The Pleiades eclipsing binary HD 23642 revisited

Context.HD 23642 is the only known eclipsing binary in the Pleiades, and therefore of importance in determining the distance to this cluster. Aims.To use new photometric and spectroscopic data in combination with existing data in the literature in order to improve the determination of the parameters of the system, its distance and reddening. Methods.New photometric and spectroscopic data are presented for HD 23642. The spectroscopic data are “spectrally disentangled” using the KOREL code. The new and literature photometric and radial velocity data are simultaneously analysed using the FOTEL code to obtain the orbital solution and derive the fundamental parameters of the two stars. The distance and reddening are determined by fitting 7-colour Geneva, $B,V$ and Strömgren colours, and considering surface-brightness relations for the two components in $(B-V)$ and Strömgren c1-index. Results.The preferred distance is $138.0 \pm 1.5$ pc for a reddening of $E(B-V) = 0.025 \pm 0.003$. The reddening value is larger than the 0.012 adopted in the recent works on this stars by Munari et al. (2004) and Southworth et al. (2005), and smaller than other values in the literature for the cluster reddening. The distance is in agreement with other recent works on the distance to the Pleiades. A comparison with evolutionary models suggests that the inclusion of convective core overshoot gives a much better fit to the empirical mass-radius relationship obtained from the binary analysis. Both this comparison and the “spectral disentangling” are consistent with HD 23642 having [ Fe/H$]=+0.06$, a value determined by the most recent spectroscopical analyses of Pleiades stars