Kepler-78 and the Ultra-Short-Period Planets

Abstract

Compared to the Earth, the exoplanet Kepler-78b has a similar size (1.2 $R_{\oplus }$) and an orbital period a thousand times shorter (8.5 hours). It is currently the smallest planet for which the mass, radius, and dayside brightness have all been measured. Kepler-78b is an exemplar of the ultra-short-period (USP) planets, a category defined by the simple criterion $P_{\mathrm{orb}}<1$ day. We describe our Fourier-based search of the Kepler data that led to the discovery of Kepler-78b, and review what has since been learned about the population of USP planets. They are about as common as hot Jupiters, and they are almost always smaller than 2 $R_{\oplus }$. They are often members of compact multi-planet systems, although they tend to have relatively large period ratios and mutual inclinations. They might be the exposed rocky cores of "gas dwarfs," the planets between 2-4 $R_{\oplus }$ in size that are commonly found in somewhat wider orbits.

arXiv commentfixed error in Eq. (4)

References in corpus (101)

• The Transiting Exoplanet Survey Satellite
• The California-Kepler Survey. III. A Gap in the Radius Distribution of Small Planets
• Planet Occurrence within 0.25 AU of Solar-type Stars from Kepler
• The false positive rate of Kepler and the occurrence of planets
• A box-fitting algorithm in the search for periodic transits
• The evaporation valley in the Kepler planets
• Architecture of Kepler's Multi-transiting Systems: II. New investigations with twice as many candidates
• Transiting exoplanets from the CoRoT space mission VIII. CoRoT-7b: the first Super-Earth with measured radius
• KEPLER's First Rocky Planet: Kepler-10b
• Planets and Stellar Activity: Hide and Seek in the CoRoT-7 system
• Validation of Kepler's Multiple Planet Candidates. III: Light Curve Analysis & Announcement of Hundreds of New Multi-planet Systems
• A disintegrating minor planet transiting a white dwarf
• False positive probabilties for all Kepler Objects of Interest: 1284 newly validated planets and 428 likely false positives
• Mass-Radius Relation for Rocky Planets based on PREM
• Kepler Eclipsing Binary Stars. II. 2165 Eclipsing Binaries in the Second Data Release
• How Thermal Evolution and Mass Loss Sculpt Populations of Super-Earths and Sub-Neptunes: Application to the Kepler-11 System and Beyond
• Detection of a NEPTUNE-mass planet in the ${\rho }^1$ Cancri system using the Hobby-Eberly Telescope
• The California-Kepler Survey. IV. Metal-rich Stars Host a Greater Diversity of Planets
• Dearth of short-period Neptunian exoplanets - a desert in period-mass and period-radius planes
• Radial velocity planets de-aliased. A new, short period for Super-Earth 55 Cnc e
• Initial Characteristics of Kepler Long Cadence Data For Detecting Transiting Planets
• Almost All of Kepler's Multiple Planet Candidates are Planets
• A map of the large day-night temperature gradient of a super-Earth exoplanet
• WASP-47: A Hot Jupiter System with Two Additional Planets Discovered by K2
• A Super-Earth Transiting a Naked-Eye Star
• Hot super-Earths stripped by their host stars
• Five Planets Orbiting 55 Cancri
• Kepler constraints on planets near hot Jupiters
• Transit Timing Observations from Kepler: IV. Confirmation of 4 Multiple Planet Systems by Simple Physical Models
• A Study of the Shortest-Period Planets Found With Kepler
• On the Low False Positive Probabilities of Kepler Planet Candidates
• Atmospheres of low-mass planets: the "boil-off"
• Evolutionary Analysis of Gaseous Sub-Neptune-Mass Planets with MESA
• Characterizing the Cool KOIs III. KOI-961: A Small Star with Large Proper Motion and Three Small Planets
• Possible Disintegrating Short-Period Super-Mercury Orbiting KIC 12557548
• An Earth-sized planet with an Earth-like density
• Chemistry of Silicate Atmospheres of Evaporating Super-Earths
• WASP-19b: the shortest period transiting exoplanet yet discovered
• Detection of a transit of the super-Earth 55 Cnc e with Warm Spitzer
• The Apparently Decaying Orbit of WASP-12
• A Rocky Composition for an Earth-sized Exoplanet
• Observable Consequences of Planet Formation Models in Systems with Close-in Terrestrial Planets
• 275 Candidates and 149 Validated Planets Orbiting Bright Stars in K2 Campaigns 0-10
• Disentangling stellar activity and planetary signals
• The extreme physical properties of the CoRoT-7b super-Earth
• Transits and Occultations of an Earth-Sized Planet in an 8.5-Hour Orbit
• Determining the Mass of Kepler-78b With Nonparametric Gaussian Process Estimation
• Variability in the super-Earth 55 Cnc e
• The K2-ESPRINT Project. I. Discovery of the Disintegrating Rocky Planet K2-22b with a Cometary Head and Leading Tail
• Departure from the constant-period ephemeris for the transiting exoplanet WASP-12 b
• Transiting extrasolar planetary candidates in the Galactic bulge
• Detection of Thermal Emission from a Super-Earth
• KOI-2700b - A Planet Candidate With Dusty Effluents on a 22-Hour Orbit
• Atmosphere-interior exchange on hot rocky exoplanets
• On the Period Distribution of Close-In Extrasolar Giant Planets
• The Roche limit for close-orbiting planets: Minimum density, composition constraints, and application to the 4.2-hour planet KOI 1843.03
• Magnetospheric Truncation, Tidal Inspiral, and the Creation of Short and Ultra-Short Period Planets
• An ultra-short period rocky super-Earth with a secondary eclipse and a Neptune-like companion around K2-141
• Catastrophic Evaporation of Rocky Planets
• A Dynamical Analysis of the Kepler-80 System of Five Transiting Planets
• An Earth-sized exoplanet with a Mercury-like composition
• Characterizing K2 Candidate Planetary Systems Orbiting Low-Mass Stars II: Planetary Systems Observed During Campaigns 1-7
• Re-inflated Warm Jupiters Around Red Giants
• A Super-Solar Metallicity For Stars With Hot Rocky Exoplanets
• The PTF Orion Project: a Possible Planet Transiting a T-Tauri Star
• Three's Company: An additional non-transiting super-Earth in the bright HD 3167 system, and masses for all three planets
• Ultra-short-period planets from secular chaos
• Detection of Potential Transit Signals in 17 Quarters of Kepler Data: Results of the Final Kepler Mission Transiting Planet Search (DR25)
• Absence of a metallicity effect for ultra-short-period planets
• Tidally-driven Roche-Lobe Overflow of Hot Jupiters with MESA
• The orbital phases and secondary transit of Kepler-10b - A physical interpretation based on the Lava-ocean planet model -
• The transiting multi-planet system HD3167: a 5.7 MEarth Super-Earth and a 8.3 MEarth mini-Neptune
• Measurement of Spin-Orbit Misalignment and Nodal Precession for the Planet around Pre-Main-Sequence Star PTFO 8-8695 From Gravity Darkening
• Larger mutual inclinations for the shortest-period planets
• 150 New transiting planet candidates from Kepler Q1-Q6 data
• K2-141 b: A 5-M${}_{\oplus }$ super-Earth transiting a K7 V star every 6.7 hours
• Two Small Planets Transiting HD 3167
• A Population of Very-Hot Super-Earths in Multiple-Planet Systems Should be Uncovered by Kepler
• The discovery and mass measurement of a new ultra-short-period planet: EPIC~228732031b
• Revised Masses and Densities of the Planets around Kepler-10
• Precise Masses in the WASP-47 System
• K2-106, a system containing a metal-rich planet and a planet of lower density
• A lack of short-period multiplanet systems with close-proximity pairs and the curious case of Kepler 42
• A Compact Multi-Planet System With A Significantly Misaligned Ultra Short Period Planet
• Interaction of Close-in Planets with the Magnetosphere of their Host Stars. II. Super-Earths as Unipolar Inductors and their Orbital Evolution
• Ultra Short Period Planets in K2: SuPerPiG Results for Campaigns 0-5
• Elemental Abundances of Kepler Objects of Interest in APOGEE. I. Two Distinct Orbital Period Regimes Inferred from Host Star Iron Abundances
• K2-137 b: an Earth-sized planet in a 4.3-hour orbit around an M-dwarf
• An Independent Planet Search In The Kepler Dataset. I. A hundred new candidates and revised KOIs
• K2-66b and K2-106b: Two extremely hot sub-Neptune-size planets with high densities
• Follow-Up Observations of PTFO 8-8695: A 3 MYr Old T-Tauri Star Hosting a Jupiter-mass Planetary Candidate
• A Survey for Very Short-Period Planets in the Kepler Data
• A dearth of small particles in the transiting material around the white dwarf WD 1145+017
• Tests of the planetary hypothesis for PTFO 8-8695b
• A population of planetary systems characterized by short-period, Earth-sized planets
• Ultra Short Period Planets in K2 with companions: a double transiting system for EPIC 220674823
• The Detection of Earth-mass Planets around Active Stars: The Mass of Kepler-78b
• Disintegrating Rocky Exoplanets
• On the origin of dynamically isolated hot Earths
• The magnetic properties of the planet host star Kepler-78
• H-alpha Variability in PTFO8-8695 and the Possible Direct Detection of Emission from a 2 Million Year Old Evaporating Hot Jupiter

