系外行星研究组知识库

The basic physical parameters of asteroids, such as spin parameters, shape and scattering parameters, can provide us with information on the formation and evolution of both the asteroids themselves and the entire solar system. In a majority of asteroids, the disk-integrated photometry measurement constitutes the primary source of the above knowledge. In the present paper, newly observed photometric data and existing data on (585) Bilkis are analyzed based on a Lommel-Seeliger ellipsoid model. With a Markov chain Monte Carlo (MCMC) method, we have determined the spin parameters (period, pole orientation) and shape (b/a, cla) of (585) Bilkis and their uncertainties. As a result, we obtained a rotational period of 8.5738209 h with an uncertainty of 9 x 10(-7) h, and derived a pole of (136.46 degrees, 29.0 degrees) in the ecliptic frame of J2000.0 with uncertainties of 0.67 degrees and 1.1 degrees in longitude and latitude respectively. We also derived triaxial ratios b/a and c/a of (585) Bilkis as 0.736 and 0.70 with uncertainties of 0.003 and 0.03 respectively.