HIPPARCOS ABSOLUTE MAGNITUDES FOR METAL-RICH K-GIANT AND THE CALIBRATION OF DDO PHOTOMETRY

Parallaxes for 581 bright K giants have been determined using the Hipp arcos satellite. We combine the trigonometric parallaxes with ground-b ased photometric data to determine the K giant absolute magnitudes. Fo r all these giants, absolute magnitude estimates can also be made usin g the intermediate-band photometric David Dunlop Observatory (DDO) sys tem. We compare the DDO absolute magnitudes with the very accurate Hip parcos absolute magnitudes, finding various systematic offsets in the DDO system. These systematic effects can be corrected, and we provide a new calibration of the DDO system allowing absolute magnitude to be determined with an accuracy of 0.35 mag in the range 2 > M-v > -1. The new calibration performs well when tested on K giants with DDO photom etry in a selection of low-reddening open clusters with well-measured distance moduli.