Issue |
A&A
Volume 666, October 2022
|
|
---|---|---|
Article Number | A184 | |
Number of page(s) | 15 | |
Section | Planets and planetary systems | |
DOI | https://doi.org/10.1051/0004-6361/202244118 | |
Published online | 26 October 2022 |
TOI-2196 b: Rare planet in the hot Neptune desert transiting a G-type star
1
Department of Space, Earth and Environment, Chalmers University of Technology, Onsala Space Observatory,
439 92
Onsala, Sweden
e-mail: carina.persson@chalmers.se
2
Dipartimento di Fisica, Universita degli Studi di Torino,
via Pietro Giuria 1,
10125
Torino, Italy
3
Aix Marseille Université, Institut Origines, CNRS, CNES, LAM,
Marseille, France
4
Department of Space, Earth and Environment, Chalmers University of Technology,
Chalmersplatsen 4,
412 96
Gothenburg, Sweden
5
Thüringer Landessternwarte Tautenburg,
Sternwarte 5,
07778
Tautenburg, Germany
6
Astrobiology Center,
2-21-1 Osawa, Mitaka,
Tokyo
181-8588, Japan
7
National Astronomical Observatory of Japan,
2-21-1 Osawa, Mitaka,
Tokyo
181-8588, Japan
8
Department of Astronomy, The Graduate University for Advanced Studies (SOKENDAI),
2-21-1 Osawa, Mitaka,
Tokyo, Japan
9
Center for Astrophysics, Harvard & Smithsonian,
60 Garden Street,
Cambridge, MA
02138, USA
10
Division of Geological and Planetary Sciences,
1200 E California Blvd,
Pasadena, CA
91125, USA
11
Leiden Observatory, University of Leiden,
PO Box 9513,
2300 RA
Leiden, The Netherlands
12
Núcleo de Astronomía, Facultad de Ingeniería y Ciencias, Universidad Diego Portales,
Av. Ejército 441,
Santiago, Chile
13
Centro de Astrofísica y Tecnologías Afines (CATA),
Casilla 36-D,
Santiago, Chile
14
Astronomical Institute of the Czech Academy of Sciences,
Fričova 298,
25165
Ondřejov, Czech Republic
15
Department of Physics and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology,
Cambridge, MA
02139, USA
16
Sub-department of Astrophysics, Department of Physics, University of Oxford,
Oxford
OX1 3RH, UK
17
Instituto de Astrofísica de Canarias,
C. Via Lactea S/N,
E-38205
La Laguna, Tenerife, Spain
18
NASA Goddard Space Flight Center, Exoplanets and Stellar Astrophysics Laboratory (Code 667),
Greenbelt, MD
20771, USA
19
McDonald Observatory and Center for Planetary Systems Habitability, The University of Texas,
Austin, TX USA
20
Caltech/IPAC-NASA Exoplanet Science Institute,
770 S. Wilson Avenue,
Pasadena, CA
91106, USA
21
Universidad de La Laguna, Dept. de Astrofísica,
38206
La Laguna, Tenerife, Spain
22
Department of Physics and Astronomy, University of New Mexico,
210 Yale Blvd NE,
Albuquerque, NM
87106, USA
23
Department of Astronomy and Tsinghua Centre for Astrophysics, Tsinghua University,
Beijing
100084, PR China
24
Rheinisches Institut für Umweltforschung an der Universität zu Köln,
Aachener Strasse 209,
50931
Köln, Germany
25
SUPA Physics and Astronomy, University of St. Andrews,
Fife
KY16 9SS
Scotland, UK
26
NASA Ames Research Center,
Moffett Field, CA
94035, USA
27
Department of Physics and Astronomy, University of Louisville,
Louisville, KY
40292, USA
28
Freie Universität Berlin, Institute of Geological Sciences,
Malteserstr. 74-100,
12249
Berlin, Germany
29
Institute of Planetary Research, German Aerospace Center (DLR),
Rutherfordstrasse 2,
12489
Berlin, Germany
30
Department of Astronomy & Astrophysics, University of Chicago,
Chicago, IL
60637, USA
31
Astrophysics Group, Cavendish Laboratory, University of Cambridge,
J.J. Thomson Avenue,
Cambridge
CB3 0HE, UK
32
Kavli Institute for Cosmology, University of Cambridge,
Madingley Road,
Cambridge
CB3 0HA, UK
33
Komaba Institute for Science, The University of Tokyo,
3-8-1 Komaba, Meguro,
Tokyo
153-8902, Japan
34
Mullard Space Science Laboratory, University College London,
Holmbury St Mary, Dorking,
Surrey
RH5 6NT, UK
35
Wild Boar Remote Observatory, San Casciano in val di Pesa,
Firenze
50026, Italy
36
Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology,
Cambridge, MA
02139, USA
37
Department of Aeronautics and Astronautics, Massachusetts Institute of Technology,
Cambridge, MA
02139, USA
38
Department of Physics & Astronomy, Vanderbilt University,
Nashville, TN
37235, USA
39
Tsinghua International School,
Beijing
100084, PR China
40
Department of Astrophysical Sciences, Princeton University,
Princeton, NJ
08544, USA
41
SETI Institute,
Mountain View, CA
94043, USA
42
Societá Astronomica Lunae,
Castelnuovo Magra, Italy
43
Department of Physics, Engineering and Astronomy, Stephen F. Austin State University,
1936 North St,
Nacogdoches, TX
75962, USA
Received:
25
May
2022
Accepted:
11
July
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 ≲ 2 R⊕) and rocky or they are gas giants with radii of ≳1 RJ. 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⊕, which, combined with the mass of 26.0 ± 1.3 M⊕, 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 MJ, 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 ≳1800 K: a hot sub-Neptune desert devoid of planets with radii of ≈ 1.8−3 R⊕ and a sub-Jovian desert for radii of ≈5−12 R⊕. 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.
Key words: planets and satellites: composition / planetary systems / planets and satellites: detection / planets and satellites: individual: TOI-2196 / techniques: photometric / techniques: radial velocities
© C. M. Persson et al. 2022
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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