Two long-period transiting exoplanets on eccentric orbits: NGTS-20 b (TOI-5152 b) and TOI-5153 b

Abstract

Long-period transiting planets provide the opportunity to better understand the formation and evolution of planetary systems. Their atmospheric properties remain largely unaltered by tidal or radiative effects of the host star, and their orbital arrangement reflects a different, and less extreme, migrational history compared to close-in objects. The sample of long-period exoplanets with well determined masses and radii is still limited, but a growing number of long-period objects reveal themselves in the TESS data. Our goal is to vet and confirm single transit planet candidates detected in the TESS space-based photometric data through spectroscopic and photometric follow up observations with ground-based instruments. We use the Next Generation Transit Survey (NGTS) to photometrically monitor the candidates in order to observe additional transits. We report the discovery of two massive, warm Jupiter-size planets, one orbiting the F8-type star TOI-5153 and the other orbiting the G1-type star NGTS-20 (=TOI-5152). From our spectroscopic analysis, both stars are metal-rich with a metallicity of 0.12 and 0.15, respectively. Follow-up radial velocity observations were carried out with CORALIE, CHIRON, FEROS, and HARPS. TOI-5153 hosts a 20.33 day period planet with a planetary mass of 3.26 (+-0.18) Mj, a radius of 1.06 (+-0.04) Rj , and an orbital eccentricity of 0.091 (+-0.026). NGTS-20 b is a 2.98 (+-0.16) Mj planet with a radius of 1.07 (+-0.04) Rj on an eccentric (0.432 +- 0.023) orbit with an orbital period of 54.19 days. Both planets are metal-enriched and their heavy element content is in line with the previously reported mass-metallicity relation for gas giants. Both warm Jupiters orbit moderately bright host stars making these objects valuable targets for follow-up studies of the planetary atmosphere and measurement of the spin-orbit angle of the system.

17 pages, 13 figures, accepted to A&A

References in corpus (34)

• The Transiting Exoplanet Survey Satellite
• A grid of MARCS model atmospheres for late-type stars I. Methods and general properties
• Improved Age Estimation for Solar-Type Dwarfs Using Activity-Rotation Diagnostics
• On the radiative equilibrium of irradiated planetary atmospheres
• Determining stellar atmospheric parameters and chemical abundances of FGK stars with iSpec
• Accurate, Empirical Radii and Masses of Planets and their Host Stars with Gaia Parallaxes
• The TESS Objects of Interest Catalog from the TESS Prime Mission
• The imprint of exoplanet formation history on observable present-day spectra of hot Jupiters
• Three regimes of extrasolar planets inferred from host star metallicities
• Parallax Systematics and Photocenter Motions of Benchmark Eclipsing Binaries in Gaia EDR3
• CERES: A Set of Automated Routines for Echelle Spectra
• Eclipsing Binary Stars as Benchmarks for Trigonometric Parallaxes in the Gaia Era
• Long Term Evolution of Close Planets Including the Effects of Secular Interactions
• Empirical, Accurate Masses and Radii of Single Stars with TESS and Gaia
• H2O abundances in the atmospheres of three hot Jupiters
• AQUA: A Collection of H${}_2$O Equations of State for Planetary Models
• Atmospheric Dynamics of Hot Giant Planets and Brown Dwarfs
• Grain opacity and the bulk composition of extrasolar planets. I. Results from scaling the ISM opacity
• A new Neptune-mass planet orbiting HD 219828
• Evidence of Three Mechanisms Explaining the Radius Anomaly of Hot Jupiters
• Bayesian priors for the eccentricity of transiting planets
• Constraining the magnetic field structure in collisionless relativistic shocks with a radio afterglow polarization upper limit in GW170817
• Do Metal-Rich Stars Make Metal-Rich Planets? New Insights on Giant Planet Formation from Host Star Abundances
• Evidence for disequilibrium chemistry from vertical mixing in hot Jupiter atmospheres. A comprehensive survey of transiting close-in gas giant exoplanets with warm-Spitzer/IRAC
• TOI-222: a single-transit TESS candidate revealed to be a 34-day eclipsing binary with CORALIE, EulerCam and NGTS
• NGTS-11 b / TOI-1847 b: A transiting warm Saturn recovered from a TESS single-transit event
• Uncovering the true periods of the young sub-Neptunes orbiting TOI-2076
• A search for transiting planets around FGKM dwarfs and sub-giants in the TESS Full Frame Images of the Southern ecliptic hemisphere
• The TESS-Keck Survey. VIII. Confirmation of a Transiting Giant Planet on an Eccentric 261 day Orbit with the Automated Planet Finder Telescope
• A Highly Eccentric Warm Jupiter Orbiting TIC 237913194
• Revisiting migration in a disc cavity to explain the high eccentricities of warm Jupiters
• Transiting Planets near the Snow Line from Kepler. I. Catalog
• NGTS 15b, 16b, 17b and 18b: four hot Jupiters from the Next Generation Transit Survey
• TIC-320687387 B: a long-period eclipsing M-dwarf close to the hydrogen burning limit

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• Three Saturn-mass planets transiting F-type stars revealed with TESS and HARPS
• A hot mini-Neptune and a temperate, highly eccentric sub-Saturn around the bright K-dwarf TOI-2134
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• Detection and characterisation of a 106-day transiting Jupiter : TOI-2449 b / NGTS-36 b
• Flows, Circulations, and Energy Transport in the Outer and Deep Atmospheres of Synchronous and Non-synchronous Hot Jupiters
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