A supermassive black hole erupted in X-rays, and its radio jets followed 300 days later

Astronomers have identified a supermassive black hole at the heart of the Perseus Cluster that suddenly erupted in X-rays in 2023 and later, about 300 days later, its radio jets also flared. This discovery, made by combining two decades of observations from NASA's Swift X-ray Telescope with radio monitoring, was detailed in a paper submitted to the preprint server arXiv and accepted for publication in the Astrophysical Journal Letters.

The black hole resides within NGC 1275, the brightest member of the Perseus Cluster, which is known for its chaotic nature and ongoing merger, as well as glowing gas filaments trailing behind bubbles blown by the central black hole. This study is significant because it provides insight into the relationship between a black hole's accretion disk and the jets it launches, a process known as disk-jet coupling which is crucial for understanding how black holes influence galaxy growth.

Despite the powerful Chandra X-ray telescope's limitations in observing the galaxy frequently enough, the team used Swift to compile nearly 20 years of X-ray data to track long-term X-ray variability. The strongest X-ray flare ever observed from NGC 1275 was recorded in February 2023, increasing the black hole's brightness by a factor of about 2 for 60 days.

The flare consisted of at least two distinct bursts, each lasting around 5 days. Researchers tested various explanations for this flare, ruling out a tidal disruption event (TDE) due to the slow fade of the flare, which doesn't match the expected pattern of a TDE. Instead, they suggest the likely cause is a fluctuation in the black hole's feeding rate or a disturbance further down the jet.

Several lines of evidence support an accretion origin for the X-ray flares, including the spectral shape of X-ray light, its rapid variability, and a specific iron emission line. The delay between the X-ray flare and the subsequent radio brightening, which is about 296 days, could represent the travel time of ejected material from near the black hole to the radio-emitting region within the jet, or from one point downstream in the jet to another.

However, this explanation remains uncertain. The researchers emphasize that coordinated X-ray and radio monitoring could help observe the disk-jet connection in action in galaxies, offering a better understanding of this complex process.