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Asiago eclipsing binaries program. I. V432 Aurigae
The orbit and physical parameters of the previously unsolved eclipsingbinary V432 Aur, discovered by Hipparcos, have been derived with errorsbetter than 1% from extensive Echelle spectroscopy and B, V photometry.Synthetic spectral analysis of both components has been performed,yielding Teff and log g in close agreement with the orbitalsolution, a metallicity [Z/Zȯ] = -0.6 and rotationalsynchronization for both components. Direct comparison on thetheoretical L, Teff plane with the Padova evolutionary tracksand isochrones for the masses of the two components (1.22 and 1.08Mȯ) provides a perfect match and a 3.75 Gyr age. Themore massive and cooler component is approaching the base of the giantbranch and displays a probable pulsation activity with an amplitude ofΔ V = 0.075 mag and Δrad.vel. = 1.5 km s-1. Witha Teff = 6080 K it falls to the red of the nearby instabilitystrip populated by δ Sct and γ Dor types of pulsatingvariables. Orbital modeling reveals a large and bright surface spot onit. The pulsations activity and the large spot(s) suggest the presenceof macro-turbulent motions in its atmosphere. They reflect in a linebroadening that at cursory inspection could be taken as indication of arotation faster than synchronization, something obviously odd for anold, expanding star.
| V432 Aur: a New Eclipsing System
V432 Aur has been discovered by the Hipparcos mission as a low amplitudevariable of unsolved nature. We have carried out extensive B, Vphotometry from Dec. 1998 to Feb. 2002 and discovered that V432 Aur isan eclipsing system with an orbital period of 3.08175 days. The primaryeclipse is about 0.37 mag deep. The secondary is well centered at phase0.5 and is about 0.26 mag deep. Both primary and secondary eclipses areflat bottomed with totality lasting about 0.035 of the orbital period.The secondary star is cooler by Delta (B-V)=0.05 (Delta T(eff) about210K) and appears to be intrinsically variable by some Delta V=0.05 mag.
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