The distance to the Pleiades from the eclipsing binary HD 23642

Abstract

The distance to the Pleiades open cluster is of fundamental importance to many aspects of stellar astrophysics but is currently controversial. The ‘long’ distance scale of $132 \pm 3$ pc is supported by main sequence fitting analyses, ground-based parallax observations and analysis of the astrometric binary Atlas. The ‘short’ distance scale of $120 \pm 3$ pc comes from parallaxes observed by the Hipparcos satellite. Munari et al. (2004) studied the detached eclipsing binary HD 23642 and found a distance of $132 \pm 2$ pc. We reanalyse the data of Munari et al. to explore the different methods of estimating the distance of an eclipsing binary system. We use the surface brightness relations of Kervella et al. (2004) to find a distance of $139 \pm 4$ pc, which is consistent with the ‘long’ Pleiades distance and in disagreement with the Hipparcos parallax distances to the Pleiades and to HD 23642 itself. By comparing the observed masses and radii of the binary with theoretical predictions we derive a metal abundance approximately equal to or slightly greater than solar. Further photometric observations of the binary are needed to improve the analysis.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html