A Transiting Super-Earth in the Radius Valley and An Outer Planet Candidate Around HD 307842

Abstract

We report the confirmation of a TESS-discovered transiting super-Earth planet orbiting a mid-G star, HD 307842 (TOI-784). The planet has a period of 2.8 days, and the radial velocity (RV) measurements constrain the mass to be 9.67+0.83/-0.82 [Earth Masses]. We also report the discovery of an additional planet candidate on an outer orbit that is most likely non-transiting. The possible periods of the planet candidate are approximately 20 to 63 days, with the corresponding RV semi-amplitudes expected to range from 3.2 to 5.4 m/s and minimum masses from 12.6 to 31.1 [Earth Masses]. The radius of the transiting planet (planet b) is 1.93+0.11/-0.09 [Earth Radii], which results in a mean density of 7.4+1.4/-1.2 g/cm^3 suggesting that TOI-784b is likely to be a rocky planet though it has a comparable radius to a sub-Neptune. We found TOI-784b is located at the lower edge of the so-called ``radius valley'' in the radius vs. insolation plane, which is consistent with the photoevaporation or core-powered mass loss prediction. The TESS data did not reveal any significant transit signal of the planet candidate, and our analysis shows that the orbital inclinations of planet b and the planet candidate are 88.60+0.84/-0.86 degrees and <= 88.3-89.2 degrees, respectively. More RV observations are needed to determine the period and mass of the second object, and search for additional planets in this system.

30 pages, 21 figures, accepted for publication in AJ

References in corpus (20)

• The Astropy Project: Sustaining and Growing a Community-oriented Open-source Project and the Latest Major Release (v5.0) of the Core Package
• The Transiting Exoplanet Survey Satellite
• The generalised Lomb-Scargle periodogram. A new formalism for the floating-mean and Keplerian periodograms
• Improved Age Estimation for Solar-Type Dwarfs Using Activity-Rotation Diagnostics
• Bayes in the sky: Bayesian inference and model selection in cosmology
• Planets and Stellar Activity: Hide and Seek in the CoRoT-7 system
• Accurate, Empirical Radii and Masses of Planets and their Host Stars with Gaia Parallaxes
• The Hipparcos-Gaia Catalog of Accelerations: Gaia EDR3 Edition
• 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
• The California-Kepler Survey. X. The Radius Gap as a Function of Stellar Mass, Metallicity, and Age
• The Precision of Mass Measurements Required for Robust Atmospheric Characterization of Transiting Exoplanets
• A Spectroscopic Analysis of the California-Kepler Survey Sample: I. Stellar Parameters, Planetary Radii and a Slope in the Radius Gap
• Accounting for Incompleteness due to Transit Multiplicity in Kepler Planet Occurrence Rates
• Two young planetary systems around field stars with ages between 20-320 Myr from TESS
• TOI-1235 b: a keystone super-Earth for testing radius valley emergence models around early M dwarfs
• Stellar Companions to TESS Objects of Interest: A Test of Planet-Companion Alignment
• The Preservation of Super Earths and the Emergence of Gas Giants after Their Progenitor Cores have Entered the Pebble Isolation Phase
• Dynamical Evolution of Closely Packed Multiple Planetary Systems Subject to Atmospheric Mass-Loss

Cited by in corpus (1)

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