Long Gamma-Ray Bursts (LGRBs), the most powerful events in the Universe, are
generated by jets that emerge from dying massive stars. Highly beamed geometry
and immense energy make jets promising gravitational wave (GW) sources.
However, their sub-Hertz GW emission is outside of ground based GW detectors’
frequency band. Using a 3D general-relativistic magnetohydrodynamic simulation
of a dying star, we show that jets inflate a turbulent, energetic bubble-cocoon
that emits strong quasi-spherical GW emission within the ground-based GW
interferometer band, $ 100-600 $ Hz, over the characteristic jet activity
timescale, $ \approx 10-100 $ s. Our prediction for the source amplitude makes
this the first non-inspiral GW source detectable by current interferometers out
to hundreds of Mpc, with $ \approx 0.1 – 3 $ detectable events expected during
LIGO/Virgo/Kagra’s observing run O4. These GWs are likely accompanied by
detectable energetic core-collapse supernova and cocoon electromagnetic
emission, making jetted stellar explosions promising multi-messenger sources.