The ground-based H-, K-, and L-band absolute emission spectra of HD 209458b

Robert T. Zellem, Caitlin A. Griffith, Pieter Deroo, Mark R. Swain, Ingo P. Waldmann

Research output: Contribution to journalArticlepeer-review

17 Scopus citations


Here we explore the capabilities of NASA's 3.0 m Infrared Telescope Facility (IRTF) and SpeX spectrometer and the 5.08 m Hale telescope with the TripleSpec spectrometer with near-infrared H-, K-, and L-band measurements of HD 209458b's secondary eclipse. Our IRTF/SpeX data are the first absolute L-band spectroscopic emission measurements of any exoplanet other than the hot Jupiter HD 189733b. Previous measurements of HD 189733b's L band indicate bright emission hypothesized to result from non-LTE CH4 ν3 fluorescence. We do not detect a similar bright 3.3 μm feature to ∼3σ, suggesting that fluorescence does not need to be invoked to explain HD 209458b's L-band measurements. The validity of our observation and reduction techniques, which decrease the flux variance by up to 2.8 orders of magnitude, is reinforced by 1σ agreement with existent Hubble/NICMOS and Spitzer/IRAC1 observations that overlap the H, K, and L bands, suggesting that both IRTF/SpeX and Palomar/TripleSpec can measure an exoplanet's emission with high precision.

Original languageEnglish (US)
Article number48
JournalAstrophysical Journal
Issue number1
StatePublished - Nov 20 2014


  • Atmospheric effects
  • Methods: numerical
  • Planets and satellites: general
  • Planets and satellites: individual (HD 209458b)
  • Techniques: spectroscopic

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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