# Physical characterization of NEA Large Super-Fast Rotator (436724) 2011 UW158

## TL;DR

This study characterizes the physical properties of NEA 2011 UW158, a large super-fast rotator, using optical and radar data to determine its rotation period, spin axis, and 3D shape, challenging the cohesionless spin barrier rule.

## Contribution

It provides the first detailed physical characterization of NEA 2011 UW158, confirming it as a large super-fast rotator and offering insights into its spin state and shape.

## Key findings

- Rotation period of 0.610752 hours
- Unique spin axis solution at ecliptic coordinates (290°, 39°)
- 3D shape model consistent with radar data

## Abstract

Asteroids of size larger than 0.15 km generally do not have periods smaller than 2.2 hours, a limit known as cohesionless spin barrier. This barrier can be explained by the cohesionless rubble-pile structure model. There are few exceptions to this <<rule>>, called LSFRs (Large Super-Fast Rotators), as (455213) 2001 OE84, (335433) 2005 UW163 and 2011 XA3. The near-Earth asteroid (436724) 2011 UW158 was followed by an international team of optical and radar observers in 2015 during the flyby with Earth. It was discovered that this NEA is a new candidate LSFR. With the collected lightcurves from optical observations we are able to obtain the amplitude-phase relationship, sideral rotation period ($PS = 0.610752 \pm 0.000001$ h), a unique spin axis solution with ecliptic coordinates $ \lambda = 290^{\circ} \pm 3^{\circ}$, $\beta = 39^{\circ} \pm 2^{\circ}$ and the asteroid 3D model. This model is in qualitative agreement with the results from radar observations.