Absolute Dimensions and Apsidal Motions of Three Binary Systems in the Large Magellanic Cloud

We present the physical properties and apsidal motion elements of three eccentric eclipsing binaries in the Large Magellanic Cloud. The time-series photometric observations were carried out for a total of 41 nights between 2018 November and 2019 February using the KMTNet 1.6 m telescopes installed in South Africa and Australia. The radial velocities of binary components were measured using about 15 spectra per system collected from the ESO Science Archive Facility, which were observed with the Very Large Telescope 8.2 m telescope. The effective temperatures of the more massive binary components were determined to be 19000 +/- 500 K for OGLE-LMCECL-05797, 17000 +/- 500 K for OGLE-LMC-ECL-05861, and 19000 +/- 500 K for OGLE-LMC-ECL-06510 by comparing the observed spectra and the stellar atmosphere models obtained from the BOSZ spectral library. The absolute dimensions of each system were derived by analyzing the radial velocity curves together with the light curves obtained from the KMTNet, OGLE, and MACHO observations during about three decades. For the apsidal motion study, new eclipse timings were derived from the KMTNet and survey photometry. The apsidal motion elements of the three binaries were determined from both light curve and eclipse timing analysis. The periods of apsidal motion were 67 +/- 2 yr for OGLE-LMC-ECL-05797, 124 +/- 6 yr for OGLE-LMC-ECL-05861, and 39 +/- 1 yr for OGLE-LMC-ECL-06510 and their internal structure constants (ISCs) were log (k) over bar (2,obs) = -2.3. 0.1, -2.4. 0.1, and -2.1 +/- 0.1 in the same order. The observed ISCs of OGLE-LMC-ECL05797 and OGLE-LMC-ECL-05861 showed a good match to the theoretical ISC values, while the value of OGLELMC-ECL-06510 was somewhat larger than the theoretical one.