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Abstract

We find strong numerical evidence for a new phenomenon in a binary black hole
spacetime, namely the merger of marginally outer trapped surfaces (MOTSs). We
show that the MOTS associated with the final black hole merges with the two
initially disjoint surfaces associated with the two initial black holes. This
yields a connected sequence of MOTSs interpolating between the initial and
final state all the way through the non-linear binary black hole merger
process. This now allows us to track physical quantities (such as mass, angular
momentum, higher multipoles, and fluxes) across the merger, which can be
potentially compared with the gravitational wave signal in the wave-zone, and
with observations by gravitational wave detectors. This also suggests a
possibility of proving the Penrose inequality for generic astrophysical binary
back hole configurations.