A New Large Super-Fast Rotator: (335433) 2005 UW163

TL;DR

The paper reports the discovery of (335433) 2005 UW163, a super-fast V-type asteroid with a rotation period of 1.290 hours, challenging the typical spin cutoff for rubble-pile asteroids larger than 150 meters.

Contribution

It presents the first observation of a super-fast rotator beyond the small monolithic asteroid regime, expanding understanding of asteroid structural diversity.

Findings

(335433) 2005 UW163 has a rotation period of 1.290 hours.

It is a V-type asteroid with a diameter of approximately 0.6 km.

This asteroid exceeds the typical spin rate limit for rubble-pile asteroids.

Abstract

Asteroids of size larger than 150 m generally do not have rotation periods smaller than 2.2 hours. This spin cutoff is believed to be due to the gravitationally bound rubble-pile structures of the asteroids. Rotation with periods exceeding this critical value will cause asteroid breakup. Up until now, only one object, 2001 OE84, has been found to be an exception to this spin cutoff. We report the discovery of a new super-fast rotator, (335433) 2005 UW163, spinning with a period of 1.290 hours and a lightcurve variation of $r'\sim0.8$ mag from the observations made at the P48 telescope and the P200 telescope of the Palomar Observatory. Its $H_{r'} = 17.69 \pm 0.27$ mag and multi-band colors (i.e., $g'-r' = 0.68\pm0.03$ mag, $r'-i' = 0.19\pm0.02$ mag and SDSS $i-z = -0.45$ mag) show it is a V-type asteroid with a diameter of $0.6 +0.3/-0.2$ km. This indicates (335433) 2005 UW163 is a super-fast rotator beyond the regime of the small monolithic asteroid.