2012A&A...537A.117T

Accurate physical properties of eclipsing stars provide important constraints on models of stellar structure and evolution, especially when combined with spectroscopic information on their chemical composition. Empirical calibrations of the data also lead to accurate mass and radius estimates for exoplanet host stars. Finally, accurate data for unusual stellar subtypes, such as Am stars, also help to unravel the cause(s) of their peculiarities. We aim to determine the masses, radii, effective temperatures, detailed chemical composition and rotational speeds for the Am-type eclipsing binaries SWCMa (A4-5m) and HWCMa (A6m) and compare them with similar normal stars. Accurate radial velocities from the Digital Speedometers of the Harvard-Smithsonian Center for Astrophysics were combined with previously published uvby photometry to determine precise physical parameters for the four stars. A detailed abundance analysis was performed from high-resolution spectra obtained with the Nordic Optical Telescope (La Palma). We find the masses of the (relatively evolved) stars in SWCMa to be 2.10 and 2.24M_☉, with radii of 2.50 and 3.01R_☉, while the (essentially zero-age) stars in HWCMa have masses of 1.72 and 1.78M_☉, radii of 1.64 and 1.66R_☉ - all with errors well below 2%. Detailed atmospheric abundances for one or both components were determined for 14 elements in SWCMa ([Fe/H]=+0.49/+0.61dex) and 16 in HWCMa ([Fe/H]=+0.33/+0.32dex); both abundance patterns are characteristic of metallic-line stars. Both systems are well fit by current stellar evolution models for assumed bulk abundances of [Fe/H]=+0.05 and +0.23, respectively ([α/Fe]=0.0), and ages of ∼700Myr and 160Myr.