Tidally excited oscillations in MACHO 80.7443.1718: Changing amplitudes and frequencies, high-frequency tidally excited mode, and a decrease in the orbital period

Eccentric ellipsoidal variables (aka heartbeat stars) is a class of eccentric binaries in which proximity effects, tidal distortion due to time-dependent potential particular, lead measurable photometric variability close the periastron passage. The varying may also give rise tidally-excited oscillations (TEOs). TEOs play an important role dynamical evolution massive systems. Our study aimed at detection and characterisation long-term behaviour their amplitudes frequencies extreme-amplitude star MACHO 80.7443.1718, consisting blue supergiant late O-type dwarf. We use two seasons Transiting Exoplanet Survey Satellite (TESS) observations target obtain new 30-min cadence photometry by means difference image analysis TESS full-frame images. In order extend longer time scales, we supplement data with 30-years long ground-based target. confirm known $n=23$, 25, 41 announce TEOs, $n=24$ 230, 80.7443.1718. Amplitudes all were found vary on scale years or months. For $n=25$ TEO amplitude frequency changes are related, indicate that main cause drop this change its increase detuning parameter. light curve $n=230$ strongly non-sinusoidal. Its high oscillation strange mode. find orbital period system decreases rate about 11 s(yr)$^{-1}$, can be explained significant mass loss transfer possible contribution from dissipation.