| 초록 |
New CCD photometric observations of GX Aur have been made between 2004 and 2015. Our light curves are the first ever compiled and display the variable O'Connell effect. The light variations are satisfactorily modeled by including time-varying cool-spots on the component stars. Our light curve synthesis indicates that the eclipsing pair is an A-type contact binary with parameters of i = 81.1 deg, ${ Delta}T=36K$ , q = 0.950 and f = 46%. Including our 25 timing measurements, a total of 83 times of minimum light spanning about 66 yr were used for a period study. It was found that the orbital period of GX Aur has varied due to two periodic oscillations superposed on an upward-opening parabolic variation. The long-term period increase rate is deduced as $+9.636{ times}10^{-10}d ;yr^{-1}$ , which can be produced as a mass transfer from the secondary star to the primary at a rate of $3.136{ times}10^{-6}M_{ odot} ;yr^{-1}$ , among the largest rates for contact systems. The periods and semi-amplitudes of the two periodic variations are about $P_3=8.7yr$ and $P_4=21.2yr$ , and $K_3=0.011d$ and $K_4=0.017d$ , respectively. The most reasonable explanation for both cycles is a pair of light-travel-time effects driven by the possible existence of an unseen third and fourth components with projected masses of $M_3=0.91M_{ odot}$ and $M_4=1.09M_{ odot}$ in eccentric orbits of $e_3=0.13$ and $e_4=0.73$ . Because no third light was detected in the light curve synthesis, each circumbinary object could be a compact star or a binary itself. |
