TOI-431/HIP 26013: A super-Earth and a sub-Neptune transiting a bright, early K dwarf, with a third RV planet

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,

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY

WILEY-BLACKWELL PUBLISHING, INC

Año: 2021 vol. 507 p. 2782 - 2803

0035-8711

We present the bright (Vmag = 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 Msin 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.