2019MNRAS.486.2290O

We report 12, 11, 9, 10, and 8 new transit light curves of CoRoT-2b, HAT-P-12b, TrES-2b, WASP-12b, and WASP-52b, respectively, obtained at Canakkale Onsekiz Mart University Observatory and TUBITAK National Observatory in 2016 and 2017. These transit light curves were analysed using JKTEBOP code. Planetary radii of CoRoT-2b, HAT-P-12b, TrES-2b, WASP-12b, and WASP-52b were found to be 1.41 ± 0.06 R_J, 0.95 ± 0.04 R_J, 1.23 ± 0.07 R_J, 1.82 ± 0.14 R_J, and 1.22 ± 0.06 R_J, respectively. The transit ephemerides of these five exoplanets were updated and transit-timing variation analyses were also performed, using the maximum likelihood method (MLM). Most of the Lomb-Scargle (LS) periodograms of the timing residuals do not give any peak above false alarm probability levels. However, LS periodograms of CoRoT-2b show several significant peaks, and they are probably due to the magnetic activity of the host star and additional bodies in the system. On the other hand, the O-C diagram of WASP-12b displays a downward parabolic variation and indicates that the orbital period of the exoplanet is secularly decreasing. The mechanism responsible for this period decrease is discussed in terms of the orbital decay model. The tidal quality parameter Q_*^′^ of the host star WASP-12 was found to be (1.75 ± 0.16) x 10⁵, which is close to theoretical predictions for sun-like stars. Classification of the five exoplanets based on their equilibrium temperatures and Safronov numbers was re-examined, comparing the sensitive data of 211 well-known exoplanets from the Exoplanet Data Explorer data base with ours.