Helium in Exoplanet Exospheres: Orbital and Stellar Influences

Abstract

Searches for helium in the exospheres of exoplanets via the metastable near-infrared triplet have yielded 17 detections and 40 non-detections. We performed a comprehensive re-analysis of published studies to investigate the influence of stellar XUV flux and orbital parameters on the detectability of helium in exoplanetary atmospheres. We identified a distinct 'orbital sweet spot' for helium detection, 0.03 to 0.08 AU from the host star, where the majority of detections occurred. This sweet spot is influenced by the stellar XUV flux and planet size. Notably, a lower ratio of XUV flux to mid-UV flux is preferred for planets compared to non-detections. We also found that helium detections occur for planets around stars with effective temperatures of 4400-6500 K, with a sharp gap at 5400 to 6000 K, where no detections occur. Additionally, our analysis of the cumulative XUV flux versus escape velocity shows planets with helium detections are found above the 'cosmic shoreline', suggesting the shoreline needs revision. The trends we found in our analysis contribute to a deeper understanding of exosphere evolution.

arXiv comment10 pages, 8 figures. Submitted to ApJ

References in corpus (68)

• The California-Kepler Survey. III. A Gap in the Radius Distribution of Small Planets
• Detection of an Extrasolar Planet Atmosphere
• Kepler planets: a tale of evaporation
• Theoretical Transmission Spectra During Extrasolar Giant Planet Transits
• The evaporation valley in the Kepler planets
• Atmospheric Escape from Hot Jupiters
• Detection of oxygen and carbon in the hydrodynamically escaping atmosphere of the extrasolar planet HD209458b
• Probabilistic Forecasting of the Masses and Radii of Other Worlds
• A Framework for Prioritizing the TESS Planetary Candidates Most Amenable to Atmospheric Characterization
• Extrasolar planet population synthesis I: Method, formation tracks and mass-distance distribution
• The California Kepler Survey VII. Precise Planet Radii Leveraging Gaia DR2 Reveal the Stellar Mass Dependence of the Planet Radius Gap
• An asteroseismic view of the radius valley: stripped cores, not born rocky
• 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
• Helium in the eroding atmosphere of an exoplanet
• Dearth of short-period Neptunian exoplanets - a desert in period-mass and period-radius planes
• The GAPS Programme with HARPS-N@TNG XIV. Investigating giant planet migration history via improved eccentricity and mass determination for 231 transiting planets
• Density, not radius, separates rocky and water-rich small planets orbiting M dwarf stars
• Breeding Super-Earths and Birthing Super-Puffs in Transitional Disks
• Make Super-Earths, Not Jupiters: Accreting Nebular Gas onto Solid Cores at 0.1 AU and Beyond
• Hot super-Earths stripped by their host stars
• The MUSCLES Treasury Survey II: Intrinsic Lyman Alpha and Extreme Ultraviolet Spectra of K and M Dwarfs with Exoplanets
• Spectrally resolved helium absorption from the extended atmosphere of a warm Neptune-mass exoplanet
• A New Window into Escaping Exoplanet Atmospheres: 10830 Å Line of Helium
• Atmospheres of low-mass planets: the "boil-off"
• The cosmic shoreline: the evidence that escape determines which planets have atmospheres, and what this may mean for Proxima Centauri b
• Hubble PanCET: An extended upper atmosphere of neutral hydrogen around the warm Neptune GJ 3470 b
• Signatures of the Core-Powered Mass-Loss Mechanism in the Exoplanet Population: Dependence on Stellar Properties and Observational Predictions
• Emerging Trends in a Period-Radius Distribution of Close-in Planets
• Detection of He I $\lambda 10830$ Å absorption on HD 189733 b with CARMENES high-resolution transmission spectroscopy
• The nature and origins of sub-Neptune size planets
