HS Hydrae about to turn off its eclipses

¹ Astronomical Institute, Faculty of Mathematics and Physics, Charles University Prague, 18000 Praha 8, V Holešovičkách 2, Czech Republic
e-mail: zasche@sirrah.troja.mff.cuni.cz
² Weierstr 30, 8630 Rueti, Switzerland

Received: 12 April 2012
Accepted: 30 April 2012

Abstract

Aims. We aim to perform the first long-term analysis of the system HS Hya.

Methods. We performed an analysis of the long-term evolution of the light curves of the detached eclipsing system HS Hya. Collecting all available photometric data since its discovery, the light curves were analyzed with a special focus on the evolution of system’s inclination.

Results. We find that the system undergoes a rapid change of inclination. Since its discovery until today the system’s inclination changed by more than 15°. The shape of the light curve changes, and now the eclipses are almost undetectable. The third distant component of the system is causing the precession of the close orbit, and the nodal period is about 631 yr.

Conclusions. New precise observations are desperately needed, preferably this year, because the amplitude of variations is decreasing rapidly every year. We know only 10 such systems on the whole sky at present.