Early $\rm TeV$ photons of GRB 221009A were absorbed by the prompt MeV photons

Duan-yuan Gao; Yuan-Chuan Zou

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arXiv · 2312.04886

Early $\rm TeV$ photons of GRB 221009A were absorbed by the prompt MeV photons

Duan-yuan Gao·Yuan-Chuan Zou

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Abstract

Gamma-ray burst (GRB) 221009A produced the highest flux of gigaelectronvolt-teraelectronvolt ($\rm GeV-TeV$) photons ever observed, allowing the construction of a detailed $\rm TeV$ light curve. We focus on explaining the noticeable dip in the light curve around $2$-$5\ \rm s$ after the onset of $\rm TeV$ emission. We propose that Megaelectronvolt (MeV) photons from the prompt emission annihilate with $\rm TeV$ photons from the afterglow, producing an optical depth that obscures the $\rm TeV$ emission during this period. We develop a two-zone model accounting for the angles of MeV photons that can successfully reproduce the time delay between MeV and $\rm TeV$ photons, the peak optical depth over 3, and the rapid decline in optical depth. Our model supports $\rm MeV-TeV$ annihilation as the cause of the dip and provides reasonable constraints on the emission region parameters.

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Duan-yuan Gao, Yuan-Chuan Zou. 2023-12-08. Early $\rm TeV$ photons of GRB 221009A were absorbed by the prompt MeV photons. https://arxiv.org/abs/2312.04886

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