Looking for timing variations in the transits of 16 exoplanets

We update the ephemerides of 16 transiting exoplanets using our ground-based observations, new Transiting Exoplanet Survey Satellite data, and previously published observations including those of amateur astronomers. All these light curves were modelled by making use of a set of quantitative criteria with the exofast code to obtain mid-transit times. We searched for statistically significant secular and/or periodic trends in the mid-transit times. We found that the timing data are well modelled by a linear ephemeris for all systems except for XO-2 b, for which we detect an orbital decay with the rate of -12.95 +/- 1.85 ms yr(-1) that can be confirmed with future observations. We also detect a hint of potential periodic variations in the transit timing variation data of HAT-P-13 b, which also requires confirmation with further precise observations.