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The Multiplanet System TOI-421: A Warm Neptune and a Super Puffy Mini-Neptune Transiting a G9 V Star in a Visual Binary

Carleo, Ilaria and Gandolfi, Davide and Barragán, Oscar and Livingston, John H. and Persson, Carina M. and Lam, Kristine W. F. and Vidotto, Aline and Lund, Michael B. and Villarreal D'Angelo, Carolina and Collins, Karen A. and Fossati, Luca and Howard, Andrew W. and Kubyshkina, Daria and Brahm, Rafael and Oklopčić, Antonija and Mollière, Paul and Redfield, Seth and Serrano, Luisa Maria and Dai, Fei and Fridlund, Malcolm and Borsa, Francesco and Korth, Judith and Esposito, Massimiliano and Díaz, Matías R. and Dyregaard Nielsen, Louise and Hellier, Coel and Mathur, Savita and Deeg, Hans J. and Hatzes, Artie P. and Benatti, Serena and Rodler, Florian and Alarcon, Javier and Spina, Lorenzo and Santos, Ângela R. G. and Georgieva, Iskra and Garcia, Rafael A. and González-Cuesta, Lucía and Ricker, George R. and Vanderspek, Roland and Latham, David W. and Seager, Sara and Winn, Joshua N. and Jenkins, Jon M. and Albrecht, Simon and Batalha, Natalie M. and Beard, Corey and Boyd, Patricia T. and Bouchy, François and Burt, Jennifer A. and Butler, R. Paul and Cabrera, Juan and Chontos, Ashley and Ciardi, David R. and Cochran, William D. and Collins, Kevin I. and Crane, Jeffrey D. and Crossfield, Ian and Csizmadia, Szilard and Dragomir, Diana and Dressing, Courtney and Eigmüller, Philipp and Endl, Michael and Erikson, Anders and Espinoza, Néstor and Fausnaugh, Michael and Feng, Fabo and Flowers, Erin and Fulton, Benjamin and Gonzales, Erica J. and Grieves, Nolan and Grziwa, Sascha and Guenther, Eike W. and Guerrero, Natalia M. and Henning, Thomas and Hidalgo, Diego and Hirano, Teruyuki and Hjorth, Maria and Huber, Daniel and Isaacson, Howard and Jones, Matias and Jordán, Andrés and Kabáth, Petr and Kane, Stephen R. and Knudstrup, Emil and Lubin, Jack and Luque, Rafael and Mireles, Ismael and Narita, Norio and Nespral, David and Niraula, Prajwal and Nowak, Grzegorz and Palle, Enric and Pätzold, Martin and Petigura, Erik A. and Prieto-Arranz, Jorge and Rauer, Heike and Robertson, Paul and Rose, Mark E. and Roy, Arpita and Sarkis, Paula and Schlieder, Joshua E. and Ségransan, Damien and Shectman, Stephen and Skarka, Marek and Smith, Alexis M. S. and Smith, Jeffrey C. and Stassun, Keivan and Teske, Johanna and Twicken, Joseph D. and Van Eylen, Vincent and Wang, Sharon and Weiss, Lauren M. and Wyttenbach, Aurélien (2020) The Multiplanet System TOI-421: A Warm Neptune and a Super Puffy Mini-Neptune Transiting a G9 V Star in a Visual Binary. Astronomical Journal, 160 (3). Art. No. 114. ISSN 1538-3881.

