TOI-431/HIP 26013: a super-Earth and a sub-Neptune transiting a bright, early K dwarf, with a third RV planet. Issue 2 (11th August 2021)

• Record Type: Journal Article
• Authors: Osborn, Ares; Armstrong, David J; Cale, Bryson; Brahm, Rafael; Wittenmyer, Robert A; Dai, Fei; Crossfield, Ian J M; Bryant, Edward M; Adibekyan, Vardan; Cloutier, Ryan; Collins, Karen A; Delgado Mena, E; Fridlund, Malcolm; Hellier, Coel; Howell, Steve B; King, George W; Lillo-Box, Jorge; Otegi, Jon; Sousa, S; Stassun, Keivan G; Matthews, Elisabeth C; Ziegler, Carl; Ricker, George; Vanderspek, Roland; Latham, David W; Seager, S; Winn, Joshua N; Jenkins, Jon M; Acton, Jack S; Addison, Brett C; Anderson, David R; Ballard, Sarah; Barrado, David; Barros, Susana C C; Batalha, Natalie; Bayliss, Daniel; Barclay, Thomas; Benneke, Björn; Berberian, John; Bouchy, Francois; Bowler, Brendan P; Briceño, César; Burke, Christopher J; Burleigh, Matthew R; Casewell, Sarah L; Ciardi, David; Collins, Kevin I; Cooke, Benjamin F; Demangeon, Olivier D S; Díaz, Rodrigo F; Dorn, C; Dragomir, Diana; Dressing, Courtney; Dumusque, Xavier; Espinoza, Néstor; Figueira, P; Fulton, Benjamin; Furlan, E; Gaidos, E; Geneser, C; Gill, Samuel; Goad, Michael R; Gonzales, Erica J; Gorjian, Varoujan; Günther, Maximilian N; Helled, Ravit; Henderson, Beth A; Henning, Thomas; Hogan, Aleisha; Hojjatpanah, Saeed; Horner, Jonathan; Howard, Andrew W; Hoyer, Sergio; Huber, Dan; Isaacson, Howard; Jenkins, James S; Jensen, Eric L N; Jordán, Andrés; Kane, Stephen R; Kidwell, Richard C; Kielkopf, John; Law, Nicholas; Lendl, Monika; Lund, M; Matson, Rachel A; Mann, Andrew W; McCormac, James; Mengel, Matthew W; Morales, Farisa Y; Nielsen, Louise D; Okumura, Jack; Osborn, Hugh P; Petigura, Erik A; Plavchan, Peter; Pollacco, Don; Quintana, Elisa V; Raynard, Liam; Robertson, Paul; Rose, Mark E; Roy, Arpita; Reefe, Michael; Santerne, Alexandre; Santos, Nuno C; Sarkis, Paula; Schlieder, J; Schwarz, Richard P; Scott, Nicholas J; Shporer, Avi; Smith, A M S; Stibbard, C; Stockdale, Chris; Strøm, Paul A; Twicken, Joseph D; Tan, Thiam-Guan; Tanner, A; Teske, J; Tilbrook, Rosanna H; Tinney, C G; Udry, Stephane; Villaseñor, Jesus Noel; Vines, Jose I; Wang, Sharon X; Weiss, Lauren M; West, Richard G; Wheatley, Peter J; Wright, Duncan J; Zhang, Hui; Zohrabi, F;
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 507:Issue 2(2021)
• Page Start: 2782
• Page End: 2803
• Publication Date: 2021-08-11
• Subjects: planets and satellites: detection -- planets and satellites: fundamental parameters -- planets and satellites: individual: (TOI-431, TIC 31374837); Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stab2313
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: We present the bright (V mag = 9.12), multiplanet system TOI-431, characterized with photometry and radial velocities (RVs). We estimate the stellar rotation period to be 30.5 ± 0.7 d using archival photometry and RVs. Transiting Exoplanet Survey Satellite ( TESS ) objects of Interest (TOI)-431 b is a super-Earth with a period of 0.49 d, a radius of 1.28 ± 0.04 R⊕, a mass of 3.07 ± 0.35 M⊕, and a density of 8.0 ± 1.0 g cm −3 ; TOI-431 d is a sub-Neptune with a period of 12.46 d, a radius of 3.29 ± 0.09 R⊕, a mass of $9.90^{+1.53}_{-1.49}$ M⊕, and a density of 1.36 ± 0.25 g cm −3 . We find a third planet, TOI-431 c, in the High Accuracy Radial velocity Planet Searcher RV data, but it is not seen to transit in the TESS light curves. It has an M sin i of $2.83^{+0.41}_{-0.34}$ M⊕, and a period of 4.85 d. TOI-431 d likely has an extended atmosphere and is one of the most well-suited TESS discoveries for atmospheric characterization, while the super-Earth TOI-431 b may be a stripped core. These planets straddle the radius gap, presenting an interesting case-study for atmospheric evolution, and TOI-431 b is a prime TESS discovery for the study of rocky planet phase curves.