By combining roughly two decades of observations from NASA’s Swift X-ray Telescope with radio monitoring, astronomers have caught a supermassive black hole at the heart of the Perseus Cluster suddenly flaring in X-rays, and about 300 days later, its powerful radio emission flared too. Their paper describing the connection between this black hole’s accretion disk and the jets it launches was submitted to the arXiv preprint server on Aug. 13 and accepted for publication in the Astrophysical Journal Letters.
Chaotic and complicated
The supermassive black hole in question sits inside NGC 1275. At the center of the Perseus Cluster, NGC 1275 is its brightest member. It’s a chaotic and complicated galaxy, showing signs of an ongoing merger and glowing filaments of gas trailing behind bubbles blown outward by the galaxy’s central black hole. It is considered an ideal natural laboratory for studying how a black hole’s feeding behavior connects to and drives its jet—a relationship astronomers call disk-jet coupling. This behavior is also critical to understanding how black holes limit galaxy growth.
Observations, however, limit the study of this connection. The powerful Chandra X-ray telescope is unable to observe this galaxy frequently enough to track rapid changes over time. Additionally, the black hole’s mass remains debated, with estimates spanning nearly two orders of magnitude.
To address this, astronomers turned to Swift, a less powerful but far more frequently available telescope, compiling nearly 20 years of X-ray monitoring data. Sarah Ketchum of the University of Michigan and her team aimed to map the galaxy’s long-term X-ray variability to offer clues about the disk-jet coupling.
Record flare
Researchers found the strongest X-ray flare ever recorded from this galaxy, starting around February 2023. Its X-ray brightness jumped by a factor of about 2. This flaring episode lasted less than 60 days and appeared to consist of at least two distinct bursts, each lasting only about 5 days.
They tested possible explanations and compared the X-ray behavior with existing radio observations to search for timing relationships between the two. The team first tested a tantalizing idea: Could this be a tidal disruption event, where a star wanders too close and gets torn apart? TDEs fade in a specific, predictable pattern, but the observed flare faded much more slowly than expected. As researchers put it: “It is unlikely that they are related to a TDE.”
Instead, the likely cause is a fluctuation in the black hole’s feeding rate, or possibly a disturbance further down the jet. “Three lines of circumstantial evidence may favor an accretion origin for the observed X-ray flares,” the team writes. The evidence includes the spectral shape of X-ray light, its rapid variability and a specific iron emission line.
However, researchers are not 100% sure that all the emission came from an X-ray-emitting corona close to the black hole, as some flares may arise farther along the jet’s path. “It is more likely that these flares result from variations in the mass accretion rate onto the black hole or downstream shocks or other processes,” researchers explain.
300-day lag
Comparing X-ray and radio data revealed a radio counterpart that followed the flare by 296 days. Researchers say that this gap between the X-ray flare and the subsequent radio brightening “could represent a propagation time from the X-ray corona surrounding the black hole to a radio-emitting region within the jet, or a propagation time between two points downstream in the jet.”
In simpler terms, they suggest this delay might be the travel time for some kind of ejected material to physically move from near the black hole outward to wherever in the jet the radio emission is being produced. However, they caution that this explanation remains uncertain.
Nevertheless, this study offers a rare glimpse into the poorly understood connection between a black hole’s accretion disk and the jets it launches. The researchers suggest that coordinated X-ray and radio monitoring could provide a way to watch this disk-jet connection in action in galaxies.
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Publication details
Sarah Ketchum et al, X-ray Flaring and Variability in NGC 1275, the Heart of the Perseus Cluster, arXiv (2026). DOI: 10.48550/arxiv.2608.13281
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A supermassive black hole erupted in X-rays, and its radio jets followed 300 days later (2026, September 1)
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