Astronomers finally observed one of the most fascinating phenomena in the universe.
The LIGO and Virgo observatories were the first to reliably register gravitational waves from the merger of a neutron star and a black hole. It is assumed that these formed black holes and the sources of the bursts are located at a distance of about a billion light-years from the Sun.
Scientists are interested not only in the interaction of objects in such a system, which can be tracked by radio pulses from a pulsar but also in the course of their merger. The properties of the resulting compact object are even more important.
Over the past four decades, in the course of electromagnetic observations, 19 double neutron stars have been found. At the same time, the gravitational wave observatories LIGO and Virgo register mainly double merging black holes. Out of all, only two events recorded in the third observational campaign were candidates for a merger of a pair of a neutron star and a black hole.
In the case of GW190426, the probability of a false alarm turned out to be quite high, and in the case of GW190814, the estimated mass of a candidate for a neutron star, which was 2.59 solar masses, turned out to be too large for an object of this kind.
Astronomers finally caught a glimpse of the merger of a neutron star and a black hole
A group of astronomers from the LIGO, Virgo, and KAGRA collaborations, led by Richard Abbott of the California Institute of Technology, reported two cases of reliable detection of gravitational waves from the merger of a neutron star and a black hole.
GW200105 was detected on January 5, 2020, by one of the LIGO detectors, and GW200115 was detected on January 15, 2020, by both LIGO detectors and the Virgo detector.
This made it possible to narrow the source localization area in the sky by an order of magnitude. The signal from GW200105 went to the Earth for 931 million years, and from GW200115 – 978 million years.
Scientists concluded that the scenario for the outbreak of GW200105 at a confidence level of 90 percent is the merger of a black hole with a mass of 8.9 solar masses and a neutron star with a mass of 1.9 solar masses.
In the case of GW200115, the black hole had a mass of 5.7 masses of the Sun, and the neutron star is 1.5 times the mass of the Sun.
The researchers note that the results are consistent with theoretical predictions for a neutron star and black hole merger events and the properties of galactic neutron stars and black holes. At the same time, it is expected that such events occur on average once a month at distances of up to one billion light-years from the Sun.
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• Abbott, R. (2021, June 29). Observation of gravitational waves from two neutron star-black hole coalescences. arXiv.org.
• Bartels, M. (2021, June 29). Scientists catch 1st glimpse of a black hole swallowing a neutron star. Space.com.
• Chu, J. (n.d.). LIGO and Virgo detect rare mergers of black holes with neutron stars for the first time. MIT News | Massachusetts Institute of Technology.
• Conover, E. (2021, June 28). Gravitational waves reveal the first known mergers of a black hole and neutron star. Science News.
• Hanna, C., & McCormick, G. (n.d.). Elusive mergers of black holes with neutron stars confirmed for first time. Penn State University.