Hot Jupiter HAT-P-1b has a Partially Transparent Atmosphere

Further constraints on the optical transmission spectrum of HAT-P-1b

Authors:

Montalto et al

Abstract:

We report on novel observations of HAT-P-1 aimed at constraining the optical transmission spectrum of the atmosphere of its transiting Hot-Jupiter exoplanet. Ground-based differential spectrophotometry was performed over two transit windows using the DOLORES spectrograph at the Telescopio Nazionale Galileo (TNG). Our measurements imply an average planet to star radius ratio equal to Rp/R⋆=(0.1159±0.0005). This result is consistent with the value obtained from recent near infrared measurements of this object but differs from previously reported optical measurements being lower by around 4.4 exoplanet scale heights. Analyzing the data over 5 different spectral bins 600\AA wide we observed a single peaked spectrum (3.7 σ level) with a blue cut-off corresponding to the blue edge of the broad absorption wing of sodium and an increased absorption in the region in between 6180-7400\AA. We also infer that the width of the broad absorption wings due to alkali metals is likely narrower than the one implied by solar abundance clear atmospheric models. We interpret the result as evidence that HAT-P-1b has a partially clear atmosphere at optical wavelengths with a more modest contribution from an optical absorber than previously reported.

Potassium Detected in hot Jupiter HAT-P-1b's Atmosphere

GTC OSIRIS transiting exoplanet atmospheric survey: detection of potassium in HAT-P-1b from narrowband spectrophotometry

Authors:

Wilson et al

Abstract:

We present the detection of potassium in the atmosphere of HAT-P-1b using optical transit narrowband photometry. The results are obtained using the 10.4 m Gran Telescopio Canarias (GTC) together with the OSIRIS instrument in tunable filter imaging mode. We observed four transits, two at continuum wavelengths outside the potassium feature, at 6792 {\AA} and 8844 {\AA}, and two probing the potassium feature in the line wing at 7582.0 {\AA} and the line core at 7664.9 {\AA} using a 12 {\AA} filter width (R~650). The planet-to-star radius ratios in the continuum are found to be Rpl/R⋆ = 0.1176 ± 0.0013 at 6792 {\AA} and Rpl/R⋆ = 0.1168 ± 0.0022 at 8844 {\AA}, significantly lower than the two observations in the potassium line: Rpl/R⋆ = 0.1248 ± 0.0014 in the line wing at 7582.0 {\AA} and Rpl/R⋆ = 0.1268 ± 0.0012 in the line core at 7664.9 {\AA}. With a weighted mean of the observations outside the potassium feature Rpl/R⋆ = 0.1174 ± 0.0010, the potassium is detected as an increase in the radius ratio of {\Delta}Rpl/R⋆ = 0.0073 ± 0.0017 at 7582.0 {\AA} and {\Delta}Rpl/R⋆ = 0.0094 ± 0.0016 at 7664.9 {\AA} (a significance of 4.3 and 6.1 σ respectively). We hypothesise that the strong detection of potassium is caused by a large scale height, which can be explained by a high-temperature at the base of the upper atmosphere. A lower mean molecular mass caused by the dissociation of molecular hydrogen into atomic hydrogen by the EUV flux from the host star may also partly explain the amplitude of our detection.

HAT-P-1b: A Case Study for the Constraint of Terrestrial Worlds in Hot Jupiter Systems

A high precision chemical abundance analysis of the HAT-P-1 stellar binary: constraints on planet formation

Authors:

Liu et al

Abstract:

We present a high-precision, differential elemental abundance analysis of the HAT-P-1 stellar binary based on high-resolution, high signal-to-noise ratio Keck/HIRES spectra. The secondary star in this double system is known to host a transiting giant planet while no planets have yet been detected around the primary star. The derived metallicities ([Fe/H]) of the primary and secondary stars are identical within the errors: 0.146±0.014 dex (σ = 0.033 dex) and 0.155±0.007 dex (σ = 0.023 dex), respectively. Extremely precise differential abundance ratios of 23 elements have been measured (mean error of σ([X/Fe]) = 0.013 dex) and are found to be indistinguishable between the two stars: Δ[X/Fe] (secondary - primary) = +0.001±0.006 dex (σ = 0.008 dex). The striking similarity in the chemical composition of the two stellar components in HAT-P-1 is contrary to the possible 0.04 dex level difference seen in 16 Cyg A+B, which also hosts a giant planet, at least 3 times more massive than the one around HAT-P-1 secondary star. We conclude that the presence of giant planets does not necessarily imply differences in the chemical compositions of the host stars. The elemental abundances of each star in HAT-P-1 relative to the Sun show an identical, positive correlation with the condensation temperature of the elements; their abundance patterns are thus very similar to those observed in the majority of solar twins. In view of the Melendez et al. (2009)'s interpretation of the peculiar solar abundance pattern, we conclude that HAT-P-1 experienced less efficient formation of terrestrial planets than the Sun. This is in line with the expectation that the presence of close-in giant planets preventing the formation or survival of terrestrial planets.