{"about":{"site":"https://codewithpapers.app","non_affiliation":"Code with Papers and Syntology are not affiliated with, endorsed by, or sponsored by Papers with Code, Meta, or the pwc-archive mirror.","licence":"CC BY-SA 4.0","licence_url":"https://creativecommons.org/licenses/by-sa/4.0/legalcode","attribution":"https://codewithpapers.app/attribution","modified":"archive material modified by Syntology; see the attribution page"},"url":"/paper/refining-the-transit-timing-and-photometric","title":"Refining the transit timing and photometric analysis of TRAPPIST-1: Masses, radii, densities, dynamics, and ephemerides","arxiv_id":"2010.01074","date":"2020-10-02","proceeding":null,"authors":["Eric Agol","Caroline Dorn","Simon L. Grimm","Martin Turbet","Elsa Ducrot","Laetitia Delrez","Michael Gillon","Brice-Olivier Demory","Artem Burdanov","Khalid Barkaoui","Zouhair Benkhaldoun","Emeline Bolmont","Adam Burgasser","Sean Carey","Julien de Wit","Daniel Fabrycky","Daniel Foreman-Mackey","Jonas Haldemann","David M. Hernandez","James Ingalls","Emmanuel Jehin","Zachary Langford","Jeremy Leconte","Susan M. Lederer","Rodrigo Luger","Renu Malhotra","Victoria S. Meadows","Brett M. Morris","Francisco J. Pozuelos","Didier Queloz","Sean M. Raymond","Franck Selsis","Marko Sestovic","Amaury H. M. J. Triaud","Valerie Van Grootel"],"abstract":"We have collected transit times for the TRAPPIST-1 system with the Spitzer Space Telescope over four years. We add to these ground-based, HST and K2 transit time measurements, and revisit an N-body dynamical analysis of the seven-planet system using our complete set of times from which we refine the mass ratios of the planets to the star. We next carry out a photodynamical analysis of the Spitzer light curves to derive the density of the host star and the planet densities. We find that all seven planets' densities may be described with a single rocky mass-radius relation which is depleted in iron relative to Earth, with Fe 21 wt% versus 32 wt% for Earth, and otherwise Earth-like in composition. Alternatively, the planets may have an Earth-like composition, but enhanced in light elements, such as a surface water layer or a core-free structure with oxidized iron in the mantle. We measure planet masses to a precision of 3-5%, equivalent to a radial-velocity (RV) precision of 2.5 cm/sec, or two orders of magnitude more precise than current RV capabilities. We find the eccentricities of the planets are very small; the orbits are extremely coplanar; and the system is stable on 10 Myr timescales. We find evidence of infrequent timing outliers which we cannot explain with an eighth planet; we instead account for the outliers using a robust likelihood function. We forecast JWST timing observations, and speculate on possible implications of the planet densities for the formation, migration and evolution of the planet system.","url_abs":"https://arxiv.org/abs/2010.01074v1","url_pdf":"https://arxiv.org/pdf/2010.01074v1.pdf","source":{"archive":"pwc-archive (Hugging Face), CC BY-SA 4.0","snapshot":"2025-07-28","licence_url":"https://creativecommons.org/licenses/by-sa/4.0/legalcode","row_kind":"links_only","authors_date_abstract":"arXiv metadata, CC0 1.0 (https://info.arxiv.org/help/license), from the Kaggle arXiv metadata snapshot of 2026-09-12"},"code_links":[{"paper_slug":"refining-the-transit-timing-and-photometric","repo_url":"https://github.com/ericagol/TRAPPIST1_Spitzer","is_official":1,"mentioned_in_paper":1,"mentioned_in_github":0,"framework":"none","reach":null}],"tasks":[],"methods":[],"datasets_introduced":[],"methods_introduced":[],"results":[],"syntology":{"atlas_url":null,"mcp":null,"developers":"https://syntology.ai/developers"},"arxiv_metadata":null,"syntology_extracted_results":null}