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; Mena, E Delgado; 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 Jr., 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;...

Abstract

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.

Citation

Osborn, A., Armstrong, D. J., Cale, B., Brahm, R., Wittenmyer, R. A., Dai, F., Crossfield, I. J. M., Bryant, E. M., Adibekyan, V., Cloutier, R., Collins, K. A., Mena, E. D., Fridlund, M., Hellier, C., Howell, S. B., King, G. W., Lillo-Box, J., Otegi, J., Sousa, S., Stassun, K. G., …Zohrabi, F. (2021). TOI-431/HIP 26013: a super-Earth and a sub-Neptune transiting a bright, early K dwarf, with a third RV planet. Monthly Notices of the Royal Astronomical Society, 507(2), 2782 - 2803. https://doi.org/10.1093/mnras/stab2313

• Journal Article Type: Article
• Acceptance Date: Aug 3, 2021
• Online Publication Date: Aug 11, 2021
• Publication Date: 2021-10
• Publicly Available Date: May 30, 2023
• Journal: Monthly Notices of the Royal Astronomical Society
• Print ISSN: 0035-8711
• Electronic ISSN: 1365-2966
• Publisher: Oxford University Press
• Peer Reviewed: Peer Reviewed
• Volume: 507
• Issue: 2
• Pages: 2782 - 2803
• DOI: https://doi.org/10.1093/mnras/stab2313
• Keywords: Space and Planetary Science, Astronomy and Astrophysics
• Public URL: https://keele-repository.worktribe.com/output/422080
• Publisher URL: https://academic.oup.com/mnras/article-abstract/507/2/2782/6348103?redirectedFrom=fulltext