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

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

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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 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.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper ItemTESS data ItemExoFOP-TESS archive
Osborn, Ares0000-0002-5899-7750
Armstrong, David J.0000-0002-5080-4117
Cale, Bryson0000-0001-6279-0595
Brahm, Rafael0000-0002-9158-7315
Wittenmyer, Robert A.0000-0001-9957-9304
Dai, Fei0000-0002-8958-0683
Crossfield, Ian J. M.0000-0002-1835-1891
Cloutier, Ryan0000-0001-5383-9393
Collins, Karen A.0000-0001-6588-9574
Fridlund, Malcolm0000-0003-2180-9936
Hellier, Coel0000-0002-3439-1439
Howell, Steve B.0000-0002-2532-2853
King, George W.0000-0002-3641-6636
Lillo-Box, Jorge0000-0003-3742-1987
Sousa, S.0000-0001-9047-2965
Stassun, Keivan G.0000-0002-3481-9052
Matthews, Elisabeth C.0000-0003-0593-1560
Ziegler, Carl0000-0002-0619-7639
Ricker, George0000-0003-2058-6662
Vanderspek, Roland0000-0001-6763-6562
Latham, David W.0000-0001-9911-7388
Seager, S.0000-0002-6892-6948
Winn, Joshua N.0000-0002-4265-047X
Jenkins, Jon M.0000-0002-4715-9460
Acton, Jack S.0000-0002-1860-7842
Addison, Brett C.0000-0003-3216-0626
Anderson, David R.0000-0001-7416-7522
Ballard, Sarah0000-0002-3247-5081
Barrado, David0000-0002-5971-9242
Batalha, Natalie0000-0002-7030-9519
Bayliss, Daniel0000-0001-6023-1335
Barclay, Thomas0000-0001-7139-2724
Benneke, Björn0000-0001-5578-1498
Bouchy, Francois0000-0002-7613-393X
Bowler, Brendan P.0000-0003-2649-2288
Briceño, César0000-0001-7124-4094
Burke, Christopher J.0000-0002-7754-9486
Burleigh, Matthew R.0000-0003-0684-7803
Casewell, Sarah L.0000-0003-2478-0120
Ciardi, David0000-0002-5741-3047
Collins, Kevin I.0000-0003-2781-3207
Demangeon, Olivier D. S.0000-0001-7918-0355
Díaz, Rodrigo F.0000-0001-9289-5160
Dorn, C.0000-0001-6516-2586
Dragomir, Diana0000-0003-2313-467X
Dressing, Courtney0000-0001-8189-0233
Dumusque, Xavier0000-0002-9332-2011
Espinoza, Néstor0000-0001-9513-1449
Fulton, Benjamin0000-0003-3504-5316
Furlan, E.0000-0001-9800-6248
Gaidos, E.0000-0002-5258-6846
Gill, Samuel0000-0002-4259-0155
Goad, Michael R.0000-0002-2908-7360
Gonzales, Erica J.0000-0002-9329-2190
Gorjian, Varoujan0000-0002-8990-2101
Günther, Maximilian N.0000-0002-3164-9086
Helled, Ravit0000-0001-5555-2652
Henning, Thomas0000-0002-1493-300X
Hogan, Aleisha0000-0001-9658-1767
Horner, Jonathan0000-0002-1160-7970
Howard, Andrew W.0000-0001-8638-0320
Huber, Dan0000-0001-8832-4488
Isaacson, Howard0000-0002-0531-1073
Jenkins, James0000-0003-2733-8725
Jensen, Eric L. N.0000-0002-4625-7333
Jordán, Andrés0000-0002-5389-3944
Kane, Stephen R.0000-0002-7084-0529
Kielkopf, John0000-0003-0497-2651
Law, Nicholas0000-0001-9380-6457
Lund, M.0000-0003-2527-1598
Matson, Rachel A.0000-0001-7233-7508
Mann, Andrew W.0000-0003-3654-1602
McCormac, James0000-0003-1631-4170
Mengel, Matthew W.0000-0002-7830-6822
Morales, Farisa Y.0000-0001-9414-3851
Nielsen, Louise D.0000-0002-5254-2499
Okumura, Jack0000-0002-4876-8540
Osborn, Hugh P.0000-0002-4047-4724
Petigura, Erik A.0000-0003-0967-2893
Plavchan, Peter0000-0002-8864-1667
Pollacco, Don0000-0001-9850-9697
Quintana, Elisa V.0000-0003-1309-2904
Raynard, Liam0000-0001-6472-9122
Robertson, Paul0000-0003-0149-9678
Rose, Mark E.0000-0003-4724-745X
Roy, Arpita0000-0001-8127-5775
Santerne, Alexandre0000-0002-3586-1316
Santos, Nuno C.0000-0003-4422-2919
Sarkis, Paula0000-0001-8128-3126
Schlieder, J.0000-0001-5347-7062
Schwarz, Richard P.0000-0001-8227-1020
Scott, Nicholas J.0000-0003-1038-9702
Shporer, Avi0000-0002-1836-3120
Stockdale, Chris0000-0003-2163-1437
Twicken, Joseph D.0000-0002-6778-7552
Tan, Thiam-Guan0000-0001-5603-6895
Tanner, A.0000-0002-2903-2140
Tinney, C. G.0000-0002-7595-0970
Udry, Stéphane0000-0001-7576-6236
Vines, Jose I.0000-0002-1896-2377
Wang, Sharon X.0000-0002-6937-9034
