Max Planck Institute for Gravitational Physics (Albert Einstein Institute)
GW230529: Numerical simulation of a compact binary merger
Shortly after the start of the fourth observing run, the LIGO-Virgo-KAGRA collaborations detected a remarkable gravitational-wave signal.
The LIGO Livingston detector observed the signal, called GW230529, on May 29, 2023, from the merger of a neutron star with an unknown compact object, most likely an unusually light-weight black hole. With a mass of only a few times that of our Sun, the object falls into the “lower mass gap” between the heaviest neutron stars and the lightest black holes.
Simulation of the compact binary system GW230529
The videos and images display the numerical simulation results of black hole-neutron star coalescence consistent with the gravitational-wave event GW230529_181500. The primary object is a 3.52 solar-mass black hole with a dimensionless spin parameter of -0.16, i.e., the black hole spin is antialigned to the binary angular momentum. The secondary object is a neutron star with a mass of 1.47 solar masses. To describe the interior material of the star, we use the SLy equation of state.
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Acknowledgements
The numerical relativity simulation was performed on the Hawk HPC system at the High-Performance Computing Center Stuttgart (HLRS). We acknowledge support through the project GWanalysis (project 44189) for Hawk. I. Markin gratefully acknowledges the support of Deutsche Forschungsgemeinschaft (DFG) through Project No. 504148597. This support enables our simulations of black hole–neutron star systems.
The visualization shows the coalescence and merger of a lower mass-gap black hole (dark grey surface) with a neutron star with colors ranging from dark orange (1 million tons per cubic centimeter) to white (600 million tons per cubic centimeter). The animation is accompanied by the gravitational-wave signal represented with a set of strain amplitude values of plus-polarization using colors from dark blue to cyan. The gravitational waveform is shown at the bottom of the video, with a moving marker displaying the time relative to the merger.
The visualization shows the coalescence and merger of a lower mass-gap black hole (dark gray surface) with a neutron star with colors ranging from dark orange (1 million tons per cubic centimeter) to white (600 million tons per cubic centimeter). The gravitational waveform is shown at the bottom of the video, with a moving marker displaying the time relative to the merger.
Images
Fig. 1: Inspiral of a lower mass-gap black hole (dark gray surface) and a neutron star (orange sphere). The emitted gravitational waves are shown in colors from dark blue to cyan.
Fig. 1: Inspiral of a lower mass-gap black hole (dark gray surface) and a neutron star (orange sphere). The emitted gravitational waves are shown in colors from dark blue to cyan.
Fig. 2: Inspiral of a lower mass-gap black hole (dark gray surface) and a neutron star (orange sphere). The emitted gravitational waves are shown in colors from dark blue to cyan.
Fig. 2: Inspiral of a lower mass-gap black hole (dark gray surface) and a neutron star (orange sphere). The emitted gravitational waves are shown in colors from dark blue to cyan.
Fig. 3: Inspiral of a lower mass-gap black hole (dark gray surface) and a neutron star (orange sphere). The emitted gravitational waves are shown in colors from dark blue to cyan.
Fig. 3: Inspiral of a lower mass-gap black hole (dark gray surface) and a neutron star (orange sphere). The emitted gravitational waves are shown in colors from dark blue to cyan.
Fig. 4: Inspiral of a lower mass-gap black hole (dark gray surface) and a neutron star (orange sphere). The emitted gravitational waves are shown in colors from dark blue to cyan.
Fig. 4: Inspiral of a lower mass-gap black hole (dark gray surface) and a neutron star (orange sphere). The emitted gravitational waves are shown in colors from dark blue to cyan.
Fig. 5: Merger of a lower mass-gap black hole (dark gray surface) and a neutron star (orange). The emitted gravitational waves are shown in colors from dark blue to cyan.
Fig. 5: Merger of a lower mass-gap black hole (dark gray surface) and a neutron star (orange). The emitted gravitational waves are shown in colors from dark blue to cyan.
Fig. 6: Merger of a lower mass-gap black hole (dark gray surface) and a neutron star (orange). The emitted gravitational waves are shown in colors from dark blue to cyan.
Fig. 6: Merger of a lower mass-gap black hole (dark gray surface) and a neutron star (orange). The emitted gravitational waves are shown in colors from dark blue to cyan.
Fig. 7: Merger of a lower mass-gap black hole (dark grey surface) with a neutron star (orange). The neutron star is highly deformed and has begun mass transfer onto the black hole.
Fig. 7: Merger of a lower mass-gap black hole (dark grey surface) with a neutron star (orange). The neutron star is highly deformed and has begun mass transfer onto the black hole.
Fig. 8: Merger of a lower mass-gap black hole (dark gray surface) with a neutron star. During the merger, the neutron star is strongly deformed by the tidal forces. The density of the neutron star's matter is shown from blue (corresponding to 60 grams per cubic centimeter) to white (corresponding to 600 kilograms per cubic centimeter).
Fig. 8: Merger of a lower mass-gap black hole (dark gray surface) with a neutron star. During the merger, the neutron star is strongly deformed by the tidal forces. The density of the neutron star's matter is shown from blue (corresponding to 60 grams per cubic centimeter) to white (corresponding to 600 kilograms per cubic centimeter).
Fig. 9: Merger of a lower mass-gap black hole (dark gray surface) with a neutron star. During the merger, the neutron star is strongly deformed by the tidal forces. The density of the neutron star's matter is shown from blue (corresponding to 60 grams per cubic centimeter) to white (corresponding to 600 kilograms per cubic centimeter).
Fig. 9: Merger of a lower mass-gap black hole (dark gray surface) with a neutron star. During the merger, the neutron star is strongly deformed by the tidal forces. The density of the neutron star's matter is shown from blue (corresponding to 60 grams per cubic centimeter) to white (corresponding to 600 kilograms per cubic centimeter).
Please note: For figures 8 and 9, the color mapping of the density has been intentionally lowered by many orders of magnitude to make the lower-density regions visible. Thus, the density levels do not correspond to those in other still frames.