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We report the discovery of a warm Neptune and a hot sub-Neptune transiting TOI-421 (BD-14 1137, TIC 94986319), a bright (V = 9.9) G9 dwarf star in a visual binary system observed by the Transiting Exoplanet Survey Satellite (TESS) space mission in Sectors 5 and 6. We performed ground-based follow-up observations—comprised of Las Cumbres Observatory Global Telescope transit photometry, NIRC2 adaptive optics imaging, and FIbre-fed Echellé Spectrograph, CORALIE, High Accuracy Radial velocity Planet Searcher, High Resolution Échelle Spectrometer, and Planet Finder Spectrograph high-precision Doppler measurements—and confirmed the planetary nature of the 16 day transiting candidate announced by the TESS team. We discovered an additional radial velocity signal with a period of five days induced by the presence of a second planet in the system, which we also found to transit its host star. We found that the inner mini-Neptune, TOI-421 b, has an orbital period of P_b = 5.19672 ± 0.00049 days, a mass of M_b = 7.17 ± 0.66 M⊕, and a radius of R_b = 2.68^(+0.19)_(-0.18) R⊕, whereas the outer warm Neptune, TOI-421 c, has a period of Pc = 16.06819 ± 0.00035 days, a mass of M_c = 16.42^(+1.06)_(-1.04) M⊕, a radius of R_c = 5.09^(+0.16)_(-0.15) R⊕ and a density of ρ_c = 0.685^(+0.080)_(-0.072) g cm⁻³. With its characteristics, the outer planet (ρ_c = 0.685^(+0.080)_(-0.072) g cm⁻³) is placed in the intriguing class of the super-puffy mini-Neptunes. TOI-421 b and TOI-421 c are found to be well-suited for atmospheric characterization. Our atmospheric simulations predict significant Lyα transit absorption, due to strong hydrogen escape in both planets, as well as the presence of detectable CH4 in the atmosphere of TOI-421 c if equilibrium chemistry is assumed.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Carleo, Ilaria0000-0002-0810-3747
Gandolfi, Davide0000-0001-8627-9628
Barragán, Oscar0000-0003-0563-0493
Livingston, John H.0000-0002-4881-3620
Persson, Carina M.0000-0003-1257-5146
Lund, Michael B.0000-0003-2527-1598
Collins, Karen A.0000-0001-6588-9574
Fossati, Luca0000-0003-4426-9530
Howard, Andrew W.0000-0001-8638-0320
Kubyshkina, Daria0000-0001-9137-9818
Brahm, Rafael0000-0002-9158-7315
Oklopčić, Antonija0000-0002-9584-6476
Mollière, Paul0000-0003-4096-7067
Redfield, Seth0000-0003-3786-3486
Serrano, Luisa Maria0000-0001-9211-3691
Dai, Fei0000-0002-8958-0683
Fridlund, Malcolm0000-0003-2180-9936
Korth, Judith0000-0002-0076-6239
Díaz, Matías R.0000-0002-2100-3257
Hellier, Coel0000-0002-3439-1439
Mathur, Savita0000-0002-0129-0316
Deeg, Hans J.0000-0003-0047-4241
Benatti, Serena0000-0002-4638-3495
Rodler, Florian0000-0003-0650-5723
Spina, Lorenzo0000-0002-9760-6249
Santos, Ângela R. G.0000-0001-7195-6542
Garcia, Rafael A.0000-0002-8854-3776
Ricker, George R.0000-0003-2058-6662
Vanderspek, Roland0000-0001-6763-6562
Latham, David W.0000-0001-9911-7388
Seager, Sara0000-0002-6892-6948
Winn, Joshua N.0000-0002-4265-047X
Jenkins, Jon M.0000-0002-4715-9460
Batalha, Natalie M.0000-0002-7030-9519
Beard, Corey0000-0001-7708-2364
Boyd, Patricia T.0000-0003-0442-4284
Burt, Jennifer A.0000-0002-0040-6815
Butler, R. Paul0000-0003-1305-3761
Cabrera, Juan0000-0001-6653-5487
Chontos, Ashley0000-0003-1125-2564
Ciardi, David R.0000-0002-5741-3047
Cochran, William D.0000-0001-9662-3496
Collins, Kevin I.0000-0003-2781-3207
Crane, Jeffrey D.0000-0002-5226-787X
Crossfield, Ian0000-0002-1835-1891
Dragomir, Diana0000-0003-2313-467X
Dressing, Courtney0000-0001-8189-0233
Eigmüller, Philipp0000-0003-4096-0594
Endl, Michael0000-0002-7714-6310
Espinoza, Néstor0000-0001-9513-1449
Fausnaugh, Michael0000-0002-9113-7162
Feng, Fabo0000-0001-6039-0555
