Prospects for detecting surface color heterogeneity on asteroid surfaces from sparse multiband photometric survey data

TL;DR

This study develops and evaluates a statistical method to detect surface color heterogeneity on asteroids using sparse multiband photometric survey data, assessing its sensitivity and reliability through simulations.

Contribution

It introduces a new statistical test for identifying asteroid surface heterogeneity from sparse photometry and analyzes its performance under various observational errors.

Findings

Surface color heterogeneity can be detected via light curve shape differences across wavelengths.

Detection sensitivity is highly affected by errors in the assumed rotational period.

False positives are most influenced by inaccuracies in phase function assumptions.

Abstract

Automated sky surveys frequently report sparse-in-time multiband photometric observations of asteroids passing through their fields of view. Photometric data are currently available for tens of thousands of asteroids, and new data collection is ongoing. We aim to describe and characterize the performance of a statistical test for identifying asteroids that display surface color heterogeneity based on sparse-in-time multiband photometric survey data. Using simulated photometry for a set of synthetic asteroids with predetermined physical properties, we estimated the sensitivity of the statistical test for surface color heterogeneity to errors in assumed model properties using a Monte Carlo approach. We evaluated the detection and false positive rates as a function of the number of observations, measurement noise, error in assumed period, pole orientation, shape, and phase function. We examined the required accuracy in various parameters of the photometric model needed to obtain reliable results to evaluate the feasibility of applying the test to realistic datasets. Regional-scale surface color heterogeneity can be detected by examining differences in the shape of an asteroid's light curve as a function of viewing geometry across multiple bandpasses. Differences in light curve shapes as a function of wavelength are highlighted in this work through comparison of the observed photometric measurements to the predictions of a well-fitting, uniformly colored photometric model. Statistically significant deviations from the prediction of the uniformly colored model are taken as evidence of surface color heterogeneity. The performance of this test depends on the accuracy of model assumptions, with the detection rate being most sensitive to errors in the assumed rotational period, while the false positive rate is most sensitive to errors in the assumed band-dependent phase functions.