  I present a re-analysis of the available observational constraints on the
trajectory of 'Oumuamua, the first confirmed interstellar object discovered in
the solar system. 'Oumuamua passed through the inner solar system on a
hyperbolic (i.e., unbound) trajectory. Its discovery occurred after perihelion
passage, and near the time of its closest approach to Earth. After being
observable for approximately four months, the object became too faint and was
lost at a heliocentric distance of around 3 au. Intriguingly, analysis of the
trajectory of 'Oumuamua revealed that a dynamical model including only
gravitational accelerations does not provide a satisfactory fit of the data,
and a non-gravitational term must be included. The detected non-gravitational
acceleration is compatible with either solar radiation pressure or recoil due
to outgassing. It has, however, proved challenging to reconcile either
interpretation with the existing quantitative models of such effects without
postulating unusual physical properties for 'Oumuamua (such as extremely low
density and/or unusual geometry, non-standard chemistry). My analysis
independently confirms the detection of the non-gravitational acceleration.
After comparing several possible parametrizations for this effects, I find a
strong preference for a radially directed non-gravitational acceleration,
pointing away from the Sun, and a moderate preference for a power-law scaling
with the heliocentric distance, with an exponent between 1 and 2. These results
provide valuable constraints on the physical mechanism behind the effect; a
conclusive identification, however, is probably not possible on the basis of
dynamical arguments alone.