Flowers, Erin0000-0001-8045-1765
Fulton, Benjamin0000-0003-3504-5316
Gonzales, Erica J.0000-0002-9329-2190
Grieves, Nolan0000-0001-8105-0373
Grziwa, Sascha0000-0003-3370-4058
Guerrero, Natalia M.0000-0002-5169-9427
Hirano, Teruyuki0000-0003-3618-7535
Huber, Daniel0000-0001-8832-4488
Isaacson, Howard0000-0002-0531-1073
Jordán, Andrés0000-0002-5389-3944
Kabáth, Petr0000-0002-1623-5352
Kane, Stephen R.0000-0002-7084-0529
Knudstrup, Emil0000-0001-7880-594X
Lubin, Jack0000-0001-8342-7736
Mireles, Ismael0000-0002-4510-2268
Narita, Norio0000-0001-8511-2981
Niraula, Prajwal0000-0002-8052-3893
Nowak, Grzegorz0000-0002-7031-7754
Palle, Enric0000-0003-0987-1593
Petigura, Erik A.0000-0003-0967-2893
Robertson, Paul0000-0003-0149-9678
Rose, Mark E.0000-0003-4724-745X
Roy, Arpita0000-0001-8127-5775
Sarkis, Paula0000-0001-8128-3126
Schlieder, Joshua E.0000-0001-5347-7062
Ségransan, Damien0000-0003-2355-8034
Skarka, Marek0000-0002-7602-0046
Smith, Alexis M. S.0000-0002-2386-4341
Smith, Jeffrey C.0000-0002-6148-7903
Stassun, Keivan0000-0002-3481-9052
Twicken, Joseph D.0000-0002-6778-7552
Van Eylen, Vincent0000-0001-5542-8870
Wang, Sharon0000-0002-6937-9034
Weiss, Lauren M.0000-0002-3725-3058
Alternate Title:The multi-planet system TOI-421 -- A warm Neptune and a super puffy mini-Neptune transiting a G9 V star in a visual binary, The Multiplanet System TOI-421
Additional Information:© 2020 The American Astronomical Society. Received 2020 April 16; revised 2020 June 19; accepted 2020 June 22; published 2020 August 14. Based on observations made with ESO Telescopes at the La Silla Observatory under programs ID 1102.C-0923, 0103.C-0874, 0103.C-0759, 0103.C-0442, and 60.A-970. Based on observations obtained with the Nordic Optical Telescope (NOT), operated on the island of La Palma jointly by Denmark, Finland, Iceland, Norway, and Sweden, in the Spanish Observatorio del Roque de los Muchachos (ORM) of the Instituto de Astrofísica de Canarias (IAC). This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile. This work makes use of observations from the LCOGT network. This work was supported by the KESPRINT collaboration, an international consortium devoted to the characterization and research of exoplanets discovered with space-based missions. We acknowledge the use of public TESS Alert data from pipelines at the TESS Science Office and at the TESS Science Processing Operations Center. Funding for the TESS mission is provided by NASA's Science Mission directorate. We acknowledge the use of public TESS Alert data from pipelines at the TESS Science Office and at the TESS Science Processing Operations Center. 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. Part of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration (NASA). We are very grateful to the NOT and ESO staff members for their unique and superb support during the observations. A.A.V. and D.K. acknowledge funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (grant agreement No 817540, ASTROFLOW). P.M. thanks Thomas Mikal-Evans and Laura Kreidberg for help computing predicted HST uncertainties for TOI-421. P.M. acknowledges support from the European Research Council under the European Union's Horizon 2020 research and innovation program under grant agreement No. 832428. L.M.S. and D.G. gratefully acknowledge financial support from the CRT foundation under grant No. 2018.2323 "Gaseous or rocky? Unveiling the nature of small worlds." R.B. acknowledges support from FONDECYT Post-doctoral Fellowship Project 3180246. A.J. and R.B. acknowledge support from project IC120009 "Millennium Institute of Astrophysics (MAS)" of the Millennium Science Initiative, Chilean Ministry of Economy. A.J. acknowledges additional support from FONDECYT