PHYSICAL STUDIES OF ASTEROIDS - XXXIII - THE SPIN RATE OF M-TYPE ASTEROIDS

The results from photometric lightcurve observations of nine M-type as teroids are presented. New rotation periods were determined for 6 aste roids: 217 Eudora (12.54 h), 322 Phaeo (17.56 h), 572 Rebekka (5.65 h) , 757 Portland (6.58 h), 857 Glasenappia (8.23 h) and 872 Holda (7.20 h), B - V colour measurements of seventeen previously unclassified ast eroids add seven asteroids to the known M-type population. An excess o f fast rotators among M-type asteroids compared to asteroids of other taxonomic types is evident. The six asteroids with slow spin rates, bu t hitherto classified as M, are shown to have classification parameter s untypical for the M-type population.