费米伽马射线暴瞬时辐射中的高能谱截断：体洛伦兹因子、发射半径及截断-峰值能量关系
High-energy spectral cutoffs in the prompt emission of Fermi gamma-ray bursts: bulk Lorentz factors, emission radii, and a cutoff-peak energy relation
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中文总结 AI 辅助
该研究系统搜索费米GRB瞬时谱中的高能截断，推断体洛伦兹因子和发射半径，并发现截断-峰值能量关系。
中文摘要 AI 辅助
伽马射线暴（GRB）瞬时谱的高能端携带着相对论性外流的物理条件信息，但具有良好表征的谱截断数量很少。我们对费米卫星在2008年7月至2025年12月期间观测到的139个GRB的时间积分瞬时谱进行了系统性的高能谱截断搜索，这些暴通过LAT探测或明亮的BGO发射被选为具有宽带覆盖。在$T_{90}$上联合GBM、LLE和LAT谱，用四种经验模型进行拟合，并使用贝叶斯信息准则进行比较，得到106个具有良好约束截断能量$E_c$的暴。对$\log_{10}(E_c/\mathrm{MeV})$应用经验双组分高斯混合模型，在$E_c=2.12$ MeV处将低$E_c$群与主分布分开；位于该边界之上的77个暴在内部$\gamma\gamma$对不透明度框架内进行解释。将$E_c$与小波基最小变时标（中位数$0.119$ s）相结合，我们推断出体洛伦兹因子在$11.7$到$2.78\times10^{3}$之间（中位数145），发射半径约为$10^{13}$到$10^{15}\\\\,\mathrm{cm}$。对于整个样本，$\Gamma$-$L_{\mathrm{iso}}$和$\Gamma$-$E_{\mathrm{iso}}$关系均不具有统计显著性，而27个具有测量红移的暴显示出中等强度的$\Gamma$-$L_{\mathrm{iso}}$相关性，斜率为$0.36_{-0.23}^{+0.22}$。我们进一步发现，对于26个具有测量红移的暴，截断能量与峰值能量之间存在强的静止系相关性，$E_{c,z}\propto E_{p,z}^{2.15_{-0.97}^{+0.96}}$，该相关性在控制红移后仍然存在。
英文摘要
The high-energy end of the gamma-ray burst (GRB) prompt spectrum carries information on the physical conditions of the relativistic outflow, but the number of well-characterized spectral cutoffs is small. We present a systematic search for high-energy spectral cutoffs in the time-integrated prompt spectra of 139 GRBs observed by Fermi between 2008 July and 2025 December, selected to have broadband coverage either through a LAT detection or through bright BGO emission. Joint GBM, LLE, and LAT spectra over $T_{90}$ are fitted with four empirical models and compared using the Bayesian information criterion, yielding 106 bursts with well-constrained cutoff energies $E_c$. An empirical two-component Gaussian mixture model applied to $\log_{10}(E_c/\mathrm{MeV})$ separates a low-$E_c$ group from the main distribution at $E_c=2.12$ MeV; the 77 bursts lying firmly above this boundary are interpreted within the internal $γγ$ pair-opacity framework. Combining $E_c$ with wavelet-based minimum variability timescales (median $0.119$ s), we infer bulk Lorentz factors of $11.7$ to $2.78\times10^{3}$ (median 145) and emission radii of $\sim10^{13}$ to $10^{15}\,\mathrm{cm}$. Neither the $Γ$-$L_{\mathrm{iso}}$ nor the $Γ$-$E_{\mathrm{iso}}$ relation is statistically significant for the full sample, whereas the 27 bursts with measured redshifts show a moderate $Γ$-$L_{\mathrm{iso}}$ correlation with a slope of $0.36_{-0.23}^{+0.22}$. We further find a strong rest-frame correlation between the cutoff and peak energies, $E_{c,z}\propto E_{p,z}^{2.15_{-0.97}^{+0.96}}$, for the 26 bursts with measured redshifts, which persists after controlling for redshift.
发表机构
- School of Physics, Huazhong University of Science and Technology（华中科技大学物理学院）
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