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arXiv · 2108.02310

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

Ares Osborn·David J. Armstrong·Bryson Cale·Rafael Brahm·Robert A. Wittenmyer·Fei Dai·Ian J. M. Crossfield·Edward M. Bryant·Vardan Adibekyan·Ryan Cloutier·Karen A. Collins·E. Delgado Mena·Malcolm Fridlund·Coel Hellier·Steve B. Howell·George W. King·Jorge Lillo-Box·Jon Otegi·S. Sousa·Keivan G. Stassun·Elisabeth C. Matthews·Carl Ziegler·George Ricker·Roland Vanderspek·David W. Latham·S. Seager·Joshua N. Winn·Jon M. Jenkins·Jack S. Acton·Brett C. Addison·David R. Anderson·Sarah Ballard·David Barrado·Susana C. C. Barros·Natalie Batalha·Daniel Bayliss·Thomas Barclay·Björn Benneke·John Berberian Jr.·Francois Bouchy·Brendan P. Bowler·César Briceño·Christopher J. Burke·Matthew R. Burleigh·Sarah L. Casewell·David Ciardi·Kevin I. Collins·Benjamin F. Cooke·Olivier D. S. Demangeon·Rodrigo F. Díaz·C. Dorn·Diana Dragomir·Courtney Dressing·Xavier Dumusque·Néstor Espinoza·P. Figueira·Benjamin Fulton·E. Furlan·E. Gaidos·C. Geneser·Samuel Gill·Michael R. Goad·Erica J. Gonzales·Varoujan Gorjian·Maximilian N. Günther·Ravit Helled·Beth A. Henderson·Thomas Henning·Aleisha Hogan·Saeed Hojjatpanah·Jonathan Horner·Andrew W. Howard·Sergio Hoyer·Dan Huber·Howard Isaacson·James S. Jenkins·Eric L. N. Jensen·Andrés Jordán·Stephen R. Kane·Richard C. Kidwell Jr.·John Kielkopf·Nicholas Law·Monika Lendl·M. Lund·Rachel A. Matson·Andrew W. Mann·James McCormac·Matthew W. Mengel·Farisa Y. Morales·Louise D. Nielsen·Jack Okumura·Hugh P. Osborn·Erik A. Petigura·Peter Plavchan·Don Pollacco·Elisa V. Quintana·Liam Raynard·Paul Robertson·Mark E. Rose·Arpita Roy
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Abstract

We present the bright (V$_{mag} = 9.12$), multi-planet system TOI-431, characterised with photometry and radial velocities. We estimate the stellar rotation period to be $30.5 \pm 0.7$ days using archival photometry and radial velocities. TOI-431b is a super-Earth with a period of 0.49 days, a radius of 1.28 $\pm$ 0.04 R$_{\oplus}$, a mass of $3.07 \pm 0.35$ M$_{\oplus}$, and a density of $8.0 \pm 1.0$ g cm$^{-3}$; TOI-431d is a sub-Neptune with a period of 12.46 days, a radius of $3.29 \pm 0.09$ R$_{\oplus}$, a mass of $9.90^{+1.53}_{-1.49}$ M$_{\oplus}$, and a density of $1.36 \pm 0.25$ g cm$^{-3}$. We find a third planet, TOI-431c, in the HARPS radial velocity 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$_{\oplus}$, and a period of 4.85 days. TOI-431d likely has an extended atmosphere and is one of the most well-suited TESS discoveries for atmospheric characterisation, while the super-Earth TOI-431b may be a stripped core. These planets straddle the radius gap, presenting an interesting case-study for atmospheric evolution, and TOI-431b is a prime TESS discovery for the study of rocky planet phase curves.

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Ares Osborn, David J. Armstrong, Bryson Cale, Rafael Brahm, Robert A. Wittenmyer, Fei Dai, Ian J. M. Crossfield, Edward M. Bryant, Vardan Adibekyan, Ryan Cloutier, Karen A. Collins, E. Delgado Mena, Malcolm Fridlund, Coel Hellier, Steve B. Howell, George W. King, Jorge Lillo-Box, Jon Otegi, S. Sousa, Keivan G. Stassun, Elisabeth C. Matthews, Carl Ziegler, George Ricker, Roland Vanderspek, David W. Latham, S. Seager, Joshua N. Winn, Jon M. Jenkins, Jack S. Acton, Brett C. Addison, David R. Anderson, Sarah Ballard, David Barrado, Susana C. C. Barros, Natalie Batalha, Daniel Bayliss, Thomas Barclay, Björn Benneke, John Berberian Jr., Francois Bouchy, Brendan P. Bowler, César Briceño, Christopher J. Burke, Matthew R. Burleigh, Sarah L. Casewell, David Ciardi, Kevin I. Collins, Benjamin F. Cooke, Olivier D. S. Demangeon, Rodrigo F. Díaz, C. Dorn, Diana Dragomir, Courtney Dressing, Xavier Dumusque, Néstor Espinoza, P. Figueira, Benjamin Fulton, E. Furlan, E. Gaidos, C. Geneser, Samuel Gill, Michael R. Goad, Erica J. Gonzales, Varoujan Gorjian, Maximilian N. Günther, Ravit Helled, Beth A. Henderson, Thomas Henning, Aleisha Hogan, Saeed Hojjatpanah, Jonathan Horner, Andrew W. Howard, Sergio Hoyer, Dan Huber, Howard Isaacson, James S. Jenkins, Eric L. N. Jensen, Andrés Jordán, Stephen R. Kane, Richard C. Kidwell Jr., John Kielkopf, Nicholas Law, Monika Lendl, M. Lund, Rachel A. Matson, Andrew W. Mann, James McCormac, Matthew W. Mengel, Farisa Y. Morales, Louise D. Nielsen, Jack Okumura, Hugh P. Osborn, Erik A. Petigura, Peter Plavchan, Don Pollacco, Elisa V. Quintana, Liam Raynard, Paul Robertson, Mark E. Rose, Arpita Roy. 2021-08-04. TOI-431/HIP 26013: a super-Earth and a sub-Neptune transiting a bright, early K dwarf, with a third RV planet. https://doi.org/10.1093/mnras%2Fstab2313

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