New Delhi: Luminous fast blue optical transients (LFBOTs) are mysterious cosmic phenomena discovered over the past few decades, that are brief flashes
of blue and ultraviolet light that rapidly fade away, leaving behind faint X-ray and radio emissions. Slightly more than a dozen have been discovered so far. Scientists do not fully understand what causes these outbursts, with theories ranging from unusual type of supernovae, or actively feeding black holes consuming gas and dust. In 2024, astronomers discovered the brightest LFBOT ever observed, designated as AT 2024wpp. Analysis of this event indicates that LFBOTs are not caused either by unusual supernovae or black holes consuming gas and dust.
The new research indicates that LFBOTs are caused by extreme tidal disruption events, where a black hole containing up to 100 times the mass of the Sun completely shreds and spaghettifies a massive companion star within a few days. The discovery resolves a decades-long puzzle, and illustrates the varieties of stellar calamities that astronomers come across. Each astronomical event is associated with a characteristic spectrum of light that evolves over time. Understanding the processes that produce these unique light signatures allows scientists to test theories on the physics of black holes, and helps astronomers better understand the life cycles of stars.
LFBOTs cannot be unusual supernovae
Analysis of the energy emitted by the event indicated that it was 100 times in excess of a regular supernova, and could not be produced by one. The radiated energy would require the conversion of about 10 per cent of the rest mass of the Sun into energy over a very short time frame. Observations by the Gemini South telescope revealed an excess of near-infrared light, which has previously been observed on only one other LFBOT designated as AT 2018cow.
The researchers believe that the black hole was siphoning off material from its binary companion, enshrouding itself in a halo of material too far from the black hole for it to swallow. When the companion star wandered too close, it was torn apart, with the new material slamming against the existing material, resulting in the X-ray, ultraviolet and blue light. Most of the gas from the companion were directed to the poles of the black hole by the magnetic fields of the accretion disk, where it was ejected as a jet of material. The scientists estimate that this jet was travelling at close to 40 per cent the speed of light. A paper of papers describing the research has been published in The Astrophysical Journal Letters.
