Upper Limits from HESS AGN Observations in 2005-2007
| dc.creator | HESS Collaboration | |
| dc.creator | Aharonian, F. | |
| dc.date | 2007-11-20 | |
| dc.date.accessioned | 2026-07-07T08:56:40Z | |
| dc.date.available | 2026-07-07T08:56:40Z | |
| dc.description | 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. | |
| dc.description | 8 Pages, 2 Figures; Accepted on Nov 6, 2007 for publication in Astronomy & Astrophysics | |
| dc.identifier | https://arxiv.org/abs/0711.3196 | |
| dc.identifier | http://arxiv.org/abs/0711.3196 | |
| dc.identifier | A&A 478, 387-393 (2008) | |
| dc.identifier | doi:10.1051/0004-6361:20078604 | |
| dc.identifier.uri | http://salesiana.dossiersoluciones.com/handle/123456789/146690 | |
| dc.subject | Astrophysics | |
| dc.title | Upper Limits from HESS AGN Observations in 2005-2007 | |
| dc.type | text |