Hee-Jae Lee

Determining the Rotation Periods of an Inactive LEO Satellite and the First Korean Space Debris on GEO, KOREASAT 1

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Confirmation of Large Super-fast Rotator (144977) 2005 EC127

(144977) 2005 EC127 is an V-/A-type inner-main-belt asteroid with a diameter of 0.6 +- 0.1 km. Asteroids of this size are believed to have rubble-pile structure, and, therefore, cannot have a rotation period shorter than 2.2 hours. However, our measurements show that asteroid 2005 EC127 completes one rotation in 1.65 +- 0.01 hours with a peak-to-peak light-curve variation of ~0.5 mag. Therefore, this asteroid is identified as a large super-fast rotator. Either a rubble-pile asteroid with a bulk density of ~6 g cm^-3 or an asteroid with an internal cohesion of 47 +- 30 Pa can explain 2005 EC127. However, the scenario of high bulk density is very unlikely for asteroids. To date, only six large super-fast rotators, including 2005 EC127, have been reported, and this number is very small when compared with the much more numerous fast rotators. We also note that none of the six reported large SFRs are classified as C-type asteroids.

PHOTOMETRIC STUDY OF NPA ROTATOR (5247) KRYLOV

We conduct BVRI and R band photometric observations of asteroid (5247) Krylov from January 2016 to April 2016 for 51 nights using the Korea Microlensing Telescope Network (KMTNet). The color indices of (5247) Krylov at the light curve maxima are determined as B − V = 0.841± 0.035, V −R = 0.418± 0.031, and V − I = 0.871± 0.031 where the phase angle is 14.1. They are acquired after the standardization of BVRI instrumental measurements using the ensemble normalization technique. Based on the color indices, (5247) Krylov is classified as a S-type asteroid. Double periods, that is, a primary period P1 = 82.188 ± 0.013h and a secondary period P2 = 67.13 ± 0.20 h are identified from period searches of its R band light curve. The light curve phases with P1 and this indicate that it is a typical Non-Principal Axis (NPA) asteroid. We discuss the possible causes of its NPA rotation.