TOI-969: a late-K dwarf with a hot mini-Neptune in the desert and an eccentric cold Jupiter^★,★★

¹ Centro de Astrobiología (CAB, CSIC-INTA), Depto. de Astrofísica, ESAC campus, 28692 Villanueva de la Cañada (Madrid), Spain
e-mail: Jorge.Lillo@cab.inta-csic.es
² Dipartimento di Fisica, Universitá degli Studi di Torino, via Pietro Giuria 1, 10125 Torino, Italy
³ Department of Physics, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK
⁴ Centre for Exoplanets and Habitability, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK
⁵ Center for Astrophysics, Harvard & Smithsonian, 60 Garden Street, Cambridge, MA 02138, USA
⁶ European Southern Observatory, Karl-Schwarzschildstr. 2, 85748 Garching bei München, Germany
⁷ Observatoire astronomique de l’Université de Genève, Chemin Pegasi 51, 1290 Versoix, Switzerland
⁸ Instituto de Astrofísica de Andalucía (IAA-CSIC), Glorieta de la Astronomía s/n, 18008 Granada, Spain
⁹ Chalmers University of Technology, Department of Space, Earth and Environment, Onsala Space Observatory, 439 92 Onsala, Sweden
¹⁰ Instituto de Astrofísica e Ciências do Espaço, Universidade do Porto, CAUP, Rua das Estrelas, 4150-762 Porto, Portugal
¹¹ Aix-Marseille Univ., CNRS, CNES, LAM, Marseille, France
¹² NASA Ames Research Center, Moffett Field, CA 94035, USA
¹³ Instituto de Astrofísica de Canarias (IAC), 38205 La Laguna, Tenerife, Spain
¹⁴ Departamento de Astrofísica, Universidad de La Laguna (ULL), 38206, La Laguna, Tenerife, Spain
¹⁵ Astrophysics Group, Keele University, Staffordshire ST5 5BG, UK
¹⁶ Department of Astronomy, University of California Berkeley, Berkeley, CA 94720, USA
¹⁷ Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37235, USA
¹⁸ Departamento de Física e Astronomia, Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre, 4169-007 Porto, Portugal
¹⁹ Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge, CB3 0HA, UK
²⁰ Komaba Institute for Science, The University of Tokyo, 3-8-1 Komaba, Meguro, Tokyo 153-8902, Japan
²¹ Astrobiology Center, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
²² Department of Astronomy, University of Maryland, College Park, MD 20742, USA
²³ Center for Space and Habitability, University of Bern, Gesellschaftsstrasse 6, 3012 Bern, Switzerland
²⁴ Carnegie Earth & Planets Laboratory, 5241 Broach Branch Road NW, Washington, DC 20015, USA
²⁵ Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544, USA
²⁶ SETI Institute/NASA Ames Research Center, Moffett Field, CA 94035, USA
²⁷ The Observatories of the Carnegie Institution for Science, 813 Santa Barbara St, Pasadena, CA 91101, USA
²⁸ International Center for Advanced Studies (ICAS) and ICIFI (CONICET), ECyT-UNSAM, Campus Miguelete, 25 de Mayo y Francia, (1650) Buenos Aires, Argentina
²⁹ Department of Astronomy of the University of Geneva, 51 Chemin de Pegasi, 1290 Versoix, Switzerland
³⁰ Thüringer Landessternwarte Tautenburg, Sternwarte 5, 07778 Tautenburg, Germany
³¹ Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD, 21218, USA
³² Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
³³ Department of Physics and Astronomy, University of New Mexico, 210 Yale Blvd NE, Albuquerque, NM 87106, USA
³⁴ Department of Physics and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
³⁵ Center for Data Intensive and Time Domain Astronomy, Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824, USA
³⁶ Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
³⁷ Department of Aeronautics and Astronautics, MIT, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
³⁸ Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata, Paseo del Bosque s/n, (B1900) Buenos Aires, Argentina
³⁹ Department of Astronomy, Tsinghua University, Beijing 100084, PR China
⁴⁰ University of Southern Queensland, Centre for Astrophysics, West Street, Toowoomba, QLD 4350 Australia

Received: 27 April 2022
Accepted: 14 October 2022

Abstract

Context. The current architecture of a given multi-planetary system is a key fingerprint of its past formation and dynamical evolution history. Long-term follow-up observations are key to complete their picture.

Aims. In this paper, we focus on the confirmation and characterization of the components of the TOI-969 planetary system, where TESS detected a Neptune-size planet candidate in a very close-in orbit around a late K-dwarf star.

Methods. We use a set of precise radial velocity observations from HARPS, PFS, and CORALIE instruments covering more than two years in combination with the TESS photometric light curve and other ground-based follow-up observations to confirm and characterize the components of this planetary system.

Results. We find that TOI-969 b is a transiting close-in (P_b ~ 1.82 days) mini-Neptune planet (m_b = 9.1_−1.0^+1.1 M_⊕, R_b = 2.765_−0.097^+0.088 R_⊕), placing it on the lower boundary of the hot-Neptune desert (T_eq,b = 941 ± 31 K). The analysis of its internal structure shows that TOI-969 b is a volatile-rich planet, suggesting it underwent an inward migration. The radial velocity model also favors the presence of a second massive body in the system, TOI-969 c, with a long period of P_c = 1700₋₂₈₀⁺²⁹⁰ days, a minimum mass of m_c sin i_c = 11.3_−0.9^+1.1 M_Jup, and a highly eccentric orbit of e_c = 0.628_−0.036^+0.043.

Conclusions. The TOI-969 planetary system is one of the few around K-dwarfs known to have this extended configuration going from a very close-in planet to a wide-separation gaseous giant. TOI-969 b has a transmission spectroscopy metric of 93 and orbits a moderately bright (G = 11.3 mag) star, making it an excellent target for atmospheric studies. The architecture of this planetary system can also provide valuable information about migration and formation of planetary systems.