The first analysis of extragalactic binary-orbit precession ⋆
Astronomical Institute, Charles University in Prague, Faculty of Mathematics and Physics, 180 00 Praha 8, V Holešovičkách 2, Czech Republic
Received: 24 July 2013
Accepted: 26 September 2013
Aims. The main aim of the present paper is the very first analysis of the binary-orbit precession out of our Galaxy.
Methods. The light curves of an eclipsing binary MACHO 82.8043.171 in the Large Magellanic cloud (LMC) were studied in order to analyse the long-term evolution of its orbit.
Results. It is a detached system that is undergoing rapid orbit precession. The inclination of the orbit towards the observer has been changing, which has caused the eclipse depth to become lower over the past decade, and this is ongoing. The period of this effect was derived as only about 77 years, so it is the second fastest nodal motion known amongst such systems nowadays. This is the first analysis of an extragalactic binary with nodal precession. This effect is probably caused by a distant third body orbiting the pair, which could potentially be detected via spectroscopy.
Conclusions. Some preliminary estimates of this body are presented. However, even such a result can tell us something about the multiplicity fraction in other galaxies.
Key words: binaries: eclipsing / stars: fundamental parameters / stars: individual: MACHO 82.8043.171
© ESO, 2013