Astronomers observe a rapid radio brightening of tidal disruption event AT2018hyz
Tomasz Nowakowski
astronomy writer
Stephanie Baum
scientific editor
Andrew Zinin
lead editor
Using various telescopes worldwide, an international team of astronomers has observed a tidal disruption event (TDE) known as AT2018hyz, which allowed them to witness a rapid brightening of this source in the radio band.
Results of the observational campaign, July 11 on the arXiv preprint server, could help us better understand the behavior and nature of TDEs.
When a star passes close enough to a supermassive black hole and is pulled apart by the black hole's tidal forces, it triggers the process of disruption, which is known as a TDE. Afterward, the tidally disrupted stellar debris starts raining down on the black hole, and radiation emerges from the innermost region of accreting debris, which is an indicator of the presence of a TDE.
AT2018hyz is a TDE at a distance of 665 million light years, discovered in 2018 by the All Sky Automated Survey for SuperNovae (ASASS-SN). The host of this event is a post-starburst galaxy designated 2MASS J10065085+0141342.
Previous observations of AT2018hyz conducted in 2022 by a group of astronomers led by Yvette Cendes of the University of Oregon detected radio emission from this source. This emission was likely due to a mildly relativistic outflow launched about two years after the optical discovery of AT2018hyz.
Now, Cendes's team presents more recent radio observations of AT2018hyz, which deliver more insights into the nature of this emission. The new observational campaign utilized a set of telescopes, including the MeerKAT radio telescope and the Atacama Large Millimeter/submillimeter Array (ALMA).
The observations spanning about two years show that the radio emission of AT2018hyz continues to rapidly rise at all frequencies and is more luminous than all previous non-relativistic TDEs, reaching a peak luminosity of about 10 duodecillion erg/s. The astronomers noted that this luminosity is comparable to that of the relativistic TDE, known as Sw 1644+57, on the same timescale.
Furthermore, the multi-frequency data indicates that the peak frequency of emission in AT2018hyz is relatively stable, with an increase of peak flux density dominating the evolution of this source.
Trying to explain the origin of the rapidly rising radio emission of AT2018hyz, the authors of the paper find two hypotheses as the most plausible. The first one includes a spherical outflow, while the second one suggests that the emission is due to a relativistic jet.
"The observed behavior is consistent with two possible scenarios: (i) a delayed spherical outflow launched about 620 days post-disruption with a velocity of ≈ 0.3c and an energy of ∼ 1050 erg, and (ii) a highly off-axis (≈ 80 − 90◦) relativistic jet with a Lorentz factor of Γ ∼ 8 and EK ≈ 1052 erg," the researchers concluded.
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More information: Yvette Cendes et al, Continued Rapid Radio Brightening of the Tidal Disruption Event AT2018hyz, arXiv (2025).
Journal information: arXiv
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