2025/09/19 by Ross Ferguson, Ben Margalit, Ferguson, Ross +1
Engineering · Physics and Astronomy · #Astrophysics and Cosmic Phenomena #Gamma-ray bursts and supernovae #Laser-Plasma Interactions and Diagnostics #Mathematical model #Neutron star #Particle Accelerators and Free-Electron Lasers #Particle accelerators and beam dynamics #Population #Pulsars and Gravitational Waves Research #Radiative transfer #Range (aeronautics) #Relativistic particle #Shock (circulatory) #Shock wave #Synchrotron radiation #Work (physics)
paper · pdf · open access · doi:10.3847/1538-4357/ae3a93
published in The Astrophysical Journal 1000(1), 16 (IOP Publishing)
openalex publication_date 2026/03/10 · openalex created_date 2026/03/11 · openalex updated_date 2026/06/26
Abstract Synchrotron emission is seen in a vast array of astrophysical transients, such as gamma-ray bursts, radio supernovae, neutron star mergers, tidal disruption events (TDEs), and fast blue optical transients (FBOTs). Despite the ubiquity of synchrotron-emitting sources, modeling of the emergent flux from these events often relies on simplified analytic approximations for the radiative transfer. These approximations are inaccurate for high-velocity shocks, where special-relativistic effects are important. Properly incorporating these effects considerably complicates calculations, and generally requires a numerical treatment. In this work, we present a novel numerical model which solves the full radiative-transfer problem in synchrotron-emitting shocks, accounting for all relativistic effects. This “full-volume” model is capable of calculating synchrotron emission from a shock of arbitrary velocity, and is designed to be flexible and applicable to a wide range of astrophysical sources. Using this new code, we evaluate the accuracy of more commonly used approximate models. We find that the full-volume treatment is generally necessary once the shock proper velocity exceeds <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mfenced close=")" open="("> <mml:mrow> <mml:mi mathvariant="normal">Γ</mml:mi> <mml:mi>β</mml:mi> </mml:mrow> </mml:mfenced> </mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">sh</mml:mi> </mml:mrow> </mml:msub> <mml:mo>≳</mml:mo> <mml:mn>0.1</mml:mn> </mml:math> , and that approximate models can be inaccurate by ≳ an order of magnitude in transrelativistic shocks. This implies that there may be a bias in the inferred physical properties of some FBOTs, jetted TDEs, and other relativistic explosions, where approximate analytic models are typically employed. The code associated with our model is made publicly available, and can be used to study the growing population of relativistic synchrotron-emitting transients.