Multiple Rebrightenings in the Optical Afterglow of GRB 210731A: Evidence for an Asymmetric Jet
The broadband afterglow of gamma-ray bursts (GRBs) is usually believed to originate from the synchrotron radiation of electrons accelerated by the external shock of relativistic jets. Therefore, the jet structure should have a significant impact on the GRB afterglow features. The latest observations...
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IOP Publishing
2024-01-01
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| Online Access: | https://doi.org/10.3847/1538-4357/ad90ac |
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| author | Jin-Da Li He Gao Shunke Ai Wei-Hua Lei |
| author_facet | Jin-Da Li He Gao Shunke Ai Wei-Hua Lei |
| author_sort | Jin-Da Li |
| collection | DOAJ |
| description | The broadband afterglow of gamma-ray bursts (GRBs) is usually believed to originate from the synchrotron radiation of electrons accelerated by the external shock of relativistic jets. Therefore, the jet structure should have a significant impact on the GRB afterglow features. The latest observations indicate that the GRB jets may possess intricate structures, such as Gaussian structure, power-law structure, or jet-cocoon structure. Most recently, an abnormal afterglow of GRB 210731A has raised extensive attention, whose optical afterglow exhibits multiple rebrightening phenomena within 4 hr, posing a serious challenge to the standard afterglow model. Here we intend to interpret the characteristics of GRB 210731A afterglows within the framework of nonaxisymmetric structured jets, where multiple distinct peaks in the afterglow light curve are caused by the uneven distribution of energy and velocity within the jet in the azimuth angle direction. Through Markov Chain Monte Carlo fitting, we show that a three-component asymmetric structured jet can well explain the multiband afterglow data. The energy difference among the three components is about 2.3 orders of magnitude, with higher-energy components exhibiting faster speeds. The radiation contribution of each component has sequentially dominated the light curve of the afterglow, resulting in multiple peaks, with the highest peak occurring at the latest time. We suggest that in the future, polarization observations should be conducted on afterglows with multiple brightening signatures, which will help to effectively distinguish the structured jet model from other alternative models, such as energy injection, and ultimately help to determine the true configuration of jets. |
| format | Article |
| id | doaj-art-8dfaee45d9e843c89e39b6bcab249baf |
| institution | DOAJ |
| issn | 1538-4357 |
| language | English |
| publishDate | 2024-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | The Astrophysical Journal |
| spelling | doaj-art-8dfaee45d9e843c89e39b6bcab249baf2025-08-20T02:39:59ZengIOP PublishingThe Astrophysical Journal1538-43572024-01-01978111610.3847/1538-4357/ad90acMultiple Rebrightenings in the Optical Afterglow of GRB 210731A: Evidence for an Asymmetric JetJin-Da Li0He Gao1https://orcid.org/0000-0003-2516-6288Shunke Ai2https://orcid.org/0000-0002-9165-8312Wei-Hua Lei3Institute for Frontier in Astronomy and Astrophysics, Beijing Normal University , Beijing 102206, People's Republic of China ; gaohe@bnu.edu.cn; School of Physics and Astronomy, Beijing Normal University , Beijing 100875, People's Republic of ChinaInstitute for Frontier in Astronomy and Astrophysics, Beijing Normal University , Beijing 102206, People's Republic of China ; gaohe@bnu.edu.cn; School of Physics and Astronomy, Beijing Normal University , Beijing 100875, People's Republic of ChinaDepartment of Astronomy, School of Physics and Technology, Wuhan University , Wuhan 430072, People's Republic of China; Niels Bohr International Academy and DARK, Niels Bohr Institute, University of Copenhagen , Blegdamsvej 17, 2100, Copenhagen, DenmarkDepartment of Astronomy, School of Physics, Huazhong University of Science and Technology , Wuhan, Hubei 430074, People's Republic of ChinaThe broadband afterglow of gamma-ray bursts (GRBs) is usually believed to originate from the synchrotron radiation of electrons accelerated by the external shock of relativistic jets. Therefore, the jet structure should have a significant impact on the GRB afterglow features. The latest observations indicate that the GRB jets may possess intricate structures, such as Gaussian structure, power-law structure, or jet-cocoon structure. Most recently, an abnormal afterglow of GRB 210731A has raised extensive attention, whose optical afterglow exhibits multiple rebrightening phenomena within 4 hr, posing a serious challenge to the standard afterglow model. Here we intend to interpret the characteristics of GRB 210731A afterglows within the framework of nonaxisymmetric structured jets, where multiple distinct peaks in the afterglow light curve are caused by the uneven distribution of energy and velocity within the jet in the azimuth angle direction. Through Markov Chain Monte Carlo fitting, we show that a three-component asymmetric structured jet can well explain the multiband afterglow data. The energy difference among the three components is about 2.3 orders of magnitude, with higher-energy components exhibiting faster speeds. The radiation contribution of each component has sequentially dominated the light curve of the afterglow, resulting in multiple peaks, with the highest peak occurring at the latest time. We suggest that in the future, polarization observations should be conducted on afterglows with multiple brightening signatures, which will help to effectively distinguish the structured jet model from other alternative models, such as energy injection, and ultimately help to determine the true configuration of jets.https://doi.org/10.3847/1538-4357/ad90acGamma-ray bursts |
| spellingShingle | Jin-Da Li He Gao Shunke Ai Wei-Hua Lei Multiple Rebrightenings in the Optical Afterglow of GRB 210731A: Evidence for an Asymmetric Jet The Astrophysical Journal Gamma-ray bursts |
| title | Multiple Rebrightenings in the Optical Afterglow of GRB 210731A: Evidence for an Asymmetric Jet |
| title_full | Multiple Rebrightenings in the Optical Afterglow of GRB 210731A: Evidence for an Asymmetric Jet |
| title_fullStr | Multiple Rebrightenings in the Optical Afterglow of GRB 210731A: Evidence for an Asymmetric Jet |
| title_full_unstemmed | Multiple Rebrightenings in the Optical Afterglow of GRB 210731A: Evidence for an Asymmetric Jet |
| title_short | Multiple Rebrightenings in the Optical Afterglow of GRB 210731A: Evidence for an Asymmetric Jet |
| title_sort | multiple rebrightenings in the optical afterglow of grb 210731a evidence for an asymmetric jet |
| topic | Gamma-ray bursts |
| url | https://doi.org/10.3847/1538-4357/ad90ac |
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