Contact binary asteroid (153201) 2000 WO₁₀₇: Rotation, shape model, and density

Context . The spectral properties and albedo of near-Earth asteroid (153201) 2000 WO 107 are consistent with a taxonomic type M. This implies that it might have a high metal abundance and higher density. Aims . We combined different methods to investigate the asteroid rotation, determine its shape, and use it to estimate its density. Methods . We carried out photometric observations of the asteroid during the 2020 apparition. We then created a program to simulate the light curves, and used it within a Markov chain Monte Carlo (MCMC) algorithm to reconstruct the asteroid shape model from the observational data. The Goldstone radar observations of the asteroid were used as an additional constraint on the asteroid model in the MCMC algorithm. The estimated shape and rotation rate of the contact binary were used to compute its density. Results . The photometric observations of (153201) 2000 WO 107 obtained at a wide range of the phase angles from 5 to 68 degrees in the time interval of November 28 – December 8, 2020, show light curves typical for contact binary asteroids, which agrees with the results of the radar data. The light curves have a maximum amplitude of up to 1.24 mag. The best-fit modeled shape of the asteroid is composed of two ellipsoidal lobes with axes of 0.68 × 0.38 × 0.36 km and 0.44 × 0.42 × 0.16 km. Its sidereal rotation period is determined to be 5.017 ± 0.002 h. The most probable solution for the angular velocity vector of the asteroid indicates ecliptic coordinates of λ = 96° ± 8° and β = −78° ± 1°, but another less probable solution of around λ = 286° ± 11°, β = −76° ± 2° cannot be disregarded. The estimated density of the asteroid ρ = 4.80 −0.63 +0.34 g/cm 3 is consistent with a possible metallic composition. From the orbital simulation of this potentially hazardous asteroid, we find that its integral probability of colliding with the Earth in the next 10 000 years is 7 · 10 −5 .