2005-2007年HESS AGN观测值的上限
Upper Limits from HESS AGN Observations in 2005-2007
摘要：
目的：对18个活动星系核（AGN）进行了甚高能（VHE; E>100 GeV）γ射线研究。方法：在2005年1月至2007年7月期间，利用高能立体系统（HESS）对14个活动星系核（被认为是VHE发射体）进行了VHE观测。还对已知发射VHE伽马射线的三个北部活动星系核（Mkn 421，Mkn 501，1 ES 1218+304）进行了大天顶角观测，以采集其超过1 TeV的光谱能量分布（SED）。此外，在2006年和2007年期间监测了HESS先前在2004-2005年探测到的来自1 ES 1101-232的VHE通量。研究结果：由于HESS观测计划的重要探测在其他地方报道，这里报道的结果主要是积分通量上限。14个VHE候选活动星系核的平均曝光时间约为7小时，观测的平均能量阈值在230 GeV和590 GeV之间。这14个活动星系核的上限范围从小于蟹状星云流量的0.9%到4.9%不等，其中8个是该天体有史以来最受限制的。短暂的（每次<2.2小时）大天顶角观测产生了Mkn 501（2.5 TeV以上<20% Crab）和1 ES 1218+304（1.0 TeV以上<17% Crab）的上限，以及Mkn 421（2.1 TeV以上50% Crab）的边缘检测（3.5 sigma）。1 ES 1101-232在2006年（13.7小时生存时间）的观测中被轻微检测到（3.6 sigma，1.7% Crab高于260 GeV），但在2007年（4.6小时生存时间）的数据中没有检测到。2007年的上限（在260 GeV以上<1.9%的Crab）低于HESS从2004-2006年测量的平均通量。
英文摘要：
AIMS: Very high energy (VHE; E>100 GeV) gamma-ray studies were performed for 18 active galactic nuclei (AGN) from a variety of AGN classes. METHODS: VHE observations of a sample of 14 AGN, considered candidate VHE emitters, were made with the High Energy Stereoscopic System (HESS) between January 2005 and July 2007. Large-zenith-angle observations of three northern AGN (Mkn 421, Mkn 501, 1ES 1218+304), known to emit VHE gamma rays, were also performed in order to sample their spectral energy distributions (SEDs) above 1 TeV. In addition, the VHE flux from 1ES 1101-232, previously detected by HESS in 2004-2005, was monitored during 2006 and 2007. RESULTS: As significant detections from the HESS observation program are reported elsewhere, the results reported here are primarily integral flux upper limits. The average exposure for each of the 14 VHE-candidate AGN is ~7 h live time, and the observations have an average energy threshold between 230 GeV and 590 GeV. Upper limits for these 14 AGN range from <0.9% to <4.9% of the Crab Nebula flux, and eight of these are the most constraining ever reported for the object. The brief (<2.2 h each) large-zenith-angle observations yield upper limits for Mkn 501 (<20% Crab above 2.5 TeV) and 1ES 1218+304 (<17% Crab above 1.0 TeV), and a marginal detection (3.5 sigma) of Mkn 421 (50% Crab above 2.1 TeV). 1ES 1101-232 was marginally detected (3.6 sigma, 1.7% Crab above 260 GeV) during the 2006 (13.7 h live time) observations, but not in the 2007 (4.6 h live time) data. The upper limit in 2007 (<1.9% Crab above 260 GeV) is below the average flux measured by HESS from 2004-2006.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
