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We introduce a method of measuring a lower limit to the amplitude of surfacedifferential rotation from high-precision, evenly sampled photometric timeseries. It is applied to main-sequence late-type stars whose optical fluxmodulation is dominated by starspots. An autocorrelation of the time series wasused to select stars that allow an accurate determination of starspot rotationperiods. A simple two-spot model was applied together with a Bayesianinformation criterion to preliminarily select intervals of the time seriesshowing evidence of differential rotation with starspots of almost constantarea. Finally, the significance of the differential rotation detection and ameasurement of its amplitude and uncertainty were obtained by an a posterioriBayesian analysis based on a Monte Carlo Markov Chain approach. We applied ourmethod to the Sun and eight other stars for which previous spot modelling hadbeen performed to compare our results with previous ones. We find thatautocorrelation is a simple method for selecting stars with a coherentrotational signal that is a prerequisite for successfully measuringdifferential rotation through spot modelling. For a proper Monte Carlo MarkovChain analysis, it is necessary to take the strong correlations among differentparameters that exist in spot modelling into account. For the planet-hostingstar Kepler-30, we derive a lower limit to the relative amplitude of thedifferential rotation of \Delta P / P = 0.0523 \pm 0.0016. We confirm that theSun as a star in the optical passband is not suitable for measuringdifferential rotation owing to the rapid evolution of its photospheric activeregions. In general, our method performs well in comparison to moresophisticated and time-consuming approaches.

Measuring stellar differential rotation with high-precision space-borne photometry