New axisymmetric general relativistic hydrodynamics code with fixed mesh refinement

We present -2, a new message passing interface and pen parallelized, fully general relativistic hydrodynamics code in dynamical spacetime under axial symmetry with the cartoon method using the finite-volume shock-capturing schemes for hydrodynamics. Specifically, we implemented the state-of-the-art Harten-Lax–Van Leer contact Riemann solver and found better accuracy than the standard total variation diminishing Lax-Friedrichs Riemann solver. The spacetime evolves under the Baumgarte-Shapiro-Shibata-Nakamura formalism with Z4c constraint propagation. We demonstrate the accuracy of the code with some benchmark tests and excellent agreement with other codes in the literature. A wide variety of test simulations, including the head-on collision of black holes, the migration and collapse of neutron stars, and the collapse of a rotating supermassive star to a massive black hole and a disk, is also performed to show the robustness of our new code.