Caught a light signal of unknown nature

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Image: Gromadzki et al

An international team of astronomers recorded an unusual phenomenon in the nuclei of galaxies GALEXASC J015624.70-710415.8, remote from the Earth is 1.7 billion light years. It is a transient (changing the brightness of the light source), identified as OGLE17aaj, whose nature remains unknown. About the discovery reported in the paper published in the repository arXiv.

The phenomenon was detected using a detection system transients OGLE-IV Transient Detection
System that searches for astronomical objects that change brightness in the near infrared region of the spectrum. Researchers conducted observations of OGLE17aaj using complex telescopes Very Large Telescope in Chile and other instruments located in Chile, South Africa and in orbit around the Earth.

The apparent magnitude in the observed range of the infrared region of the spectrum 60 days changed from 21m up to a maximum of 20m (the lower the value, the brighter the object), after which the transient was damped within 200 days before reaching a plateau. The absolute magnitude, that is, that the object would have at a distance of ten parsec (32,6 light years) from the observer, reached 18m. In the ultraviolet region of the spectrum maximum apparent magnitude reached about 19m. The total number emitted by the transient energy currently reaches seven sexdecillion (7 of 10 at 51 degree) erg, which corresponds to the lower limit of the energy released in the accretion disc of 0.04 solar masses.

According to scientists, the maximum flash temperature reached 4 for 10 in 4-th degree Kelvin, which is not typical for a supernova, however, is often observed in the event of a tidal destruction (eng. tidal disruption event, TDE) when a star passes too close to a black hole or a neutron star being torn apart. However, the increase in magnitude was too smooth for TDE, and its reduction is even slower. Therefore, the researchers rejected this option.

According to astronomers, OGLE17aaj more likely associated with active galactic nuclei. Inside the latter should be relatively small supermassive black hole with accretion disk. Thus, the scientists conclude, changes in their brightness caused by unknown changes in the flow of the material forming the disk.

Video, photo All from Russia.

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