HST PanCET program: Non-detection of atmospheric escape in the warm Saturn-sized planet WASP-29 b

Abstract

(Abridged) Short-period gas giant exoplanets are susceptible to intense atmospheric escape due to their large scale heights and strong high-energy irradiation. This process is thought to occur ubiquitously, but to date we have only detected direct evidence of atmospheric escape in hot Jupiters and warm Neptunes. The paucity of cases for intermediate, Saturn-sized exoplanets at varying levels of irradiation precludes a detailed understanding of the underlying physics in atmospheric escape of hot gas giants. Our objectives here are to assess the high-energy environment of the warm ($T_{\mathrm{eq}}=970$ K) Saturn WASP-29 b and search for signatures of atmospheric escape. We used far-ultraviolet (FUV) observations from the Hubble Space Telescope to analyze the flux time series of H I, C II, Si III, Si IV, and N V during the transit of WASP-29 b. At 3$\sigma$ confidence, we rule out any in-transit absorption of H Ilarger than 92% in the Lyman-$\alpha$ blue wing and 19% in the red wing. We found an in-transit flux decrease of $39{\%}_{-11\%}^{+12\%}$ in the ground-state C II emission line at 133.45 nm. But due to this signal being significantly present in only one visit, it is difficult to attribute a planetary or stellar origin for the ground-state C II signal. We place 3$\sigma$ absorption upper limits of 40%, 49% and 24% for Si III, Si IV, and for excited-state C II at 133.57 nm, respectively. Low activity levels and the faint X-ray luminosity suggest that WASP-29 is an old, inactive star. An energy-limited approximation combined with the reconstructed EUV spectrum of the host suggests that the planet is losing its atmosphere at a rate of $4\times 10^9$ g s${}^{-1}$. The non-detection at Lyman-$\alpha$ could be partly explained by a low fraction of escaping neutral hydrogen, or by the state of fast radiative blow-out we infer from the reconstructed stellar Lyman-$\alpha$ line.

arXiv comment10 pages, 8 figures, accepted for publication in Astronomy & Astrophysics. v2 with a few text changes for consistency

References in corpus (68)

