Observed epochs of minima, marked with red dots for even number minima and with green dots for odd minima, minus computed minima epochs calculated with the relation T(E) = E₀ + P E, with P = 1.88 d, which is half the sidereal period. E is the number count of the minima starting with zero. The dashed curve is a quadratic fit to all measured minima. The blue crosses mark the calculated minima from the final orbital solution relative to the linear ephemeris.