TOI-836: A super-Earth and mini-Neptune transiting a nearby K-dwarf
Authors: Hawthorn Faith , Bayliss Daniel , Wilson Thomas G , Bonfanti Andrea , Adibekyan Vardan , Alibert Yann , Sousa Sérgio G , Collins Karen A , Bryant Edward M , Osborn Ares , Armstrong David J , Abe Lyu , Acton Jack S , Addison Brett C , Agabi Karim , Alonso Roi , Alves Douglas R , Anglada-Escudé Guillem , Bárczy Tamas , Barclay Thomas , Barrado David , Barros Susana C C , Baumjohann Wolfgang , Bendjoya Philippe , Benz Willy , Bieryla Allyson , Bonfils Xavier , Bouchy François , Brandeker Alexis , Broeg Christopher , Brown David J A , Burleigh Matthew R , Buttu Marco , Cabrera Juan , Caldwell Douglas A , Casewell Sarah L , Charbonneau David , Charnoz Sébastian , Cloutier Ryan , Cameron Andrew Collier , Collins Kevin I , Conti Dennis M , Crouzet Nicolas , Czismadia Szilárd , Davies Melvyn B , Deleuil Magali , Delgado-Mena Elisa , Delrez Laetitia , Demangeon Olivier D S , Demory Brice-Olivier , Dransfield Georgina , Dumusque Xavier , Egger Jo Ann , Ehrenreich David , Eigmüller Philipp , Erickson Anders , Essack Zahra , Fortier Andrea , Fossati Luca , Fridlund Malcolm , Günther Maximilian N , Güdel Manuel , Gandolfi Davide , Gillard Harvey , Gillon Michaël , Gnilka Crystal , Goad Michael R , Goeke Robert F , Guillot Tristan , Hadjigeorghiou Andreas , Hellier Coel , Henderson Beth A , Heng Kevin , Hooton Matthew J , Horne Keith , Howell Steve B , Hoyer Sergio , Irwin Jonathan M , Jenkins James S , Jenkins Jon M , Jensen Eric L N , Kane Stephen R , Kendall Alicia , Kielkopf John F , Kiss Laszlo L , Lacedelli Gaia , Laskar Jacques , Latham David W , Etangs Alain Lecavalier des , Leleu Adrien , Lendl Monika , Lillo-Box Jorge , Lovis Christophe , Mékarnia Djamel , Massey Bob , Masters Tamzin , Maxted Pierre F L , Nascimbeni Valerio , Nielsen Louise D , O’Brien Sean M , Olofsson Göran , Osborn Hugh P , Pagano Isabella , Pallé Enric , Persson Carina M , Piotto Giampaolo , Plavchan Peter , Pollacco Don , Queloz Didier , Ragazzoni Roberto , Rauer Heike , Ribas Ignasi , Ricker George , Ségransan Damien , Salmon Sébastien , Santerne Alexandre , Santos Nuno C , Scandariato Gaetano , Schmider François-Xavier , Schwarz Richard P , Seager Sara , Shporer Avi , Simon Attila E , Smith Alexis M S , Srdoc Gregor , Steller Manfred , Suarez Olga , Szabó Gyula M , Teske Johanna , Thomas Nicolas , Tilbrook Rosanna H , Triaud Amaury H M J , Udry Stéphane , Van Grootel Valérie , Walton Nicholas , Wang Sharon X , Wheatley Peter J , Winn Joshua N , Wittenmyer Robert A , Zhang Hui 
Published: February 2023

ABSTRACT
We present the discovery of two exoplanets transiting TOI-836 (TIC 440887364) using data from TESS Sector 11 and Sector 38. TOI-836 is a bright (T = 8.5 mag), high proper motion (∼200 mas yr−1), low metallicity ([Fe/H]≈−0.28) K-dwarf with a mass of 0.68 ± 0.05 M⊙ and a radius of 0.67 ± 0.01 R⊙. We obtain photometric follow-up observations with a variety of facilities, and we use these data sets to determine that the inner planet, TOI-836 b, is a 1.70 ± 0.07 R⊕ super-Earth in a 3.82-d orbit, placing it directly within the so-called ‘radius valley’. The outer planet, TOI-836 c, is a 2.59 ± 0.09 R⊕ mini-Neptune in an 8.60-d orbit. Radial velocity measurements reveal that TOI-836 b has a mass of 4.5 ± 0.9 M⊕, while TOI-836 c has a mass of 9.6 ± 2.6 M⊕. Photometric observations show Transit Timing Variations (TTVs) on the order of 20 min for TOI-836 c, although there are no detectable TTVs for TOI-836 b. The TTVs of planet TOI-836 c may be caused by an undetected exterior planet.