MULTI-BAND, MULTI-EPOCH OBSERVATIONS OF THE TRANSITING WARM JUPITER WASP-80b

Abstract

WASP-80b is a warm Jupiter transiting a bright late-K/early-M dwarf,\nproviding a good opportunity to extend the atmospheric study of hot Jupiters\ntoward the lower temperature regime. We report multi-band, multi-epoch transit\nobservations of WASP-80b by using three ground-based telescopes covering from\noptical (g', Rc, and Ic bands) to near-infrared (NIR; J, H, and Ks bands)\nwavelengths. We observe 5 primary transits, each of which in 3 or 4 different\nbands simultaneously, obtaining 17 independent transit light curves. Combining\nthem with results from previous works, we find that the observed transmission\nspectrum is largely consistent with both a solar abundance and thick cloud\natmospheric models at 1.7$\\sigma$ discrepancy level. On the other hand, we find\na marginal spectral rise in optical region compared to the NIR region at\n2.9$\\sigma$ level, which possibly indicates the existence of haze in the\natmosphere. We simulate theoretical transmission spectra for a solar abundance\nbut hazy atmosphere, finding that a model with equilibrium temperature of 600 K\ncan explain the observed data well, having a discrepancy level of 1.0$\\sigma$.\nWe also search for transit timing variations, but find no timing excess larger\nthan 50 s from a linear ephemeris. In addition, we conduct 43 day long\nphotometric monitoring of the host star in the optical bands, finding no\nsignificant variation in the stellar brightness. Combined with the fact that no\nspot-crossing event is observed in the five transits, our results confirm\nprevious findings that the host star appears quiet for spot activities, despite\nthe indications of strong chromospheric activities.\n