TOI-2196 b: Rare planet in the hot Neptune desert transiting a G-type star
Journal article, 2022

The hot Neptune desert is a region hosting a small number of short-period Neptunes in the radius-instellation diagram. Highly irradiated planets are usually either small (R less than or similar to 2 R-circle plus) and rocky or they are gas giants with radii of greater than or similar to 1 R-J. Here, we report on the intermediate-sized planet TOI-2196 b (TIC 372172128.01) on a 1.2 day orbit around a G-type star (V = 12.0, [Fe/H] = 0.14 dex) discovered by the Transiting Exoplanet Survey Satellite in sector 27. We collected 41 radial velocity measurements with the HARPS spectrograph to confirm the planetary nature of the transit signal and to determine the mass. The radius of TOI-2196 b is 3.51 +/- 0.15 R-circle plus, which, combined with the mass of 26.0 +/- 1.3 M-circle plus, results in a bulk density of 3.31(-0.43)(+0.51) g cm(-3). Hence, the radius implies that this planet is a sub-Neptune, although the density is twice than that of Neptune. A significant trend in the HARPS radial velocity measurements points to the presence of a distant companion with a lower limit on the period and mass of 220 days and 0.65 M-J, respectively, assuming zero eccentricity. The short period of planet b implies a high equilibrium temperature of 1860 +/- 20 K, for zero albedo and isotropic emission. This places the planet in the hot Neptune desert, joining a group of very few planets in this parameter space discovered in recent years. These planets suggest that the hot Neptune desert may be divided in two parts for planets with equilibrium temperatures of greater than or similar to 1800 K: a hot sub-Neptune desert devoid of planets with radii of approximate to 1.8-3 R-circle plus and a sub-Jovian desert for radii of approximate to 5-12 R-circle plus. More planets in this parameter space are needed to further investigate this finding. Planetary interior structure models of TOI-2196 b are consistent with a H/He atmosphere mass fraction between 0.4% and 3%, with a mean value of 0.7% on top of a rocky interior. We estimated the amount of mass this planet might have lost at a young age and we find that while the mass loss could have been significant, the planet had not changed in terms of character: it was born as a small volatile-rich planet and it remains one at present.

individual

photometric

planets and satellites

TOI-2196

planets and satellites

radial velocities

techniques

detection

planetary systems

techniques

composition

planets and satellites

Author

Carina Persson

Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics

Iskra Georgieva

Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics

Davide Gandolfi

University of Turin

Lorena Acuna

Aix Marseille University

Artem Aguichine

Aix Marseille University

Alexandra Muresan

Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics

Eike Guenther

Thüringer Landessternwarte Tautenburg

John Livingston

National Astronomical Observatory of Japan

Astrobiology Center, Japan

The Graduate University for Advanced Studies (SOKENDAI)

Karen A. Collins

Harvard-Smithsonian Center for Astrophysics

Fei Dai

California Institute of Technology (Caltech)

Malcolm Fridlund

Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics

Elisa Goffo

University of Turin

Thüringer Landessternwarte Tautenburg

James S. Jenkins

Diego Portales University

Centro de Astrofísica y Tecnologías Afines (CATA),

Petr Kabath

Czech Academy of Sciences

Judith Korth

Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics

Alan M. Levine

Massachusetts Institute of Technology (MIT)

Luisa M. Serrano

University of Turin

Jose Vines

Centro de Astrofísica y Tecnologías Afines (CATA),

Oscar Barragan

University of Oxford

Ilaria Carleo

Instituto de Astrofísica de Canarias

Knicole D. Colon

NASA Goddard Space Flight Center

William D. Cochran

The University of Texas at Austin

J.L. Christiansen

California Institute of Technology (Caltech)

Hans J. Deeg

University of La Laguna

Instituto de Astrofísica de Canarias

Magali Deleuil

Aix Marseille University

Diana Dragomir

University of New Mexico

Massimiliamo Esposito

Thüringer Landessternwarte Tautenburg

Tianjun Gan

Tsinghua University

Sascha Grziwa

University of Cologne

Artie P. Hatzes

Thüringer Landessternwarte Tautenburg

Katharine Hesse

Massachusetts Institute of Technology (MIT)

Keith Horne

University of St Andrews

Jon M. Jenkins

NASA Ames Research Center

John F. Kielkopf

University of Louisville

P. Klagyivik

Freie Universität Berlin

Kristine W. F. Lam

German Aerospace Center (DLR)

David W. Latham

Harvard-Smithsonian Center for Astrophysics

Rafa Luque

University of Chicago

Jaume Orell-Miquel

Instituto de Astrofísica de Canarias

University of La Laguna

Annelies Mortier

University of Cambridge

Olivier Mousis

Aix Marseille University

Noria Narita

University of Tokyo

Astrobiology Center, Japan

Instituto de Astrofísica de Canarias

Hannah L. M. Osborne

University College London (UCL)

Enric Palle

Instituto de Astrofísica de Canarias

Riccardo Papini

Wild Boar Remote Observatory (WBRO-K49)

George R. Ricker

Massachusetts Institute of Technology (MIT)

Hendrik Schmerling

University of Cologne

Sara Seager

Massachusetts Institute of Technology (MIT)

Keivan G. Stassun

Vanderbilt University

V. Van Eylen

University College London (UCL)

Roland Vanderspek

Massachusetts Institute of Technology (MIT)

Gavin Wang

Tsinghua International School

Joshua N. Winn

Princeton University

Bill Wohler

SETI Institute

NASA Ames Research Center

Roberto Zambelli

Lunae Astronomical Society

Carl Ziegler

Stephen F. Austin State University

Astronomy and Astrophysics

0004-6361 (ISSN) 1432-0746 (eISSN)

Vol. 666 A184

Exoplanets from space -CHEOPS and PLATO ESA's next two projects (Phase 2)

Swedish National Space Board (65/19), 2020-01-01 -- 2022-12-31.

Swedish National Space Board (177/19), 2020-01-01 -- 2022-12-31.

Exoplanets from space – CHEOPS and PLATO, ESA’s next two projects

Swedish National Space Board (174/18), 2017-01-01 -- 2022-12-31.

Subject Categories

Subatomic Physics

Meteorology and Atmospheric Sciences

Astronomy, Astrophysics and Cosmology

DOI

10.1051/0004-6361/202244118

More information

Latest update

12/13/2022