Top: observed-minus-calculated (O–C) diagram for the whole set of transit timing available to date in the literature, calculated on the ephemeris given by Bean et al. (2011). Our measurements are drawn as filled squares and in addition highlighted by colors in the online version. The dashed line represents the new ephemeris calculated in this work. Bottom: same data set after removing the new ephemeris, including its 1-σ errors (dashed lines).