Spectral Hardening Reveals Afterglow Emergence in Long-duration Fast X-Ray Transients: A Case Study of GRB 250404A/EP250404a
文献类型：期刊论文
| 作者 | Yin, Yi-Han Iris4,5; Fang, Yuan6; Zhang, Bin-Bin4,5; Deng, Chen4,5; Yang, Jun4,5; Chen, Run-Chao4,5; Liu, Yuan7; Cheng, Yehao6; Xu, Dong7,8; Wang, Xiaofeng9 |
| 刊名 | ASTROPHYSICAL JOURNAL LETTERS
 |
| 出版日期 | 2025-08-20 |
| 卷号 | 989期号:2页码:L39 |
| ISSN号 | 2041-8205 |
| DOI | 10.3847/2041-8213/adf552 |
| 产权排序 | 18 |
| 英文摘要 | The prompt emission and afterglow phases of gamma-ray bursts (GRBs) have been extensively studied, yet the transition between these two phases remains inadequately characterized due to limited multiwavelength observational coverage. Among the recent growing samples of fast X-ray transients observed by Einstein Probe (EP), a subgroup of GRBs are captured with long-duration X-ray emission, potentially containing featured evolution from prompt emission to the afterglow phase. In this Letter, we present a detailed analysis of GRB 250404A/EP250404a, a bright, fast X-ray transient detected simultaneously by EP and the Fermi Gamma-ray Burst Monitor in X-rays and gamma rays. Its continuous X-ray emission reveals a long-duration tail, accompanied by distinct spectral evolution manifested by the spectral index alpha X with an initial softening, followed by an evident hardening, eventually reaching a plateau at the value of similar to-2. Early optical and near-infrared observations enable broadband modeling with forward- and reverse-shock components, confirming that the X-ray hardening signals the emergence of the external-shock afterglow. From this spectral hardening, we infer that the prompt phase in soft X-rays lasted similar to 300 s, which is more than 3 times longer than the gamma-ray T90. This well-tracked soft-hard-flat spectral pattern provides a clear indication of afterglow emergence from the fading prompt emission and offers a practical criterion for identifying a distinct population of GRBs among fast X-ray transients, even when the detection of the gamma-ray counterpart or obvious temporal break is absent. |
| WOS关键词 | TIME-DEPENDENT PHOTOIONIZATION ; LIGHT CURVES ; EINSTEIN PROBE ; DUSTY MEDIUM ; BURST ; EVOLUTION ; EMISSION ; ABSORPTION ; TELESCOPE ; MODELS |
| 资助项目 | National Key Research and Development Programs of China[2022YFF0711404] ; National Key Research and Development Programs of China[2022SKA0130102] ; National Key Research and Development Programs of China[2021YFA0718500] ; National SKA Program of China[2022SKA0130100] ; National Natural Science Foundation of China[11833003] ; National Natural Science Foundation of China[U2038105] ; National Natural Science Foundation of China[U1831135] ; National Natural Science Foundation of China[12121003] ; National Natural Science Foundation of China[12393811] ; National Natural Science Foundation of China[13001106] ; China Manned Space Project[CMS-CSST-2021-B11] ; Fundamental Research Funds for the Central Universities ; Strategic Priority Program on Space Science of the Chinese Academy of Sciences ; ESA ; MPE ; CNES[XDA15310000] ; CNES[XDA15052100] ; South-Western Institute for Astronomy Research of Yunnan University (SWIFAR-YNU) - Yunnan University Development Plan for WorldClass University ; National Key RD Program ; Yunnan University Development Plan for World-Class Astronomy Discipline ; Strategic Priority Research Program of CAS ; Science & Technology Champion Project[202005AB160002] ; European Union (ERC) ; Yunnan Revitalization Talent Support Program[202105AE160021] ; Yunnan Revitalization Talent Support Program[202305AT350002] ; Danish National Research Foundation ; National Key Research and Development Program of China[2024YFA1611603] ; Yunnan Provincial Key Laboratory of Survey Science[202449CE340002] ; Yunnan Fundamental Research Projects[202301AU070006] ; NSFC[12288102] ; NSFC[12033003] ; NSFC[12120101003] ; NSFC[12373010] ; New Cornerstone Science Foundation through the XPLORER PRIZE ; Natural Science Foundation of Xinjiang Uygur Autonomous Region[2024D01D32] ; Tianshan Talent Training Program[2023TSYCLJ0053] ; Tianshan