Here are some preprints from arxiv about TRAPPIST-1 and its planets: [1703.01424] Seven temperate terrestrial planets around the nearby ultracool dwarf star TRAPPIST-1 -- the announcement paper for the seven planets. Some of them had been written about in earlier publications, however. [1703.04166] A terrestrial-sized exoplanet at the snow line of TRAPPIST-1 (12 Mar 2017) -- from the K2 observations, it's been possible to get the mass of planet h. [1704.02957] Limits on the Stability of TRAPPIST-1 (10 Apr 2017) -- "Due to uncertain system parameters, most orbital configurations drawn from the inferred posterior distribution are unstable on short timescales, even when including the eccentricity damping effect of tides." [1704.04290] Updated Masses for the TRAPPIST-1 Planets (13 Apr 2017) -- some of the mass values revised downward, and a mass estimate for h. The new masses are more dynamically stable, and e, f, g, and h are most consistent with being water worlds, planets with superdeep water oceans. Planet b is likely a water world also, planet d straddles the all-rock line, and planet c is between all-rock and all-iron, much like the Earth and Venus.