The differential rotation of ε Eri from MOST data

From high-precision MOST photometry spanning 35 days the existence of two spots rotating with slightly differing periods is confirmed. From the marginal probability distribution of the derived differential rotation parameter k its expectation value as well as confidence limits are computed directly from the data. The result depends on the assumed range in inclination i, not on the shape of the prior distributions. Two cases have been considered: (a) The priors for angles, inclination i of the star and spot latitudes β1,2, are assumed to be constant over i, β1, and β2. (b) The priors are assumed to be constant over cos i, sin β1, and sin β2. In both cases the full range of inclination is considered: 0 ≤ i ≤ 90. Scalefree parameters, i. e. periods and spot areas (in case of small spots) are taken logarithmically. Irrespective of the shape of the prior, k is restricted to 0.03 ≤ k ≤ 0.10 (one-σ limits). The inclination i of the star is photometrically ill-defined.