标题： 耀变体马克arian 501的可变甚高能伽马射线辐射 显示英文标题

标题： Variable VHE gamma-ray emission from Markarian 501

摘要： 活动星系核Markarian 501 (Mrk 501)在2005年5月至7月期间使用MAGIC望远镜在0.10 TeV以上的能量上进行了观测。 该仪器的高灵敏度使我们能够在每个夜晚确定源的流量和光谱。 在整个观测活动中，发现Mrk 501的流量变化了一个数量级。 在两个最活跃的夜晚（即6月30日和7月9日），观察到了两次流量翻倍时间缩短至2分钟的流量变化。 这些是迄今为止在Mrk 501中观察到最快的流量变化。 7月9日约20分钟长的耀发显示了F(<0.25 TeV)和F(>1.2 TeV)峰值之间可能存在4±1分钟的时间延迟，这可能表明电子在发射等离子体团中的加速过程。 流量的变化在几个能段内被量化，并且发现随着伽马射线光子的能量增加而增强。 随着流量的增加，光谱显著变硬，在两个最活跃的夜晚，分别在6月30日和7月9日，清晰检测到光谱峰值分别为0.43 ± 0.06 TeV和0.25 ± 0.07 TeV。 在其他夜晚，没有能量低至0.10 TeV时出现类似的光谱特征，因此表明光谱峰值与源亮度相关。 这些观测特性可以在同步自康普顿(SSC)框架内得到解释，其中伽马射线流量的增加是由新注入的（高能）电子群体引起的。 显示英文摘要

摘要： The blazar Markarian 501 (Mrk 501) was observed at energies above 0.10 TeV with the MAGIC telescope from May through July 2005. The high sensitivity of the instrument enabled the determination of the flux and spectrum of the source on a night-by-night basis. Throughout our observational campaign, the flux from Mrk 501 was found to vary by an order of magnitude. Intra-night flux variability with flux-doubling times down to 2 minutes was observed during the two most active nights, namely June 30 and July 9. These are the fastest flux variations ever observed in Mrk 501. The ~20-minute long flare of July 9 showed an indication of a 4 +/- 1 min time delay between the peaks of F(<0.25 TeV) and F(>1.2 TeV), which may indicate a progressive acceleration of electrons in the emitting plasma blob. The flux variability was quantified for several energy ranges, and found to increase with the energy of the gamma-ray photons. The spectra hardened significantly with increasing flux, and during the two most active nights, a spectral peak was clearly detected at 0.43 +/- 0.06 TeV and 0.25 +/- 0.07 TeV, respectively for June 30 and July 9. There is no evidence of such spectral feature for the other nights at energies down to 0.10 TeV, thus suggesting that the spectral peak is correlated with the source luminosity. These observed characteristics could be accommodated in a Synchrotron-Self-Compton (SSC) framework in which the increase in gamma-ray flux is produced by a freshly injected (high energy) electron population.