Astrophysics Luncheon Seminar Cloud Atlas: Characterizing the Directly-Imaged Exoplanets with Time-Resolved Observations Presented by Yifan Zhou University of Arizona Monday, November 19, 2018 12:00 noon in 169-336 and on Webex Abstract Directly-imaged exoplanets and planetary-mass companions form a valuable sample for exoplanet atmospheric studies. They have similar properties to both transiting planets and brown dwarfs, which elevates directly-imaged planets to be the key in connecting atmospheric characterizations of all substellar objects. Condensate clouds as the primary source of uncertainties in the studies of transiting planets and brown dwarfs are also the most intriguing component in the atmospheres of directly-imaged planets. Time-resolved observations that monitor the brightness and spectral variabilities induced by heterogeneous atmospheres have achieved great success in studying the cloud structures of brown dwarfs. These observations will be particularly powerful when applied to high-contrast directly-imaged planets. In Cloud Atlas, an HST Large Treasury program, we use time-resolved precision photometry and spectroscopy to study different cloud structures in brown dwarfs and planetary mass companions. In this talk, I will present the latest HST/WFC3 near-infrared light curves of directly-imaged planetary-mass companions and address both the observational techniques and the scientific implications. By placing the multi-wavelength modulation amplitude measurements of planetary-mass companions into the context of brown dwarfs, I will discuss the cloud properties in intermediate- and low-surface gravity atmospheres. I will also explore the angular momentum evolution of planetary-mass companions based on rotational period measurements. With the development of high-contrast imaging instruments in the near future, time-resolved observations will be even more effective in characterizing directly-imaged exoplanets. JPL Contact: Jacqueline McCleary (4-9886)   Site Manager: Webmaster: CL 08-3220