Abstract
(Abridged) We observed one transit and one occultation of the hot Jupiter WASP-43b simultaneously in the g'r'i'z'JHK bands using the GROND instrument on the MPG/ESO 2.2-meter telescope. From the transit event, we have independently derived WASP-43's system parameters with high precision, and improved the period to be 0.81347437(13) days. No significant variation in transit depths is detected, with the largest deviations coming from the i', H, and K bands. Given the observational uncertainties, the broad-band transmission spectrum can be explained by either a flat featureless straight line that indicates thick clouds, synthetic spectra with absorption signatures of atomic Na/K or molecular TiO/VO that indicate cloud-free atmosphere, or a Rayleigh scattering profile that indicates high-altitude hazes. From the occultation event, we have detected planetary dayside thermal emission in the K-band with a flux ratio of 0.197 +/- 0.042%, which confirms previous detections obtained in the 2.09 micron narrow band and Ks-band. The K-band brightness temperature 1878 +108/-116 K favors an atmosphere with poor day- to night-side heat redistribution. We also have a marginal detection in the i'-band (0.037 +0.023/-0.021%), which is either a false positive, a signature of non-blackbody radiation at this wavelength, or an indication of reflective hazes at high altitude.
Highlights
Transiting hot Jupiters are highly valuable in the characterization study of planetary orbits, structures, and atmospheres
Through observations of primary transits, transmission spectrum can be constructed by measuring the transit depths at different wavelengths, which carries information of planetary atomic (e.g., Na, K) and molecular (e.g., H2O, CH4, CO) absorption features when the stellar lights are transmitted in the planetary day-night terminator region (Seager & Sasselov 2000; Fortney et al 2008, 2010, etc.)
In addition to our seven timing measurements on one transit and 27 reanalyzed timings from TRESCA, we collected the 23 timings listed in Table 6 of Gillon et al (2012)
Summary
Transiting hot Jupiters are highly valuable in the characterization study of planetary orbits, structures, and atmospheres They orbit the host stars closely while they possess relatively large sizes and high masses, thereby producing strong transit and radial velocity signals, which together result in precise determination of the planetary system parameters, such as planetary mass, radius, surface gravity, orbital distance, and stellar density (e.g., Seager & Mallén-Ornelas 2003; Southworth et al 2007). In 2011, we started a project to characterize hot-Jupiter atmospheres using the GROND instrument (e.g., Paper I on WASP-5b; Chen et al 2013), which is able to do simultaneous multiband photometry This technique has been performed on several transiting planets to investigate their atmospheres (de Mooij et al 2012; Southworth et al 2012; Mancini et al 2013a,b,c; Nikolov et al 2013; Fukui et al 2013; Copperwheat et al 2013; Nascimbeni et al 2013).
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