  Neutron stars (NS) that are born in binary systems with a main-sequence star
companion can experience mass transfer, resulting in the accumulation of
material at the surface of the NS. This, in turn, leads to the continuous
growth of the NS mass and the associated steepening of the gravitational
potential. Supposing the central density surpasses the onset for the phase
transition from nuclear, generally hadronic matter to deconfined quark-gluon
plasma, which is a quantity currently constrained solely from an upper limit by
asymptotic freedom in quantum chromodynamics (QCD), the system may experience a
dynamic response due to the appearance of additional degrees of freedom in the
equation of state (EOS). This dynamical response might give rise to a rapid
softening of the EOS during the transition in the hadron-quark matter
co-existence region. While this phenomenon has long been studied in the context
of hydrostatic configurations, the dynamical implications of this problem are
still incompletely understood. It is the purpose of the present paper to
simulate the dynamics of NSs with previously accreted envelopes caused by the
presence of a first-order QCD phase transition. Therefore, we employed the
neutrino radiation hydrodynamics treatment based on the fully general
relativistic approach in spherical symmetry, implementing a three-flavor
Boltzmann neutrino transport and a microscopic model EOS that contains a
first-order hadron-quark phase transition. The associated neutrino signal shows
a sudden rise in the neutrino fluxes and average energies, becoming observable
for the present generation of neutrino detectors for a galactic event, and a
gravitational wave mode analysis revealed the behaviors of the dominant $f$
mode and the first and the second gravity $g$ modes that are excited during the
NS evolution across the QCD phase transition.
