Transit timing variations in the HAT-P-13 planetary system

In this Letter we present observations of recent HAT-P-13b transits. The combined analysis of published and newly obtained transit epochs shows evidence for significant transit timing variations (TTVs) since the last publicly available ephemerides. Variation of transit timings results in a sudden switch of transit times. The detected full range of TTV spans ≈0.015 d, which is significantly more than the known TTV events exhibited by hot Jupiter. If we have detected a periodic process, its period should be at least ≈3 yr because there are no signs of variations in the previous observations. This argument makes unlikely that the measured TTV is due to perturbations by HAT-P-13c.