My name is Ryan Cloutier. I am currently a postdoctoral fellow at the Center for Astrophysics | Harvard & Smithsonian and will be continuing as a Banting Fellow starting in July 2021.
I earned my PhD in Astronomy and Astrophysics in 2019 from the University of Toronto with my thesis entitled Semi-parametric Methods to Aid in the Detection and Characterization of Distant Worlds Around Small Stars.
My research focuses on the detection and characterization of exoplanets smaller than Neptune and orbiting M dwarf stars, the most common type of star in the galaxy. My main interests are in understanding the composition of super-Earths and sub-Neptunes to inform our understanding of how these planets form.
...my research focuses on using the transit and radial velocity techniques to discover new exoplanets that are smaller than Neptune and orbit nearby M dwarf stars. I conduct detailed follow-up observations to uncover the global architectures of these planetary systems and to measure the planets' compositions. In addition to studying individual planetary systems, I also focus on exoplanet population studies to try and identify the physical processes that dictate planet formation and evolution at the low mass end of the main sequence.
Click here for my list of publications on ADS.
An Ultra-Short Period Keystone Planet Sitting Inside the M Dwarf Radius Valley
In this paper we presented the discovery of the ultra-short period planet TOI-1634 b from the TESS mission. The radius and orbital period of TOI-1634 b (0.99 days and 1.79 R⊕) place it within the radius valley around low mass stars, and specifically, between the predictions from competing models of the emergence of the radius valley (i.e. thermally-driven mass loss versus gas-depleted formation). Using precise radial velocity observations from HARPS-N/TNG we measured the mass of TOI-1634 b and determined its bulk composition to be under-dense relative to an Earth-like composition, such that the planet requires either an extended gaseous envelope, a large volatile-rich layer, or a rocky portion that is not dominated by iron and silicates to explain its mass and radius. The discovery that the bulk composition of TOI-1634 b is inconsistent with that of the Earth favours the gas-depleted formation mechanism to explain the emergence of the radius valley around M dwarfs with masses ≤ 0.5 M⊙.
Evolution of the Radius Valley around Low-mass Stars from Kepler and K2
In this paper we computed the occurrence rate of small planets around mid-K to mid-M dwarfs from the Kepler and K2 missions. Similarly to what has been shown around Sun-like stars from Kepler, we resolved the radius valley structure in the planetary occurrence rate distribution and showed that the valley shifts to smaller planet radii with decreasing stellar mass. This trend agrees qualitatively with physical models aimed at explaining possible emergence pathways of the radius valley (e.g. photoevaporation, core-powered mass loss, gas-depleted terrestrial planet formation). We also showed that the slope of the rocky/non-rocky transition around low mass stars is much shallower than around Sun-like stars. This suggests that thermally-driven atmospheric mass loss may not dominate the evolution of planets in the low stellar mass regime and that we may be witnessing the emergence of a separate channel of planet formation.
A Pair of TESS Planets Spanning the Radius Valley around the Nearby Mid-M Dwarf LTT 3780
In this paper we presented the discovery of a multi-transiting system around the nearby mid-M dwarf LTT 3780. The system contains the ultra-short period super-Earth LTT 3780 b (0.77 days, 1.33 R⊕, 2.26 M⊕) and the warm sub-Neptune LTT 3780 c (12.25 days, 2.30 R⊕, 8.6 M⊕), which sit on opposing sides of the radius valley around low mass stars. The brightness and small size of their host star help to make both LTT 3780 b and c attractive targets for the atmospheric characterization of planets spanning the radius valley via transmission and thermal emission observations respectively.
The following is a link to a PDF version of my full CV.