The Multiplanet System TOI-421*
Journal article, 2020
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 Echelle Spectrograph, CORALIE, High Accuracy Radial velocity Planet Searcher, High Resolution echelle 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-circle plus, and a radius of R-b = R-circle plus, whereas the outer warm Neptune, TOI-421 c, has a period of P-c = 16.06819 +/- 0.00035 days, a mass of M-c = 16.42(-1.04)(+1.06)M(circle plus), a radius of R-c = 5.09(-0.15)(+0.16)R(circle plus), and a density of rho(c) = 0.685(-0.072)(+0.080) cm(-3). With its characteristics, the outer planet (rho(c) = 0.685(-0.0072)(+0.080) 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 Ly alpha 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.
Author
Ilaria Carleo
Osservatorio Astronomico di Padova
Wesleyan University
Davide Gandolfi
University of Turin
Oscar Barragan
University of Oxford
John H. Livingston
University of Tokyo
Carina Persson
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics, Galactic Astrophysics
Kristine W. F. Lam
Technische Universität Berlin
Aline Vidotto
Trinity College Dublin
Michael B. Lund
California Institute of Technology (Caltech)
Carolina Villarreal D'Angelo
Trinity College Dublin
Karen A. Collins
Harvard-Smithsonian Center for Astrophysics
Luca Fossati
Austrian Academy of Sciences
Andrew W. Howard
California Institute of Technology (Caltech)
Daria Kubyshkina
Austrian Academy of Sciences
Rafael Brahm
Millennium Institute of Astrophysics
Adolfo Ibáñez University
Antonija Oklopcic
Harvard-Smithsonian Center for Astrophysics
Paul Molliere
Max Planck Society
Seth Redfield
Wesleyan University
Luisa Maria Serrano
University of Porto
University of Turin
Fei Dai
Princeton University
Massachusetts Institute of Technology (MIT)
Malcolm Fridlund
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics, Galactic Astrophysics
Francesco Borsa
Osservatorio Astronomico di Brera
Judith Korth
University of Cologne
Massimiliano Esposito
Thüringer Landessternwarte Tautenburg
Matias R. Diaz
University of Chile (UCH)
Louise Dyregaard Nielsen
University of Geneva
Coel Hellier
Keele University
Savita Mathur
University of La Laguna
Instituto Astrofisico de Canarias
Hans J. Deeg
Instituto Astrofisico de Canarias
University of La Laguna
Artie P. Hatzes
Thüringer Landessternwarte Tautenburg
Serena Benatti
Osservatorio Astronomico di Palermo Guiseppe S. Vaiana
Florian Rodler
European Southern Observatory (ESO)
Javier Alarcon
European Southern Observatory (ESO)
Lorenzo Spina
Monash University
ARC Centre of Excellence for All-sky Astrophysics (CAASTRO)
Angela R. G. Santos
Space Science Institute
Iskra Georgieva
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics, Galactic Astrophysics
Rafael A. Garcia
University Paris-Saclay
Paris Diderot University
Lucia Gonzalez-Cuesta
Instituto Astrofisico de Canarias
George R. Ricker
Massachusetts Institute of Technology (MIT)
Roland Vanderspek
Massachusetts Institute of Technology (MIT)
David W. Latham
Harvard-Smithsonian Center for Astrophysics
Sara Seager
Massachusetts Institute of Technology (MIT)
Joshua N. Winn
Princeton University
Jon M. Jenkins
NASA Ames Research Center
Simon Albrecht
Aarhus University
Natalie M. Batalha
University of California at Santa Cruz
Corey Beard
University of California at Irvine (UCI)
Patricia T. Boyd
NASA Goddard Space Flight Center
Francois Bouchy
University of Geneva
Jennifer A. Burt
California Institute of Technology (Caltech)
R. Paul Butler
Carnegie Institution for Science
Juan Cabrera
