Temporal variations in the evaporating atmosphere of the exoplanet HD 189733b

By A. D. Étangs, V. Bourrier, P. Wheatley, H. Dupuy, David Ehrenreich, A. Vidal-Madjar, G. H'ebrard, Gilda E. Ballester, J. D'esert, R. Ferlet and 1 more. 2012

206 citations recorded by the source corpus.

Atmospheric escape has been detected from the exoplanet HD 209458b through transit observations of the hydrogen Lyman-α line. Here we present spectrally resolved Lyman-α transit observations of the exoplanet HD 189733b at two different epochs. These HST/STIS observations show for the first time that there are significant temporal variations in the physical conditions of an evaporating planetary atmosphere. While atmospheric hydrogen is not detected in the first epoch observations, it is observed at the second epoch, producing a transit absorption depth of 14.4 ± 3.6% between velocities of −230 to −140 km s −1 . Contrary to HD 209458b, these high velocities cannot arise from radiation pressure alone and require an additional acceleration mechanism, such as interactions with stellar wind protons. The observed absorption can be explained by an atmospheric escape rate of neutral hydrogen atoms of about 10 9 gs −1 , a stellar wind with a velocity of 190 km s −1 and a temperature of ∼10 5 K. An X-ray flare from the active star seen with Swift/XRT 8 h before the second-epoch observation supports the idea that the observed changes within the upper atmosphere of the planet can be caused by variations in the stellar wind properties, or by variations in the stellar energy input to the planetary escaping gas (or a mix of the two effects). These observations provide the first indication of interaction between the exoplanet’s atmosphere and stellar variations.

Subfields: Astronomy and Astrophysics, Education, Instrumentation

View Paper: https://www.semanticscholar.org/paper/c3c4b6cee0f417a15da619c99f9dd5a8238747b3

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Citations in the corpus

THE ULTRAVIOLET RADIATION ENVIRONMENT AROUND M DWARF EXOPLANET HOST STARS (2012, methodology): “…disk can be sustained for mass-loss rates Ṁloss & 6 × 10 10 g s−1, well within the range of mass-loss estimates of short-period planets around G, K, andM-type stars (Vidal-Madjar et al. 2008; Linsky et al. 2010; Lecavelier des Etangs et al. 2012; Ehrenreich et al. 2011; Ehrenreich & Désert 2011).”
Extremely Irradiated Hot Jupiters: Non-oxide Inversions, H− Opacity, and Thermal Dissociation of Molecules (2018, background): “The Upper Atmosphere and Atmospheric Escape on Hot Jupiters Atmospheric escape has been observed on a handful of hot Jupiters to date, namely HD209458b, HD189733b, and WASP-12b (Vidal-Madjar et al. 2003; Lecavelier des Etangs et al. 2010, 2012; Fossati et al. 2010).”
The Hubble Space Telescope PanCET Program: Exospheric Mg ii and Fe ii in the Near-ultraviolet Transmission Spectrum of WASP-121b Using Jitter Decorrelation (2019, background): “Detections of H i and O i have also been made in HD 189733b (Lecavelier Des Etangs et al. 2010; Lecavelier des Etangs et al. 2012; Ben-Jaffel & Ballester 2013).”
A FRAMEWORK FOR CHARACTERIZING THE ATMOSPHERES OF LOW-MASS LOW-DENSITY TRANSITING PLANETS (2013, background): “Most prominent are the observations that hot Jupiters lose atmospheric mass (Vidal-Madjar et al. 2003; Linsky et al. 2010; Lecavelier Des Etangs et al. 2010; Lecavelier des Etangs et al. 2012), as has been observed in the UV with the HST.”
HOW THERMAL EVOLUTION AND MASS-LOSS SCULPT POPULATIONS OF SUPER-EARTHS AND SUB-NEPTUNES: APPLICATION TO THE KEPLER-11 SYSTEM AND BEYOND (2012, methodology): “One possible solution to the composition problem is to obtain multi-wavelength transmission spectra, as has been done for GJ 1214b (Bean et al. 2011; Désert et al. 2011; Croll et al. 2011).”
LYα TRANSIT SPECTROSCOPY AND THE NEUTRAL HYDROGEN TAIL OF THE HOT NEPTUNE GJ 436b (2014, methodology): “Models by Lecavelier des Etangs et al. (2012) suggest that stellar radiation pressure can accelerate particles up to 120 km s−1, but an additional mechanism is necessary to explain the large observed radial velocities.”