Photometric investigation of the eclipsing binary TX Herculis observed by LUT

Abstract

Abstract The lander of China’s Chang’E-3 spacecraft is equippedwith a 15-cmtelescope that is very useful for monitoring celestial objects in the ultraviolet (UV) band (245–340 nm). The Lunar-based Ultraviolet Telescope (LUT) is the first long-term lunar-based astronomical observatory, that can make uninterrupted observations of a target from the Moon. Here we present the continuous complete UV light curve of the eclipsing binary TX Herculis (TX Her). The analysis of the light curve suggests that TX Her is a detached binary. The dip in the light curve was explained by the emergence of a stellar dark spot on the less massive F0 type component. The cyclic change of arrival eclipse times for the system reveals that it contains an additional stellar companion with a minimal mass of 0.35 M ⊙ and a period of 48.92 yr, which is supported by the detected light contribution of the third body from light curve analysis. This third body may play an important role in the formation of the present short-period system TX Her.