9 Conclusion

The simultaneous adjustment of the light curve model on high precision photometric data in seven passbands, ranging from 3400 to 6000 Å, put strong constraints on the physical and orbital parameters of TZ Eri. This is our first analysis of an Algol system on the basis of measurements made in the Geneva photometric system. The essential results are presented in Figs. 4 and 5, Tables 8 and 9, and in the Abstract. The quality of the fits on the light curves and the uncertainties on the parameters show that this analysis has been successful.

A further improvement on the determination of the physical parameters of the components of TZ Eri, in particular the mass ratio, would result from the acquisition of additional high S/N spectra of the secondary cool component. Indeed, the present study is based on only one spectrum of the secondary and this is not completely satisfying. However, this spectrum was obtained using the 3.5 m NTT telescope at La Silla and we were extremely lucky to have access to this large telescope for this single measurement.

According to Maxted & Hilditch (1996), the number of Algol-type binary systems for which the absolute parameters are determined on the basis of a self-consistent solution of both the light and radial velocity curves is very limited. They mentioned only 9 systems for which masses, radii and luminosities are known to accuracies typically better than 5%. In this context, it is important to enlarge the sample of very well known Algols, and this was the aim of our study on TZ Eri.

Acknowledgements

This work has been initiated by our late colleague Zdenek Kviz who obtained himself the major part of the photometric data; indeed, we would have preferred to do this analysis with him. We are grateful to Drs. R.E. Wilson for the programme of analysis of the light curves, B. Nicolet for the treatment of the Kurucz's fluxes, D. Raboud for the NTT observations of the secondary, J.-C. Mermilliod and J. Andersen for the CORAVEL measurements, M. Künzli for the photometric observations of 1996 and M. Studer for the reduction of the NTT spectrum. All graphs have been produced using the SuperMongo package (Lupton & Monger 1998). This work has been partly supported by the Swiss National Science Foundation. The Mount Laguna Observatory is operated jointly by San Diego State University and the University of Illinois.