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• Planets Across Space and Time (PAST). III. Morphology of the Planetary Radius Valley as a Function of Stellar Age and Metallicity in the Galactic Context Revealed by the LAMOST-Gaia-Kepler Sample
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• Generalized Peas-in-a-Pod: Extending Intra-System Mass Uniformity to Non-TTV Systems via the Gini Index
• TOI-1416: A system with a super-Earth planet with a 1.07d period
• 3D magneto-hydrodynamical simulations of stellar convective noise for improved exoplanet detection. I. Case of regularly sampled radial velocity observations
• Dust formation in the outflows of catastrophically evaporating planets
• HD 20329b: An ultra-short-period planet around a solar-type star found by TESS
• The HD 93963 A transiting system: A 1.04d super-Earth and a 3.65 d sub-Neptune discovered by TESS and CHEOPS
• The LHS 1678 System: Two Earth-Sized Transiting Planets and an Astrometric Companion Orbiting an M Dwarf Near the Convective Boundary at 20 pc
• Probing Kepler's hottest small planets via homogeneous search and analysis of optical secondary eclipses and phase variations
• Alternative solvents for life: framework for evaluation, current status and future research
• Relativistic Dynamical Stability Criterion of Multi-Planet Systems with a Distant Companion
• Migrating Planets into Ultra-Short-Period Orbits during Episodic Accretion Events
• A CHEOPS-enhanced view of the HD3167 system
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• A Reanalysis of the Composition of K2-106b: an Ultra-short Period Super-Mercury Candidate
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• Architecture Classification for Extrasolar Planetary Systems
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• The GALAH Survey: Improving our understanding of confirmed and candidate planetary systems with large stellar surveys
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• Discovering planets with PLATO: Comparison of algorithms for stellar activity filtering
• The tidal heating of the exoplanet 55 Cnc e. The role of the orbital eccentricity
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