{"paper":{"title":"EP251023a: A fast X-ray transient featuring a magnetar-powered optical internal plateau followed by a steep decay","license":"http://arxiv.org/licenses/nonexclusive-distrib/1.0/","headline":"","cross_cats":[],"primary_cat":"astro-ph.HE","authors_text":"A. J. Castro-Tirado, Alexandra L. Lysenko, A. Maury, Anastasia Tsvetkova, Anna Ridnaia, B.-B. Zhang, Curtis McCully, D. Andrew Howell, Ding-Fang Hu, Dmitry Frederiks, Dmitry Svinkin, Dong Xu, D.-R. Xiong, E. Fern\\'andez-Garc\\'ia, Hao-Nan Yang, I. P\\'erez-Garc\\'ia, Jie An, Joseph R. Farah, Kathryn Wynn, Lin-Bo He, M. Gritsevich, Mikhail Ulanov, Moira Andrews, Ryan Chornock, S. B. Pandey, Shao-Yu Fu, Shuai-Qing Jiang, S.-Y. Wu, Tong Zhao, Wei-Hua Lei, Wen-Da Zhang, Wen-Xiong Li, Xing Liu, Yuan-Chuan Zou, Yue Wu, Zi-Pei Zhu","submitted_at":"2026-06-23T09:04:56Z","abstract_excerpt":"EP251023a is an extragalactic fast X-ray transient (eFXT) detected solely by EP without a gamma-ray counterpart. The prompt emission consists of a main emission with a duration $T_{90}=292\\pm19$ s, followed by a long-lasting tail emission that persists until the observation ends at $T_0+1571$ s. With the upper limit of Konus--Wind, we derived a conservative upper limit on the isotropic gamma-ray energy $E_{\\gamma,\\rm{iso}}$ of $5.7 \\times 10^{52}$ erg for the main emission phase. A redshift of $z = 2.232\\pm0.001$ is identified from strong absorption features in the Keck spectrum, which also in"},"claims":{"count":0,"items":[],"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"source":{"id":"2606.24329","kind":"arxiv","version":1},"verdict":{"id":null,"model_set":{},"created_at":null,"strongest_claim":"","one_line_summary":"","pipeline_version":null,"weakest_assumption":"","pith_extraction_headline":""},"integrity":{"clean":true,"summary":{"advisory":0,"critical":0,"by_detector":{},"informational":0},"endpoint":"/pith/2606.24329/integrity.json","findings":[],"available":true,"detectors_run":[],"snapshot_sha256":"c28c3603d3b5d939e8dc4c7e95fa8dfce3d595e45f758748cecf8e644a296938"},"references":{"count":0,"sample":[],"resolved_work":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57","internal_anchors":0},"formal_canon":{"evidence_count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"author_claims":{"count":0,"strong_count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"builder_version":"pith-number-builder-2026-05-17-v1"}