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    The First Multiband Photometric Light Curve Solutions of the V Gru Binary System from the Southern Hemisphere
    (Institute of Physics, 2023) Tanrıver, Mehmet; Poro, Atila; Bulut, Ahmet; Keskin, Ahmet; Blackford, Mark G.
    The first multiband photometric solutions of the short-period V Gru eclipsing binary from the southern hemisphere are presented in this study. Light curves of the system were observed through BVI filters at the Congarinni Observatory in Australia for 15 nights. In addition to the new ground-based data, we also used the TESS observations in two sectors. We analyzed the light curves of the system using the PHysics Of Eclipsing BinariEs (PHOEBE) 2.4.7 version code to achieve the best accordance with the photometric observations. The solutions suggest that V Gru is a near-contact binary system with q = 1.302(81) mass ratio, f 1 = 0.010(23), f 2 = −0.0.009(21), and i = 73.45(38). We considered the two hot spots on the hotter and cooler components for the light curve analysis. We extracted the minima times from the light curves based on the Markov Chain Monte Carlo (MCMC) approach. Using our new light curves, TESS, and additional literature minima, we computed the ephemeris of V Gru. The system’s eclipse timing variation trend was determined using the MCMC method. This system is a good and challenging case for future studies.
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    THE FIRST MULTICOLOUR PHOTOMETRY OF THE V840 LYR CONTACT BINARY STAR
    (Univ Nacional Autonoma Mexico, Inst De Astronomia, 2024) Tanrıver, Mehmet; Michel, Ral; Bulut, Ahmet; Aceves, Hector; Keskin, Ahmet
    Light curves for the total-eclipsing binary system V840 Lyr in the V, R degrees, and I degrees bands are presented; these display the O'Connell effect. Analysis was performed with the Phoebe031a software revealing that V840 Lyr is a W-type contact binary with a degree of contact factor of f = 15.1 +/- 5.6%, a mass ratio of q = 0.4509 +/- 0.0705, an inclination of i = 86.7 degrees, and a temperature difference of triangle T = 45 K. An asymmetry in the light curves was modeled assuming a cool spot located on the secondary star. The period changes of the system are examined by combining our recently found times of light minima together with those in the literature. Absolute parameters were obtained as M1 = 0.74M((R)), M2 = 0.34M((R)), R1 = 0.74R((R)), and R2 = 0.51R((R)) from our photometric solutions, using some empirical relations. The long-term period increase and the contact configuration indicate that V840 Lyr will evolve into a fill-out overcontact binary.