MeV absorption in gamma-ray bursts as a probe of their progenitor winds
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arXiv
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| Autori principali: | , , , , , , , , , , |
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| Natura: | Preprint |
| Pubblicazione: |
2026
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| _version_ | 1866918298264797184 |
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| author | Oganesyan, Gor Salafia, Om Sharan Sobacchi, Emanuele Macera, Samanta Ghirlanda, Giancarlo Nava, Lara Ierardi, Annarita Banerjee, Biswajit Mei, Alessio Ascenzi, Stefano Branchesi, Marica |
| author_facet | Oganesyan, Gor Salafia, Om Sharan Sobacchi, Emanuele Macera, Samanta Ghirlanda, Giancarlo Nava, Lara Ierardi, Annarita Banerjee, Biswajit Mei, Alessio Ascenzi, Stefano Branchesi, Marica |
| contents | A small fraction of X-ray photons from gamma-ray bursts (GRBs), after escaping the relativistic jet, are scattered by electrons in the circumburst medium. Subsequent photon-photon absorption between the incoming MeV $γ$-rays and the back-scattered X-rays generate electron-positron pairs, enriching the surrounding medium with leptons. We investigate how these back-scattered photons modify the prompt GRB spectrum through $γ-γ$ absorption. In a dense and pair-loaded wind environment, the emerging spectra exhibit a broad attenuation structure, whose morphology is sensitive to the low-energy spectral index $α$. In particular, spectra with $α> -1$ develop a pronounced, saddle-shaped absorption between 1 and 100 MeV (rest frame). Such external MeV absorption could account for the spectral curvature seen in some bright GRBs, and may point to enhanced mass loss from their progenitor stars, consistent with early observations of core-collapse supernovae. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2601_14393 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | MeV absorption in gamma-ray bursts as a probe of their progenitor winds Oganesyan, Gor Salafia, Om Sharan Sobacchi, Emanuele Macera, Samanta Ghirlanda, Giancarlo Nava, Lara Ierardi, Annarita Banerjee, Biswajit Mei, Alessio Ascenzi, Stefano Branchesi, Marica High Energy Astrophysical Phenomena A small fraction of X-ray photons from gamma-ray bursts (GRBs), after escaping the relativistic jet, are scattered by electrons in the circumburst medium. Subsequent photon-photon absorption between the incoming MeV $γ$-rays and the back-scattered X-rays generate electron-positron pairs, enriching the surrounding medium with leptons. We investigate how these back-scattered photons modify the prompt GRB spectrum through $γ-γ$ absorption. In a dense and pair-loaded wind environment, the emerging spectra exhibit a broad attenuation structure, whose morphology is sensitive to the low-energy spectral index $α$. In particular, spectra with $α> -1$ develop a pronounced, saddle-shaped absorption between 1 and 100 MeV (rest frame). Such external MeV absorption could account for the spectral curvature seen in some bright GRBs, and may point to enhanced mass loss from their progenitor stars, consistent with early observations of core-collapse supernovae. |
| title | MeV absorption in gamma-ray bursts as a probe of their progenitor winds |
| topic | High Energy Astrophysical Phenomena |
| url | https://arxiv.org/abs/2601.14393 |