Two young planetary systems around field stars with ages between 20-320 Myr from TESS

Abstract

Planets around young stars trace the early evolution of planetary systems. We report the discovery and validation of two planetary systems with ages $\lesssim 300$ Myr from observations by the Transiting Exoplanet Survey Satellite. TOI-251 is a 40-320 Myr old G star hosting a 2.74 +0.18/-0.18 REarth mini-Neptune with a 4.94 day period. TOI-942 is a 20-160 Myr old K star hosting a system of inflated Neptune-sized planets, with TOI-942b orbiting with a period of 4.32 days, with a radius of 4.81 +0.20/-0.20 REarth, and TOI-942c orbiting in a period of 10.16 days with a radius of 5.79 +0.19/-0.18 REarth. Though we cannot place either host star into a known stellar association or cluster, we can estimate their ages via their photometric and spectroscopic properties. Both stars exhibit significant photometric variability due to spot modulation, with measured rotation periods of $\sim 3.5$ days. These stars also exhibit significant chromospheric activity, with age estimates from the chromospheric calcium emission lines and X-ray fluxes matching that estimated from gyrochronology. Both stars also exhibit significant lithium absorption, similar in equivalent width to well-characterized young cluster members. TESS has the potential to deliver a population of young planet-bearing field stars, contributing significantly to tracing the properties of planets as a function of their age.

Accepted for publication in AJ

References in corpus (15)

• Improved Age Estimation for Solar-Type Dwarfs Using Activity-Rotation Diagnostics
• A planet within the debris disk around the pre-main-sequence star AU Microscopii
• A Stellar Census of the Tucana-Horologium Moving Group
• Four newborn planets transiting the young solar analog V1298 Tau
• Zodiacal Exoplanets in Time (ZEIT) IV: seven transiting planets in the Praesepe cluster
• On the Inference of a Star's Inclination Angle from its Rotation Velocity and Projected Rotation Velocity
• TESS Hunt for Young and Maturing Exoplanets (THYME) II: A 17 Myr Old Transiting Hot Jupiter in the Sco-Cen Association
• The Monitor project: Data processing and lightcurve production
• Zodiacal Exoplanets in Time (ZEIT) VI: a three-planet system in the Hyades cluster including an Earth-sized planet
• Zodiacal Exoplanets in Time (ZEIT) V: A Uniform Search for Transiting Planets in Young Clusters Observed by K2
• K2 Discovers a Busy Bee: An Unusual Transiting Neptune Found in the Beehive Cluster
• Cluster Difference Imaging Photometric Survey. I. Light Curves of Stars in Open Clusters from TESS Sectors 6 & 7
• Speckle Imaging Excludes Low-Mass Companions Orbiting the Exoplanet Host Star TRAPPIST-1
• Chromospherically Active Stars in the RAVE Survey. II. Young dwarfs in the Solar neighborhood
• The Young Planet DS Tuc Ab has a Low Obliquity

Cited by in corpus (33)

• Stellar obliquities in exoplanetary systems
• The Gaia-ESO Survey: Empirical estimates of stellar ages from lithium equivalent widths (EAGLES)
• Creating the Radius Gap without Mass Loss
• 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
• TESS Delivers Five New Hot Giant Planets Orbiting Bright Stars from the Full Frame Images
• The GAPS Programme at TNG XXVIII -- A pair of hot-Neptunes orbiting the young star TOI-942
• The TESS Grand Unified Hot Jupiter Survey. II. Twenty New Giant Planets
• Removal of Hot Saturns in Mass-Radius Plane by Runaway Mass Loss
• V1298 Tau with TESS: Updated Ephemerides, Radii, and Period Constraints from a Second Transit of V1298 Tau e
• A Mini-Neptune from TESS and CHEOPS Around the 120 Myr Old AB Dor member HIP 94235
• Another Shipment of Six Short-Period Giant Planets from TESS
• The obliquity of HIP 67522 b: a 17 Myr old transiting hot Jupiter-sized planet
• TOI-942b: A Prograde Neptune in a ~60 Myr old Multi-transiting System
• The TESS Grand Unified Hot Jupiter Survey. I. Ten TESS Planets
• NEID Rossiter-McLaughlin Measurement of TOI-1268b: A Young Warm Saturn Aligned with Its Cool Host Star
• A 38 Million Year Old Neptune-Sized Planet in the Kepler Field
• Using the Gaia excess uncertainty as a proxy for stellar variability and age
• Characterization of a set of small planets with TESS and CHEOPS and an analysis of photometric performance
• TOI-179: a young system with a transiting compact Neptune-mass planet and a low-mass companion in outer orbit
• TOI-4562 b: A highly eccentric temperate Jupiter analog orbiting a young field star
• TOI-1801 b: A temperate mini-Neptune around a young M0.5 dwarf
• First Comparative Exoplanetology Within a Transiting Multi-planet System: Comparing the atmospheres of V1298 Tau b and c
• Dynamical masses of two young transiting sub-Neptunes orbiting HD 63433
• TOI-712: a system of adolescent mini-Neptunes extending to the habitable zone
• NGTS clusters survey $-$ V: Rotation in the Orion Star-forming Complex
• True spin-orbit obliquities distribution: data-driven confirmation of no clustering of misaligned planets
• A Transiting Super-Earth in the Radius Valley and An Outer Planet Candidate Around HD 307842
• Migration and Evolution of giant ExoPlanets (MEEP) II: Super-Jupiters and Lithium-rich Host Stars
• A transiting multi-planet system in the 61 million year old association Theia 116
• A search for stellar siblings of the ~ 200 Myr TOI-251b planetary system
• Constraints on the Spindown of Fully-Convective M Dwarfs Using Wide Field Binaries
• Atmospheric mass loss and stellar wind effects in young and old systems I: comparative 3D study of TOI-942 and TOI-421 systems