project 1171208. C.V.D. acknowledges the funding from the Irish Research Council through the postdoctoral fellowship (Project ID: GOIPD/2018/659). C.M.P., M.F., and I.G. gratefully acknowledge the support of the Swedish National Space Agency (DNR 65/19 and 136/13). L.S. acknowledges financial support from the Australian Research Council (Discovery Project 170100521). D.D. acknowledges support from NASA through Caltech/JPL grant RSA-1006130 and through the TESS Guest Investigator Program grant 80NSSC19K1727. D.H. acknowledges support from the Alfred P. Sloan Foundation, the National Aeronautics and Space Administration (80NSSC18K1585, 80NSSC19K0379), and the National Science Foundation (AST-1717000). S.M. acknowledges support from the Spanish Ministry with the Ramon y Cajal fellowship number RYC-2015-17697. L.G.C. thanks the support from grant FPI-SO from the Spanish Ministry of Economy and Competitiveness (MINECO), under research project SEV-2015-0548-17-2 and predoctoral contract BES-2017-082610. A.R.G.S. acknowledges support from NASA under grant No. NNX17AF27G. J.N.W. thanks the Heising-Simons foundation for support. R.A.G. acknowledges support from PLATO and GOLF CNES grants. M.R.D. acknowledges support from CONICYT-PFCHA/Doctorado Nacional-21140646, Chile. K.W.F.L., J.K., S.z.C.s., M.E., S.G., A.P.H., M.P., and H.R. acknowledge support by DFG grants PA525/18-1, PA525/19-1, PA525/20-1, HA3279/12-1, and RA714/14-1 within the DFG Schwerpunkt SPP 1992, "Exploring the Diversity of Extrasolar Planets" This research has made use of the Exoplanet Follow-up Observation Program website, which is operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration under the Exoplanet Exploration Program.
Group:Astronomy Department
Funding AgencyGrant Number
European Research Council (ERC)817540
European Research Council (ERC)832428
CRT Foundation2018.2323
Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT)3180246
Iniciativa Científica Milenio del Ministerio de Economía, Fomento y TurismoIC120009
Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT)1171208
Irish Research CouncilGOIPD/2018/659
Swedish National Space AgencyDNR 65/19
Swedish National Space AgencyDNR 136/13
Australian Research Council170100521
Alfred P. Sloan FoundationUNSPECIFIED
Ramón y Cajal ProgrammeRYC-2015-17697
Ministerio de Economía, Industria y Competitividad (MINECO)SEV-2015-0548-17-2
Ministerio de Economía, Industria y Competitividad (MINECO)BES-2017-082610
Heising-Simons FoundationUNSPECIFIED
Centre National d'Études Spatiales (CNES)UNSPECIFIED
Comisión Nacional de Investigación Científica y Tecnológica (CONICYT)21140646
Deutsche Forschungsgemeinschaft (DFG)PA525/18-1
Deutsche Forschungsgemeinschaft (DFG)PA525/19-1
Deutsche Forschungsgemeinschaft (DFG)PA525/20-1
Deutsche Forschungsgemeinschaft (DFG)HA3279/12-1
Deutsche Forschungsgemeinschaft (DFG)RA714/14-1
Deutsche Forschungsgemeinschaft (DFG)SPP 1992
Subject Keywords:Exoplanet astronomy ; Exoplanet systems ; Exoplanets ; Mini Neptunes ; Hot Neptunes ; Fundamental parameters of stars ; High resolution spectroscopy ; Transit photometry ; Radial velocity
Issue or Number:3
Classification Code:Unified Astronomy Thesaurus concepts: Exoplanet astronomy (486); Exoplanet systems (484); Exoplanets (498); Mini Neptunes (1063); Hot Neptunes (754); Fundamental parameters of stars (555); High resolution spectroscopy (2096); Transit photometry (1709)
Record Number:CaltechAUTHORS:20200519-124339801
Persistent URL:
Official Citation:Ilaria Carleo et al 2020 AJ 160 114
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:103317
Deposited By: Tony Diaz
Deposited On:19 May 2020 20:34
Last Modified:10 Sep 2020 16:03

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