AT2019ijn Transient Points to Potential New Class of Cosmic Explosions

The night sky often presents a calm and unchanging backdrop, but the universe is frequently punctuated by catastrophic detonations. Among the most enigmatic are fast-evolving blue optical transients, or FBOTs. These rare events typically feature a rapid rise to peak brightness within days and blue colors near their peak, followed by a swift exponential decay over the course of a month. Yet, recent analysis of specific cosmic outbursts has forced researchers to rethink these classifications entirely.

AT2019ijn and the Dwarf Galaxy Discovery

Chinese astronomers report the detection of a peculiar optical transient event that occurred in the center of a dwarf galaxy. The newly discovered event, designated AT2019ijn, is a fast-rising, slow-decaying blue optical transient with exceptionally bright radio emission.

The observations revealed that the transient rapidly surged in the optical band to a peak luminosity while maintaining a persistently blue color. Furthermore, radio emissions from the source proved exceptionally long-lasting, causing that emission to brighten dramatically years after the initial event. An artist’s conception illustrates the aftermath of an intermediate-mass black hole tearing apart a passing star, resulting in an accretion disk and narrow relativistic jet. The dotted line indicates our line of sight from Earth, and the jet’s off-axis afterglow only became visible once the expanding radio emission had grown wide enough to sweep into our line of sight.

Evaluating the Tidal Disruption Scenario

To explain the nature of AT2019ijn, researchers can look to similar extreme phenomena. NOIRLab describes LFBOTs as among the more puzzling cosmic phenomena discovered over the past few decades, adding that only slightly more than a dozen of these events have been discovered so far.

This discovery builds upon a growing catalog of peculiar cosmic transients that defy conventional categorization. In 2018 astronomers witnessed an intense explosion far more powerful than the average supernova — 10 –100 times brighter. It was designated AT2018cow, nicknamed ‘the Cow’, and became the first example of a new class of astronomical phenomena: luminous fast blue optical transients (LFBOTs). Only a handful of these events have been discovered so far, and scientists don’t know how they occur, but discoveries help solve part of the puzzle. Another member of the rare class of Luminous Fast Blue Optical Transients (LFBOTs) was designated AT2024wpp and nicknamed the Whippet. These events brighten and fade rapidly while releasing extremely large amounts of energy, exceeding those of typical stellar explosions.

Broader Mysteries Across the Cosmos

The expanding study of luminous fast blue optical transients continues to challenge established theories regarding stellar deaths and black hole interactions. Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) and other radio observatories have detected dense gas surrounding one of the most energetic cosmic explosions ever observed. The findings show that material initially thought to be absent was present but rendered invisible to optical telescopes by intense radiation, becoming detectable only at radio and millimeter wavelengths.

Even though we suspected what it was, it was still extraordinary, said Daniel A. Perley, principal investigator of the study. This was many times more energetic than any similar event and more than any known explosion powered by the collapse of a star. Scientists now believe the blue cosmic outburst is caused by black holes shredding massive cosmic companions, like stars. As wide-field sky surveys continue to scan the night sky, astronomers are actively investigating these cosmic fireworks.