ALBEDO PROPERTIES OF MAIN BELT ASTEROIDS BASED ON THE ALL-SKY SURVEY OF THE INFRARED ASTRONOMICAL SATELLITEAKARI

Abstract

We present an analysis of the albedo properties of main belt asteroids detected by the All-Sky Survey of the infrared astronomical satellite AKARI. The characteristics of 5120 asteroids detected by the survey, including their sizes and albedos, were cataloged in the Asteroid Catalog Using AKARI (AcuA). Size and albedo measurements were based on the Standard Thermal Model, using inputs of infrared fluxes and absolute magnitudes measured at optical wavelengths. Main belt asteroids, which account for 4722 of the 5120 AcuA asteroids, have semimajor axes of 2.06 to 3.27 AU, except for the near-Earth asteroids. AcuA provides a complete data set of all main belt asteroids brighter than the absolute magnitude of H < 10.3, which corresponds to the diameter of d > 20 km. We confirmed that the albedo distribution of the main belt asteroids is strongly bimodal as was already known from the past observations, and that the bimodal distribution occurs not only in the total population, but also within inner, middle, and outer regions of the main belt. The bimodal distribution in each group consists of low-albedo components in C-type asteroids and high albedo components in S-type asteroids. We found that the small asteroids have much more variety in -2albedo than the large asteroids. In spite of the albedo transition process like space weathering, the heliocentric distribution of the mean albedo of asteroids in each taxonomic type is nearly flat. The mean albedo of the total, on the other hand, gradually decreases with an increase in semimajor axis. This can be explained by the compositional ratio of taxonomic types; that is, the proportion of dark asteroids such as C-and D-types increases, while that of bright asteroids such as S-type decreases, with increasing heliocentric distance. The heliocentric distributions of X-subclasses: E-, M-, and P-type, which can be divided based on albedo values, are also examined. P-type, which is the major component in X-types, are distributed throughout the main belt regions, and the abundance of P-type increases beyond 3 AU. This distribution is similar to that of C-or D-types.

Shape and Rotational Motion Models for Tumbling and Monolithic Asteroid 2012 TC4: High Time Resolution Light Curve with the Tomo-e Gozen Camera

“…where p V is the geometric albedo. Assuming an albedo of 0.098 ± 0.081 for the X-type (Usui et al 2013), the effective diameter and range were found to be 8 m and 6 m < D < 20 m, respectively. Since Mainzer et al (2011b) also showed the albedo of 0.099 ± 0.161 for Tholen X-complex class and the albedo of 0.111 ± 0.143 for Bus-DeMeo X-complex class, the assumption of ∼0.1 for the X-type albedo was reasonable.…”

PROSPECTS FOR CHARACTERIZING THE ATMOSPHERE OF PROXIMA CENTAURI b

“…For both scenarios, we assumed an inclination of 60 • (the median value for an isotropic distribution of inclinations) and a Bond albedo of 0.1 (a typical value for rocky bodies; Usui et al 2013). Physically realistic atmospheres would likely have a higher albedo (e.g., Earth's albedo is 0.3).…”

Near-Earth asteroid (3200) Phaethon: Characterization of its orbit, spin state, and thermophysical parameters

“…Although thermal infrared data of Phaethon exist that allowed determining a radiometric diameter (Green et al 1985;Tedesco et al 2002;Usui et al 2011Usui et al , 2013, there is currently no estimate available for the thermal inertia for this body.…”