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 amongst these components of
Δv=0.33±0.03 m s−1 and find that their separation times are
staggered over an interval of ∼5 months. Dust enveloping the system has,
in the first observations, a cross-section ∼30 km2 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 ∼100 to 200 m (geometric albedo 0.05 assumed). Combined,
the components of P/2013 R3 would form a single spherical body with radius
≲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 ∼50 to 100 N m−2) parent body, ∼400 m in
radius. Estimated radiation (YORP) spin-up times of this parent are ≲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 ≳103 kg s−1, which is at least 4% of the rate needed to
maintain the Zodiacal Cloud.Comment: 44 pages, 13 figures, accepted by Astronomical Journa