Spin State of (5247) Krylov

The spin states of asteroids are regarded as critical evidence for their evolutionary processes. In particular, the spin states of NPA (Non-Principal Axis) rotators offer significant clue to the evolutionary processes of these asteroids because their excited spin states are thought to be caused by internal and/or external forces in the past. The NPA rotation of asteroid (5247) Krylov was confirmed by Lee et al. (2017) based on photometry data in 2016. We also conducted observations of the body during the 2006 and 2017 apparitions using 0.5-2.1m telescopes. Incorporating the datasets obtained from the three apparitions, we constructed its spin state and shape model of Krylov. We found that the asteroid is rotating in Short Axis Mode (SAM) with rotation and precession periods of 68.15 h and 396.30 h, respectively. The ecliptic longitude and latitude of the angular momentum vector is 182 ° and 59 °, respectively. The largest and intermediate principal inertia moments are nearly the same: I_b/I_c = 0.98. However, the smallest principal inertia moments is less than the half of the others: I_a/I_c = 0.23. In this presentation, we will discuss the spin state and shape model of Krylov, and elaborate on the possible evolutionary processes which led to the observed spin state.