The Einstein Probe (EP) achieved its first detection and localization of a bright X-ray flare, EP240219a, on 2024 February 19, during its commissioning phase. Subsequent targeted searches triggered by the EP240219a alert identified a faint, untriggered gamma-ray burst (GRB) in the archived data of Fermi Gamma-ray Burst Monitor (GBM), Swift Burst Alert Telescope (BAT), and Insight-HXMT/HE. The EP Wide-field X-ray Telescope (WXT) light curve reveals a long duration of approximately 160 s with a slow decay, whereas the Fermi/GBM light curve shows a total duration of approximately 70 s. The peak in the Fermi/GBM light curve occurs slightly later with respect to the peak seen in the EP/WXT light curve. Our spectral analysis shows that a single cutoff power-law (PL) model effectively describes the joint EP/WXT–Fermi/GBM spectra in general, indicating coherent broad emission typical of GRBs. The model yielded a photon index of ∼–1.70 ± 0.05 and a peak energy of ∼257 ± 134 keV. After detection of GRB 240219A, long-term observations identified several candidates in optical and radio wavelengths, none of which was confirmed as the afterglow counterpart during subsequent optical and near-infrared follow-ups. The analysis of GRB 240219A classifies it as an X-ray-rich GRB (XRR) with a high peak energy, presenting both challenges and opportunities for studying the physical origins of X-ray flashes, XRRs, and classical GRBs. Furthermore, linking the cutoff PL component to nonthermal synchrotron radiation suggests that the burst is driven by a Poynting flux-dominated outflow.

中文翻译：

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触发未触发的：第一个被爱因斯坦探测器探测到的伽马射线暴 240219A 及其影响


爱因斯坦探测器 （EP） 于 2024 年 2 月 19 日在其调试阶段首次探测和定位了明亮的 X 射线耀斑 EP240219a。EP240219a 警报触发的后续目标搜索在费米伽马射线暴监视器 （GBM）、斯威夫特暴警报望远镜 （BAT） 和 Insight-HXMT/HE 的存档数据中发现了一个微弱的、未触发的伽马射线暴 （GRB）。EP 宽视场 X 射线望远镜 （WXT） 光曲线显示持续时间长，约为 160 秒，衰减缓慢，而费米/GBM 光曲线显示总持续时间约为 70 秒。费米/GBM 光曲线中的峰值相对于 EP/WXT 光曲线中的峰值出现得稍晚。我们的光谱分析表明，单个截止幂律 （PL） 模型通常有效地描述了 EP/WXT-Fermi/GBM 联合光谱，表明 GRB 典型的相干宽发射。该模型产生的光子指数为 ∼–1.70 ± 0.05，峰值能量为 ∼257 ± 134 keV。在检测到 GRB 240219A 后，长期观察在光学和无线电波长中确定了几个候选者，在随后的光学和近红外随访中，没有一个被证实为余辉对应物。GRB 240219A 的分析将其归类为具有高峰值能量的富含 X 射线的 GRB （XRR），为研究 X 射线闪光、XRR 和经典 GRB 的物理起源带来了挑战和机遇。此外，将截止 PL 分量与非热同步辐射联系起来表明，爆发是由坡印廷通量主导的流出驱动的。