We study the transit timings of 10 exoplanets in order to investigate potential Transit Timing Variations (TTVs) in them. We model their available ground-based light curves, some presented here and others taken from the literature, and homogeneously measure the mid-transit times. We statistically compare our results with published values and find that the measurement errors agree. However, in terms of recovering the possible frequencies, homogeneous sets can be found to be more useful, of which no statistically relevant example has been found for the planets in our study. We corrected the ephemeris information of all ten planets we studied and provide these most precise light elements as references for future transit observations with space-borne and ground-based instruments. We found no evidence for secular or periodic changes in the orbital periods of the planets in our sample, including the ultra-short period WASP-103 b, whose orbit is expected to decay on an observable timescale. Therefore, we derive the lower limits for the reduced tidal quality factors (Q$^{\prime }_{\star }$) for the host stars based on best fitting quadratic functions to their timing data. We also present a global model of all available data for WASP-74 b, which has a Gaia parallax-based distance value ∼25 per cent larger than the published value.

We announce the discovery of GPX-1 b, a transiting brown dwarf with a mass of 19.7 ± 1.6 MJup and a radius of 1.47 ± 0.10 RJup, the first sub-stellar object discovered by the Galactic Plane eXoplanet (GPX) survey. The brown dwarf transits a moderately bright (V = 12.3 mag) fast-rotating F-type star with a projected rotational velocity vsin  i* = 40 ± 10 km/s. We use the isochrone placement algorithm to characterize the host star, which has effective temperature 7000 ± 200 K, mass 1.68 ± 0.10 M⊙, radius 1.56 ± 0.10 R⊙ and approximate age $0.27_{-0.15}^{+0.09}$ Gyr. GPX-1 b has an orbital period of ∼1.75 d, and a transit depth of 0.90 ± 0.03 per cent. We describe the GPX transit detection observations, subsequent photometric and speckle-interferometric follow-up observations, and SOPHIE spectroscopic measurements, which allowed us to establish the presence of a sub-stellar object around the host star. GPX-1 was observed at 30-min integrations by TESS in Sector 18, but the data is affected by blending with a 3.4 mag brighter star 42 arcsec away. GPX-1 b is one of about two dozen transiting brown dwarfs known to date, with a mass close to the theoretical brown dwarf/gas giant planet mass transition boundary. Since GPX-1 is a moderately bright and fast-rotating star, it can be followed-up by the means of Doppler tomography.

4116 exoplanets have been discovered so far in 3062 planetary systems in total, 669 of which are multi-planet systems (http://exoplanet.eu, 2019-09-14). Finding a large, short orbital period planet transiting its star is a relatively easy task thanks to space born and ground based transit surveys. Whether they are the sole planets orbiting their host stars or they have companion planets is a worthy question to ask, because an average of ~1.34 planets per star is not a number expected from planet formation theories and a comparison with our own Solar System hosting at least 8 planets and many more bodies in planetary mass limits Transiting planets provide a unique opportunity to search for unseen additional bodies gravitationally bound to the system, which doesn't have to transit the host star. It is possible to detect the motion of the center of mass of the observed transiting planet host star duo due to the gravitational tugs of the unseen bodies from the Roemer delay. In order to achieve the goal, determination of the mid times of the transits of the planets in high precision and accuracy is a primary condition. These mid transit times have to be detrended from the orbital motion of the Earth about the Sun, which brings its own delay because it also changes the distance between the observed planet system and the Earth. Then potential periodic variations in the transit timings due to the so-called Light Travel Time Effect (LiTE) is searched. We present transit timing variations and update the ephemeris information of 5 transiting planets; HAT P 23b, WASP 103b, GJ 1214b, WASP 69b, and KELT 3b within this contribution. We have collected all the quality transit light curves of these exoplanets from the literature and observations of amateur astronomers made available through Exoplanet Transit Database (ETD), converted them to Dynamic Barycentric Julian days (BJD-TDB), constituted their Transit Timing Variation (TTV) diagrams, and updated their ephemeris information based on Markov Chain Monte Carlo (MCMC) analyses. Finally, we have carried out frequency analyses for all the planets in our sample and present the results.