Confirmation of Large Super-fast Rotator (144977) 2005 EC_(127)

Abstract

(144977) 2005 EC_(127) is a 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 hr. However, our measurements show that asteroid 2005 EC_(127) completes one rotation in 1.65 ± 0.01 hr 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 ρ ~ 6 g cm^(−3) or an asteroid with an internal cohesion of 47 ± 30 Pa can explain 2005 EC_(127). However, the scenario of high bulk density is very unlikely for asteroids. To date, only six large super-fast rotators, including 2005 EC_(127), 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 reporting large SFRs are classified as C-type asteroids.

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