TESS Hunt for Young and Maturing Exoplanets (THYME) IV: Three small planets orbiting a 120 Myr-old star in the Pisces--Eridanus stream

Abstract

Young exoplanets can offer insight into the evolution of planetary atmospheres, compositions, and architectures. We present the discovery of the young planetary system TOI 451 (TIC 257605131, Gaia DR2 4844691297067063424). TOI 451 is a member of the 120-Myr-old Pisces--Eridanus stream (Psc--Eri). We confirm membership in the stream with its kinematics, its lithium abundance, and the rotation and UV excesses of both TOI 451 and its wide binary companion, TOI 451 B (itself likely an M dwarf binary). We identified three candidate planets transiting in the TESS data and followed up the signals with photometry from Spitzer and ground-based telescopes. The system comprises three validated planets at periods of 1.9, 9.2 and 16 days, with radii of 1.9, 3.1, and 4.1 Earth radii, respectively. The host star is near-solar mass with V=11.0 and H=9.3 and displays an infrared excess indicative of a debris disk. The planets offer excellent prospects for transmission spectroscopy with HST and JWST, providing the opportunity to study planetary atmospheres that may still be in the process of evolving.

20 pages, appendix on UV excess

References in corpus (42)

• Array Programming with NumPy
• The Gaia mission
• The Transiting Exoplanet Survey Satellite
• A grid of MARCS model atmospheres for late-type stars I. Methods and general properties
• New evolutionary models for pre-main sequence and main sequence low-mass stars down to the hydrogen-burning limit
• astroquery: An Astronomical Web-Querying Package in Python
• Most 1.6 Earth-Radius Planets are not Rocky
• EXOFAST: A fast exoplanetary fitting suite in IDL
• How to Constrain Your M Dwarf: measuring effective temperature, bolometric luminosity, mass, and radius
• Growth Model Interpretation of Planet Size Distribution
• Planetary population synthesis coupled with atmospheric escape: a statistical view of evaporation
• Search for Associations Containing Young stars (SACY): I. Sample & Searching Method
• CH in stellar atmospheres: an extensive linelist
• Spitzer Secondary Eclipses of the Dense, Modestly-irradiated, Giant Exoplanet HAT-P-20b Using Pixel-Level Decorrelation
• Water Vapour Absorption in the Clear Atmosphere of an exo-Neptune
• Limb darkening and exoplanets: testing stellar model atmospheres and identifying biases in transit parameters
• The Atmospheric Signatures of Super-Earths: How to Distinguish Between Hydrogen-Rich and Hydrogen-Poor Atmospheres
• Inferring probabilistic stellar rotation periods using Gaussian processes
• Formation and Evolution of Planetary Systems (FEPS): Properties of Debris Dust around Solar-type Stars
• HAZMAT I: The Evolution of Far-UV and Near-UV Emission from Early M Stars
• The effect of stellar limb darkening values on the accuracy of the planet radii derived from photometric transit observations
• On the Inference of a Star's Inclination Angle from its Rotation Velocity and Projected Rotation Velocity
• EXOFASTv2: A public, generalized, publication-quality exoplanet modeling code
• Evolution of Mid-IR Excess Around Sun-like Stars: Constraints on Models of Terrestrial Planet Formation
• TESS Hunt for Young and Maturing Exoplanets (THYME) II: A 17 Myr Old Transiting Hot Jupiter in the Sco-Cen Association
• Spatial Distributions of Young Stars
• Extended stellar systems in the solar neighborhood - II. Discovery of a nearby 120° stellar stream in Gaia DR2
• Identical or fraternal twins? : The chemical homogeneity of wide binaries from Gaia DR2
• Spitzer 24 Micron Observations of Open Cluster IC 2391 and Debris Disk Evolution of FGK Stars
• A New Method to Identify Nearby, Young, Low-mass Stars
• Zodiacal Exoplanets in Time (ZEIT) V: A Uniform Search for Transiting Planets in Young Clusters Observed by K2
• Deflating Super-Puffs: Impact of Photochemical Hazes on the Observed Mass-Radius Relationship of Low Mass Planets
• Low False-Positive Rate of Kepler Candidates Estimated From A Combination Of Spitzer And Follow-Up Observations
• Cluster Difference Imaging Photometric Survey. I. Light Curves of Stars in Open Clusters from TESS Sectors 6 & 7
• Exploring the age dependent properties of M and L dwarfs using Gaia and SDSS
• Spitzer 24 micron Survey of Debris Disks in the Pleiades
• A PSF-based Approach to TESS High quality data Of Stellar clusters (PATHOS) -- I. Search for exoplanets and variable stars in the field of 47 Tuc
• Updated Parameters and a New Transmission Spectrum of HD 97658b
• Transit Light Curves with Finite Integration Time: Fisher Information Analysis
• Orbital Parameter Determination for Wide Stellar Binary Systems in the Age of Gaia
• Introducing a New Spitzer Master BLISS Map to Remove the Instrument-Systematic -- Phase-Curve-Parameter Degeneracy, as Demonstrated by a Reanalysis of the 4.5$\mu m$ WASP-43b Phase Curve
• Spitzer transit follow-up of planet candidates from the K2 mission

Cited by in corpus (12)

• The Gaia-ESO Survey: Empirical estimates of stellar ages from lithium equivalent widths (EAGLES)
• TESS Hunt for Young and Maturing Exoplanets (THYME) V: A Sub-Neptune Transiting a Young Star in a Newly Discovered 250 Myr Association
• One year of AU Mic with HARPS: I -- measuring the masses of the two transiting planets
• TOI-2076 and TOI-1807: Two young, comoving planetary systems within 50 pc identified by TESS that are ideal candidates for further follow-up
• Rotation and Lithium Confirmation of a 500 Parsec Halo for the Open Cluster NGC 2516
• A PSF-based Approach to TESS High quality data Of Stellar clusters (PATHOS) -- IV. Candidate exoplanets around stars in open clusters: frequency and age-planetary radius distribution
• A Mini-Neptune from TESS and CHEOPS Around the 120 Myr Old AB Dor member HIP 94235
• Revisiting K2-233 spectroscopic time-series with multidimensional Gaussian Processes
• Dynamical Evolution of Closely Packed Multiple Planetary Systems Subject to Atmospheric Mass-Loss
• Dynamical masses of two young transiting sub-Neptunes orbiting HD 63433
• Companion Mass Limits for 17 Binary Systems Obtained with Binary Differential Imaging and MagAO/Clio
• YOUNG Star detrending for Transiting Exoplanet Recovery (YOUNGSTER) II: Using Self-Organising Maps to explore young star variability in Sectors 1-13 of TESS data