2004A&A...417.1083S

The orbit and physical parameters of the previously unsolved eclipsing binary V432 Aur, discovered by Hipparcos, have been derived with errors better than 1% from extensive Echelle spectroscopy and B, V photometry. Synthetic spectral analysis of both components has been performed, yielding T_eff and logg in close agreement with the orbital solution, a metallicity [Z/Z_☉]=-0.6 and rotational synchronization for both components. Direct comparison on the theoretical L, T_eff plane with the Padova evolutionary tracks and isochrones for the masses of the two components (1.22 and 1.08M_☉) provides a perfect match and a 3.75 Gyr age. The more massive and cooler component is approaching the base of the giant branch and displays a probable pulsation activity with an amplitude of ΔV=0.075mag and Δrad.vel.=1.5km/s. With a T_eff=6080K it falls to the red of the nearby instability strip populated by δ Sct and γ Dor types of pulsating variables. Orbital modeling reveals a large and bright surface spot on it. The pulsations activity and the large spot(s) suggest the presence of macro-turbulent motions in its atmosphere. They reflect in a line broadening that at cursory inspection could be taken as indication of a rotation faster than synchronization, something obviously odd for an old, expanding star.