系外行星研究组知识库

The physical properties of asteroids, such as their spin and shape, are very important for understanding the formation and evolution of the entire asteroid belt, as well as the individual asteroid itself. However, only a small part of asteroids had been determined accurately for their spin parameters and shapes due to lack of data or narrow aspect angle distribution of dataset. In the present paper, the spin parameters and convex shapes of two C-type main-belt asteroids (362) Havnia and (506) Marion are analyzed using the convex inversion method and the virtual-photometry Monte Carlo method. A pair of poles are found for (362) Havnia at (96 degrees. 2(-2.0)(+3.0), + 38 degrees. 8(-2.4)(+6.8)) and (273 degrees. 0(-6.5)(+1.3), + 40 degrees. 0(-9.9)(+1.2)) in ecliptic coordinates, the spin period values corresponding to the two poles are 16. 918773(-6.4(-6))(+2.8(-5)) h (here +2.8(-5) represents +2.8 x 10(-5)) and 16. 918935(-4.3(-5))(+1.2(-5)) h, respectively. Similarly, two candidate poles are found for (506) Marion at (88 degrees. 0(-0.3)(+1.3), + 22 degrees. 3(-1.5)(+1.3)) and (264 degrees. 5(-0.03)(+1.2), - 7 degrees. 5(-0.92)(+1.1)). The spin periods for the two poles are 13. 549826(-9.8(-6))(+1.2(-5)) h and 13.549751(-5.9(-6))(+1.3(-5)) h. The shapes of Havnia for the pair of poles approximate to Maclaurin spheroids. Whereas the convex shapes of Marion for the two poles are prolate shapes, and it rotates around the longest axis. The significant divergence of weight coefficients c for Havina and Marion implies different materials on the two asteroids' surface. (C) 2015 Elsevier Ltd. All rights reserved.