Black-hole jets emerge in two feeding regimes

When a star passes too close to a supermassive black hole, tidal gravity can tear it apart. By combining radio observations of 20 tidal disruption events, Adelle Goodwin and Andrew Mummery identified two regimes in which jets and other outflows appear: during the initial intense feeding and much later.

The first regime occurs while matter is flowing above the Eddington limit, where radiation pressure becomes comparable to gravity. The second appeared hundreds to thousands of days later, when luminosity fell to about 2% of the Eddington luminosity.

That late threshold resembles state transitions in much smaller stellar-mass black holes. Those systems evolve in days or months; tidal disruptions compress the otherwise millennia-long evolution of supermassive accretion flows into years that astronomers can monitor.

Published on September 17 in Nature Astronomy, the study argues that accretion–outflow coupling may persist across black-hole mass scales. Radio emission traced expelled material, while luminosity and accretion estimates located each event in its feeding cycle.

The result can guide scarce radio-telescope time toward the super-Eddington stage and the approach to the 2% threshold. A sample of 20 remains limited, however, and radio selection favors sufficiently bright and observable outflows.