Exploring the Existence of an Additional Planet in the hot-Jupiter
Extra-solar Planetary System TrES-5
Abstract
We present seven new transit light curves of the hot-Jupiter TrES-5b
observed with the 2-m Himalayan Chandra Telescope, Hanle, India during
2016-2020 to look for the transit timing variation (TTV). For this
study, total 59 transit light curves have been considered which include
seven light curves from our new observations, 37 from the literature,
and 15 from the Exoplanet Transit Database (ETD). In order to have
homogeneously derived mid-transit times for precise TTV study, all the
light curves were analyzed with a uniform procedure using the Transit
Analysis Package (TAP). By fitting a linear ephemeris model to the
mid-transit time data, we derive new transit ephemeris with
$\chi^{2}_{red}= 2.43$ for TrES-5b, which is
consistent and even more precise than the previous results. The best-fit
ephemeris with $\chi^{2}_{red} >1$
indicates that the linear ephemeris model does not represent the transit
time data well. To look for the periodicity in the timing residuals of
linear ephemeris model, a generalized Lomb-Scargle periodogram is
computed. However, we have not found any significant periodicity in the
timing residuals. The highest peak power obtained in the periodogram at
the frequency of 0.005232 rad/period has the false alarm probability
(FAP) of 12%, which is found below from the threshold values (i.e. FAP
=5% and 1%). This result enable us to conclude that the additional
planet might not be present in the TrES-5 system. To confirm this, the
further high-precision follow-up observation of the TrES-5 system would
be required.