Abstract
We present optical to near-infrared transmission spectra of HAT-P-1b and
WASP-6b, part of a Large HST/STIS hot Jupiter transmission spectral
survey (P.I. David Sing). The spectra for each target cover the regimes
2900-5700Å and 5240-10270Å, with resolving power of R = 500.
The HAT-P-1b data is coupled with a recent HST/WFC3 transit, spanning
the wavelength range 1.087-1.687microns (R=130), acquired in spatial
scan mode. The WASP-6b data is complemented with Spritzer/IRAC 3.6 and
4.5 micron transit observations, part of a comparative exoplanetology
program (P.I. Jean-Michel Desert). The transmission spectrum of HAT-P-1b
shows a strong absorption signature shortward of 5500Å, with a
strong blueward slope into the near-UV. We detect atmospheric sodium
absorption at a 3.3s significance level, but see no evidence for the
potassium feature. The red data implies a marginally flat spectrum with
a tentative absorption enhancement at wavelength longer than
~8500Å. The combined STIS and WFC3 optical to NIR spectra differ
significantly in absolute radius level (4.3+/-1.6 pressure scale
heights), implying strong optical absorption in the atmosphere of
HAT-P-1b. The optical to nearinfrared difference cannot be explained by
stellar activity, as simultaneous stellar activity monitoring of the G0V
HAT-P-1b host star and its identical companion show no significant
activity that could explain the result. The red transmission spectrum of
WASP-6b is flat with tentative detection of sodium and potassium. We
compare both spectra with theoretical atmospheric models, which include
haze, sodium and an extra optical absorber in the case of HAT-P-1b. We
find that both an optical absorber and a super-solar sodium to water
abundance ratio might be a scenario explaining the HAT-P-1b
observations.
Original language | English |
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Title of host publication | Search for Life Beyond the Solar System. Exoplanets, Biosignatures amp Instruments |
Editors | D. Apai, P. Gabor |
Pages | P3.50 |
Publication status | Published - 01 Mar 2014 |