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

Abstract

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. 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. 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. We find that TOI-969 b is a transiting close-in ($P_b\sim 1.82$ days) mini-Neptune planet ($m_b=9.1_{-1.0}^{+1.1}$ M${}_{\oplus }$, $R_b=2.765_{-0.097}^{+0.088}$ R${}_{\oplus }$), thus placing it on the {lower boundary} of the hot-Neptune desert ($T_{\mathrm{eq},\mathrm{b}}=941\pm 31$ 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 and a minimum mass of $m_c\sin i_c=11.3_{-0.9}^{+1.1}$ M${}_{\mathrm{Jup}}$, and with a highly-eccentric orbit of $e_c=0.628_{-0.036}^{+0.043}$. 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 it orbits a moderately bright ($G=11.3$ mag) star, thus becoming an excellent target for atmospheric studies. The architecture of this planetary system can also provide valuable information about migration and formation of planetary systems.

Accepted for publication in A&A. 25 pages, 15 figures, 12 tables

References in corpus (40)

• Array Programming with NumPy
• The Gaia mission
• Gaia Data Release 3: Summary of the content and survey properties
• The James Webb Space Telescope
• Bayes in the sky: Bayesian inference and model selection in cosmology
• Gaia Early Data Release 3: The astrometric solution
• Growth Model Interpretation of Planet Size Distribution
• Basic physical parameters of a selected sample of evolved stars
• Roche lobe effects on the atmospheric loss of "Hot Jupiters"
• Accurate, Empirical Radii and Masses of Planets and their Host Stars with Gaia Parallaxes
• Can we constrain interior structure of rocky exoplanets from mass and radius measurements?
• A new code for automatic determination of equivalent widths: Automatic Routine for line Equivalent widths in stellar Spectra (ARES)
• Parallax Systematics and Photocenter Motions of Benchmark Eclipsing Binaries in Gaia EDR3
• Limb darkening and exoplanets: testing stellar model atmospheres and identifying biases in transit parameters
• The Kepler Follow-Up Observation Program. I. A Catalog of Companions to Kepler Stars from High-Resolution Imaging
• ARES v2 - new features and improved performance
• Magnetic Cycles and Rotation Periods of Late Type Stars from photometric time series
• Eclipsing Binary Stars as Benchmarks for Trigonometric Parallaxes in the Gaia Era
• Empirical, Accurate Masses and Radii of Single Stars with TESS and Gaia
• High-resolution imaging of $Kepler$ planet host candidates. A comprehensive comparison of different techniques
• Irradiated ocean planets bridge super-Earth and sub-Neptune populations
• A remnant planetary core in the hot-Neptune desert
• Mass-radius relationships for irradiated ocean planets
• SWEET-Cat 2.0: The Cat just got SWEETer; Higher quality spectra and precise parallaxes from GAIA eDR3
• TESS Hunt for Young and Maturing Exoplanets (THYME) III: a two-planet system in the 400 Myr Ursa Major Group
• WASP-107b's density is even lower: a case study for the physics of planetary gas envelope accretion and orbital migration
• Constraining planet structure and composition from stellar chemistry: trends in different stellar populations
• The Monitor project: Data processing and lightcurve production
• Revised Filter Profiles and Zero Points for Broadband Photometry
• Transit detection of the long-period volatile-rich super-Earth ${\nu }^2$ Lupi d with $CHEOPS$
• An Ultra-Hot Neptune in the Neptune desert
• Constraints on Super-Earths Interiors from Stellar Abundances
• Planet formation and migration near the silicate sublimation front in protoplanetary disks
• Speckle Imaging Excludes Low-Mass Companions Orbiting the Exoplanet Host Star TRAPPIST-1
• Characterisation of the hydrospheres of TRAPPIST-1 planets
• The eccentricity distribution of giant planets and their relation to super-Earths in the pebble accretion scenario
• A Closer Look at Exoplanet Occurrence Rates: Considering the Multiplicity of Stars Without Detected Planets
• Hydrodynamic Escape of Mineral Atmosphere from Hot Rocky Exoplanet. I. Model Description
• Phase curve pollution of exoplanet transmission spectra
• The KOBE experiment: K-dwarfs Orbited By habitable Exoplanets. Project goals, target selection and stellar characterization

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