Weiss, Lauren M.0000-0002-3725-3058
West, Richard G.0000-0001-6604-5533
Wheatley, Peter J.0000-0003-1452-2240
Wright, Duncan J.0000-0001-7294-5386
Zhang, Hui0000-0003-3491-6394
Additional Information:© 2021 The Author(s). Published by Oxford University Press on behalf of Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model ( Accepted 2021 August 3. Received 2021 July 26; in original form 2020 September 30. Published: 11 August 2021. This paper includes data collected by the TESS mission. Funding for the TESS mission is provided by the NASA Explorer Program. Resources supporting this work were provided by the NASA High-End Computing (HEC) Program through the NASA Advanced Supercomputing (NAS) Division at Ames Research Center for the production of the SPOC data products. We acknowledge the use of public TESS Alert data from pipelines at the TESS Science Office and at the TESS Science Processing Operations Center. This study is based on observations collected at the European Southern Observatory under ESO programme 1102.C-0249 (PI: Armstrong). Additionally, the archival HARPS data dating from 2004 to 2015 were obtained under the following programmes: 072.C-0488 (PI: Mayor); 183.C-0972 (PI: Udry); 085.C-0019 (PI: Lo Curto); 087.C-0831 (PI: Lo Curto); and 094.C-0428 (PI: Brahm). This work was supported by grants to P.P. from NASA (award 18-2XRP18_2-0113), the National Science Foundation (Astronomy and Astrophysics grant 1716202), the Mount Cuba Astronomical Foundation, and George Mason University start-up funds. The NASA Infrared Telescope Facility is operated by the University of Hawaii under contract NNH14CK55B with NASA. This paper is, in part, based on data collected under the NGTS project at the ESO La Silla Paranal Observatory. The NGTS facility is operated by the consortium institutes with support from the UK Science and Technology Facilities Council (STFC) projects ST/M001962/1 and ST/S002642/1. This work makes use of observations from the LCOGT network. M INERVA-Australis is supported by Australian Research Council LIEF grant LE160100001, Discovery grant DP180100972, Mount Cuba Astronomical Foundation, and institutional partners University of Southern Queensland, UNSW Sydney, MIT, Nanjing University, George Mason University, University of Louisville, University of California Riverside, University of Florida, and The University of Texas at Austin. We respectfully acknowledge the traditional custodians of all lands throughout Australia, and recognize their continued cultural and spiritual connection to the land, waterways, cosmos, and community. We pay our deepest respects to all Elders, ancestors, and descendants of the Giabal, Jarowair, and Kambuwal nations, upon whose lands the M INERVA-Australis facility at Mt Kent is situated. This work is based in part on observations made with the Spitzer Space Telescope, which was operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. Support for this work was provided by NASA through an award issued by JPL/Caltech. Based on observations obtained at the international Gemini Observatory, a program of NSF’s NOIRLab acquired through the Gemini Observatory Archive at NSF’s NOIRLab, which is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation on behalf of the Gemini Observatory partnership: the National Science Foundation (United States), National Research Council (Canada), Agencia Nacional de Investigación y Desarrollo (Chile), Ministerio de Ciencia, Tecnología e Innovación (Argentina), Ministério da Ciência, Tecnologia, Inovaííes e Comunicações (Brazil), and Korea Astronomy and Space Science Institute (Republic of Korea). Data collected under program GN-2019A-LP-101. This work was enabled by observations made from the Gemini North telescope, located within the Maunakea Science Reserve and adjacent to the summit of Maunakea. We are grateful for the privilege of observing