The first multi-color CCD photometric study of 27 δ Scuti stars is presented, which was performed over the three observing years. We obtained the maximum times and magnitude changes in the observation period for each star. The ephemeris of our δ Scuti stars was calculated based on the Markov chain Monte Carlo (MCMC) method, using the observed times of maxima and the period of star oscillations. We used Gaia EDR3 parallax for calculating the absolute magnitude of δ Scuti stars. The precise fundamental physical parameters of all studied stars, such as mass, radius, luminosity, and temperature, were estimated. The pulsation modes of stars were investigated according to their Periodogram, indicating they are all in radial pulsation modes. Since the period changing of pulsating variable stars indicates the stellar evolution, the Period-Luminosity (𝑃 − 𝐿) relation was calculated and discussed. Moreover, we present new 𝑃 − 𝐿 relations for fundamental and overtone modes; Machine Learning Classification was used for this purpose.

We present the photometric analysis of six short-period systems (EI Oct, V336 TrA, NX Boo, V356 Boo, PS Boo, and V2282 Cyg). This is the first photometric analysis of these systems except for V336 TrA. Observations were conducted for 27 nights at three observatories in the northern and southern hemispheres. We calculated a new ephemeris for each of the systems using our minimum times and additional literature. The Markov Chain Monte Carlo (MCMC) approach was used to determine the eclipse timing variation trends of the systems. We found a likely orbital growth for V336 TrA and PS Boo; four other systems show a linear trend in orbital period changes, which is most likely due to the accumulation of measurement errors in their linear ephemeris parameters. The light curve analysis was performed using the Physics of Eclipsing Binaries (PHOEBE) 2.3.59 version code with the MCMC approach. The absolute parameters of the systems were calculated by using the Gaia Early Data Release 3 (EDR3) parallax. The positions of the systems were also depicted on the Hertzsprung–Russell (H-R) and log J 0 – log M diagrams. According to a sample, we were able to present relations for the mass–radius (M–R) relationships of contact binary systems. There is also a strong relationship between the mass ratio and the radius ratio in the W UMa systems for which we also provided a new relation. We compared the M–R updated relationships in this study with seven systems in other studies obtained using the spectroscopic method. In addition, we estimated some of the absolute parameters for 1734 EW systems, based on the new relationships.

No abstract

Transit Timing Variation (TTV) is a powerful method to study the dynamics of multiple transiting planetary systems. We examined the TTV of four planetary systems: WASP-12b, WASP-33b, WASP-36b, and WASP-46b. The purpose of this work is to refine the reference ephemeris of these four systems and to draw inferences on any apparent variability of the transits' periodicity. We used the light curves of these systems from the Transiting light Exoplanet Survey Satellite (TESS) observations and some ground-based telescopes. We modeled these light curves to measure the transit times using Exofast. We plotted their TTV diagrams built from our obtained midtransit times and those available in the literature. Our MCMC analysis of these timings enabled us to refined the transit ephemeris of the four systems. We found an apparent variation of the orbital period, 𝑝̇= −24 ± 2 𝑚𝑠 𝑦𝑟 for WASP-12b and 𝑄 * = (2.16 ± 0.35) × 10 for the tidal quality parameter of its host star. We realized that the orbital period is increasing in the WASP-46b system, so its star magnetic activity is a stronger model than orbital decay for period variation of this system. We obtained ∆𝑃 = 7.37 ± 8.64 𝑚𝑠 during 10 years for WASP-36b; It indicates that orbital decay may be present in this system. But since there is no obvious quadratic trend in its TTV diagram, variations are likely due to wrong linear ephemeris that increased over 10 years.