Shallow transit follow-up from Next-Generation Transit Survey: Simultaneous observations of HD 106315 with 11 identical telescopes

Abstract

The Next Generation Transit Survey (NGTS) is a photometric survey for transiting exoplanets, consisting of 12 identical 0.2-m telescopes. We report a measurement of the transit of HD 106315 c using a novel observing mode in which multiple NGTS telescopes observed the same target, with the aim of increasing the signal-to-noise ratio. Combining the data allows the robust detection of the transit, which has a depth less than 0.1%, rivaling the performance of much larger telescopes. We demonstrate the capability of NGTS to contribute to the follow-up of K2 and Transiting Exoplanet Survey Satellite discoveries using this observing mode. In particular, NGTS is well-suited to the measurement of shallow transits of bright targets. This is particularly important to improve orbital ephemerides of relatively long-period planets, where only a small number of transits are observed from space.