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A 12-minute conference talk from the Exoplanets III conference held virtually in July 2020. (Planetary System Architectures and Dynamics 1 session)

Authors: Agol, Eric; Bolmont, Emeline; Burgasser, Adam; Burdanov, Artem; Carey, Sean; Delrez, Laetitia; Demory, Brice; De Wit, Julien; Ducrot, Elsa; Fabrycky, Dan; Gillon, Michael; Grimm, Simon; Hernandez, David M.; Ingalls, Jim; Jehin, Emmanuel; Leconte, Jeremy; Lederer, Susan; Malhotra, Renu; Morris, Brett; Queloz, Didier; Raymond, Sean; Selsis, Franck; Sestovic, Marko; Triaud, Amaury; Turbet, Martin; Van Grootel, Valerie; Meadows, Victoria; Luger, Rodrigo; Barkaoui, Khalid; Benkhaldoun, Zouhair; Dorn, Caroline; Foreman-Mackey, Daniel; Langford, Zachary; Pozuelos, Francisco

Abstract: We collected transits of 7 planets in the TRAPPIST-1 system over 3+ years with Spitzer in a campaign which completed in Oct '19 with the final transit detected before the end of the Spitzer extended mission. Adding to this transits from K2, HST and the ground, we present a transit-timing variation (TTV) analysis of the full 447 transits. The extended duration of these observations enables a more precise constraint upon the near-resonant and chopping TTVs, which improves the precision of the mass measurements significantly. We use a robust likelihood distribution to carry out inference of the dynamics of the system. From the TTV analysis, we obtain measurements of the mass-ratios of the planets to the star, which combined with the stellar mass yield the most precise measurements of these planets' masses to date, equivalent to a ~3 cm/sec precision if the masses had been measured with radial velocity (about 2 orders of magnitude more precise than actual RV measurements). Combining these measurements with estimates of the density of the star and planet radii from transit depths, we present an updated mass-radius relation for these planets. We find that the planets are consistent with a single mass-radius relation, which is slightly under-dense relative to a composition consistent with the Earth and Venus. We discuss the implications of these density measurements for the possible compositions of these planets. The transit-timing model also constrains the dynamics of the system. We discuss the eccentricities of the orbits as it relates to the possible Laplace resonances in the system. We also will examine the long-term stability and constraints upon additional planets. The timing model enables a more precise forecast of the times of transit and secondary eclipse for the James Webb Space Telescope, enabling efficient use of JWST.

The completed Spitzer campaign to monitor transit times of the TRAPPIST-1 system: improved masses, densities and dynamics.

Hi Eric, Sorry to bother you, but I am testing this website, and wondered what would happen if I wrote text in the "question/comment" box, but asked it to be private.

Hi Amaury - I did not see your message before logging in, but now that I am logged in I can see it.  I hope you are doing fine.  Take care, Eric

Thanks Eric! I hope you are doing well too!