TY - JOUR
T1 - Atmospheric escape from HD 189733b observed in H i Lyman-α
T2 - Detailed analysis of HST/STIS September 2011 observations
AU - Bourrier, V.
AU - Lecavelier Des Etangs, A.
AU - Dupuy, H.
AU - Ehrenreich, D.
AU - Vidal-Madjar, A.
AU - Hébrard, G.
AU - Ballester, G. E.
AU - Désert, J. M.
AU - Ferlet, R.
AU - Sing, D. K.
AU - Wheatley, P. J.
N1 - Funding Information:
Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. We thank the referee for its clarifying comments. D.E. acknowledges the funding from the European Commission’s Seventh Framework Programme as a Marie Curie Intra-European Fellow (PIEF-GA-2011-298916). G.E.B. acknowledges financial support by this program through STScI grant HST-GO-11673.01-A to the University of Arizona. These observations are associated with program #11673. The authors acknowledge financial support from the Centre National d’Études Spatiales (CNES). This work has also been supported by an award from the Fondation Simone et Cino Del Duca.
PY - 2013
Y1 - 2013
N2 - Observations of transits of the hot giant exoplanet HD 189733b in the unresolved H i Lyman-α line show signs of hydrogen escaping the upper atmosphere of the planet. New resolved Lyman-α observations obtained with the STIS spectrograph onboard the Hubble Space Telescope in April 2010 and September 2011 confirmed that the planet is evaporating, and furthermore discovered significant temporal variations in the physical conditions of its evaporating atmosphere. Here we present a detailed analysis of the September 2011 observations of HD 189733b, when an atmospheric signature was detected. We present specific methods to find and characterize this absorption signature of escaping hydrogen in the Lyman-α line, and to calculate its false-positive probability, found to be 3.6%. Taking advantage of the spectral resolution and high sensitivity of the STIS spectrograph, we also present new results on temporal and spectro-temporal variability of this absorption feature. We also report the observation of HD 189733b in other lines (Si iii at 1206.5 Å, N v at 1240 Å). Variations in these lines could be explained either by early occultation by a bow-shock rich in highly ionized species, or by stellar variations.
AB - Observations of transits of the hot giant exoplanet HD 189733b in the unresolved H i Lyman-α line show signs of hydrogen escaping the upper atmosphere of the planet. New resolved Lyman-α observations obtained with the STIS spectrograph onboard the Hubble Space Telescope in April 2010 and September 2011 confirmed that the planet is evaporating, and furthermore discovered significant temporal variations in the physical conditions of its evaporating atmosphere. Here we present a detailed analysis of the September 2011 observations of HD 189733b, when an atmospheric signature was detected. We present specific methods to find and characterize this absorption signature of escaping hydrogen in the Lyman-α line, and to calculate its false-positive probability, found to be 3.6%. Taking advantage of the spectral resolution and high sensitivity of the STIS spectrograph, we also present new results on temporal and spectro-temporal variability of this absorption feature. We also report the observation of HD 189733b in other lines (Si iii at 1206.5 Å, N v at 1240 Å). Variations in these lines could be explained either by early occultation by a bow-shock rich in highly ionized species, or by stellar variations.
KW - Planets and satellites: atmospheres
KW - Stars: individual: HD 189733
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U2 - 10.1051/0004-6361/201220533
DO - 10.1051/0004-6361/201220533
M3 - Article
AN - SCOPUS:84874255498
SN - 0004-6361
VL - 551
JO - Astronomy and astrophysics
JF - Astronomy and astrophysics
M1 - A63
ER -