Pseudomagnitude distances applied to the Pleiades

Pseudomagnitudes are distance indicators, which have the remarkable property of being reddening free. In this study, we use Hipparcos parallax measurements to compute the mean absolute pseudomagnitudes of solar neighbourhood dwarf stars as a function of their spectral type.

To illustrate the use of absolute pseudomagnitudes, we derive the distance moduli of 360 Pleiades stars and find that the centroid of their distribution is 5.71+/-0.018, corresponding to a distance of 139.0+/-1.2pc. We locate the subset of ~50 Pleiades stars observed by Hipparcos at a mean distance of 135.5+/-3.7pc, thus confirming the frequently reported anomaly in the Hipparcos measurements of these stars.