Phase Modeling of the TRAPPIST-1 Planetary Atmospheres

The combined flux variations of the TRAPPIST-1 system due to the reflected light from the planetary surfaces as a function of orbital phase. Individual planetary phase variations are shown are solid lines and the combined signature for all planets is shown as a dotted line. These calculations assume planetary albedos of unity so that the amplitudes may be scaled linearly to lower albedos. The top panel shows the phase variations for one complete orbit of the outermost planet, and the bottom panel is phased on the orbital period of planet e.

Transiting compact multi-planet systems provide many unique opportunities to characterize the planets, including studies of size distributions, mean densities, orbital dynamics, and atmospheric compositions.

The relatively short orbital periods in these systems ensure that events requiring specific orbital locations of the planets (such as primary transit and secondary eclipse points) occur with high frequency. The orbital motion and associated phase variations of the planets provide a means to constrain the atmospheric compositions through measurement of their albedos. Here we describe the expected phase variations of the TRAPPIST-1 system and times of superior conjunction when the summation of phase effects produce maximum amplitudes.

We also describe the infrared flux emitted by the TRAPPIST-1 planets and the influence on the overall phase amplitudes. We further present the results from using the global circulation model ROCKE-3D to model the atmospheres of TRAPPIST-1e and TRAPPIST-1f assuming modern Earth and Archean atmospheric compositions. These simulations are used to calculate predicted phase curves for both reflected light and thermal emission components. We discuss the detectability of these signatures and the future prospects for similar studies of phase variations for relatively faint M stars.

Stephen R. Kane, Tiffany Jansen, Thomas Fauchez, Franck Selsis, Alma Y. Ceja

Comments: 14 pages, 6 figures, 2 tables, accepted for publication in the Astronomical Journal
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2012.00080 [astro-ph.EP] (or arXiv:2012.00080v1 [astro-ph.EP] for this version)
Submission history
From: Stephen Kane
[v1] Mon, 30 Nov 2020 20:05:48 UTC (5,139 KB)

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