Issue |
A&A
Volume 675, July 2023
|
|
---|---|---|
Article Number | A52 | |
Number of page(s) | 23 | |
Section | Planets and planetary systems | |
DOI | https://doi.org/10.1051/0004-6361/202346550 | |
Published online | 30 June 2023 |
An unusually low-density super-Earth transiting the bright early-type M-dwarf GJ 1018 (TOI-244)★,★★
1
Centro de Astrobiología, CSIC-INTA,
ESAC campus,
28692
Villanueva de la Cañada, Madrid, Spain
e-mail: acastro@cab.inta-csic.es
2
Instituto de Astrofísica e Ciências do Espaço, Universidade do Porto, CAUP,
Rua das Estrelas,
4150-762
Porto, Portugal
3
Departamento de Fisica e Astronomia, Universidade do Porto,
Rua do Campo Alegre,
4169-007
Porto, Portugal
4
Observatoire de l’Université de Genève,
51 chemin Pegasi,
1290
Sauverny, Switzerland
5
Max Planck Institute for Astronomy,
Königstuhl 17,
69117
Heidelberg, Germany
6
Aix-Marseille Univ., CNRS, CNES, LAM,
38 rue Frédéric Joliot-Curie,
13388
Marseille, France ;
Division Technique INSU,
CS20330,
83507
La Seyne-sur-Mer cedex, France
7
Department of Astronomy and Astrophysics, University of California,
1156 High St,
Santa Cruz, CA
95064, USA
8
Centro de Astrobiología, CSIC-INTA,
Carretera de Ajalvir km 4,
28850
Torrejón de Ardoz, Madrid, Spain
9
Physikalisches Institut, University of Bern,
Gesellsschaftstrasse 6,
3012
Bern, Switzerland
10
Center for Space and Habitability, University of Bern,
Gesellsschaftstrasse 6,
3012
Bern, Switzerland
11
INAF - Osservatorio Astronomico di Brera,
Via E. Bianchi 46,
23807
Merate (LC), Italy
12
Department of Astrophysical Sciences, Princeton University,
Princeton, NJ
08544, USA
13
Instituto de Astrofísica de Canarias,
C. Vía Láctea 1,
38205
La Laguna, Santa Cruz de Tenerife, Spain
14
Universidad de La Laguna, Dept. Astrofísica,
38206
La Laguna, Tenerife, Spain
15
NASA Ames Research Center,
Building N-254
Moffett Field, CA
94035, USA
16
INAF – Osservatorio Astrofisico di Torin,
Via Osservatorio 20,
10025
Pino Torinese, Italy
17
Departamento de Matemática y Física Aplicadas, Universidad Católica de la Santísima Concepción,
Alonso de Rivera
2850,
Concepción, Chile
18
Univ. Grenoble Alpes, CNRS, IPAG,
38000
Grenoble, France
19
INAF – Osservatorio Astronomico di Trieste,
via G. B. Tiepolo 11,
34143
Trieste, Italy
20
European Southern Observatory,
Av. Alonso de Cordova 3107, Casilla
19001,
Santiago de Chile, Chile
21
Centro de Astrofísica da Universidade do Porto,
Rua das Estrelas,
4150-762
Porto, Portugal
22
Instituto de Astrofísica e Ciências do Espaço, Faculdade de Ciências da Universidade de Lisboa,
Campo Grande,
1749-016
Lisboa, Portugal
23
Département d’Astronomie, Université de Genève,
Ch. des Maillettes 51,
1290
Versoix, Switzerland
24
Department of Physics and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology,
Cambridge, MA
02139, USA
25
Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology,
Cambridge, MA
02139, USA
26
Department of Aeronautics and Astronautics, MIT,
77 Massachusetts Avenue,
Cambridge, MA
02139, USA
Received:
30
March
2023
Accepted:
2
May
2023
Context. Small planets located at the lower mode of the bimodal radius distribution are generally assumed to be composed of iron and silicates in a proportion similar to that of the Earth. However, recent discoveries are revealing a new group of low-density planets that are inconsistent with that description.
Aims. We intend to confirm and characterize the TESS planet candidate TOI-244.01, which orbits the bright (K = 7.97 mag), nearby (d = 22 pc), and early-type (M2.5 V) M-dwarf star GJ 1018 with an orbital period of 7.4 days.
Methods. We used Markov chain Monte Carlo methods to model 57 precise radial velocity measurements acquired by the ESPRESSO spectrograph together with TESS photometry and complementary HARPS data. Our model includes a planetary component and Gaussian processes aimed at modeling the correlated stellar and instrumental noise.
Results. We find TOI-244 b to be a super-Earth with a radius of Rp = 1.52 ± 0.12 R⊕ and a mass of Mp = 2.68 ± 0.30 M⊕. These values correspond to a density of ρ = 4.2 ± 1.1 g cm−3, which is below what would be expected for an Earth-like composition. We find that atmospheric loss processes may have been efficient to remove a potential primordial hydrogen envelope, but high mean molecular weight volatiles such as water could have been retained. Our internal structure modeling suggests that TOI-244 b has a 479−96+128 km thick hydrosphere over a 1.17 ± 0.09 R⊕ solid structure composed of a Fe-rich core and a silicate-dominated mantle compatible with that of the Earth. On a population level, we find two tentative trends in the density-metallicity and density-insolation parameter space for the low-density super-Earths, which may hint at their composition.
Conclusions. With a 8% precision in radius and 12% precision in mass, TOI-244 b is among the most precisely characterized super-Earths, which, together with the likely presence of an extended hydrosphere, makes it a key target for atmospheric observations.
Key words: planets and satellites: individual: TOI-244 b / planets and satellites: detection / planets and satellites: composition / stars: individual: GJ 1018 / techniques: radial velocities / techniques: photometric
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© The Authors 2023
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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