Poster abstract details

New follow-up study of the atmosphere of GJ1214b
C. Cáceres, P. Kabath,, S. Hoyer, V. D. Ivanov, P. Rojo, J. H. Girard, E. Miller-Ricci Kempton, J. J. Fortney, and D. Minniti


GJ1214b is an extremely interesting 6.55 $M_{earth}$ and 2.6 Earth radii sub-Neptune planet orbiting a M-dwarf host. Its proximity, only 14pc, makes it an excellent target for studies of exoplanetary atmospheres. Furthermore, the sub-Neptunes/Super Earth-sized planets are only one step between Jupiter-sized and habitable Earth-sized planets with a biosphere. Due to favourable parameters of GJ1214 system, we posses great coverage of many wavelengths in planetary transmission spectra from optical to NIR regions. However, the scenarios for the atmospheric compositions are still open. Based on the available measurements, the solar composition (hydrogen rich) atmosphere can be most probably ruled out. That is given by fact that we observe rather a flat spectrum than the absorption features in the hydrogen rich model. Thus, currently more plausible models are atmosphere composed of heavy elements such as water or atmosphere covered by clouds. Here, we present our new spectrophotometric and photometric measurements obtained with SOI and OSIRIS instruments (both SOAR telescope) and SOFI (ESO NTT). We observed 5 transit events of GJ1214b and determined the Rp/Rs ratios for every measured wavelength. Our photometric measurements at 0.8 micron (Bessel-I) and at 2.14 micron (NIR narrow band) correlate with the flat transmission spectrum, therefore strongly supporting the water or cloudy atmosphere. Our spectrophotometric measurements in the H+K region do not posses the sufficient precision in the Rp/Rs ratios. We conclude that the hydrogen rich model is less probable. However, to be able to decide if the planetary atmosphere is hidden in clouds or if we encountered a water world, we still need more measurements with extremely high accuracy. Here, literally, every new point counts.

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