Light flash accompanied by gravitational waves from the probable mergers of black holes

Astrophysicists first discovered compelling evidence that the merger of pairs of black holes may be accompanied by electromagnetic flash. This is indicated by the mapped data of the gravitational wave detector and ground-based optical telescope: after the first recorded gravitational event (most likely from the merger of black holes), the second was a picture of a burst of radiation in the same region of the sky. Work published in Physical Review Letters.

Gravitational waves arise at any movement of matter with variable acceleration. The magnitude of these perturbations is proportional to the mass of the body, which generates oscillations, and is usually very small: the amplitude of the wave becomes significant (that is available for registration), should produce a heavy object. Modern gravitational detectors can pick up signals arising from the merger of compact massive bodies — neutron stars or black holes.

The observation of the collisions of black holes is usually hampered by the fact that such events happen in very sparse regions of space, but because not accompanied by electromagnetic radiation — basic to date source of astrophysical data. However, there are situations where merging black holes takes place surrounded by dense clouds of matter — for example, in the accretion disk of an active galactic core — a supermassive black hole. As showed recent researches, in this case, the collision may cause electromagnetic outbreak, which is caused by collisions of gas flows after the merger.

Scientists from the UK, Israel and the United States under the leadership of Matthew Graham (Matthew Graham) from the California Institute of technology have processed the archival observations in search of bursts of study, accompanying the collisions of black holes. For this, astrophysicists have used the data detector LIGO (Laser Interferometer Gravitational-Wave Observatory), which in the period from 1 April to 30 September 2019 identified 21 event as a likely merger of black holes. Among them the authors identified those collisions that occurred near the active nuclei of galaxies, and then turned to the observations of Samuel Ochina telescope in the Palomar Observatory in California. Scientists included in the sample those pictures of the electromagnetic flares, which are localized in the same region of the sky that gravity event happened no later than 60 days after the registration of the collision in LIGO.

As a result, researchers were able to identify in observations the flash, which probably was the consequence of merging black holes — a surge of electromagnetic radiation ZTF19abanrhr near the active galactic nucleus J124942.3+344929 occurred 34 days after gravity events S190521g localized in the same region.

The authors emphasize that the gravitational wave detector recorded may 21, 2019, and at the time of writing the event has not yet received final confirmation from LIGO: that is, while it is only alleged merging of black holes. However, based on the duration (about 40 days) and energy (total of 1051 erg) flashes, the scientists were able with certainty of more than 99.9% to eliminate several other possible causes for its occurrence. So unlikely was the surge of self-activity of the galactic nucleus, the supernova microlensing and star destruction under the influence of gravity of a supermassive black hole.

In addition, assuming that the emission was really linked with the collision of black holes, the authors are predicting another outbreak in the same region on the time scale of the order of 1.6 years is approximately how long it would take the product of the merger, to return to the region of the accretion disk and again to form gas streams. Observation of a re-surge will be an additional argument in favor of such a scenario and would allow a more thorough collection of information for further research.

Earlier we talked about how the most powerful quasar allowed us to obtain constraints on the masses of the nuclei of black holes and the speed of their growth and how supermassive black holes stripped dwarf galaxy of new stars.

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