  Gravitational wave observations of quasicircular compact binary mergers in
principle provide an arbitrarily complex likelihood over eight independent
intrinsic parameters: the masses and spins of the two merging objects. In this
work, we demonstrate by example that a simple normal approximation over fewer
(usually, three) effective dimensions provides a very accurate representation
of the likelihood, and allows us to replicate the eight-dimensional posterior
over the mass and spin degrees of freedom. Alongside this paper, we provide the
parameters for multivariate normal fits for each event published in GWTC-1 and
GWTC-2, using the posterior samples from the catalog for each associated
release. These normal approximations provide a highly efficient way to
characterize gravitational wave observations when combining large numbers of
events.
