Convective excitation of inertial modes in binary neutron star mergers.

We present the first very long-term simulations of binary neutron star mergers with piecewise polytropic equations of state and in full general relativity. Our simulations reveal that at a time of 30-50 ms after merger, parts of the star become convectively unstable, which triggers the excitation of inertial modes. The excited inertial modes are sustained up to several tens of ms and are detectable by the planned third-generation gravitational-wave detectors at frequencies of a few kHz. Since inertial modes depend on the rotation rate of the star and they are triggered by a convective instability in the post-merger remnant, their detection in gravitational waves will provide a unique opportunity to probe the rotational and thermal state of the merger remnant. In addition, our findings have implications for the long-term evolution and stability of binary neutron star remnants.