  We study the post-quench unitary dynamics of a quantum sunburst spin model,
composed of a transverse-field quantum Ising ring which is suddenly coupled to
a set of independent external qubits along the longitudinal direction, in a way
to respect a residual translation invariance and the Ising $\mathbb{Z}_2$
symmetry. Starting from the different equilibrium quantum phases of the system,
we characterize the decoherence and the energy storage in the external qubits,
which may be interpreted as a probing apparatus for the inner Ising ring. Our
results show that, in proximity of the quantum transitions of the Ising ring,
either first-order or continuous, it is possible to put forward dynamic FSS
frameworks which unveil peculiar scaling regimes, depending on the way in which
the large-size limit is taken: either by fixing the number $n$ of probing
qubits, or their interspace distance $b$. In any case, the dependence of the
various observables on $n$ can be reabsorbed into a redefinition of the quench
parameter by a $\sqrt{n}$ prefactor. We also address the role of a
nearest-neighbor coupling between the external qubits.
