Approximate shock models fail at sufficiently high velocities

What the study found: The authors found that a full-volume numerical treatment of synchrotron-emitting shocks is generally necessary once the shock proper velocity exceeds about 0.1. They also found that commonly used approximate models can be inaccurate by more than an order of magnitude in transrelativistic shocks.
Why the authors say this matters: The study suggests there may be bias in inferred physical properties for some fast blue optical transients (FBOTs), jetted tidal disruption events (TDEs), and other relativistic explosions when approximate analytic models are used. The authors conclude that their publicly available code can be used to study a growing population of relativistic synchrotron-emitting transients.
What the researchers tested: The researchers developed a new numerical model that solves the full radiative-transfer problem in synchrotron-emitting shocks, including special-relativistic effects. They used this “full-volume” model to calculate emission from shocks of arbitrary velocity and to evaluate the accuracy of more commonly used approximate models.
What worked and what didn't: The full-volume model is described as flexible and applicable to a wide range of astrophysical sources. By contrast, the approximate models tested against it were found to become unreliable at higher shock speeds, with errors exceeding an order of magnitude in transrelativistic shocks.
What to keep in mind: The abstract does not describe detailed limitations beyond the velocity range where approximate models fail. The summary provided here is limited to the title and abstract, so no additional performance metrics or source-specific tests can be stated.

Key points

• A full-volume numerical treatment is generally needed once shock proper velocity exceeds about 0.1.
• Approximate models can be inaccurate by more than an order of magnitude in transrelativistic shocks.
• The model includes full radiative transfer and special-relativistic effects.
• The authors suggest approximate analytic models may bias inferred properties of some FBOTs and jetted TDEs.
• The associated code is publicly available.