Thick (thin) solid lines are 1, 2, and 3σ constraint contours for the XCDM parametrization from a joint analysis of the BAO and SNeIa (with systematic errors) data, with (and without) the ADD data. The cross (“+”) marks the best-fit point determined from the joint sample without the ADD data at Ω_m0 = 0.28 and ω_X =  −1.04 with . The star (“ ∗ ”) marks the best-fit point determined from the joint sample with the ADD data at Ω_m0 = 0.28 and ω_X =  −0.99 with . The dashed horizontal line at ω_X =  −1 corresponds to spatially flat ΛCDM models.