VLT, GROND, AND DANISH TELESCOPE OBSERVATIONS OF TRANSITS IN THE TRAPPIST-I SYSTEM

TRAPPIST-1 is an ultra-cool dwarf that hosts seven known transiting planets. We present photometry of the system obtained using three telescopes at ESO La Silla (the Danish 1.54 m telescope and the 2.2 m MPI telescope) and Paranal (Unit Telescope 1 of the Very Large Telescope). We obtained 18 light curves from the Danish telescope, eight from the 2.2 m and four from the VLT. From these we measure 25 times of mid-transit for four of the planets (b, c, f, g). These light curves and times of mid-transit will be useful in determining the masses and radii of the planets, which show variations in their transit times due to gravitational interactions