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

Creators: 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; 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, Stéphane; 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.

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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 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.

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 (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_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 https://dace.unige.ch. This work has made use of data from the European Space Agency (ESA) mission Gaia (https://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC, https://www.cosmos.esa.int/web/gaia/dpac/consortium). 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 https://heasarc.gsfc.nasa.gov/docs/tess/data-access.html. 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 https://exofop.ipac.caltech.edu/tess/target.php?id=31374837. 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.

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