atmosphere that can be explained by the loss of a primordial envelope following migration through the protoplanetary disc. It is likely that TOI-1064 c has an extended atmosphere due to the tentative low density, however further RVs are needed to confirm this scenario and the similar radii, different masses nature of this system. The high-precision data and modelling of TOI-1064 b are important for planets in this region of mass-radius space, and it allows us to identify a trend in bulk density-stellar metallicity for massive sub-Neptunes that may hint at the formation of this population of planets.
description: 30 pages, 24 figures, 6 tables including the Appendix; accepted for publication in MNRAS