the Universe from a place that is unique in both its astronomical quality and its cultural significance. This work is based in part on observations obtained at the SOAR telescope, which is a joint project of the Ministério da Ciência, Tecnologia e Inovações (MCTI/LNA) do Brasil, the US National Science Foundation’s NOIRLab, the University of North Carolina at Chapel Hill (UNC), and Michigan State University (MSU). This research made use of EXOPLANET (Foreman-Mackey et al. 2020) and its dependencies (Astropy Collaboration 2013, 2018; Kipping 2013a; Agol, Luger & Foreman-Mackey 2019; Luger et al. 2019; Salvatier et al. 2016; Theano Development Team 2016; Foreman-Mackey et al. 2020). This publication makes use of The Data & Analysis Center for Exoplanets (DACE), which is a facility based at the University of Geneva (CH) dedicated to extrasolar planets data visualization, exchange and analysis. DACE is a platform of the Swiss National Centre of Competence in Research (NCCR) PlanetS, federating the Swiss expertise in Exoplanet research. The DACE platform is available at This work has made use of data from the European Space Agency (ESA) mission Gaia (, processed by the Gaia Data Processing and Analysis Consortium (DPAC, Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. AO is supported by an STFC studentship. DJA acknowledges support from the STFC via an Ernest Rutherford Fellowship (ST/R00384X/1). RB acknowledges support from FONDECYT Post-doctoral Fellowship Project 3180246, and from the Millennium Institute of Astrophysics (MAS). IJMC acknowledges support from the NSF through grant AST-1824644. AJ acknowledges support from FONDECYT project 1210718, and from ANID - Millennium Science Initiative - ICN12_009. MNG acknowledges support from MIT’s Kavli Institute as a Juan Carlos Torres Fellow. JSJ acknowledges support by FONDECYT grant 1201371 and partial support from CONICYT project Basal AFB-170002. We acknowledge support by FCT - Fundação para a Ciência e a Tecnologia through national funds and by FEDER through COMPETE2020 - Programa Operacional Competitividade e Internacionalização by these grants: UID/FIS/04434/2019; UIDB/04434/2020; UIDP/04434/2020; PTDC/FIS-AST/32113/2017 & POCI-01-0145-FEDER-032113; PTDC/FIS-AST/28953/2017 & POCI-01-0145-FEDER-028953. VA, EDM, and SCCB acknowledge the support from FCT through Investigador FCT contracts IF/00650/2015/CP1273/CT0001, IF/00849/2015/CP1273/CT0003, and IF/01312/2014/CP1215/CT0004, respectively. ODSD is supported in the form of work contract (DL 57/2016/CP1364/CT0004) funded by FCT. CD acknowledges the SNSF Ambizione grant 174028. SH acknowledge support by the fellowships PD/BD/128119/2016 funded by FCT (Portugal). JKT acknowledges that support for this work was provided by NASA through Hubble Fellowship grant HST-HF2-51399.001 awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS5-26555. DD acknowledges support through the TESS Guest Investigator Program grant 80NSSC19K1727. JLB and DB have been supported by the Spanish State Research Agency (AEI) Project No. MDM-2017-0737 Unidad de Excelencia ‘María de Maeztu’- Centro de Astrobiología (CSIC/INTA). SH acknowledges CNES funding through the grant 837319. PJW acknowledges support from STFC through consolidated grants ST/P000495/1 and ST/T000406/1. LMW is supported by the Beatrice Watson Parrent Fellowship and NASA ADAP grant 80NSSC19K0597. Data Availability: The TESS data are available from the Mikulski Archive for Space Telescopes (MAST), at The other photometry from the LCOGT, NGTS, and Spitzer as well as all of the RV data, are available for public download from the ExoFOP-TESS archive at This data are labeled ‘Osborn+ 2021’ in their descriptions. The high-resolution imaging data are also available from the ExoFOP TESS archive. The model code underlying this article will be shared on reasonable request to the corresponding author.
