Visualizations of GW200105 and GW200115

Gravitational waves from two black holes swallowing neutron stars whole

The signal observed by the LIGO and Virgo detectors in January 2020 is the first robust detection of a black hole merging with a neutron star. The waves came from distances of more than 900 million light-years, where the neutron stars were swallowed whole by their black hole partners.

GW200105

The first of the two events, GW200105, was detected as a strong signal by one of the LIGO detectors, while the other was temporarily offline. From the gravitational waves the astronomers inferred that the signal was caused by a 9-solar mass black hole colliding with a 1.9-solar mass compact object. They concluded that the latter object is a neutron star. This merger happened at a distance of about 900 million light-years. Because it was found by a single detector, the direction to the waves’ origin cannot be determined very precisely: to about 17% of the entire sky, equivalent to the area covered by 34,000 full moons.

GW200115

The second event, which was detected only 10 days later (GW200115), was seen by all three large detectors: both LIGO instruments and the Virgo instrument. While it is less prominent than GW200105 in each single detector, the combined information and coincident detections make it a strong signal. GW200115 comes from the merger of a 6-solar mass black hole with a 1.5-solar mass neutron star. The collision took place roughly 1 billion light-years from Earth.

With observations of the three widely separated detectors on Earth, the direction to the waves’ origin can be determined to a part of the sky equivalent to the area covered by 2,900 full moons.

Simulation of GW200115

Movie

The movie represents a system compatible to GW200115, i.e., the black hole mass was chosen to be 6.1 solar masses and the neutron star mass was set to 1.4 solar masses. Both objects were non-spinning. Due to this parameter choice, and in agreement with the non-detection of an electromagnetic counterpart, the neutron star is swallowed by the black hole without being tidally disrupted. Therefore, no noticeable accretion disk forms around the black hole during the merger process.
The simulation shows the gravitational wave signal in blue, and the density of the neutron stars from yellow to orange (yellow representing lower densities, orange representing higher densities). We also show the gravitational wave strain in the bottom part of the video, indicating the time evolution.

Credit
Numerical relativity simulation: S.V. Chaurasia (Stockholm University), T. Dietrich (Potsdam University and Max Planck Institute for Gravitational Physics)
Scientific visualization: T. Dietrich (Potsdam University and Max Planck Institute for Gravitational Physics), N. Fischer, S. Ossokine, H. Pfeiffer (Max Planck Institute for Gravitational Physics)

Acknowledgments
We acknowledge support through the High-Performance Computing Center Stuttgart (HLRS) through project GWanalysis (project 44189) for HAWK, through the Norddeutsche Verbund für Hoch- und Höchstleistungsrechnen (project bbp00049), and through the PDC Center for High Performance Computing (SNIC 2020/1-34) for Beskow. This support enables our simulations of black hole - neutron star systems.

Note: Publication of these images and movies requires proper credits and written permission. Please contact the AEI press office in advance of publication or for higher-resolution versions.

The movie represents a system compatible to GW200115, i.e., the black hole mass was chosen to be 6.1 solar masses and the neutron star mass was set to 1.4 solar masses. Both objects were non-spinning.

Simulation of GW200115 – a Neutron-Star–Black-Hole merger

https://www.youtube.com/watch?v=Rd3p3xPtWn4

Images

The images represent a system compatible to GW200115, i.e., the black hole mass was chosen to be 6.1 solar masses and the neutron star mass was set to 1.4 solar masses. Both objects were non-spinning. Due to this parameter choice, and in agreement with the non-detection of an electromagnetic counterpart, the neutron star is swallowed by the black hole without being tidally disrupted. Therefore, no noticeable accretion disk forms around the black hole during the merger process.
The simulation shows the density of the neutron stars from yellow to orange (yellow representing lower densities, orange representing higher densities).

Acknowledgments
We acknowledge support through the High-Performance Computing Center Stuttgart (HLRS) through project GWanalysis (project 44189) for HAWK, through the Norddeutsche Verbund für Hoch- und Höchstleistungsrechnen (project bbp00049), and through the PDC Center for High Performance Computing (SNIC 2020/1-34) for Beskow. This support enables our simulations of black hole - neutron star systems.