  The multimessenger event GW170817/GRB 170817A confirmed that binary neutron
star (BNS) mergers can produce short gamma-ray burst (SGRB) jets. This evidence
promoted new investigations on the mechanisms through which a BNS merger
remnant can launch such a powerful relativistic outflow and on the propagation
of the latter across the surrounding post-merger environment. In particular,
great strides have been made in jet propagation models, establishing
connections between the initial jet launching conditions, including the
incipient jet launching time (with respect to merger) and the injection
parameters, and the observable SGRB prompt and afterglow emission. However,
present semi-analytical models and numerical simulations (with one notable
exception) adopt simple hand-made prescriptions to account for the post-merger
environment, lacking a direct association with any specific merging BNS system.
Here, we present the first three-dimensional relativistic hydrodynamics
simulations of incipient SGRB jets propagating through a post-merger
environment that is directly imported from the outcome of a previous general
relativistic BNS merger simulation. Our results show that the evolution and
final properties of the jet can be largely affected by the anisotropies and the
deviations from axisymmetry and homologous expansion characterizing more
realistic BNS merger environments. In addition, we find that the inclusion of
the gravitational pull from the central compact object, often overlooked, can
have a major impact. Finally, we consider different jet launching times
referred to the same BNS merger model and discuss the consequences for the
ultimate jet properties.
