Issue |
A&A
Volume 658, February 2022
|
|
---|---|---|
Article Number | A138 | |
Number of page(s) | 27 | |
Section | Planets and planetary systems | |
DOI | https://doi.org/10.1051/0004-6361/202142128 | |
Published online | 11 February 2022 |
A multi-planetary system orbiting the early-M dwarf TOI-1238
1
Centro de Astrobiología (CSIC-INTA),
Carretera de Ajalvir km 4,
28850
Torrejón de Ardoz,
Madrid,
Spain
e-mail: egonzalez@cab.inta-csic.es
2
Landessternwarte, Zentrum für Astronomie der Universität Heidelberg,
Königstuhl 12,
69117
Heidelberg,
Germany
3
Instituto de Astrofísica de Canarias, Avenida Vía Láctea s/n,
38205
La Laguna,
Tenerife,
Spain
4
Departamento de Astrofísica, Universidad de La Laguna,
38206
La Laguna,
Tenerife,
Spain
5
Thüringer Landessternwarte Tautenburg,
Sternwarte 5,
07778
Tautenburg,
Germany
6
Institut de Ciències de l’Espai (IEEC-CSIC), Campus UAB, Carrer de Can Magrans s/n,
08193
Bellaterra,
Spain
7
Institut d’Estudis Espacials de Catalunya (IEEC),
08034
Barcelona,
Spain
8
Max-Planck-Institut für Sonnensystemforschung,
37077
Göttingen,
Germany
9
Instituto de Astrofísica de Andalucía (IAA-CSIC), Glorieta de la Astronomía s/n,
18008
Granada,
Spain
10
Max-Planck-Institut für Astronomie,
Königstuhl 17,
69117
Heidelberg,
Germany
11
Universitäts-Sternwarte, Ludwig-Maximilians-Universität München,
Scheinerstrasse 1,
81679
München,
Germany
12
Hamburger Sternwarte, Universität Hamburg,
Gojenbergsweg 112,
21029
Hamburg,
Germany
13
Homer L. Dodge Department of Physics and Astronomy, University of Oklahoma,
440 West Brooks Street,
Norman,
OK
73019,
USA
14
Physics Department, Austin College,
Sherman,
TX
75090,
USA
15
Astrophysics Science Division, NASA Goddard Space Flight Center,
Greenbelt,
MD
20771,
USA
16
Université de Montréal, Département de Physique,
C.P. 6128 Succ. Centre-ville,
Montréal,
QC H3C 3J7,
Canada
17
Center for Astrophysics, Harvard & Smithsonian,
60 Garden Street,
Cambridge,
MA
02138,
USA
18
Institut für Astrophysik, Georg-August-Universität Göttingen,
Friedrich-Hund-Platz 1,
37077
Göttingen,
Germany
19
Space Telescope Science Institute,
Baltimore,
MD
21218,
USA
20
Department of Physics and Kavli Institute for Astrophysics and Space Science, Massachusetts Institute of Technology,
Cambridge,
MA
02139,
USA
21
NASA Exoplanet Science Institute, Caltech/IPAC,
Mail Code 100-22, 1200 E. California Blvd.,
Pasadena,
CA
91125,
USA
22
Wesleyan University,
Middletown,
CT
06459,
USA
23
Intelligent Systems Division, NASA Ames Research Center,
Moffett Field,
CA
94035,
USA
24
Department of Astronomy, Wellesley College,
Wellesley,
MA
02481,
USA
25
Departamento de Física de la Tierra y Astrofísica & IPARCOS-UCM (Instituto de Física de Partículas y del Cosmos de la UCM), Facultad de Ciencias Físicas, Universidad Complutense de Madrid,
28040
Madrid,
Spain
26
Centro Astronómico Hispano Alemán, Observatorio de Calar Alto, Sierra de los Filabres,
04550
Gérgal,
Spain
27
Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology,
54–1718, 77 Massachusetts Avenue
Cambridge,
MA
02139,
USA
28
Department of Aeronautics and Astronautics, Massachusetts Institute of Technology,
77 Massachusetts Avenue,
Cambridge,
MA
02139,
USA
29
Patashnick Voorheesville Observatory,
Voorheesville,
NY
12186,
USA
30
Princeton University,
Cambridge,
MA,
USA
Received:
1
September
2021
Accepted:
16
November
2021
Context. The number of super-Earth and Earth-mass planet discoveries has increased significantly in the last two decades thanks to the Doppler radial velocity and planetary transit observing techniques. Either technique can detect planet candidates on its own, but the power of a combined photometric and spectroscopic analysis is unique for an insightful characterization of the planets, which in turn has repercussions for our understanding of the architecture of planetary systems and, therefore, their formation and evolution.
Aims. Two transiting planet candidates with super-Earth radii around the nearby (d = 70.64 ± 0.06 pc) K7–M0 dwarf star TOI-1238 were announced by NASA’s Transiting Exoplanet Survey Satellite (TESS), which observed the field of TOI-1238 in four different sectors. We aim to validate their planetary nature using precise radial velocities taken with the CARMENES spectrograph.
Methods. We obtained 55 CARMENES radial velocity measurements that span the 11 months between 9 May 2020 and 5 April 2021. For a better characterization of the parent star’s activity, we also collected contemporaneous optical photometric observations at the Joan Oró and Sierra Nevada observatories and retrieved archival photometry from the literature. We performed a combined TESS+CARMENES photometric and spectroscopic analysis by including Gaussian processes and Keplerian orbits to account for the stellar activity and planetary signals simultaneously.
Results. We estimate that TOI-1238 has a rotation period of 40 ± 5 d based on photometric and spectroscopic data. The combined analysis confirms the discovery of two transiting planets, TOI-1238 b and c, with orbital periods of 0.764597−0.000011+0.000013 d and 3.294736−0.000036+0.000034 d, masses of 3.76−1.07+1.15 M⊕ and 8.32−1.88+1.90 M⊕, and radii of 1.21−0.10+0.11 R⊕ and 2.11−0.14+0.14 R⊕. They orbit their parent star at semimajor axes of 0.0137 ± 0.0004 au and 0.036 ± 0.001 au, respectively.The two planets are placed on opposite sides of the radius valley for M dwarfs and lie between the star and the inner border of TOI-1238’s habitable zone. The inner super-Earth TOI-1238 b is one of the densest ultra-short-period planets ever discovered (ρ = 11.7−3.4+4.2 g cm−3). The CARMENES data also reveal the presence of an outer, non-transiting, more massive companion with an orbital period and radial velocity amplitude of ≥600 d and ≥70 m s−1, which implies a likely mass of M ≥ 2 √(1− e2) MJup and a separation ≥1.1 au from its parent star.
Key words: techniques: photometric / techniques: radial velocities / stars: individual: TOI-1238 / stars: late-type / planetary systems
© ESO 2022
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