Principal Component Analysis in the Modeling of Colors of Comae of Comets Hale-Bopp and Tabur

The temporal variability of the colors of comae of comets has been reported for some decades. The color indices B-R of comets Hale-Bopp and Tabur were estimated with a variation of the model of Kolokolova et al., according to geometrical, populational, and compositional parameters of cometary dust. A principal component analysis of five model parameters points that the variation of these color indices is usually associated with changes in population or geometric parameters, and their extremes with a compositional variation of the dust grains.