German Aerospace Center (DLR)
Ashley Chontos
University of Hawaii
David R. Ciardi
California Institute of Technology (Caltech)
William D. Cochran
The University of Texas at Austin
Collins
George Mason University
Jeffrey D. Crane
Carnegie Institution for Science
Ian Crossfield
University of Kansas
Szilard Csizmadia
German Aerospace Center (DLR)
Diana Dragomir
University of New Mexico
Courtney Dressing
University of California at Berkeley
Philipp Eigmueller
German Aerospace Center (DLR)
Michael Endl
The University of Texas at Austin
Anders Erikson
German Aerospace Center (DLR)
Nestor Espinoza
Space Telescope Science Institute (STScI)
Michael Fausnaugh
Massachusetts Institute of Technology (MIT)
Fabo Feng
Carnegie Institution for Science
Erin Flowers
Princeton University
Benjamin Fulton
California Institute of Technology (Caltech)
Erica J. Gonzales
University of California at Santa Cruz
Nolan Grieves
University of Geneva
Sascha Grziwa
University of Cologne
Eike W. Guenther
Thüringer Landessternwarte Tautenburg
Natalia M. Guerrero
Massachusetts Institute of Technology (MIT)
Thomas Henning
Max Planck Society
Diego Hidalgo
Instituto Astrofisico de Canarias
Teruyuki Hirano
Tokyo Institute of Technology
Maria Hjorth
Aarhus University
Daniel Huber
University of Hawaii
Howard Isaacson
University of California at Berkeley
University of Southern Queensland
Matias Jones
European Southern Observatory (ESO)
Andres Jordan
Adolfo Ibáñez University
Millennium Institute of Astrophysics
Petr Kabath
Czech Academy of Sciences
Stephen R. Kane
University of California at Riverside
Emil Knudstrup
Aarhus University
Jack Lubin
University of California at Irvine (UCI)
Rafael Luque
Instituto Astrofisico de Canarias
University of La Laguna
Ismael Mireles
Massachusetts Institute of Technology (MIT)
Norio Narita
Japan Science and Technology Agency
National Institutes of Natural Sciences
Instituto Astrofisico de Canarias
University of Tokyo
David Nespral
University of La Laguna
Instituto Astrofisico de Canarias
Prajwal Niraula
Massachusetts Institute of Technology (MIT)
Grzegorz Nowak
Instituto Astrofisico de Canarias
University of La Laguna
Enric Palle
University of La Laguna
Instituto Astrofisico de Canarias
Martin Paetzold
University of Cologne
Erik A. Petigura
University of California at Los Angeles
Jorge Prieto-Arranz
University of La Laguna
Instituto Astrofisico de Canarias
Heike Rauer
Freie Universität Berlin
Technische Universität Berlin
German Aerospace Center (DLR)
Paul Robertson
University of California at Irvine (UCI)
Mark E. Rose
NASA Ames Research Center
Arpita Roy
California Institute of Technology (Caltech)
Paula Sarkis
Max Planck Society
Joshua E. Schlieder
NASA Goddard Space Flight Center
Damien Segransan
University of Geneva
Stephen Shectman
Carnegie Institution for Science
Marek Skarka
Masaryk University
Czech Academy of Sciences
Alexis M. S. Smith
German Aerospace Center (DLR)
Jeffrey C. Smith
NASA Ames Research Center
Keivan Stassun
Vanderbilt University
Johanna Teske
Carnegie Institution for Science
Joseph D. Twicken
NASA Ames Research Center
Vincent Van Eylen
University College London (UCL)
Sharon Wang
Carnegie Institution for Science
Lauren M. Weiss
University of Hawaii
Aurelien Wyttenbach
Max Planck Inst Ur Astron
Université Grenoble Alpes
Leiden University
University of Geneva
Astronomical Journal
0004-6256 (ISSN) 1538-3881 (eISSN)
Vol. 160 3 114Subject Categories
Meteorology and Atmospheric Sciences
Astronomy, Astrophysics and Cosmology
Atom and Molecular Physics and Optics
DOI
10.3847/1538-3881/aba124