  Natal kicks and spins are characteristic properties of neutron stars (NSs)
and black holes (BHs). Both offer valuable clues to dynamical processes during
stellar core collapse and explosion. Moreover, they influence the evolution of
stellar multiple systems and the gravitational-wave signals from their inspiral
and merger. Observational evidence of possibly generic spin-kick alignment has
been interpreted as indication that NS spins are either induced with the NS
kicks or inherited from progenitor rotation, which thus might play a
dynamically important role during stellar collapse. Current three-dimensional
supernova simulations suggest that NS kicks are transferred in the first
seconds of the explosion, mainly by anisotropic mass ejection and, on a
secondary level, anisotropic neutrino emission. In contrast, the NS spins are
only determined minutes to hours later by angular momentum associated with
fallback of matter that does not become gravitationally unbound in the
supernova. Here, we propose a novel scenario to explain spin-kick alignment as
a consequence of tangential vortex flows in the fallback matter that is
accreted mostly from the direction of the NS's motion. For this effect the
initial NS kick is crucial, because it produces a growing offset of the NS away
from the explosion center, thus promoting onesided accretion. In this new
scenario conclusions based on traditional concepts are reversed. For example,
pre-kick NS spins are not required, and rapid progenitor-core rotation can
hamper spin-kick alignment. We also discuss implications for natal BH kicks and
the possibility of tossing the BH's spin axis during its formation.

High Energy Astrophysical Phenomena;High Energy Physics - Phenomenology