Superabundance of Exoplanet Sub-Neptunes Explained by Fugacity Crisis
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The Planetary Systems Imager for TMT Astro2020 APC White Paper Optical and Infrared Observations from the Ground Corresponding Author: Michael P
The Planetary Systems Imager for TMT Astro2020 APC White Paper Optical and Infrared Observations from the Ground Corresponding Author: Michael P. Fitzgerald (University of California, Los Angeles; mpfi[email protected]) Co-authors: Diego) Vanessa Bailey (Jet Propulsion Laboratory) Takayuki Kotani (Astrobiology Center/NAOJ) Christoph Baranec (University of Hawaii) David Lafreniere` (Universite´ de Montreal)´ Natasha Batalha (University of California Santa Michael Liu (University of Hawaii) Cruz) Julien Lozi (Subaru) Bjorn¨ Benneke (Universite´ de Montreal)´ Jessica R. Lu (University of California, Berkeley) Charles Beichman (California Institute of Jared Males (University of Arizona) Technology) Mark Marley (NASA Ames Research Center) Timothy Brandt (University of California, Santa Christian Marois (NRC Canada) Barbara) Dimitri Mawet (California Institute of Jeffrey Chilcote (Notre Dame) Technology/JPL) Mark Chun (University of Hawaii) Benjamin Mazin (University of California Santa Ian Crossfield (MIT) Barbara) Thayne Currie (NASA Ames Research Center) Maxwell Millar-Blanchaer (Jet Propulsion Kristina Davis (University of California Santa Laboratory) Barbara) Soumen Mondal (SN Bose National Centre for Richard Dekany (California Institute of Technology) Basic Sciences) Jacques-Robert Delorme (California Institute of Naoshi Murakami (Hokkaido University) Technology) Ruth Murray-Clay (University of California, Santa Ruobing Dong (University of Victoria) Cruz) Rene Doyon (Universite´ de Montreal)´ Norio Narita (Astrobiology Center) Courtney Dressing -
Lurking in the Shadows: Wide-Separation Gas Giants As Tracers of Planet Formation
Lurking in the Shadows: Wide-Separation Gas Giants as Tracers of Planet Formation Thesis by Marta Levesque Bryan In Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy CALIFORNIA INSTITUTE OF TECHNOLOGY Pasadena, California 2018 Defended May 1, 2018 ii © 2018 Marta Levesque Bryan ORCID: [0000-0002-6076-5967] All rights reserved iii ACKNOWLEDGEMENTS First and foremost I would like to thank Heather Knutson, who I had the great privilege of working with as my thesis advisor. Her encouragement, guidance, and perspective helped me navigate many a challenging problem, and my conversations with her were a consistent source of positivity and learning throughout my time at Caltech. I leave graduate school a better scientist and person for having her as a role model. Heather fostered a wonderfully positive and supportive environment for her students, giving us the space to explore and grow - I could not have asked for a better advisor or research experience. I would also like to thank Konstantin Batygin for enthusiastic and illuminating discussions that always left me more excited to explore the result at hand. Thank you as well to Dimitri Mawet for providing both expertise and contagious optimism for some of my latest direct imaging endeavors. Thank you to the rest of my thesis committee, namely Geoff Blake, Evan Kirby, and Chuck Steidel for their support, helpful conversations, and insightful questions. I am grateful to have had the opportunity to collaborate with Brendan Bowler. His talk at Caltech my second year of graduate school introduced me to an unexpected population of massive wide-separation planetary-mass companions, and lead to a long-running collaboration from which several of my thesis projects were born. -
1D Atmospheric Study of the Temperate Sub-Neptune K2-18B D
A&A 646, A15 (2021) Astronomy https://doi.org/10.1051/0004-6361/202039072 & © D. Blain et al. 2021 Astrophysics 1D atmospheric study of the temperate sub-Neptune K2-18b D. Blain, B. Charnay, and B. Bézard LESIA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Université, Université de Paris, 92195 Meudon, France e-mail: [email protected] Received 30 July 2020 / Accepted 13 November 2020 ABSTRACT Context. The atmospheric composition of exoplanets with masses between 2 and 10 M is poorly understood. In that regard, the sub-Neptune K2-18b, which is subject to Earth-like stellar irradiation, offers a valuable opportunity⊕ for the characterisation of such atmospheres. Previous analyses of its transmission spectrum from the Kepler, Hubble (HST), and Spitzer space telescopes data using both retrieval algorithms and forward-modelling suggest the presence of H2O and an H2–He atmosphere, but have not detected other gases, such as CH4. Aims. We present simulations of the atmosphere of K2-18 b using Exo-REM, our self-consistent 1D radiative-equilibrium model, using a large grid of atmospheric parameters to infer constraints on its chemical composition. Methods. We compared the transmission spectra computed by our model with the above-mentioned data (0.4–5 µm), assuming an H2–He dominated atmosphere. We investigated the effects of irradiation, eddy diffusion coefficient, internal temperature, clouds, C/O ratio, and metallicity on the atmospheric structure and transit spectrum. Results. We show that our simulations favour atmospheric metallicities between 40 and 500 times solar and indicate, in some cases, the formation of H2O-ice clouds, but not liquid H2O clouds. -