• Astropy: A Community Python Package for Astronomy
• emcee: The MCMC Hammer
• Gaia Data Release 2. Summary of the contents and survey properties
• batman: BAsic Transit Model cAlculatioN in Python
• Theoretical Transmission Spectra During Extrasolar Giant Planet Transits
• Detection of oxygen and carbon in the hydrodynamically escaping atmosphere of the extrasolar planet HD209458b
• A giant comet-like cloud of hydrogen escaping the warm Neptune-mass exoplanet GJ 436b
• Biosignatures from Earth-Like Planets Around M Dwarfs
• Estimation of the XUV radiation onto close planets and their evaporation
• Helium in the eroding atmosphere of an exoplanet
• Evaporation of the planet HD189733b observed in HI Lyman-alpha
• The Structure of the Local Interstellar Medium V: Electron Densities
• 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
• The GAPS Programme with HARPS-N@TNG XIV. Investigating giant planet migration history via improved eccentricity and mass determination for 231 transiting planets
• Metals in the Exosphere of the Highly Irradiated Planet WASP-12b
• Observations of Mass Loss from the Transiting Exoplanet HD 209458b
• What is the Total Deuterium Abundance in the Local Galactic Disk?
• Atmospheric Escape and the Evolution of Close-in Exoplanets
• Stellar Lyman-alpha Emission Lines in the Hubble Space Telescope Archive: Intrinsic Line Fluxes and Absorption from the Heliosphere and Astrospheres
• Formation and Structure of Low Density Exo-Neptunes
• Ground-based detection of an extended helium atmosphere in the Saturn-mass exoplanet WASP-69b
• A diagram for the evaporation status of extrasolar planets
• The MUSCLES Treasury Survey II: Intrinsic Lyman Alpha and Extreme Ultraviolet Spectra of K and M Dwarfs with Exoplanets
• Lyman-$\alpha$ Transit Spectroscopy and the Neutral Hydrogen Tail of the Hot Neptune GJ436b
• Temporal variations in the evaporating atmosphere of the exoplanet HD 189733b
• Photoevaporation and High-Eccentricity Migration Created the Sub-Jovian Desert
• 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
• A short-period censor of sub-Jupiter mass exoplanets with low density
• Hubble PanCET: An extended upper atmosphere of neutral hydrogen around the warm Neptune GJ 3470 b
• 3D model of hydrogen atmospheric escape from HD209458b and HD189733b: radiative blow-out and stellar wind interactions
• The HST PanCET Program: Exospheric Mg II and Fe II in the Near-UV transmission spectrum of WASP-121b using Jitter Decorrelation
• Emerging Trends in a Period-Radius Distribution of Close-in Planets
• Simulating the escaping atmospheres of hot gas planets in the solar neighborhood
• An evaporating planet in the wind: stellar wind interactions with the radiatively braked exosphere of GJ436 b
• Atmospheric escape from HD 189733b observed in HI Lyman-alpha: detailed analysis of HST/STIS September 2011 observations
• Energy-limited escape revised
• A Gemini ground-based transmission spectrum of WASP-29b: a featureless spectrum from 515 to 720nm
• New observations of the extended hydrogen exosphere of the extrasolar planet HD209458b
• The long egress of GJ~436b's giant exosphere
• Magnesium in the atmosphere of the planet HD209458b: Observations of the thermosphere-exosphere transition region
• Mass-loss rates for transiting exoplanets
• A remnant planetary core in the hot-Neptune desert
• Hubble Space Telescope detection of oxygen in the atmosphere of exoplanet HD189733b
• Temporal evolution of the high-energy irradiation and water content of TRAPPIST-1 exoplanets
• He I $\lambda$ 10830 Å in the transmission spectrum of HD 209458 b
• Superabundance of Exoplanet Sub-Neptunes Explained by Fugacity Crisis
• Detection of Helium in the Atmosphere of the Exo-Neptune HAT-P-11b
• On the origin of the sub-Jovian desert in the orbital-period--planetary-mass plane
• Mass-Loss Evolution of Close-In Exoplanets: Evaporation of Hot Jupiters and the Effect on Population
• Confirmation of WASP-107b's extended Helium atmosphere with Keck II/NIRSPEC
• The deuterium-to-oxygen ratio in the interstellar medium
• WASP-29b: A Saturn-sized transiting exoplanet
• Stellar wind effects on the atmospheres of close-in giants: a possible reduction in escape instead of increased erosion
• The sub-Neptune desert and its dependence on stellar type: Controlled by lifetime X-ray irradiation
• Rapid escape of ultra-hot exoplanet atmospheres driven by Hydrogen Balmer absorption
• An Overabundance of Low-density Neptune-like Planets
• No hydrogen exosphere detected around the super-Earth HD97658 b
• Evolution of atmospheric escape in close-in giant planets and their associated Ly$\alpha$ and H$\alpha$ transit predictions
• A Heavy Molecular Weight Atmosphere for the Super-Earth π Men c
• The Hubble PanCET program: An extensive search for metallic ions in the exosphere of GJ 436 b
• Ultraviolet C II and Si III Transit Spectroscopy and Modeling of the Evaporating Atmosphere of GJ436b
• The high-energy environment and atmospheric escape of the mini-Neptune K2-18 b
• Strong HI Lyman-$\alpha$ variations from the 11 Gyr-old host star Kepler-444: a planetary origin ?
• Search for helium in the upper atmosphere of the hot Jupiter WASP-127 b using Gemini/Phoenix
• First Detection of Hydrogen in the β Pictoris Gas Disk
• A possible correlation between planetary radius and orbital period for small planets

Cited by in corpus (7)

• p-winds: an open-source Python code to model planetary outflows and upper atmospheres
• Detection of Ongoing Mass Loss from HD 63433c, a Young Mini Neptune
• Planetary parameters, XUV environments and mass-loss rates for nearby gaseous planets with X-ray detected host-stars
• Sub-Jovian desert of exoplanets at its boundaries. Parameter dependence along the main sequence
• A Population Analysis of 20 Exoplanets Observed from the Optical to the Near-infrared Wavelengths with HST: Evidence for Widespread Stellar Contamination
• Converting the sub-Jovian desert of exoplanets to a savanna with TESS, PLATO and Ariel
• The Hubble PanCET Program: A Featureless Transmission Spectrum for WASP-29b and Evidence of Enhanced Atmospheric Metallicity on WASP-80b