{"about":{"site":"https://codewithpapers.app","non_affiliation":"Code with Papers and Syntology are not affiliated with, endorsed by, or sponsored by Papers with Code, Meta, or the pwc-archive mirror.","licence":"CC BY-SA 4.0","licence_url":"https://creativecommons.org/licenses/by-sa/4.0/legalcode","attribution":"https://codewithpapers.app/attribution","modified":"archive material modified by Syntology; see the attribution page"},"url":"/paper/thermal-electrons-in-mildly-relativistic","title":"Thermal Electrons in Mildly-relativistic Synchrotron Blast-waves","arxiv_id":"2111.00012","date":"2021-10-29","proceeding":null,"authors":["Ben Margalit","Eliot Quataert"],"abstract":"Numerical models of collisionless shocks robustly predict an electron distribution comprised of both thermal and non-thermal electrons. Here, we explore in detail the effect of thermal electrons on the emergent synchrotron emission from sub-relativistic shocks. We present a complete `thermal + non-thermal' synchrotron model and derive properties of the resulting spectrum and light-curves. Using these results we delineate the relative importance of thermal and non-thermal electrons for sub-relativistic shock-powered synchrotron transients. We find that thermal electrons are naturally expected to contribute significantly to the peak emission if the shock velocity is $\\gtrsim 0.2c$, but would be mostly undetectable in non-relativistic shocks. This helps explain the dichotomy between typical radio supernovae and the emerging class of `AT2018cow-like' events. The signpost of thermal electron synchrotron emission is a steep optically-thin spectral index and a $\\nu^2$ optically-thick spectrum. These spectral features are also predicted to correlate with a steep post-peak light-curve decline rate, broadly consistent with observed AT2018cow-like events. We expect that thermal electrons may be observable in other contexts where mildly-relativistic shocks are present, and briefly estimate this effect for gamma-ray burst afterglows and binary neutron star mergers. Our model can be used to fit spectra and light-curves of events and accounts for both thermal and non-thermal electron populations with no additional physical degrees of freedom.","url_abs":"https://arxiv.org/abs/2111.00012v1","url_pdf":"https://arxiv.org/pdf/2111.00012v1.pdf","source":{"archive":"pwc-archive (Hugging Face), CC BY-SA 4.0","snapshot":"2025-07-28","licence_url":"https://creativecommons.org/licenses/by-sa/4.0/legalcode","row_kind":"links_only","authors_date_abstract":"arXiv metadata, CC0 1.0 (https://info.arxiv.org/help/license), from the Kaggle arXiv metadata snapshot of 2026-09-12"},"code_links":[{"paper_slug":"thermal-electrons-in-mildly-relativistic","repo_url":"https://github.com/bmargalit/thermal-synchrotron","is_official":1,"mentioned_in_paper":1,"mentioned_in_github":0,"framework":"none","reach":null}],"tasks":[],"methods":[],"datasets_introduced":[],"methods_introduced":[],"results":[],"syntology":{"atlas_url":null,"mcp":null,"developers":"https://syntology.ai/developers"},"arxiv_metadata":null,"syntology_extracted_results":null}