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

被引：191

作者：

des Etangs, A. Lecavelier ^{[1
,2
]}

Bourrier, V. ^{[1
,2
]}

Wheatley, P. J. ^{[3
]}

Dupuy, H. ^{[1
,2
]}

Ehrenreich, D. ^{[4
]}

Vidal-Madjar, A. ^{[1
,2
]}

Hebrard, G. ^{[1
,2
]}

Ballester, G. E. ^{[5
]}

Desert, J. -M. ^{[6
]}

Ferlet, R. ^{[1
,2
]}

Sing, D. K. ^{[7
]}

机构：

[1] CNRS, UMR 7095, Inst Astrophys Paris, F-75014 Paris, France

[2] Univ Paris 06, UMR 7095, Inst Astrophys Paris, F-75014 Paris, France

[3] Univ Warwick, Dept Phys, Coventry CV4 7AL, W Midlands, England

[4] UJF Grenoble 1, CNRS, INSU, IPAG,UMR 5274, Grenoble, France

[5] Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA

[6] Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA

[7] Univ Exeter, Astrophys Grp, Sch Phys, Exeter EX4 4QL, Devon, England

来源：

ASTRONOMY & ASTROPHYSICS | 2012年 / 543卷

关键词：

planetary systems; stars: individual: HD 189733; techniques: spectroscopic; planets and satellites: atmospheres; stars: flare; ENERGETIC NEUTRAL ATOMS; X-RAY; MASS-LOSS; HYDROGEN; PLANETS; ULTRAVIOLET; EXOSPHERE; AERONOMY; TRANSIT; ESCAPE;

D O I：

10.1051/0004-6361/201219363

中图分类号：

P1 [天文学];

学科分类号：

0704 ;

摘要：

Atmospheric escape has been detected from the exoplanet HD 209458b through transit observations of the hydrogen Lyman-alpha line. Here we present spectrally resolved Lyman-alpha 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) g s(-1), a stellar wind with a velocity of 190 kms(-1) and a temperature of similar to 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.

引用

页数：4

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