  The orbital motion of the transiting hot Jupiter TrES-5 b was reported to be
perturbed by a planetary companion on a nearby orbit. Such compact systems do
not frequently occur in nature, and learning their orbital architecture could
shed some light on hot Jupiters' formation processes. We acquired fifteen new
precise photometric time series for twelve transits of TrES-5 b between June
2019 and October 2020 using 0.9-2.0 m telescopes. The method of precise transit
timing was employed to verify the deviation of the planet from the Keplerian
motion. Although our results show no detectable short-time variation in the
orbital period of TrES-5 b and the existence of the additional nearby planet is
not confirmed, the new transits were observed about two minutes earlier than
expected. We conclude that the orbital period of the planet could vary in a
long timescale. We found that the most likely explanation of the observations
is the line-of-sight acceleration of the system's barycentre due to the orbital
motion induced by a massive, wide-orbiting companion.