• A grid of upper atmosphere models for 1--40 MEARTH planets: application to CoRoT-7 b and HD219134 b,c
• A Detection Of H-alpha In An Exoplanetary Exosphere
• Computing Intrinsic Lyman-alpha Fluxes of F5 V to M5 V Stars
• Helium Absorption at 1083 nm from Extended Exoplanet Atmospheres: Dependence on Stellar Radiation
• Revised mass-radius relationships for water-rich rocky planets more irradiated than the runaway greenhouse limit
• Primordial Radius Gap and Potentially Broad Core Mass Distributions of Super-Earths and Sub-Neptunes
• The Upper Edge of the Neptune Desert Is Stable Against Photoevaporation
• Limits on the Spin-Orbit Angle and Atmospheric Escape for the 22 Myr-old Planet AU Mic b
• Detection of Atmospheric Escape from Four Young Mini Neptunes
• On the Role of Dissolved Gases in the Atmosphere Retention of Low-Mass Low-Density Planets
• A decade of H$\alpha$ transits for HD 189733 b: stellar activity versus absorption in the extended atmosphere
• Creating the Radius Gap without Mass Loss
• High-energy irradiation and mass loss rates of hot Jupiters in the solar neighborhood
• The post-transit tail of WASP-107b observed at 10830A
• Keck/NIRSPEC studies of He I in the atmospheres of two inflated hot gas giants orbiting K dwarfs: WASP-52b and WASP-177b
• Ultraviolet C II and Si III Transit Spectroscopy and Modeling of the Evaporating Atmosphere of GJ436b
• WASP-52b. The effect of starspot correction on atmospheric retrievals
• Investigation of the environment around close-in transiting exoplanets using CLOUDY
• HST/STIS Lyman-alpha observations of the quiet M dwarf GJ436: Predictions for the exospheric transit signature of the hot neptune GJ436b
• The fundamentals of Lyman-alpha exoplanet transits
• The HST PanCET Program: Hints of Na I & Evidence of a Cloudy Atmosphere for the Inflated Hot Jupiter WASP-52b
• Homogeneous search for helium in the atmosphere of 11 gas giant exoplanets with SPIRou
• The K2-3 system revisited: testing photoevaporation and core-powered mass loss with three small planets spanning the radius valley
• Removal of Hot Saturns in Mass-Radius Plane by Runaway Mass Loss
• Search for helium in the upper atmosphere of the hot Jupiter WASP-127 b using Gemini/Phoenix
• Using helium 10830 Å transits to constrain planetary magnetic fields
• Sculpting the sub-Saturn Occurrence Rate via Atmospheric Mass Loss
• On the origin of the non-detection of metastable HeI in the upper atmosphere of the hot Jupiter WASP-80b
• Confirmation of an He I evaporating atmosphere around the 650-Myr-old sub-Neptune HD235088 b (TOI-1430 b) with CARMENES
• Planet(esimal)s Around Stars with TESS (PAST) III: A Search for Triplet He I in the Atmospheres of Two 200 Myr-old Planets
• Active Stars in the Spectroscopic Survey of Mid-to-Late M Dwarfs Within 15pc
• Absence of extended atmospheres in low-mass star radius-gap planets GJ 9827 b, GJ 9827 d and TOI-1235 b
• Observing atmospheric escape in sub-Jovian worlds with JWST
• Evolution of helium triplet transits of close-in gas giants orbiting K-dwarfs

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• Connection between planetary He I $\lambda$10830 Å absorption and extreme-ultraviolet emission of planet-host stars
• The open-source sunbather code: modeling escaping planetary atmospheres and their transit spectra
• NIRPS detection of delayed atmospheric escape from the warm and misaligned Saturn-mass exoplanet WASP-69b
• sunset: A database of synthetic atmospheric-escape transmission spectra for nearly every transiting planet
• Helium escape signatures are generally strongest during younger ages but this age dependence is lost in the diversity of observed exoplanets
• A Search for helium in the atmospheres of three sub-Neptunes and a super-Earth around M-dwarfs
• The effects of stellar activity cycles on planetary atmospheric escape and the HeI 1083nm transit signature