NEAR-INFRARED TRANSIT PHOTOMETRY OF THE EXOPLANET HD 149026b
- 14 April 2009
- journal article
- Published by American Astronomical Society in The Astrophysical Journal
- Vol. 696 (1), 241-253
- https://doi.org/10.1088/0004-637x/696/1/241
Abstract
The transiting exoplanet HD 149026b is an important case for theories of planet formation and planetary structure, for the planet's relatively small size has been interpreted as evidence for a highly metal-enriched composition. We present observations of four transits with the Near-Infrared Camera and Multi-Object Spectrometer (NICMOS) on the Hubble Space Telescope within a wavelength range of 1.1-2.0 μm. Analysis of the light curve gives the most precise estimate yet of the stellar mean density, ρ = 0.497+0.042 –0.057 g cm–3. By requiring agreement between the observed stellar properties (including ρ) and stellar evolutionary models, we refine the estimate of the stellar radius: R = 1.541+0.046 –0.042 R ☉. We also find a deeper transit than has been measured at optical and mid-infrared wavelengths. Taken together, these findings imply a planetary radius of Rp = 0.813+0.027 –0.025 R Jup, which is larger than earlier estimates. Models of the planetary interior still require a metal-enriched composition, although the required degree of metal enrichment is reduced. It is also possible that the deeper NICMOS transit is caused by wavelength-dependent absorption by constituents in the planet's atmosphere, although simple model atmospheres do not predict this effect to be strong enough to account for the discrepancy. We use the four newly measured transit times to compute a refined transit ephemeris.This publication has 44 references indexed in Scilit:
- Analytic Approximations for Transit Light‐Curve Observables, Uncertainties, and CovariancesThe Astrophysical Journal, 2008
- XO‐2b: Transiting Hot Jupiter in a Metal‐rich Common Proper Motion BinaryThe Astrophysical Journal, 2007
- Possible Solutions to the Radius Anomalies of Transiting Giant PlanetsThe Astrophysical Journal, 2007
- New grids of stellar models including tidal-evolution constants up to carbon burningAstronomy & Astrophysics, 2007
- The formation of HD 149026 bMonthly Notices of the Royal Astronomical Society: Letters, 2007
- Transit Photometry of the Core‐dominated Planet HD 149026bThe Astrophysical Journal, 2006
- On detecting terrestrial planets with timing of giant planet transitsMonthly Notices of the Royal Astronomical Society, 2005
- Detection of an Extrasolar Planet AtmosphereThe Astrophysical Journal, 2002
- Transmission Spectra as Diagnostics of Extrasolar Giant Planet AtmospheresThe Astrophysical Journal, 2001
- Non-Gaussian likelihood function and COBE dataMonthly Notices of the Royal Astronomical Society, 1996