The DECam Ecliptic Exploration Project (DEEP). VII. The Strengths of Three Superfast Rotating Main-belt Asteroids from a Preliminary Search of DEEP Data

TL;DR

This study identifies three superfast rotating main-belt asteroids from DEEP data, revealing a higher occurrence rate in small sub-kilometer objects and providing insights into their internal cohesion and evolution.

Contribution

It presents the first detection of multiple superfast rotators in the main belt within a large survey, highlighting the prevalence of cohesive forces in small asteroids.

Findings

Three SFRs found among 686 asteroids, indicating a 0.4% occurrence rate.

All three SFRs require cohesive strengths exceeding weak regolith.

Estimated ~300 SFRs in the entire DEEP dataset.

Abstract

Superfast rotators (SFRs) are small solar system objects that rotate faster than generally possible for a cohesionless rubble pile. Their rotational characteristics allow us to make inferences about their interior structure and composition. Here, we present the methods and results from a preliminary search for SFRs in the DECam Ecliptic Exploration Project (DEEP) data set. We find three SFRs from a sample of 686 main-belt asteroids, implying an occurrence rate of 0.4 -0.3/+0.1 percent - a higher incidence rate than has been measured by previous studies. We suggest that this high occurrence rate is due to the small sub-kilometer size regime to which DEEP has access: the objects searched here were as small as 500 m. We compute the minimum required cohesive strength for each of these SFRs and discuss the implications of these strengths in the context of likely evolution mechanisms. We find that all three of these SFRs require strengths that are more than that of weak regolith but consistent with many cohesive asteroid strengths reported in the literature. Across the full DEEP data set, we have identified ~70,000 Main-Belt Asteroids and expect ~300 SFRs - a result that will be assessed in a future paper.