TOI-836: A super-Earth and mini-Neptune transiting a nearby K-dwarf

Hawthorn, F.; Bayliss, D.; Wilson, T. G.; Bonfanti, A.; Adibekyan, V.; Alibert, Y.; Sousa, S. G.; Collins, K. A.; Bryant, E. M.; Osborn, A.; Armstrong, D. J.; Abe, L.; Acton, J. S.; Addison, B. C.; Agabi, K.; Alonso, R.; Alves, D. R.; Anglada-Escude, G.; Barczy, T.; Barclay, T.; Barrado, D.; Barros, S. C. C.; Baumjohann, W.; Bendjoya, P.; Benz, W.; Bieryla, A.; Bonfils, X.; Bouchy, F.; Brandeker, A.; Broeg, C.; Brown, D. J. A.; Burleigh, M. R.; Buttu, M.; Cabrera, J.; Caldwell, D. A.; Casewell, S. L.; Charbonneau, D.; Charnoz, S.; Cloutier, R.; Cameron, A. C.; Collins, K. I.; Conti, D. M.; Crouzet, N.; Czismadia, S.; Davies, M. B.; Deleuil, M.; Delgado-Mena, E.; Delrez, L.; Demangeon, O. D. S.; Demory, B. -O.; Dransfield, G.; Dumusque, X.; Egger, J. A.; Ehrenreich, D.; Eigmuller, P.; Erickson, A.; Essack, Z.; Fortier, A.; Fossati, L.; Fridlund, M.; Gunther, M. N.; Gudel, M.; Gandolfi, D.; Gillard, H.; Gillon, M.; Gnilka, C.; Goad, M. R.; Goeke, R. F.; Guillot, T.; Hadjigeorghiou, A.; Hellier, C.; Henderson, B. A.; Heng, K.; Hooton, M. J.; Horne, K.; Howell, S. B.; Hoyer, S.; Irwin, J. M.; Jenkins, J. S.; Jenkins, J. M.; Jensen, E. L. N.; Kane, S. R.; Kendall, A.; Kielkopf, J. F.; Kiss, L. L.; Lacedelli, G.; Laskar, J.; Latham, D. W.; Des Etangs, A. L.; Leleu, A.; Lendl, M.; Lillo-Box, J.; Lovis, C.; Mekarnia, D.; Massey, B.; Masters, T.; Maxted, P. F. L.; Nascimbeni, V.; Nielsen, L. D.; O'Brien, S. M.; Olofsson, G.; Osborn, H. P.; Pagano, I.; Palle, E.; Persson, C. M.; Piotto, G.; Plavchan, P.; Pollacco, D.; Queloz, D.; Ragazzoni, R.; Rauer, H.; Ribas, I.; Ricker, G.; Segransan, D.; Salmon, S.; Santerne, A.; Santos, N. C.; Scandariato, G.; Schmider, F. -X.; Schwarz, R. P.; Seager, S.; Shporer, A.; Simon, A. E.; Smith, A. M. S.; Srdoc, G.; Steller, M.; Suarez, O.; Szabo, G. M.; Teske, J.; Thomas, N.; Tilbrook, R. H.; Triaud, A. H. M. J.; Udry, S.; Van Grootel, V.; Walton, N.; Wang, S. X.; Wheatley, P. J.; Winn, J. N.; Wittenmyer, R. A.; Zhang, H.

doi:10.1093/mnras/stad306

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.