More Evidence for Variable Helium Absorption from HD 189733b

Abstract

We present a new Keck/NIRSPEC observation of metastable helium absorption from the upper atmosphere of HD 189733b, a hot Jupiter orbiting a nearby moderately active star. We measure an average helium transit depth of $0.420\pm 0.013$% integrated over the [-20, 20] km/s velocity range. Comparing this measurement to eight previously published transit observations with different instruments, we find that our depth is 32% (9$\sigma$) lower than the average of the three CARMENES transits, but only 16% (4.4$\sigma$) lower than the average of the five GIANO transits. We perform 1D hydrodynamical simulations of the outflow, and find that XUV variability on the order of 33%--common for this star--can change the helium absorption depth by 60%. We conclude that changes in stellar XUV flux can explain the observational variability in helium absorption. 3D models are necessary to explore other sources of variability, such as shear instability and changing stellar wind conditions.

Published by AJ

References in corpus (18)

• The NumPy array: a structure for efficient numerical computation
• PLUTO: a Numerical Code for Computational Astrophysics
• Water Vapor in the Spectrum of the Extrasolar Planet HD 189733b: 1. the Transit
• High-resolution confirmation of an extended helium atmosphere around WASP-107b
• The GAPS programme at TNG XXII. The GIARPS view of the extended helium atmosphere of HD189733 b accounting for stellar activity
• Detection of Ongoing Mass Loss from HD 63433c, a Young Mini Neptune
• Irradiation-driven escape of primordial planetary atmospheres II. Evaporation efficiency of sub-Neptunes through hot Jupiters
• Escaping Helium from TOI 560.01, a Young Mini Neptune
• High-energy irradiation and mass loss rates of hot Jupiters in the solar neighborhood
• Stellar Wind Confinement of Evaporating Exoplanet Atmospheres and its Signatures in 1083 nm Observations
• No escaping helium from 55 Cnc e
• TPCI: The PLUTO-CLOUDY Interface
• Modelling the He I triplet absorption at 10830 Angstroms in the atmospheres of HD 189733 b and GJ 3470 b
• MOVES III. Simultaneous X-ray and ultraviolet observations unveiling the variable environment of the hot Jupiter HD 189733b
• Evidence of energy-, recombination-, and photon-limited escape regimes in giant planet H/He atmospheres
• Helium absorption in exoplanet atmospheres is connected to stellar coronal abundances
• X-ray variability of HD 189733 across eight years of XMM-Newton observations
• The California Legacy Survey I. A Catalog of 178 Planets from Precision Radial Velocity Monitoring of 719 Nearby Stars over Three Decades

Cited by in corpus (15)

• Detection of Atmospheric Escape from Four Young Mini Neptunes
• Homogeneous search for helium in the atmosphere of 11 gas giant exoplanets with SPIRou
• The MOPYS project: A survey of 70 planets in search of extended He I and H atmospheres. No evidence of enhanced evaporation in young planets
• Probing atmospheric escape through metastable He I triplet lines in 15 exoplanets observed with SPIRou
• Planetary parameters, XUV environments and mass-loss rates for nearby gaseous planets with X-ray detected host-stars
• Hydrodynamic atmospheric escape in HD 189733 b: Signatures of carbon and hydrogen measured with the Hubble Space Telescope
• The Cosmic Shoreline Revisited: A Metric for Atmospheric Retention Informed by Hydrodynamic Escape
• Non-detection of Helium in the Hot Jupiter WASP-48b
• The Hubble/STIS Near-ultraviolet Transmission Spectrum of HD 189733b
• NIGHT: a compact, near-infrared, high-resolution spectrograph to survey helium in exoplanet systems
• Atmospheric Mass Loss from TOI-1259 A b, a Gas Giant Planet With a White Dwarf Companion
• Helium escaping from the atmosphere of a nearby rocky exoplanet orbiting in a habitable zone
• Detectability of Emission from Exoplanet Outflows Calculated by pyTPCI, a New 1D Radiation-Hydrodynamic Code
• 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