  Short gamma-ray bursts are associated with binary neutron star mergers, which
are multimessenger astronomical events that have been observed both in
gravitational waves and in the multiband electromagnetic spectrum. Depending on
the masses of the stars in the binary and on details of their largely unknown
equation of state, a dynamically evolving and short-lived neutron star may be
formed after the merger, existing for approximately 10-300 ms before collapsing
to a black hole. Numerical relativity simulations across different groups
consistently show broad power spectral features in the 1-5 kHz range in the
post-merger gravitational wave signal, which is inaccessible by current
gravitational-wave detectors but could be seen by future third generation
ground-based detectors in the next decade. This implies the possibility of
quasiperiodic modulation of the emitted gamma-rays in a subset of events where
a neutron star is formed shortly prior to the final collapse to a black hole.
Here we present two such signals identified in the short bursts GRB 910711 and
GRB 931101B from archival BATSE data, which are compatible with the predictions
from numerical relativity.
