论文标题
Fermi大面积的望远镜观测值60-600 MEV的快速降低蟹状星云
Fermi Large Area Telescope Observations of the Fast-dimming Crab Nebula in 60-600 MeV
论文作者
论文摘要
上下文：螃蟹脉冲星及其星云是相对论电子的起源，可以通过其同步加速器和逆综合群发射来观察。以同步加速器为主导的和逆通的主导排放之间的过渡发生在$ \ 10^9 $ eV。目的：从最有能力的电子中，同步器发射的短期（数周到数月）的磁通量可变性，该数据与Fermi大面积望远镜（LAT）的十年观测数据中进行了研究，其能量范围为60 MEV至600 MEV。方法：脉冲曲线已从相位分辨的数据中重建。通量测量值的相应直方图用于识别通量状态的分布，并使用对模拟光曲线的专用模拟来估计下液量分量的统计显着性。重建了不同通量状态的能量光谱。结果：我们确认存在遵循对数正常通量分布的耀斑的存在。此外，我们发现了一个低通量状态，其中通量降至中等州平均通量的18.4％，并在那里停留几周。观察到过渡时间短达2天。低通量状态期间的能量光谱类似于在几个GEV能量以外的能量下测量的反孔子光谱的外推，这意味着同步基因发射的高能量部分非常降低。结论：此处找到的低通量状态和最多10天的过渡时间表明，超过$ 10^8 $ eV的同步器发射的体积（$> 75 $％）起源于紧凑型体积，具有明显的角度大小为$θ\ \ \ \ \ \ bout of0.4” t_ \ mathrm {var}/cellive in Inter（5）功能是$γ$ ray排放的大部分的起源。
Context: The Crab pulsar and its nebula are the origin of relativistic electrons which can be observed through their synchrotron and inverse Compton emission. The transition between synchrotron-dominated and inverse-Compton-dominated emissions takes place at $\approx 10^9$ eV. Aims: The short-term (weeks to months) flux variability of the synchrotron emission from the most energetic electrons is investigated with data from ten years of observations with the Fermi Large Area Telescope (LAT) in the energy range from 60 MeV to 600 MeV. Methods: The off-pulse light-curve has been reconstructed from phase-resolved data. The corresponding histogram of flux measurements is used to identify distributions of flux-states and the statistical significance of a lower-flux component is estimated with dedicated simulations of mock light-curves. The energy spectra for different flux states are reconstructed. Results: We confirm the presence of flaring-states which follow a log-normal flux distribution. Additionally, we discover a low-flux state where the flux drops to as low as 18.4% of the intermediate-state average flux and stays there for several weeks. The transition time is observed to be as short as 2 days. The energy spectrum during the low-flux state resembles the extrapolation of the inverse-Compton spectrum measured at energies beyond several GeV energy, implying that the high-energy part of the synchrotron emission is dramatically depressed. Conclusions: The low-flux state found here and the transition time of at most 10 days indicate that the bulk ($>75$%) of the synchrotron emission above $10^8$ eV originates in a compact volume with apparent angular size of $θ\approx0.4" t_\mathrm{var}/(5 \mathrm{d})$. We tentatively infer that the so-called inner knot feature is the origin of the bulk of the $γ$-ray emission.
