Asteroid phase curves and phase coloring effect using the ATLAS survey data

Abstract: We determined phase curves for 301,272 asteroids in the orange filter and 280,953 in the cyan filter from the latest ATLAS Solar System Catalog V2 (SSCAT-2). Among them, 3,345 and 492 asteroids in the orange and cyan filters, respectively, have uncertainties below 15%. Our simple model, which considers only the apparition effect, showed good consistency with more sophisticated methods requiring much less computational time. Database cross-matching allowed us to analyze G1 and G2 distributions according to taxonomy. We conducted two-dimensional Kolmogorov-Smirnov tests to investigate two distinct aspects: similarities in paired G1, G2 distributions across different taxa and wavelength dependency within the same taxa. When comparing different taxa, we couldn't reject the null hypothesis for 11% of the orange sample and 31% of the cyan sample, indicating more disparities in the orange filter. For wavelength dependency, paired distributions of G1, G2 (o) vs. G1, G2 (c) showed statistically significant differences across all complexes, except for the A class. Our analysis suggests that while phase coloring behaviors are observed without a clear preference for reddening or bluening at phase angles below 5 degrees, reddening predominates in the 10 - 30 degrees range. We also observed smaller uncertainties in G2 than in G1. Simulations showed that G2 is less sensitive to lack of data at small phase angles. This is related to the definition of the H,G1,G2 function, where G1 contributes more to the opposition effect and G2 the linear part of the phase curve. Our catalog-independent algorithms are adaptable to new data sets, including future LSST data.