Determination of 1929 Asteroid Rotation Periods from WISE Data

Abstract

We used 22 μm (W4) Wide-field Infrared Survey Explorer (WISE) observations of 4420 asteroids to analyze lightcurves, and determined spin period estimates for 1929 asteroids. We fit second-order Fourier models at a large number of trial frequencies to the W4 data and analyzed the resulting periodograms. We initially excluded rotational frequencies exceeding 7.57 rotations per day (P < 3.17 hr), which are not sampled adequately by WISE, and periods that exceed twice the WISE observation interval, which is typically 36 hr. We found that three solutions accurately capture the vast majority of the rotational frequencies in our sample: the best-fit frequency and its mirrors around 3.78 and 7.57 rotations per day. By comparing our solutions with a high-quality control group of 752 asteroid spin periods, we found that one of our solutions is accurate (within 5%) in 88% of the cases. The best-fit, secondary, and tertiary solutions are accurate in 55%, 27%, and 6% of the cases, respectively. We also observed that suppression of aliased solutions was more effective with nonuniform sampling than with quasi-uniform sampling.

Thermal Models of Asteroids with Two-band Combinations of Wide-field Infrared Survey Explorer Cryogenic Data

“…They found correction factors that can be multiplied by the WISE uncertainties to obtain more realistic uncertainty values. These correction factors are 1.224 for W1, 1.120 for W2, 1.479 for W3, and 1.218 for W4 (Lam et al 2023), and they have been applied to the σ i used in Equation (B1).…”