Abstract
We present Hubble Space Telescope near-infrared transit photometry of the nearby hot-Jupiter HD 189733b. The observations were taken with the NICMOS instrument during five transits, with three transits executed with a narrowband filter at 1.87 μm and two performed with a narrowband filter at 1.66 μm. Our observing strategy using narrowband filters is insensitive to the usual HST intra-orbit and orbit-to-orbit measurement of systematic errors, allowing us to accurately and robustly measure the near-IR wavelength dependance of the planetary radius. Our measurements fail to reproduce the previously claimed detection of an absorption signature of atmospheric H2O below 2 μm at a 5σ confidence level. We measure a planet-to-star radius contrast of 0.15498±0.00035 at 1.66 μm and a contrast of 0.15517 ± 0.00019 at 1.87 μm. Both of our near-IR planetary radii values are in excellent agreement with the levels expected from Rayleigh scattering by sub-micron haze particles, observed at optical wavelengths, indicating that upper-atmospheric haze still dominates the near-IR transmission spectra over the absorption from gaseous molecular species at least below 2 μm.
Original language | English (US) |
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Pages (from-to) | 891-899 |
Number of pages | 9 |
Journal | Astronomy and astrophysics |
Volume | 505 |
Issue number | 2 |
DOIs | |
State | Published - Oct 2 2009 |
Keywords
- Binaries: eclipsing
- Planetary systems
- Stars: individual: HD 189733
- Techniques: photometric
ASJC Scopus subject areas
- Astronomy and Astrophysics
- Space and Planetary Science