Methane in the atmosphere of the transiting hot Neptune GJ436B?

J. P. Beaulieu, G. Tinetti, D. M. Kipping, I. Ribas, R. J. Barber, J. Y K Cho, I. Polichtchouk, J. Tennyson, S. N. Yurchenko, Caitlin Griffith, V. Batista, I. Waldmann, S. Miller, S. Carey, O. Mousis, S. J. Fossey, A. Aylward

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Abstract

We present an analysis of seven primary transit observations of the hot Neptune GJ436b at 3.6, 4.5, and 8 μm obtained with the Infrared Array Camera on the Spitzer Space Telescope. After correcting for systematic effects, we fitted the light curves using the Markov Chain Monte Carlo technique. Combining these new data with the EPOXI, Hubble Space Telescope, and ground-based V, I, H, and Ks published observations, the range 0.5-10 μm can be covered. Due to the low level of activity of GJ436, the effect of starspots on the combination of transits at different epochs is negligible at the accuracy of the data set. Representative climate models were calculated by using a three-dimensional, pseudospectral general circulation model with idealized thermal forcing. Simulated transit spectra of GJ436b were generated using line-by-line radiative transfer models including the opacities of the molecular species expected to be present in such a planetary atmosphere. A new, ab-initio-calculated, line list for hot ammonia has been used for the first time. The photometric data observed at multiple wavelengths can be interpreted with methane being the dominant absorption after molecular hydrogen, possibly with minor contributions from ammonia, water, and other molecules. No clear evidence of carbon monoxide and carbon dioxide is found from transit photometry. We discuss this result in the light of a recent paper where photochemical disequilibrium is hypothesized to interpret secondary transit photometric data. We show that the emission photometric data are not incompatible with the presence of abundant methane, but further spectroscopic data are desirable to confirm this scenario.

Original languageEnglish (US)
Article number16
JournalAstrophysical Journal
Volume731
Issue number1
DOIs
StatePublished - Apr 10 2011

Fingerprint

Neptune (planet)
Neptune
transit
methane
atmospheres
atmosphere
ammonia
planetary atmosphere
starspots
Markov chain
molecular absorption
planetary atmospheres
carbon monoxide
Space Infrared Telescope Facility
disequilibrium
climate models
Markov chains
radiative transfer
general circulation model
climate modeling

Keywords

  • planetary systems
  • techniques: spectroscopic

ASJC Scopus subject areas

  • Space and Planetary Science
  • Astronomy and Astrophysics

Cite this

Beaulieu, J. P., Tinetti, G., Kipping, D. M., Ribas, I., Barber, R. J., Cho, J. Y. K., ... Aylward, A. (2011). Methane in the atmosphere of the transiting hot Neptune GJ436B? Astrophysical Journal, 731(1), [16]. https://doi.org/10.1088/0004-637X/731/1/16

Methane in the atmosphere of the transiting hot Neptune GJ436B? / Beaulieu, J. P.; Tinetti, G.; Kipping, D. M.; Ribas, I.; Barber, R. J.; Cho, J. Y K; Polichtchouk, I.; Tennyson, J.; Yurchenko, S. N.; Griffith, Caitlin; Batista, V.; Waldmann, I.; Miller, S.; Carey, S.; Mousis, O.; Fossey, S. J.; Aylward, A.

In: Astrophysical Journal, Vol. 731, No. 1, 16, 10.04.2011.

Research output: Contribution to journalArticle

Beaulieu, JP, Tinetti, G, Kipping, DM, Ribas, I, Barber, RJ, Cho, JYK, Polichtchouk, I, Tennyson, J, Yurchenko, SN, Griffith, C, Batista, V, Waldmann, I, Miller, S, Carey, S, Mousis, O, Fossey, SJ & Aylward, A 2011, 'Methane in the atmosphere of the transiting hot Neptune GJ436B?', Astrophysical Journal, vol. 731, no. 1, 16. https://doi.org/10.1088/0004-637X/731/1/16
Beaulieu JP, Tinetti G, Kipping DM, Ribas I, Barber RJ, Cho JYK et al. Methane in the atmosphere of the transiting hot Neptune GJ436B? Astrophysical Journal. 2011 Apr 10;731(1). 16. https://doi.org/10.1088/0004-637X/731/1/16
Beaulieu, J. P. ; Tinetti, G. ; Kipping, D. M. ; Ribas, I. ; Barber, R. J. ; Cho, J. Y K ; Polichtchouk, I. ; Tennyson, J. ; Yurchenko, S. N. ; Griffith, Caitlin ; Batista, V. ; Waldmann, I. ; Miller, S. ; Carey, S. ; Mousis, O. ; Fossey, S. J. ; Aylward, A. / Methane in the atmosphere of the transiting hot Neptune GJ436B?. In: Astrophysical Journal. 2011 ; Vol. 731, No. 1.
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AU - Griffith, Caitlin

AU - Batista, V.

AU - Waldmann, I.

AU - Miller, S.

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