Constraining the shape distribution and binary fractions of asteroids observed by NEOWISE
Abstract
Knowing the shape distribution of an asteroid population gives clues to its collisional and dynamical history. Constraining light curve amplitudes (brightness variations) offers a first-order approximation to the shape distribution, provided all asteroids in the distribution were subject to the same observing biases. Asteroids observed by the NEOWISE space mission at roughly the same heliocentric distances have essentially the same observing biases and can therefore be inter-compared. We used the archival NEOWISE photometry of a statistically significant sample of Jovian Trojans, Hildas, and Main belt asteroids to compare the amplitude (and by proxy, shape) distributions of L4 vs. L5 Trojans, Trojans vs. Hildas of the same size range, and several subpopulations of Main belt asteroids.For asteroids with near-fluid rubble pile structures, very large light curve amplitudes can only be explained by close or contact binary systems, offering the potential to catalog and characterize binaries within a population and gleaning more information on its dynamical evolution. Because the structure of most asteroids is not known to a high confidence level, objects with very high light curve amplitudes can only be considered candidate binaries. In Sonnett et al. (2015), we identified several binary candidates in the Jovian Trojan and Hilda populations. We have since been conducting a follow-up campaign to obtain densely sampled light curves of the binary candidates to allow detailed shape and binary modeling, helping identify true binaries. Here, we present preliminary results from the follow-up campaign, including rotation properties.This research was carried out at the Jet Propulsion Laboratory (JPL), California Institute of Technology (CalTech) under a contract with the National Aeronautics and Space Administration (NASA) and was supported by the NASA Postdoctoral Program at JPL. We make use of data products from the Wide-field Infrared Survey Explorer, which is a joint project of the University of California, Los Angeles, and JPL/CalTech, funded by NASA. This publication also makes use of data products from NEOWISE, which is a project of JPL/CalTech, funded by the Planetary Science Division of NASA.