An international team of astronomers has recorded an unusual phenomenon in the core of the galaxy GALEXASC J015624.70-710415.8, 1.7 billion light-years from Earth. It is a transient (brightness-changing light source) designated OGLE17aaj, whose nature is still unknown. The discovery is reported in a preprint published in the arXiv repository.
The phenomenon was detected using the OGLE-IV Transient Detection System, which searches for astronomical objects that change brightness in the near infrared region of the spectrum. Scientists have carried out observations of OGLE17aaj using the 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 infrared region of the spectrum for 60 days changed from 21m to a maximum of 20m (the lower the magnitude, the brighter the object), after which the transient faded for 200 days before reaching a plateau. At the same time, the absolute stellar magnitude, that is, what the object would have at a distance of 10 parsecs (32.6 light years) from the observer, reached -18m. In the ultraviolet region of the spectrum, the maximum apparent magnitude reached about 19m. At the same time, the total amount of energy emitted by the transient currently reaches 7 sexdecillion (7 to 10 to the 51st power) erg, which corresponds to the lower limit of the energy released by the accretion disk of 0.04 solar masses.
Scientists estimate that the maximum flare temperature reached 4 x 10 to the 4th power of Kelvin, which is not typical for a supernova, but is often observed during tidal disruption events (TDE), when a star passes too close to a black hole or neutron star. and is torn apart. However, the increase in magnitude was too smooth for TDE, and its decrease was even slower. Therefore, the researchers rejected this version.
According to astronomers, OGLE17aaj is more likely associated with the activity of the galactic core. The latter should contain a relatively small supermassive black hole with an accretion disk. Thus, the scientists conclude, the brightness fluctuations are caused by unknown changes in the flow of matter that forms this disk.