The period--luminosity relation of classical Cepheids is calibrated using the Hipparcos parallax data for Cepheids within 1 kpc. The effects of physical companions and pulsation mode have been taken into account. It is pointed out that the (still) unresolved physical companions falsify the geometrical parallax and this feature may throw doubt upon the calibration performed by Feast and Catchpole (1997).
IAU Joint Discussion
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