A survey of small fast rotating asteroids among the near-Earth asteroid population

摘要

A survey of 62 small near-Earth asteroids was conducted to determine the rotation state of these objects and to search for rapid rotation. Since results for 9 of the asteroids were previously published (Pravec, P., Hergenrother, C.W., Whiteley, R.J., ?arounová, L., Ku?nirák, P., Wolf, M. [2000]. Icarus 147, 477-486; Pravec, P. et al. [2005] Icarus 173, 108-131; Whiteley, R.J., Tholen, D.J., Hergenrother, C.W. [2002a]. Icarus 157, 139-154; Hergenrother, C.W., Whiteley, R.J., Christensen, E.J. [2009]. Minor Planet Bull. 36, 16-18.), this paper will present results for the remaining 53 objects. Rotation periods significantly less than 2h are indicative of intrinsic strength in the asteroids, while periods longer than 2h are typically associated with gravitationally bound aggregates. Asteroids with absolute magnitude (H) values ranging from 20.4 to 27.4 were characterized. The slowest rotator with a definite period is 2004 BW_(18) with a period of 8.3h, while 2000 DO_8 and 2000 WH_(10) are the fastest with periods of 1.3min. A minimum of two-thirds of asteroids with H>20 are fast rotating and have periods significantly faster than 2.0h. The percentage of rapid rotators increases with decreasing size and a minimum of 79% of H≥24 objects are rapid rotators. Slowly-rotating objects, some with periods as long as 10-20h, make up a small though significant fraction of the small asteroid population. There are three fast rotators with relatively large possible diameters (D): 2001 OE_(84) with 470≤D≤820m (Pravec, P., Ku?nirák, P., ?arounová, L., Harris, A.W., Binzel, R.P., Rivkin, A.S. [2002b]. Large coherent Asteroid 2001 OE84. In: Warmbein, B. (Eds.), Proceedings of Asteroids, Comets, Meteors - ACM 2002. Springer, Berlin, pp. 743-745), 2001 FE90 with 265≤D≤594m (Hicks, M., Lawrence, K., Rhoades, H., Somers, J., McAuley, A., Barajas, T. [2009]. The Astronomer's Telegrams, # 2116), and 2001 VF_2 with a possible D of 145≤D≤665m. Using the diameters derived from nominal absolute magnitudes and albedos, the remainder of the fast rotating population is completely consistent with D≤200m. Even when taking into account the largest possible uncertainties in the determination of diameters, the remainder must all have D≤400m. With the exceptions of 2001 OE_(84), this result agrees with previous upper diameter limits for fast rotators in Pravec and Harris (Pravec, P., Harris, A.W. [2000]. Icarus 148, 589-593) and Whiteley et al. (Whiteley, R.J, Tholen, D.J., Hergenrother, C.W. [2002a]. Icarus 157, 139-154.