A team of astronomers using the U.S. National Science Foundation Very Large Array (NSF VLA) has detected an extraordinary burst of radio light from a rare cosmic event involving an intermediate-mass black hole. This event, known as AT2019ijn, occurred on July 8, 2026, and marks a significant discovery in understanding black holes and their behavior.
Understanding the AT2019ijn Event
The AT2019ijn event first appeared as a bright blue flash in optical surveys, peaking in brightness within days. However, it faded much more slowly than similar transient events. Upon further examination of radio observations, astronomers discovered that the radio emission continued to brighten for nearly two years, reaching a luminosity over 100 times brighter than typical stellar explosions.
The researchers believe this phenomenon is a tidal disruption event, which happens when a star comes too close to a black hole and is torn apart by its gravitational pull. The rapid rise in optical brightness indicates the presence of an intermediate-mass black hole, a long-sought class of black holes that exists between stellar-mass black holes and supermassive black holes.
Significance of the Discovery
This discovery is crucial because it expands astronomers' methods for identifying hidden black holes and the powerful jets they emit. The delayed brightening observed in the radio signals suggests that some optical transients may belong to a broader category of black-hole-powered events that have previously gone unnoticed due to their radio emissions arriving long after the initial flash.
As new sky surveys are conducted in both visible light and radio waves, astronomers anticipate finding more events similar to AT2019ijn. Each new detection could provide insights into how intermediate-mass black holes form, how often they disrupt stars, and the conditions that lead to the production of powerful jets.
Multi-facility Observations and Results
The research team combined optical survey data with radio observations from the NSF VLA and other facilities, including ASKAP in Australia and the upgraded Giant Metrewave Radio Telescope in India. This comprehensive radio coverage allowed researchers to track changes in the signal over time and test models for an expanding outflow driven by the tidal disruption event.
The modeling indicates that the radio emission originated from material moving at a significant fraction of the speed of light. The data suggests that the observed radio flare was from a narrow relativistic jet viewed from an off-axis perspective, explaining why the radio signal appeared with a delay.
- AT2019ijn peaked in brightness in just a few days.
- The radio emission continued brightening for nearly two years.
- Radio luminosity exceeded 100 times that of typical stellar explosions.
- Event offers a new pathway to identify intermediate-mass black holes.
“The delayed brightening is one of the most striking features of this discovery,” said the research team.
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