This paper provides an extended exploration of the inverse-chirp
gravitational-wave signals from stellar collapse in massive scalar-tensor
gravity reported in [Phys. Rev. Lett. {\bf 119}, 201103]. We systematically
explore the parameter space that characterizes the progenitor stars, the
equation of state and the scalar-tensor theory of the core collapse events. We
identify a remarkably simple and straightforward classification scheme of the
resulting collapse events. For any given set of parameters, the collapse leads
to one of three end states, a weakly scalarized neutron star, a strongly
scalarized neutron star or a black hole, possibly formed in multiple stages.
The latter two end states can lead to strong gravitational-wave signals that
may be detectable in present continuous-wave searches with ground-based
detectors. We identify a very sharp boundary in the parameter space that
separates events with strong gravitational-wave emission from those with
negligible radiation.STFC Consolidator Grant No. ST/P000673/1
GWverse COST Action Grant No. CA16104
H2020-ERC-MaGRaTh–646597
NSF-XSEDE Grant No. PHY-090003
DiRRAC through STFC capital Grants No. ST/P002307/1 and No. ST/R002452/1, and STFC operations Grant No. ST/R00689X/