http://arxiv.org/abs/1801.04460
TRAPPIST-1 hosts seven Earth-sized planets transiting an M8 star. We observed mid-transit times of each of the inner two planets with the Astrophysical Research Consortium (ARC) 3.5 m Telescope at Apache Point Observatory (APO) to help constrain the planet masses with transit timing variations, and we outline a procedure for analyzing transit observations of late-M stars with APO. The transit times of TRAPPIST-1 b and c are $\mathrm{BJD}{\mathrm{TDB}} = 2457580.87634^{+0.00034}{-0.00034}$ and $2457558.89477^{+0.00080}_{-0.00085}$, respectively, which will help constrain the planet masses.
B. Morris, E. Agol and S. Hawley
Tue, 16 Jan 18
13/79
Comments: 1 figure, 2 pages, accepted to RNAAS