Phase curve wavelength dependency as revealed by shape- and geometry-corrected asteroid phase curves

Through the use of inverse methods, we investigated the photometric properties of 35 well-observed asteroids by combining dense ground-based and sparse ATLAS survey data. Our rigorous analysis allowed us to derive phase curve parameters that were corrected for shape and geometry, providing insights into the waveleMilagngth dependence of asteroid photometry. Notably, we discovered distinct domains (G₁, G₂) for cyan and orange filters among S-complex asteroids, indicating wavelength sensitivity. For other asteroids, significant uncertainties exist, or their distributions of phase curve parameters overlap, making it challenging to draw definitive conclusions on wavelength dependence. This effect can be explained by considering the known correlation between geometric albedo and phase curve shape: higher albedo corresponds to flatter phase curves, while lower albedo corresponds to steeper phase curves. In cases of equal albedo, asteroids with red spectral slopes exhibit a more pronounced opposition effect in red filters, while those with blue spectral slopes show it in blue filters.

Analyzing the phase curve parameters enabled us to distinguish between more likely rotational pole solutions and estimate taxonomic complexes for unclassified objects. Additionally, examining color slope variations with phase angle revealed significant differences at smaller angles, albeit with increased uncertainties due to limited data points. While caution is necessary when extrapolating phase curves at such angles, comparisons to previous observations of (433) Eros highlight the importance of further exploration in this area.

We stress the importance of cautious interpretation and acknowledge the potential variability of observed effects across different filters. Future investigations, supported by comprehensive multi-wavelength observations, offer the potential to uncover the intricate details of asteroid photometry and enhance our understanding of the diverse characteristics of asteroids.