Detection of Helium in the Atmosphere of the Exo-Neptune HAT-P-11b

Megan Mansfield, Jacob L. Bean, Antonija Oklopčić, Laura Kreidberg, Jean Michel Désert, Eliza M.R. Kempton, Michael Line, Jonathan J. Fortney, Gregory W. Henry, Matthias Mallonn, Kevin B. Stevenson, Diana Dragomir, Romain Allart, Vincent Bourrier

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

The helium absorption triplet at a wavelength of 10833 a has been proposed as a way to probe the escaping atmospheres of exoplanets. Recently this feature was detected for the first time using Hubble Space Telescope (HST) WFC3 observations of the hot Jupiter WASP-107b. We use similar HST/WFC3 observations to detect helium in the atmosphere of the hot Neptune HAT-P-11b at the 4σ confidence level. We compare our observations to a grid of 1D models of hydrodynamic escape to constrain the thermospheric temperatures and mass loss rate. We find that our data are best fit by models with high mass loss rates of g s-1. Although we do not detect the planetary wind directly, our data are consistent with the prediction that HAT-P-11b is experiencing hydrodynamic atmospheric escape. Nevertheless, the mass loss rate is low enough that the planet has only lost up to a few percent of its mass over its history, leaving its bulk composition largely unaffected. This matches the expectation from population statistics, which indicate that close-in planets with radii greater than 2 R form and retain H/He-dominated atmospheres. We also confirm the independent detection of helium in HAT-P-11b obtained with the CARMENES instrument, making this the first exoplanet with the detection of the same signature of photoevaporation from both ground- and space-based facilities.

Original languageEnglish (US)
Article numberL34
JournalAstrophysical Journal Letters
Volume868
Issue number2
DOIs
StatePublished - Dec 1 2018
Externally publishedYes

Fingerprint

Neptune (planet)
Neptune
helium
atmospheres
atmosphere
extrasolar planets
Hubble Space Telescope
escape
planets
planet
hydrodynamics
Jupiter (planet)
Jupiter
confidence
grids
probe
signatures
statistics
histories
wavelength

Keywords

  • planets and satellites: atmospheres
  • planets and satellites: individual (HAT-P-11b)

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Mansfield, M., Bean, J. L., Oklopčić, A., Kreidberg, L., Désert, J. M., Kempton, E. M. R., ... Bourrier, V. (2018). Detection of Helium in the Atmosphere of the Exo-Neptune HAT-P-11b. Astrophysical Journal Letters, 868(2), [L34]. https://doi.org/10.3847/2041-8213/aaf166

Detection of Helium in the Atmosphere of the Exo-Neptune HAT-P-11b. / Mansfield, Megan; Bean, Jacob L.; Oklopčić, Antonija; Kreidberg, Laura; Désert, Jean Michel; Kempton, Eliza M.R.; Line, Michael; Fortney, Jonathan J.; Henry, Gregory W.; Mallonn, Matthias; Stevenson, Kevin B.; Dragomir, Diana; Allart, Romain; Bourrier, Vincent.

In: Astrophysical Journal Letters, Vol. 868, No. 2, L34, 01.12.2018.

Research output: Contribution to journalArticle

Mansfield, M, Bean, JL, Oklopčić, A, Kreidberg, L, Désert, JM, Kempton, EMR, Line, M, Fortney, JJ, Henry, GW, Mallonn, M, Stevenson, KB, Dragomir, D, Allart, R & Bourrier, V 2018, 'Detection of Helium in the Atmosphere of the Exo-Neptune HAT-P-11b', Astrophysical Journal Letters, vol. 868, no. 2, L34. https://doi.org/10.3847/2041-8213/aaf166
Mansfield M, Bean JL, Oklopčić A, Kreidberg L, Désert JM, Kempton EMR et al. Detection of Helium in the Atmosphere of the Exo-Neptune HAT-P-11b. Astrophysical Journal Letters. 2018 Dec 1;868(2). L34. https://doi.org/10.3847/2041-8213/aaf166
Mansfield, Megan ; Bean, Jacob L. ; Oklopčić, Antonija ; Kreidberg, Laura ; Désert, Jean Michel ; Kempton, Eliza M.R. ; Line, Michael ; Fortney, Jonathan J. ; Henry, Gregory W. ; Mallonn, Matthias ; Stevenson, Kevin B. ; Dragomir, Diana ; Allart, Romain ; Bourrier, Vincent. / Detection of Helium in the Atmosphere of the Exo-Neptune HAT-P-11b. In: Astrophysical Journal Letters. 2018 ; Vol. 868, No. 2.
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