Talent Training Program[2023TSYCCX0101] ; Central Guidance for Local Science and Technology Development Fund[ZYYD2025QY27] ; National Natural Science Foundation of China NSFC[12433007] ; National Key R&D Program of China[2023YFE0101200] ; Natural Science Foundation of China[12393813] ; Yunnan Revitalization Talent Support Program (YunLing Scholar Project) ; Spanish Ministry project[PID2023-151905OB-I00] ; Junta de Andalucia[P20_010168] ; Severo Ochoa - MCIN/AEI[CEX2021-001131-S] ; CAS Special Funds for Observatory and Facility Development ; Zhengjia Enterprise Group ; [2022YFA1602902] ; [2023YFA1607804] ; [XDB0550100] ; [XDB0550000] ; [101071865] ; [DNRF140] |
| WOS研究方向 | Astronomy & Astrophysics |
| 语种 | 英语 |
| WOS记录号 | WOS:001563108200001 |
| 出版者 | IOP Publishing Ltd |
| 资助机构 | National Key Research and Development Programs of China ; National SKA Program of China ; National Natural Science Foundation of China ; China Manned Space Project ; Fundamental Research Funds for the Central Universities ; Strategic Priority Program on Space Science of the Chinese Academy of Sciences ; ESA ; MPE ; CNES ; South-Western Institute for Astronomy Research of Yunnan University (SWIFAR-YNU) - Yunnan University Development Plan for WorldClass University ; National Key RD Program ; Yunnan University Development Plan for World-Class Astronomy Discipline ; Strategic Priority Research Program of CAS ; Science & Technology Champion Project ; European Union (ERC) ; Yunnan Revitalization Talent Support Program ; Danish National Research Foundation ; National Key Research and Development Program of China ; Yunnan Provincial Key Laboratory of Survey Science ; Yunnan Fundamental Research Projects ; NSFC ; New Cornerstone Science Foundation through the XPLORER PRIZE ; Natural Science Foundation of Xinjiang Uygur Autonomous Region ; Tianshan Talent Training Program ; Central Guidance for Local Science and Technology Development Fund ; National Natural Science Foundation of China NSFC ; National Key R&D Program of China ; Natural Science Foundation of China ; Yunnan Revitalization Talent Support Program (YunLing Scholar Project) ; Spanish Ministry project ; Junta de Andalucia ; Severo Ochoa - MCIN/AEI ; CAS Special Funds for Observatory and Facility Development ; Zhengjia Enterprise Group |
| 源URL | [http://ir.xao.ac.cn/handle/45760611-7/8107]  |
| 专题 | 光学天文与技术应用研究室_变星研究团组 |
| 通讯作者 | Yin, Yi-Han Iris; Fang, Yuan; Zhang, Bin-Bin |
| 作者单位 | 1.Sun Yat Sen Univ, CSST Sci Ctr Guangdong Hong Kong Macau Greater Bay, Hong Kong 519082, Peoples R China 2.Chinese Acad Sci, Xinjiang Astron Observ, Urumqi 830011, Xinjiang, Peoples R China 3.Univ Helsinki, Fac Sci, Gustav Hallstromin Katu 2, FI-00014 Helsinki, Finland 4.Nanjing Univ, Sch Astron & Space Sci, Nanjing 210093, Peoples R China 5.Nanjing Univ, Minist Educ, Key Lab Modern Astron & Astrophys, Nanjing, Peoples R China 6.Yunnan Univ, South Western Inst Astron Res, Kunming 650504, Yunnan, Peoples R China 7.Chinese Acad Sci, Natl Astron Observ, Beijing 100101, Peoples R China 8.Altay Astron Observ, Altay 836500, Xinjiang, Peoples R China 9.Tsinghua Univ, Phys Dept, Beijing 100084, Peoples R China 10.Ural Fed Univ, Inst Phys & Technol, Mira Str 19, Ekaterinburg 620002, Russia |
| 推荐引用方式 GB/T 7714 | Yin, Yi-Han Iris,Fang, Yuan,Zhang, Bin-Bin,et al. Spectral Hardening Reveals Afterglow Emergence in Long-duration Fast X-Ray Transients: A Case Study of GRB 250404A/EP250404a[J]. ASTROPHYSICAL JOURNAL LETTERS,2025,989(2):L39. |
| APA | Yin, Yi-Han Iris.,Fang, Yuan.,Zhang, Bin-Bin.,Deng, Chen.,Yang, Jun.,...&Zhang, Bing.(2025).Spectral Hardening Reveals Afterglow Emergence in Long-duration Fast X-Ray Transients: A Case Study of GRB 250404A/EP250404a.ASTROPHYSICAL JOURNAL LETTERS,989(2),L39. |
| MLA | Yin, Yi-Han Iris,et al."Spectral Hardening Reveals Afterglow Emergence in Long-duration Fast X-Ray Transients: A Case Study of GRB 250404A/EP250404a".ASTROPHYSICAL JOURNAL LETTERS 989.2(2025):L39. |
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来源：新疆天文台
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