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 3 114

Subject Categories

Meteorology and Atmospheric Sciences

Astronomy, Astrophysics and Cosmology

Atom and Molecular Physics and Optics

DOI

10.3847/1538-3881/aba124

More information

Latest update

9/24/2020