Possible detection of a bimodal cloud distribution in the atmosphere of HAT-P-32Ab

Possible detection of a bimodal cloud distribution in the atmosphere of HAT-P-32Ab from multi-band photometry

Authors:

Tregloan-Reed et al

Abstract:
We present high-precision photometry of eight separate transit events in the HAT-P-32 planetary system. One transit event was observed simultaneously by two telescopes of which one obtained a simultaneous multi-band light curve in three optical bands, giving a total of 11 transit light curves. Due to the filter selection and in conjunction with using the defocussed photometry technique we were able to obtain an extremely high precision, ground-based transit in the \textit{u}-band (350\,nm), with an rms scatter of ≈1\,mmag. All 11 transits were modelled using \textsc{prism} and \textsc{gemc}, and the physical properties of the system calculated. We find the mass and radius of the host star to be $1.182\pm 0.041\Msun$ and $1.225\pm0.015\Rsun$, respectively. For the planet we find a mass of $0.80\pm 0.14\Mjup$, a radius of $1.807\pm0.022\Rjup$ and a density of $0.126\pm0.023\pjup$. These values are consistent with those found in the literature. We also obtain a new orbital ephemeris for the system T0=BJD/TDB2454420.447187(96)+2.15000800(10)×E. We measured the transmission spectrum of HAT-P-32\,A\,b and compared it to theoretical transmission spectra. Our results indicate a bimodal cloud particle distribution consisting of Rayleigh--like haze and grey absorbing cloud particles within the atmosphere of HAT-P-32\,A\,b.