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Register a new userProbing the atmosphere of a sub-Jovian planet orbiting a cool dwarf
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Elyar Sedaghati
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We derive the 0.01 $mu$m binned transmission spectrum, between 0.74 and 1.0 $mu$m, of WASP-80b from low resolution spectra obtained with the FORS2 instrument attached to ESOs Very Large Telescope. The combination of the fact that WASP-80 is an active star, together with instrumental and telluric factors, introduces correlated noise in the observed transit light curves, which we treat quantitatively using Gaussian Processes. Comparison of our results together with those from previous studies, to theoretically calculated models reveals an equilibrium temperature in agreement with the previously measured value of 825K, and a sub-solar metallicity, as well as an atmosphere depleted of molecular species with absorption bands in the IR ($gg 5sigma$). Our transmission spectrum alone shows evidence for additional absorption from the potassium core and wing, whereby its presence is detected from analysis of narrow 0.003 $mu$m bin light curves ($gg 5sigma$). Further observations with visible and near-UV filters will be required to expand this spectrum and provide more in-depth knowledge of the atmosphere. These detections are only made possible through an instrument-dependent baseline model and a careful analysis of systematics in the data.
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We report the discovery of a Jupiter-mass planet orbiting an M-dwarf star that gave rise to the microlensing event OGLE-2011-BLG-0265. Such a system is very rare among known planetary systems and thus the discovery is important for theoretical studies of planetary formation and evolution. High-cadence temporal coverage of the planetary signal combined with extended observations throughout the event allows us to accurately model the observed light curve. The final microlensing solution remains, however, degenerate yielding two possible configurations of the planet and the host star. In the case of the preferred solution, the mass of the planet is $M_{rm p} = 0.9pm 0.3 M_{rm J}$, and the planet is orbiting a star with a mass $M = 0.22pm 0.06 M_odot$. The second possible configuration (2$sigma$ away) consists of a planet with $M_{rm p}=0.6pm 0.3 M_{rm J}$ and host star with $M=0.14pm 0.06 M_odot$. The system is located in the Galactic disk 3 -- 4 kpc towards the Galactic bulge. In both cases, with an orbit size of 1.5 -- 2.0 AU, the planet is a cold Jupiter -- located well beyond the snow line of the host star. Currently available data make the secure selection of the correct solution difficult, but there are prospects for lifting the degeneracy with additional follow-up observations in the future, when the lens and source star separate.
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