The Peculiar Radio Evolution of the Tidal Disruption Event ASASSN-19bt

The Peculiar Radio Evolution of the Tidal Disruption Event ASASSN-19bt
Collin T. Christy, Kate D. Alexander, Yvette Cendes, Ryan Chornock, Tanmoy Laskar, Raffaella Margutti, Edo Berger, Michael Bietenholz, Deanne Coppejans, Fabio De Colle, Tarraneh Eftekhari, Thomas W. -S. Holoien, Tatsuya Matsumoto, James C. A. Miller-Jones, Enrico Ramirez-Ruiz, Richard Saxton, Sjoert van Velzen, Mark Wieringa
arXiv:2404.12431v1 Announce Type: new
Abstract: We present detailed radio observations of the tidal disruption event (TDE) ASASSN-19bt/AT2019ahk, obtained with the Australia Telescope Compact Array (ATCA), the Atacama Large Millimeter/submillimeter Array (ALMA), and the MeerKAT radio telescopes, spanning 40 to 1464 days after the onset of the optical flare. We find that ASASSN-19bt displays unusual radio evolution compared to other TDEs, as the peak brightness of its radio emission increases rapidly until 457 days post-optical discovery and then plateaus. Using a generalized approach to standard equipartition techniques, we estimate the energy and corresponding physical parameters for two possible emission geometries: a non-relativistic spherical outflow and a relativistic outflow observed from an arbitrary viewing angle. We find that the non-relativistic solution implies a continuous energy rise in the outflow from $Esim10^{46}$ erg to $Esim10^{49}$ erg with $beta approx 0.05$, while the off-axis relativistic jet solution instead suggests $Eapprox10^{52}$ erg with $Gammasim10$ erg at late times in the maximally off-axis case. We find that neither model provides a holistic explanation for the origin and evolution of the radio emission, emphasizing the need for more complex models. ASASSN-19bt joins the population of TDEs that display unusual radio emission at late times. Conducting long-term radio observations of these TDEs, especially during the later phases, will be crucial for understanding how these types of radio emission in TDEs are produced.arXiv:2404.12431v1 Announce Type: new
Abstract: We present detailed radio observations of the tidal disruption event (TDE) ASASSN-19bt/AT2019ahk, obtained with the Australia Telescope Compact Array (ATCA), the Atacama Large Millimeter/submillimeter Array (ALMA), and the MeerKAT radio telescopes, spanning 40 to 1464 days after the onset of the optical flare. We find that ASASSN-19bt displays unusual radio evolution compared to other TDEs, as the peak brightness of its radio emission increases rapidly until 457 days post-optical discovery and then plateaus. Using a generalized approach to standard equipartition techniques, we estimate the energy and corresponding physical parameters for two possible emission geometries: a non-relativistic spherical outflow and a relativistic outflow observed from an arbitrary viewing angle. We find that the non-relativistic solution implies a continuous energy rise in the outflow from $Esim10^{46}$ erg to $Esim10^{49}$ erg with $beta approx 0.05$, while the off-axis relativistic jet solution instead suggests $Eapprox10^{52}$ erg with $Gammasim10$ erg at late times in the maximally off-axis case. We find that neither model provides a holistic explanation for the origin and evolution of the radio emission, emphasizing the need for more complex models. ASASSN-19bt joins the population of TDEs that display unusual radio emission at late times. Conducting long-term radio observations of these TDEs, especially during the later phases, will be crucial for understanding how these types of radio emission in TDEs are produced.