Photometric Properties of the HW Vir-type Binary OGLE-GD-ECL-11388

We present the first extensive photometric results for the eclipsing binary OGLE-GD-ECL-11388 with a period of about 3.5 hours located in the Galactic disk. For the photometric solutions, we obtained the BVI light curves from both the KMTNet observations in 2015 and the OGLE -III survey data from 2001-2009, which show striking reflection effects and very sharp eclipses. The light curve synthesis indicates that the eclipsing system is a HW Virtype binary with a mass ratio of q = 0.289, an orbital inclination of i = 81.9 deg, and a temperature ratio between both components of T-2/T-1 = 0.091. A frequency analysis was applied to the light residuals from our binary model; however, no pulsating periodicity from the subdwarf B -type primary component was detected under signal-tonoise amplitude ratios larger than 4 0 A total of 27 minimum epochs spanning 15 yr were used to analyze the eclipse timing variations of OGLE-GD-ECL-11388. It was found that the orbital period has varied due to a continuous period decrease at a rate of dP/dt = -1.1 x 10(-8) day yr(-1) or a sinusoidal oscillation with a semiamplitude of K = 35 s and a cycle of P-3 = 8.9 yr. The period decrease may be explained by an angular momentum loss via magnetic stellar wind braking or may be only a part of the sinusoidal variation. We think the most likely interpretation of the orbital period change, at present, is the light -time effect via the presence of a third body with a mass of M-3 sin i(3) = 12.5 M-Jup, putting it in the boundary zone between planets and brown dwarfs.