V608 Cassiopeiae: A W UMa-type eclipsing binary with two possible circumbinary companions

We present the photometric properties of V608 Cas from detailed studies of light curves and eclipse timings. The light curve synthesis indicates that the eclipsing pair is an overcontact binary with parameters of $ΔT$ = 155 K, $q$ = 0.328, and $f$ = 26 %. We detected the third light $\ell_{3}$, which corresponds to about 8 % and 5 % of the total systemic light in $V$ and $R$ bands, respectively. Including our 6 timing measurements, a total of 38 times of minimum light were used for a period study. It was found that the orbital period of V608 Cas has varied in some combination of an upward parabola and two periodic variations. The continuous period increase with a rate of $+$3.99$\times$10$^{-7}$ d yr$^{-1}$ can be interpreted as a mass transfer from the secondary component to the primary star at a rate of 1.51$\times$10$^{-7}$ M$_\odot$ yr$^{-1}$. The periods and semi-amplitudes of the two periodic variations are about $P_3$ = 16.0 yr and $P_4$ = 26.3 yr, and $K_3$ = 0.0341 d and $K_4$ = 0.0305 d, respectively. The most likely explanation of both cycles is a pair of light-traveling time effects operated by the possible presence of third and fourth components with estimated masses of $M_3$ = 2.20 M$_\odot$ and $M_4$ = 1.27 M$_\odot$ in eccentric orbits of $e_3$ = 0.66 and $e_4$ = 0.52. Because the contribution of $\ell_{3}$ is very low compared to the estimated masses of two circumbinary objects, they can be inferred as very faint compact objects.

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