Issue |
A&A
Volume 642, October 2020
|
|
---|---|---|
Article Number | A173 | |
Number of page(s) | 21 | |
Section | Planets and planetary systems | |
DOI | https://doi.org/10.1051/0004-6361/202037867 | |
Published online | 19 October 2020 |
The CARMENES search for exoplanets around M dwarfs
Two planets on opposite sides of the radius gap transiting the nearby M dwarf LTT 3780
1
Instituto de Astrofísica de Canarias (IAC),
38205 La Laguna, Tenerife, Spain
e-mail: gnowak@iac.es
2
Departamento de Astrofísica, Universidad de La Laguna (ULL),
38206
La Laguna, Tenerife, Spain
3
Max-Planck-Institut für Astronomie, Königstuhl 17,
69117 Heidelberg, Germany
4
Centro de Astrobiología (CSIC-INTA), ESAC, Camino bajo del castillo s/n, 28692 Villanueva de la Cañada, Madrid, Spain
5
Instituto de Astrofísica de Andalucía (IAA-CSIC), Glorieta de la Astronomía s/n,
18008 Granada, Spain
6
Institut für Astrophysik, Georg-August-Universität, Friedrich-Hund-Platz 1,
37077 Göttingen, Germany
7
Homer L. Dodge Department of Physics and Astronomy, University of Oklahoma, 440 West Brooks Street, Norman, OK 73019, USA
8
Hamburger Sternwarte, Universität Hamburg, Gojenbergsweg 112,
21029 Hamburg, Germany
9
Astrobiology Center, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
10
JST, PRESTO, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
11
National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
12
Department of Physics and Astronomy, George Mason University, 4400 University Drive MS 3F3, Fairfax, VA 22030, USA
13
Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
14
Centro de Astrobiología (CSIC-INTA), Carretera de Ajalvir km 4, 28850 Torrejón de Ardoz, Madrid, Spain
15
Space Sciences, Technologies and Astrophysics Research (STAR) Institute, Université de Liège, 19C Allée du 6 Août, 4000 Liège, Belgium
16
Astrobiology Research Unit, Université de Liège, 19C Allée du 6 Août,
4000 Liège, Belgium
17
Oukaimeden Observatory, High Energy Physics and Astrophysics Laboratory, Cadi Ayyad University, Marrakech, Morocco
18
SETI Institute, Mountain View, CA 94043, USA
19
NASA Ames Research Center, Moffett Field, CA 94035, USA
20
Thüringer Landessternwarte Tautenburg, Sternwarte 5, 0777 Tautenburg, Germany
21
Key Laboratory of Planetary Sciences, Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008, PR China
22
Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
23
Department of Physics and Astronomy, University of Kansas, Lawrence, KS, USA
24
Department of Astronomy, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
25
Instituto Universitario de Ciencias y Tecnologías del Espacio de Asturias (ICTEA), C/ Independencia, 13, 33004 Oviedo, Spain
26
Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
27
Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
28
Department of Earth and Planetary Science, The University of Tokyo, Tokyo, Japan
29
Department of Earth Sciences, University of Hawai’i at Manoa, Honolulu, HI 96822, USA
30
Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064, USA
31
Observatori Astronómic Albanyá, Camí de Bassegoda S/N, Albanyá 17733, Girona, Spain
32
Institut d’Estudis Espacials de Catalunya (IEEC), C/ Gran Capità 2-4, 08034 Barcelona, Spain
33
Department of Astronomy, Wesleyan University, Middletown, CT 06459, USA
34
Department of Earth and Planetary Sciences, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8551, Japan
35
Landessternwarte, Zentrum für Astronomie der Universität Heidelberg, Königstuhl 12, 69117 Heidelberg, Germany
36
Department of Physics and Astronomy, University of Louisville, Louisville, KY 40292, USA
37
Institut de Ciències de l’Espai (ICE, CSIC), Campus UAB, C/Can Magrans s/n, 08193 Bellaterra, Spain
38
Department of Physics and Astronomy, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3255, USA
39
Villa ’39 Observatory, Landers, CA 92285, USA
40
US Naval Observatory, Washington, DC 20392, USA
41
Department of Physics, and Kavli Institute for Astrophysics and Space Science, M.I.T., Cambridge, MA 02193, USA
42
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
43
Centro Astronómico Hispano-Alemán (CSIC-MPG), Observatorio Astronómico de Calar Alto, Sierra de los Filabres-04550 Gérgal, Almería, Spain
44
Department of Physics, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK
45
Centre for Exoplanets and Habitability, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK
46
Exoplanets and Stellar Astrophysics Laboratory, Code 667, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
47
Department of Aeronautics and Astronautics, MIT, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
48
Observatories of the Carnegie Institution of Washington, 813 Santa Barbara Street, Pasadena, CA 91101, USA
49
Planetary Discoveries in Fredericksburg, Fredericksburg, Virginia 22401, USA
50
Dunlap Institute for Astronomy and Astrophysics, University of Toronto, 50 St. George Street, Toronto, Ontario M5S 3H4, Canada
51
Mississippi State University, 355 Lee Boulevard, Mississippi State, MS 39762, USA
Received:
2
March
2020
Accepted:
17
July
2020
We present the discovery and characterisation of two transiting planets observed by the Transiting Exoplanet Survey Satellite (TESS) orbiting the nearby (d⋆ ≈ 22 pc), bright (J ≈ 9 mag) M3.5 dwarf LTT 3780 (TOI–732). We confirm both planets and their association with LTT 3780 via ground-based photometry and determine their masses using precise radial velocities measured with the CARMENES spectrograph. Precise stellar parameters determined from CARMENES high-resolution spectra confirm that LTT 3780 is a mid-M dwarf with an effective temperature of Teff = 3360 ± 51 K, a surface gravity of log g⋆ = 4.81 ± 0.04 (cgs), and an iron abundance of [Fe/H] = 0.09 ± 0.16 dex, with an inferred mass of M⋆ = 0.379 ± 0.016M⊙ and a radius of R⋆ = 0.382 ± 0.012R⊙. The ultra-short-period planet LTT 3780 b (Pb = 0.77 d) with a radius of 1.35−0.06+0.06 R⊕, a mass of 2.34−0.23+0.24 M⊕, and a bulk density of 5.24−0.81+0.94 g cm−3 joins the population of Earth-size planets with rocky, terrestrial composition. The outer planet, LTT 3780 c, with an orbital period of 12.25 d, radius of 2.42−0.10+0.10 R⊕, mass of 6.29−0.61+0.63 M⊕, and mean density of 2.45−0.37+0.44 g cm−3 belongs to the population of dense sub-Neptunes. With the two planets located on opposite sides of the radius gap, this planetary system is anexcellent target for testing planetary formation, evolution, and atmospheric models. In particular, LTT 3780 c is an ideal object for atmospheric studies with the James Webb Space Telescope (JWST).
Key words: techniques: photometric / techniques: radial velocities / stars: individual: LTT 3780 / stars: late-type / planets and satellites: detection
© ESO 2020
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