Presenter: Ilaria CARLEO
Abstract:
Super-Earth characterization continues to be a particular focus of the field given that it is the interface between terrestrial planets and gas-dominated planets. The implications of this division reverberate in planet formation, planetary interiors, and the origins and evolution of planetary atmospheres. Our team recently announced the detection of three super-Earth planets in 1:3:5 commensurability, with the innermost planet having a period of 1.2 days. At 30 pc, GJ9827 is the nearest planetary system that Kepler or K2 has ever found. Given its brightness, it is one of the top systems for follow-up characterization. GJ9827b has a relatively hot atmosphere, which makes it an ideal target for measuring atmospheric hydrogen escape, particularly given the high activity of its host star. Measurements of hydrogen escape provides constraints on the evolution of the planetary atmosphere including the photodissociation of water. We measured the stellar Lyman-alpha emission line and searched for signatures of an extended hydrogen atmosphere. The Lyman-alpha line is also the dominant source of UV emission for cool stars, and thereby has a tremendous impact on planetary atmospheres. These observations, along with a short near-UV observation of MgII, the second most dominant emission line, provide a vital characterization for the atmospheric mass loss.