Dix Planetary Science Seminar

Speaker: Cam Buzard

Title: Simulating the Multi-Epoch Exoplanet Direct Detection Technique: Detecting HD187123b and Planning Future Observations

Abstract: In recent years, high-resolution, ground-based telescopes have been used to detect the thermal emission from non-transiting hot Jupiters and learn more about the chemical and physical properties of their atmospheres. These data are analyzed using cross correlation techniques that treat the systems as spectroscopic binaries to tease apart the stellar and planetary signals. In the Blake group, we study one such technique that combines multiple epochs of data across the planet's orbit to constrain the planetary line-of-sight Keplerian orbital velocity, Kp. While this multi-epoch technique is not limited to very close-in planets in the same way other cross correlation techniques are, detections have proven difficult due to large levels of nonrandom structure in the cross correlation space. In this talk, we present a simple simulation framework that was able to reproduce much of the nonrandom structure present in the cross correlation results from the non-transiting hot Jupiter HD187123b. Using these simulations to remove nonrandom structure, we were able to detect water in the hot Jupiter's atmosphere, and measure its mass and orbital inclination, at a 6.5-sigma confidence level. We go on to describe some new observing strategies that the simulations predict will allow for more confident measurements of Kp, as well as some stronger constraints on atmospheric properties like C/O. The ability to reduce nonrandom structure from these cross correlation detections either through model fitting or through optimized observing strategies will be critical as we look to target cooler and lower contrast planets, en route to those in habitable zones.

Speaker: Jiazheng Li

Title: Modelling the electron irradiation of ice and its application to Europa

Abstract: Electron irradiation on icy surface is an important process in the Solar System, especially for the icy satellites with tenuous atmospheres which are originated from the outgassing of the icy surface. People have done experiments on the electron irradiation on ice to study the chemical compositions (e.g. H_2O_2) that are forming inside the ice and the gases (e.g. H_2, O_2) that are leaving the surface. Meanwhile, models have been developed to predict the production of the gases versus electron energy and ice temperature. However, these models are semi-empirical and cannot fully describe the distribution of different chemical species in the ice and how they are formed and transported. In this study, we develop a chemical-transport model based on the Caltech/JPL model KINETICS to realistically simulate the chemical processes occurring in the ice during electron irradiation. The goals of this study are twofold. First, we want to apply this model to icy satellites (e.g. Europa) to better constraint the amount of gases that go into the atmosphere. Second, this model can help us understand the oxidants in the surface of icy satellites. Those oxidants in the surface may eventually end up in the subsurface ocean and provide potential habitability to the ocean.