Anatomy of an Asteroid Breakup: The Case of P/2013 R3

Abstract

We present an analysis of new and published data on P/2013 R3, the first asteroid detected while disintegrating. Thirteen discrete components are measured in the interval between UT 2013 October 01 and 2014 February 13. We determine a mean, pair-wise velocity dispersion among these components of Delta nu = 0.33. +/- 0.03 ms(-1) and find that their separation times are staggered over an interval of similar to 5 months. Dust enveloping the system has, in the first observations, a cross-section of. similar to 30 km(2) but fades monotonically at a rate consistent with the action of radiation pressure sweeping. The individual components exhibit comet-like morphologies and also fade except where secondary fragmentation is accompanied by the release of additional dust. We find only upper limits to the radii of any embedded solid nuclei, typically similar to 100-200 m (geometric albedo 0.05 assumed). Combined, the components of P/2013 R3 would form a single spherical body with a. radius of less than or similar to 400 m, which is our best estimate of the size of the precursor object. The observations are consistent with rotational disruption of a weak (cohesive strength of similar to 50 to 100 N m(-2)) parent body, similar to 400 m in radius. Estimated radiation (YORP) spin-up times of this parent are. less than or similar to 1 Myr, shorter than the collisional lifetime. If present, water ice sublimating at as little as 10-3 kg s(-1) could generate a torque on the parent body rivaling the YORP torque. Under conservative assumptions about the frequency of similar disruptions, the inferred asteroid debris production rate is greater than or similar to 10(3) kg s-1, which is at least 4% of the rate needed to maintain the Zodiacal Cloud.