Shape model and spin state of non-principal axis rotator (5247) Krylov

¹ Chungbuk National University, 1 Chungdae-ro, Seowon-gu, Cheongju, Chungbuk 28644, Korea
² Korea Astronomy and Space Science Institute, 776, Daedeokdae-ro, Yuseong-gu, Daejeon 34055, Korea
e-mail: hjlee@kasi.re.kr
³ Astronomical Institute, Faculty of Mathematics and Physics, Charles University, V Holešovičkách 2, 180 00 Prague 8, Czech Republic
⁴ University of Science and Technology, 217, Gajeong-ro, Yuseong-gu, Daejeon 34113, Korea
⁵ Modra Observatory, Department of Astronomy, Physics of the Earth, and Meteorology, FMPI UK, Bratislava 84248, Slovakia
⁶ Sugarloaf Mountain Observatory, South Deerfield, MA, USA
⁷ Astronomical Observatory Institute, Faculty of Physics, Adam Mickiewicz University, Słoneczna 36, 60-286 Poznaǹ, Poland
⁸ Akdeniz University, Department of Space Sciences and Technologies, 07058 Antalya, Turkey
⁹ TÜBİTAK National Observatory, Akdeniz University Campus, 07058 Antalya, Turkey
¹⁰ Departamento de Sistema Solar, Instituto de Astrofísica de Andalucía (CSIC), Glorieta de la Astronomía s/n, 18008 Granada, Spain

Received: 30 September 2019
Accepted: 5 February 2020

Abstract

Context. The study of non-principal axis (NPA) rotators can provide important clues to the evolution of the spin state of asteroids. However, very few studies to date have focused on NPA-rotating main belt asteroids (MBAs). One MBA known to be in an excited rotation state is asteroid (5247) Krylov.

Aims. By using disk-integrated photometric data, we construct a physical model of (5247) Krylov including shape and spin state.

Methods. We applied the light curve convex inversion method employing optical light curves obtained by using ground-based telescopes in three apparitions during 2006, 2016, and 2017, along with infrared light curves obtained by the Wide-field Infrared Survey Explorer satellite in 2010.

Results. Asteroid (5247) Krylov is spinning in a short axis mode characterized by rotation and precession periods of 368.7 and 67.27 h, respectively. The angular momentum vector orientation of Krylov is found to be λ_L = 298° and β_L = −58°. The ratio of the rotational kinetic energy to the basic spin-state energy E∕E₀ ≃ 1.02 shows that the (5247) Krylov is about 2% excited state compared to the principal axis rotation state. The shape of (5247) Krylov can be approximated by an elongated prolate ellipsoid with a ratio of moments of inertia of I_a : I_b : I_c = 0.36 : 0.96 : 1. This is the first physical model of an NPA rotator among MBAs. The physical processes that led to the current NPA rotation cannot be unambiguously reconstructed.