EP240801a/XRF 240801B: An X-Ray Flash Detected by the Einstein Probe and the Implications of Its Multiband Afterglow

作者：Shuai-Qing Jiang, D. Xu, Agnes P. C. van Hoof, Wei‐Hua Lei, Yuan Liu, Hao Zhou, Yong Chen, Shao-Yu Fu, Jun Yang, Xing Liu, Zi-Pei Zhu, A. V. Filippenko, P. G. Jonker, A. Pozanenko, He Gao, Xue-Feng Wu, Bing Zhang, Gavin P. Lamb, M. de Pasquale, S. Kobayashi, F. E. Bauer, Hui Sun, G. Pugliese, Jie An, Valerio D’Elia, J. P. U. Fynbo, WeiKang Zheng, A. J. Castro‐Tirado, Yi-Han Iris Yin, Yuan-Chuan Zou, Adam T. Deller, N. Pankov, A. Volnova, А. С. Москвитин, O. I. Spiridonova, Д. В. Опарин, V. Rumyantsev, О. Бурхонов, Sh. A. Ehgamberdiev, V. Kim, M. Krugov, А. М. Татарников, R. Inasaridze, A. J. Levan, D. Malesani, M. E. Ravasio, J. Quirola-Vásquez, Joyce N. D. van Dalen, J. Sánchez-Sierras, D. Mata Sánchez, S. P. Littlefair, J. Chacon, M. A. P. Torres, A A Chrimes, Nikhil Sarin, A. Martín-Carrillo, V. S. Dhillon, Yi Yang, Thomas G. Brink, R. L. Davies, S. Yang, Amar Aryan, T. W. Chen, A. K. H. Kong, Wenxiong Li, R.L Li, Jirong Mao, Ignacio Pérez-García, Emilio J. Fernández-García, Moira Andrews, Joseph Farah, Zhou Fan, Estefania Padilla Gonzalez, D. A. Howell, D. H. Hartmann, J. Y. Hu, P. Jakobsson, Cheng-Kui Li, Zhi-Xing Ling, C. McCully, Megan Newsome, Benjamin Schneider, Samaporn Tinyanont, Ning-Chen Sun, G. Terreran, Qing-Wen Tang, Wenxin Wang, Jingjing Xu, Weimin Yuan, Bin‐Bin Zhang, Haisheng Zhao, Juan Zhang · 发表于：The Astrophysical Journal Letters · 年份：2025 · DOI：10.3847/2041-8213/addebf · 被引用次数：16 · 研究领域：Gamma-ray bursts and supernovae、Pulsars and Gravitational Waves Research、Astrophysical Phenomena and Observations

Abstract We present multiband observations and analysis of EP240801a, a low-energy, extremely soft gamma-ray burst (GRB) discovered on 2024 August 1 by the Einstein Probe (EP) satellite with a weak contemporaneous signal also detected by the Fermi Gamma-ray Burst Monitor (GBM). Optical spectroscopy of the afterglow, obtained by Gran Telescopio Canarias and Keck, identified the redshift of z = 1.6734. EP240801a exhibits a burst duration of 148 s in X-rays and 22.3 s in gamma rays, with X-rays leading by 80.61 s. Spectral lag analysis indicates that the gamma-ray signal arrived 8.3 s earlier than the X-rays. Joint spectral fitting of EP Wide-field X-ray Telescope and Fermi/GBM data yields an isotropic energy E γ , iso = ( 5.5 7 − 0.50 + 0.54 ) × 1 0 51 erg , a peak energy E peak = 14.9 0 − 4.71 + 7.08 keV , and a fluence ratio S (25–50 keV)/ S ( 50 – 100 keV ) = 1.6 7 − 0.46 + 0.74 , classifying EP240801a as an X-ray flash (XRF). The host-galaxy continuum spectrum, inferred using Prospector , was used to correct its contribution for the observed outburst optical data. Unusual early R -band behavior and EP Follow-up X-ray Telescope observations suggest multiple components in the afterglow. Three models are considered: a two-component jet model, a forward-reverse shock model, and a forward shock...