Title: Asteroid 2017 FZ2 et al.: signs of recent mass-shedding from YORP?,
Abstract: The first direct detection of the asteroidal YORP effect, a phenomenon that
changes the spin states of small bodies due to thermal reemission of sunlight
from their surfaces, was obtained for (54509) YORP 2000 PH5. Such an alteration
can slowly increase the rotation rate of asteroids, driving them to reach their
fission limit and causing their disruption. This process can produce binaries
and unbound asteroid pairs. Secondary fission opens the door to the eventual
formation of transient but genetically-related groupings. Here, we show that
the small near-Earth asteroid (NEA) 2017 FZ2 was a co-orbital of our planet of
the quasi-satellite type prior to their close encounter on 2017 March 23.
Because of this flyby with the Earth, 2017 FZ2 has become a non-resonant NEA.
Our N-body simulations indicate that this object may have experienced
quasi-satellite engagements with our planet in the past and it may return as a
co-orbital in the future. We identify a number of NEAs that follow similar
paths, the largest named being YORP, which is also an Earth's co-orbital. An
apparent excess of NEAs moving in these peculiar orbits is studied within the
framework of two orbit population models. A possibility that emerges from this
analysis is that such an excess, if real, could be the result of mass shedding
from YORP itself or a putative larger object that produced YORP. Future
spectroscopic observations of 2017 FZ2 during its next visit in 2018 (and of
related objects when feasible) may be able to confirm or reject this
interpretation.