Fast Rotating Asteroids 1999 TY₂, 1999 SF₁₀, and 1998 WB₂

Petr Pravec
Astronomical Institute, Academy of Sciences of the Czech Republic, CZ-25165 Ondrejov, Czech Republic
E-mail: ppravec@asu.cas.cz


Carl Hergenrother
Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721, USA


Rob Whiteley
Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822, USA


Lenka Sarounová and Peter Kusnirák
Astronomical Institute, Academy of Sciences of the Czech Republic, CZ-25165 Ondrejov, Czech Republic


and


Marek Wolf
Astronomical Institute, Charles University Prague, V Holesovickách 2, CZ-18000 Praha, Czech Republic

Submitted to Icarus, 1999 December 13.

Pages: 21, Figures: 7, Tables: 4

Abstract:

An analysis of our photometric observations of near-Earth asteroids 1999 TY₂, 1999 SF₁₀ and 1998 WB₂ has revealed their rotation periods to be $(7.2807 \pm 0.0003)$ min, $(2.4663 \pm 0.0005)$ min and $(18.8 \pm 0.3)$ min, respectively. Their rotations are so fast that the bodies cannot be held together by self-gravitation alone, and must therefore be monoliths. Their absolute magnitudes, $23.1 \pm 0.3, 24.0 \pm 0.5$ and $22.1 \pm 0.2$, respectively, indicate that they are small bodies with mean diameters in the range 60-120 meters. The current statistics of asteroid spin rates vs. size suggest that the range where monoliths start to dominate among asteroids is below a diameter of about 200 meters, corresponding to $H\approx 22$, as suggested by Pravec and Harris (1999, Icarus, submitted).