EUV irradiation of exoplanet atmospheres occurs on Gyr timescales

Abstract

Exoplanet atmospheres are known to be vulnerable to mass loss through irradiation by stellar X-ray and extreme-ultraviolet emission. We investigate how this high-energy irradiation varies with time by combining an empirical relation describing stellar X-ray emission with a second relation describing the ratio of Solar X-ray to extreme-ultraviolet emission. In contrast to assumptions commonly made when modelling atmospheric escape, we find that the decline in stellar extreme-ultraviolet emission is much slower than in X-rays, and that the total extreme-ultraviolet irradiation of planetary atmospheres is dominated by emission after the saturated phase of high energy emission (which lasts around 100 Myr after the formation of the star). The extreme-ultraviolet spectrum also becomes much softer during this slow decline. Furthermore, we find that the total combined X-ray and extreme-ultraviolet emission of stars also occurs mostly after this saturated phase. Our results suggest that models of atmospheric escape that focus on the saturated phase of high-energy emission are over-simplified, and when considering the evolution of planetary atmospheres it is necessary to follow EUV-driven escape on Gyr timescales. This may make it more difficult to use stellar age to separate the effects of photoevaporation and core-powered mass-loss when considering the origin the planet radius valley.

arXiv comment5 pages, 2 figures, 1 table; accepted MNRAS letters

References in corpus (37)

• The California-Kepler Survey. III. A Gap in the Radius Distribution of Small Planets
• The stellar activity-rotation relationship and the evolution of stellar dynamos
• Evolution of the Solar Activity over Time and Effects on Planetary Atmospheres: I. High-energy Irradiances (1-1700 A)
• Kepler planets: a tale of evaporation
• The evaporation valley in the Kepler planets
• Atmospheric Escape from Hot Jupiters
• Extreme Water Loss and Abiotic O${}_2$ Buildup On Planets Throughout the Habitable Zones of M Dwarfs
• A giant comet-like cloud of hydrogen escaping the warm Neptune-mass exoplanet GJ 436b
• An asteroseismic view of the radius valley: stripped cores, not born rocky
• The Role of Core Mass in Controlling Evaporation: the Kepler Radius Distribution and the Kepler-36 Density Dichotomy
• Core-powered mass loss and the radius distribution of small exoplanets
• Roche lobe effects on the atmospheric loss of "Hot Jupiters"
• Planetary evaporation by UV & X-ray radiation: basic hydrodynamics
• Sculpting the Valley in the Radius Distribution of Small Exoplanets as a by-product of Planet Formation: The Core-Powered Mass-Loss Mechanism
• Estimation of the XUV radiation onto close planets and their evaporation
• Planetary population synthesis coupled with atmospheric escape: a statistical view of evaporation
• Dearth of short-period Neptunian exoplanets - a desert in period-mass and period-radius planes
• Super-Earth Atmospheres: Self-Consistent Gas Accretion and Retention
• The MUSCLES Treasury Survey II: Intrinsic Lyman Alpha and Extreme Ultraviolet Spectra of K and M Dwarfs with Exoplanets
• The Extreme Ultraviolet and X-Ray Sun in Time: High-Energy Evolutionary Tracks of a Solar-Like Star
• Photoevaporation and High-Eccentricity Migration Created the Sub-Jovian Desert
• The coronal X-ray - age relation and its implications for the evaporation of exoplanets
• Coronal Evolution of the Sun in Time: High-Resolution X-Ray Spectroscopy of Solar Analogs with Different Ages
• Born Dry in the Photo-Evaporation Desert: Kepler's Ultra-Short-Period Planets Formed Water-Poor
• Origin and Loss of nebula-captured hydrogen envelopes from "sub"- to "super-Earths" in the habitable zone of Sun-like stars
• A grid of upper atmosphere models for 1--40 MEARTH planets: application to CoRoT-7 b and HD219134 b,c
• XUV-driven mass loss from extrasolar giant planets orbiting active stars
• UV driven evaporation of close-in planets: energy-limited; recombination-limited and photon-limited flows
• Aeronomical constraints to the minimum mass and maximum radius of hot low-mass planets
• Stellar coronal astronomy - a review
• Mass-Loss Evolution of Close-In Exoplanets: Evaporation of Hot Jupiters and the Effect on Population
• Survival of a planet in short-period Neptunian desert under effect of photo-evaporation
• No hydrogen exosphere detected around the super-Earth HD97658 b
• The XUV environments of exoplanets from Jupiter-size to super-Earth
• An Improved Age-Activity Relationship for Cool Stars older than a Gigayear
• Coupling thermal evolution of planets and hydrodynamic atmospheric escape in MESA
• Unveiling the Planet Population at Birth

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• The New Generation Planetary Population Synthesis (NGPPS). V. Predetermination of planet types in global core accretion models
• Evolution of the Exoplanet Size Distribution: Forming Large Super-Earths Over Billions of Years
• The JADE code: Coupling secular exoplanetary dynamics and photo-evaporation
• Homogeneous search for helium in the atmosphere of 11 gas giant exoplanets with SPIRou
• New Perspectives on the Exoplanet Radius Gap from a Mathematica Tool and Visualized Water Equation of State
• Exoplanet X-ray irradiation and evaporation rates with eROSITA
• 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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• HAZMAT. VII. The Evolution of Ultraviolet Emission with Age and Rotation for Early M Dwarf Stars
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• The Thermal Emission Spectrum of the Nearby Rocky Exoplanet LTT 1445A b from JWST MIRI/LRS
• The GAPS Programme at TNG XLII. A characterisation study of the multi-planet system around the 400 Myr-old star HD 63433 (TOI-1726)
• A Lyman-alpha transit left undetected: the environment and atmospheric behavior of K2-25b
• A 38 Million Year Old Neptune-Sized Planet in the Kepler Field
• The influence of host star activity evolution on the population of super-Earths and mini-Neptunes
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• The young mini-Neptune HD 207496b that is either a naked core or on the verge of becoming one
• The shared evaporation history of three sub-Neptunes spanning the radius-period valley of a Hyades star
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• Population-level Hypothesis Testing with Rocky Planet Emission Data: A Tentative Trend in the Brightness Temperatures of M-Earths
• Eta-Earth Revisited II: Deriving a Maximum Number of Earth-like Habitats in the Galactic Disk
• The Cosmic Shoreline Revisited: A Metric for Atmospheric Retention Informed by Hydrodynamic Escape
• The key impact of the host star's rotational history on the evolution of TOI-849b
• Rocky sub-Neptunes formed by pebble accretion: Rain of rocks from polluted envelopes
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• Star-planet interactions VI. Tides, stellar activity and planet evaporation
• Interior redox state effects on the stability of secondary atmospheres and observational manifestations: LP 791-18 d as a case study for outgassing rocky exoplanets
• Five new hot-Jupiter transits investigated with Swift-UVOT
• The strongly irradiated planets in Praesepe
• X-ray irradiation of three planets around Hyades star K2-136
• The Occurrence-weighted Median Planets Discovered by Transit Surveys Orbiting Solar-type Stars and Their Implications for Planet Formation and Evolution
• A Search for Planetary Metastable Helium Absorption in the V1298 Tau System
• An Adolescent and Near-Resonant Planetary System Near the End of Photoevaporation
• A Multi-Planet System's Sole Super-Puff: Exploring Allowable Physical Parameters for the Cold Super-Puff HIP 41378 f
• Revisiting the exoplanet radius valley with host stars from SWEET-Cat