Group:Astronomy Department, Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Mt. Cuba Astronomical FoundationUNSPECIFIED
George Mason UniversityUNSPECIFIED
Science and Technology Facilities Council (STFC)ST/M001962/1
Science and Technology Facilities Council (STFC)ST/S002642/1
Australian Research CouncilLE160100001
Australian Research CouncilDP180100972
University of Southern QueenslandUNSPECIFIED
University of New South WalesUNSPECIFIED
Massachusetts Institute of Technology (MIT)UNSPECIFIED
Nanjing UniversityUNSPECIFIED
University of LouisvilleUNSPECIFIED
University of California, RiversideUNSPECIFIED
University of FloridaUNSPECIFIED
University of Texas at AustinUNSPECIFIED
Gaia Multilateral AgreementUNSPECIFIED
Science and Technology Facilities Council (STFC)ST/R00384X/1
Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT)3180246
Millennium Institute of Astrophysics (MAS)UNSPECIFIED
Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT)1210718
Comisión Nacional de Investigación Científica y Tecnológica (CONICYT)ICN12_009
Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT)1201371
Fundação para a Ciência e a Tecnologia (FCT)UID/FIS/04434/2019
Fundação para a Ciência e a Tecnologia (FCT)UIDB/04434/2020
Fundação para a Ciência e a Tecnologia (FCT)UIDP/04434/2020
Fundação para a Ciência e a Tecnologia (FCT)PTDC/FIS-AST/32113/2017
Fundação para a Ciência e a Tecnologia (FCT)POCI-01-0145-FEDER-032113
Fundação para a Ciência e a Tecnologia (FCT)PTDC/FIS-AST/28953/2017
Fundação para a Ciência e a Tecnologia (FCT)POCI-01-0145-FEDER-028953
Fundação para a Ciência e a Tecnologia (FCT)IF/00650/2015/CP1273/CT0001
Fundação para a Ciência e a Tecnologia (FCT)IF/00849/2015/CP1273/CT0003
Fundação para a Ciência e a Tecnologia (FCT)IF/01312/2014/CP1215/CT0004
Fundação para a Ciência e a Tecnologia (FCT)57/2016/CP1364/CT0004
Swiss National Science Foundation (SNSF)174028
Fundação para a Ciência e a Tecnologia (FCT)PD/BD/128119/2016
NASA Hubble FellowshipHST-HF2-51399.001
Ministerio de Ciencia e Innovación (MCINN)MDM-2017-0737
Centre National d'Études Spatiales (CNES)837319
Science and Technology Facilities Council (STFC)ST/P000495/1
Science and Technology Facilities Council (STFC)ST/T000406/1
Beatrice Watson Parrent FellowshipUNSPECIFIED
Subject Keywords:planets and satellites: detection, planets and satellites: fundamental parameters, planets and satellites: individual: (TOI-431, TIC 31374837)
Issue or Number:2
Record Number:CaltechAUTHORS:20211008-175558303
Persistent URL:
Official Citation: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, Michael Reefe, Alexandre Santerne, Nuno C Santos, Paula Sarkis, J Schlieder, Richard P Schwarz, Nicholas J Scott, Avi Shporer, A M S Smith, C Stibbard, Chris Stockdale, Paul A Strøm, Joseph D Twicken, Thiam-Guan Tan, A Tanner, J Teske, Rosanna H Tilbrook, C G Tinney, Stephane Udry, Jesus Noel Villaseñor, Jose I Vines, Sharon X Wang, Lauren M Weiss, Richard G West, Peter J Wheatley, Duncan J Wright, Hui Zhang, F Zohrabi, 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, Volume 507, Issue 2, October 2021, Pages 2782–2803,
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ID Code:111284
Deposited By: Tony Diaz
Deposited On:08 Oct 2021 18:58
Last Modified:08 Oct 2021 18:58

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