Double-Peaked Optical Afterglow in GRB 110213A Inferring a Magnetized Thick Shell Ejecta

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Main Authors: Kusafuka, Yo, Obayashi, Kaori, Asano, Katsuaki, Yamazaki, Ryo
Format: Preprint
Published: 2025
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_version_ 1866917056167804928
author Kusafuka, Yo
Obayashi, Kaori
Asano, Katsuaki
Yamazaki, Ryo
author_facet Kusafuka, Yo
Obayashi, Kaori
Asano, Katsuaki
Yamazaki, Ryo
contents Gamma-ray bursts early afterglows are important tracers for determining the radial structure and magnetization of the ejecta. In this paper, we focus on GRB 110213A that shows double-peaked optical afterglow lightcurves and the shallow decay feature of the X-ray afterglow. We adopt a semi-analytic model for the dynamics of forward and reverse shocks generated through an interaction between an arbitrary magnetized ejecta with a finite thickness and a stratified circumstellar medium. Multiwavelength radiation from forward and reverse shocks seen from an arbitrary viewing angle is calculated under a thin-shell approximation. Our analysis with multimodal nested sampling methods for GRB 110213A suggests that the thick shell ejecta naturally explains the shallow decay feature of the X-ray afterglow. The combination of the reverse shock emission in the strongly magnetized jet and forward shock emission in the weakly magnetized circumstellar medium makes the double peak feature of the optical afterglows. The estimated low radiative efficiency in the prompt phase may be a consequence of the high magnetization of the jet in this case. A multi-messenger emission simulator based on the magnetic bullet afterglow model is publicly available as the open source Julia package "Magglow".
format Preprint
id arxiv_https___arxiv_org_abs_2508_13066
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Double-Peaked Optical Afterglow in GRB 110213A Inferring a Magnetized Thick Shell Ejecta
Kusafuka, Yo
Obayashi, Kaori
Asano, Katsuaki
Yamazaki, Ryo
High Energy Astrophysical Phenomena
Gamma-ray bursts early afterglows are important tracers for determining the radial structure and magnetization of the ejecta. In this paper, we focus on GRB 110213A that shows double-peaked optical afterglow lightcurves and the shallow decay feature of the X-ray afterglow. We adopt a semi-analytic model for the dynamics of forward and reverse shocks generated through an interaction between an arbitrary magnetized ejecta with a finite thickness and a stratified circumstellar medium. Multiwavelength radiation from forward and reverse shocks seen from an arbitrary viewing angle is calculated under a thin-shell approximation. Our analysis with multimodal nested sampling methods for GRB 110213A suggests that the thick shell ejecta naturally explains the shallow decay feature of the X-ray afterglow. The combination of the reverse shock emission in the strongly magnetized jet and forward shock emission in the weakly magnetized circumstellar medium makes the double peak feature of the optical afterglows. The estimated low radiative efficiency in the prompt phase may be a consequence of the high magnetization of the jet in this case. A multi-messenger emission simulator based on the magnetic bullet afterglow model is publicly available as the open source Julia package "Magglow".
title Double-Peaked Optical Afterglow in GRB 110213A Inferring a Magnetized Thick Shell Ejecta
topic High Energy Astrophysical Phenomena
url https://arxiv.org/abs/2508.13066