Variable phase factors and color indices during the rotation of 51 Nemausa and a comparison of six apparitions

The phase factor varied between 0.032 and 0.045 mag/deg on the different sides shown during the rotation of the asteroid 51 Nemausa in the 1990 opposition. Color index variations with amplitudes 0.015 mag in u-b and 0.004 mag in v-y confirm the variations found in 1989. The effects are single periodic with one extremum and are caused by differences in composition and texture over the surface. Differences between the opposite pairs 1983–1989, 1985–1990 and 1986–1991 show identical deviations from the theoretical sine curve.