I completed my undergraduate studies in Physics at the University of Montreal from 2015 to 2018, and then moved on to a PhD in Astrophysics specializing in exoplanetary atmospheres in 2019 at the institute for research on exoplanets. My research interests range from the search for atmospheres on small temperate planets to the detailed characterization of puffy giant planet atmospheres.
The population of planets smaller than approximately 1.7 Rearth is widely interpreted as consisting of rocky worlds. This picture is largely corroborated by radial-velocity (RV) mass measurements for close-in super-Earths, but lacks constraints at lower instellations. Here we present the results of a detailed study of the Kepler-138 system using 13 Hubble and Spitzer transit observations of the warm-temperate 1.51 Rearth planet Kepler-138d combined with Keck/HIRES RV measurements of its host star. We find evidence for a volatile-rich “water world” nature of Kepler-138d, independently supported by transit timing variations, RV observations, as well as the flat optical/IR transmission spectrum. The bulk composition of Kepler-138d resembles those of the icy moons rather than the terrestrial planets in the solar system. Our photodynamical analysis provides important revisions of the parameters of the three known small planets in the system and we infer the presence of Kepler-138e, a likely non-transiting planet at the inner edge of the habitable zone.
Tue Giang Nguyen
I am a PhD student at York University currently studying the atmosphere of lava planets. I have a background in meteorology and had worked extensively on Martian climatology. Outside of work, you can find me jamming on the piano or sketching some pictures.
Lava planets are a class of rocky exoplanets that orbit very close to their star where their molten surfaces are hot enough to vaporize rocks. This results in a thin mineral vapour atmosphere that may be detectable due to lava planets’ high signal-to-noise ratio. The extreme atmosphere on a lava planet is expected to be non-global which makes it difficult for general circulation models to handle. Much of the atmospheric modelling on lava planets either fundamentally focus on radiative transfer or hydrodynamics. For this work, we couple the two processes to simulate the flow and observability of the silicate atmosphere on lava planet K2-141b. Because SiO has very strong UV spectral features, we find that UV radiative heating and cooling interact to keep atmospheric temperature nearly constant horizontally. A strong negative lapse rate induced by UV absorption at high altitudes greatly increases wind speeds which in turn, cools the overall atmosphere. We use our results to simulate transit and emission spectroscopy. At transit, the biggest spectral features lie in the UV band, but the atmosphere is too thin to produce a signal detectable with current or near-term instruments. Simulated emission spectra at eclipse are more promising and show strong signals detectable with Spitzer and the James Webb Space Telescope.
Pelletier Stefan Pelletier is a fourth year Ph.D. student at the Institute for Research on Exoplanets (iREx) at the University of Montreal. His work focuses on the atmospheres of hot giant gas exoplanets under the supervision of Prof. Björn Benneke. Stefan is currently in Sweden, working at Lund Observatory as part of a TEPS internship program. He loves collecting data of his favourite exoplanets using all sorts of telescopes.
Orbiting extremely close to their host stars and blasted by enormous amounts of radiation, ultra-hot Jupiters are giant gas planets that are home to some of the most extreme known atmospheric conditions. With orbital periods of a few days at most, these exoplanet are tidally-locked (like the moon around the Earth), causing a permanent hot dayside facing towards, and a cooler nightside facing away from their host star. This makes ultra-hot Jupiters unique astrophysical laboratories for probing the chemical contrasts governing their opposing, potentially drastically different hemispheres. The ultra-hot Jupiter WASP-76b took the exoplanet community by storm at the turn of the decade with evidence of iron condensation occurring from its hot dayside to its colder nightside (literally iron raining down). This landmark discovery was inferred from a distinct asymmetry in the absorption signal of gaseous iron evolving throughout the transit and introduced a new realm of opportunities for studying the day-to-night dichotomy of exoplanet atmospheres. In this talk I will present the results of follow-up transit observations of this fascinating planet using the new ultra-stable high-resolution MAROON-X spectrograph operating on Gemini-North.