  Here we present new adaptive optics observations of the Quaoar-Weywot system.
With these new observations we determine an improved system orbit. Due to a
0.39 day alias that exists in available observations, four possible orbital
solutions are available with periods of $\sim11.6$, $\sim12.0$, $\sim12.4$, and
$\sim12.8$ days. From the possible orbital solutions, system masses of
$1.3-1.5\pm0.1\times10^{21}$ kg are found. These observations provide an
updated density for Quaoar of $2.7-5.0{g cm$^{-3}$}$. In all cases, Weywot's
orbit is eccentric, with possible values $\sim0.13-0.16$. We present a
reanalysis of the tidal orbital evolution of the Quoaor-Weywot system. We have
found that Weywot has probably evolved to a state of synchronous rotation, and
have likely preserved their initial inclinations over the age of the Solar
system. We find that for plausible values of the effective tidal dissipation
factor tides produce a very slow evolution of Weywot's eccentricity and
semi-major axis. Accordingly, it appears that Weywot's eccentricity likely did
not tidally evolve to its current value from an initially circular orbit.
Rather, it seems that some other mechanism has raised its eccentricity
post-formation, or Weywot formed with a non-negligible eccentricity.

Earth and Planetary Astrophysics