  We investigate the non-adiabatic effect of time-dependent deformations in the
Milky Way (MW) halo potential on stellar streams. Specifically, we consider the
MW's response to the infall of the Large Magellanic Cloud (LMC) and how this
impacts our ability to recover the spherically averaged MW mass profile from
observation using stream actions. Previously, action clustering methods have
only been applied to static or adiabatic MW systems to constrain the properties
of the host system. We use a time-evolving MW--LMC simulation described by
basis function expansions. We find that for streams with realistic
observational uncertainties on shorter orbital periods and without close
encounters with the LMC, e.g. GD-1, the radial action distribution is
sufficiently clustered to locally recover the spherical MW mass profile across
the stream radial range within a 2 sigma confidence interval determined using a
Fisher information approach. For streams with longer orbital periods and close
encounters with the LMC, e.g. Orphan-Chenab (OC), the radial action
distribution disperses as the MW halo has deformed non-adiabatically. Hence,
for OC streams generated in potentials that include a MW halo with any
deformations, action clustering methods will fail to recover the spherical mass
profile within a 2 sigma uncertainty. Finally, we investigate whether the
clustering of stream energies can provide similar constraints. Surprisingly, we
find for OC-like streams, the recovered spherically averaged mass profiles
demonstrate less sensitivity to the time-dependent deformations in the
potential.
