Eclipsing binaries with candidate CP stars I . Parameters of the systems

Lightcurves of three eclipsing binaries (HD 143654 = TV Nor, HD 184035 = HR 7422 and HD 185257 = HR 7464) in seven colours are analyzed and their photometric elements are given. Published radial velocities of two of them allow some constraints to be put on the masses of the components, while new radial velocities allow us to estimate the mass and absolute radius of each component of the system TVNor. There seems to be no Ap star in this system, in spite of its EuCrSr classification in the Michigan catalogue. The position of each component of TVNor in the HR diagram is in excellent agreement with stellar evolution models having Z = 0.020 and an age t = 2.51× 108 years. There is an Am star in the system HD 185257, but no CP star in the system HD 184035 in spite of its sharp lines. The physical parameters of these two binaries could be determined, but less accurately and in a less fundamental way than those of TV Nor. They match theoretical isochrones and evolutionary tracks in a satisfactory way for HD 185257, but the measured mass function of HD 184035 seems slightly too small compared with the expected theoretical masses. More data, both photometric and spectroscopic, would be useful, especially for the last two systems.