Astronomers Observe Unprecedented Radio Brightening in Tidal Disruption Event AT2018hyz
Astronomers have observed a significant and rapid increase in radio emissions from the tidal disruption event AT2018hyz, suggesting a delayed outflow launched years after the initial stellar disruption.
In 2018, astronomers detected a tidal disruption event (TDE) designated AT2018hyz, occurring 665 million light-years away, where a star was torn apart by a supermassive black hole. Initial observations did not reveal significant radio emissions. However, recent studies have documented a rapid and substantial increase in radio brightness from this event.
The new observations, spanning approximately 1,370 to 2,160 days post-disruption, indicate that the radio light curves continue to rise across all frequencies during this period. This behavior is atypical for TDEs, where radio emissions usually peak shortly after the initial event.
Researchers propose two main scenarios to explain this delayed radio brightening. One possibility is a delayed spherical outflow launched about 620 days after the disruption, traveling at approximately 30% of the speed of light. Alternatively, the emissions could result from a highly off-axis relativistic jet with a Lorentz factor around 8, becoming visible as it decelerates and spreads into our line of sight.
The energy output from AT2018hyz has reached levels comparable to gamma-ray bursts, among the most energetic events in the universe. This suggests that such delayed outflows may be more common in TDEs than previously thought, prompting further investigation into the mechanisms driving these phenomena.