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

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

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.

Keywords
techniques: photometric, techniques: radial velocities, planets and satellites: detection, stars: individual: TOI-836 (TIC 440887364, GAIA EDR3 6230733559097425152)

Monthly Notices of the Royal Astronomical Society
Volume 520, Issue 3, Page 19
2023 April

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Faculdade de Ciências da Universidade de Lisboa Universidade do Porto Faculdade de Ciências e Tecnologia da Universidade de Coimbra
Fundação para a Ciência e a Tecnologia COMPETE 2020 PORTUGAL 2020 União Europeia