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We present a detailed study of the G0V detached eclipsing binary EW Ori,based on new photometric and spectroscopic observations. Masses and radii thatare precise to 0.9% and 0.5%, respectively, have been established for bothcomponents. The 1.12 Msun secondary component reveals weak Ca II H and Kemission and is probably mildly active; no signs of activity are seen for the1.17 Msun primary. We derive an [Fe/H] abundance of +0.05 +/- 0.09 and similarabundances for Si, Ca, Sc, Ti, Cr, and Ni. Yonsai-Yale and Granada solar-scaledevolutionary models for the observed metal abundance reproduce the componentsfairly well at an age of approx. 2 Gyr. Perfect agreement is, however, obtainedat an age of 2.3 Gyr for a combination of a) a slight downwards adjustment ofthe envelope mixing length parameter for the secondary, as seen for otheractive solar-type stars, and b) a slightly lower helium content than prescribedby the Y-Z relations adopted for the standard model grids. The orbit iseccentric (e = 0.0758 +/- 0.0020), and apsidal motion with a 62% relativisticcontribution has been detected. The apsidal motion period is U = 16300 +/- 3900yr, and the inferred mean central density concentration coefficient, log(k_2) =-1.66 +/- 0.30, agrees marginally with model predictions. The measuredrotational velocities, 9.0 +/- 0.7 (primary) and 8.8 +/- 0.6 (secondary) km/s,are in agreement with both the synchronous velocities and the theoreticallypredicted pseudo-synchronous velocities. Finally, the distance (175 +/- 7 pc),age, and center-of mass velocity (6 km/s) exclude suggested membership of theopen cluster Collinder 70. EW Ori now belongs to the small group of solar-typeeclipsing binaries with well-established astrophysical properties.

Absolute dimensions of solar-type eclipsing binaries. III. EW Orionis. Stellar evolutionary models tested by a G0V system