Gamma-Ray Burst Jets in Circumstellar Material: Dynamics, Breakout, and Diversity of Transients

Mar 20, 2025
20 pages
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Abstract: (arXiv)
Recent observations indicate that stripped-envelope core-collapse supernovae are often surrounded by dense circumstellar material (CSM). Motivated by this, we develop an analytic model to systematically study the dynamics of long gamma-ray burst (LGRB) jet propagation in various CSM environments. We derive a general expression for the jet head velocity (βh\beta_{\rm h}) and breakout time (tbt_{\rm b}) valid across Newtonian, relativistic, and intermediate regimes, accounting for a previously unrecognized dependence on 1βh1 - \beta_{\rm h}. Our results highlight a fundamental distinction between jet propagation in massive stars, where βh1\beta_{\rm h}\ll 1, and in extended CSM, where 1βh11-\beta_{\rm h}\ll 1. We establish an analytic success/failure criterion for jets and express it in terms of jet and CSM parameters, revealing a strong dependence on CSM radius. To quantify the relativistic nature of the jet-cocoon system, we introduce the energy-weighted proper velocity Γβ\overline{\Gamma\beta}. We identify three possible jet outcomes-(a) successful jets (Γβ10100\overline{\Gamma\beta} \sim 10-100), (b) barely failed jets (Γβ1\overline{\Gamma\beta} \sim 1), and (c) completely failed jets (Γβ0.1\overline{\Gamma\beta} \sim 0.1)-and constrain their respective jet/CSM parameter spaces. We show that in (b) and (c), large CSM radii can result in luminous fast blue optical transients via cocoon cooling emission. This theoretical framework provides a basis for future observational and theoretical studies to understand the link between LGRBs, intermediate GRBs, low-luminosity LGRBs, and their environments.
Note:
  • 20 pages, 8 figures. Submitted to ApJ