Shape-driven selection effects for aspherical near-Earth objects in systematic surveys

Abstract

The apparent magnitude of elongated small bodies is time-dependent over their rotation phase. Therefore, previously undiscovered aspherical minor planets may experience a shape-driven selection effect in systematic surveys versus their spherical counterparts. In this study, we conduct injection-recovery exercises of synthetic asteroid lightcurves using a simple model to quantify the effect of varying axial ratio on detection efficiencies. We find that high-amplitude lightcurves are confronted with adverse selection effects for survey cadences and discovery thresholds for constructing tracklets that are representative of modern and proposed future near-Earth object searches. Furthermore, we illustrate the possible hazards of drawing population-level inferences on an underlying reservoir of elongated small bodies. If physical size and characteristic axial ratios are correlated, then size-frequency distributions may require revision at small diameters. In particular, this effect could alter the estimated populations of near-Earth objects. We conclude by discussing the applicability of our results to various other classes of solar system minor planets and interstellar interlopers, as well as discussing future work that may further interrogate this detection bias.