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Humboldt-Universität zu Berlin - Mathematisch-Naturwissen­schaft­liche Fakultät - Experimentelle Elementarteilchenphysik

Humboldt-Universität zu Berlin | Mathematisch-Naturwissen­schaft­liche Fakultät | Institut für Physik | Experimentelle Elementarteilchenphysik | H.E.S.S. | Talks & Papers | Detection of VHE gamma-ray emission from the distant blazar 1ESthinsp1101-232 with HESS and broadband characterisation

The H Collaboration (2007)

Detection of VHE gamma-ray emission from the distant blazar 1ESthinsp1101-232 with HESS and broadband characterisation

aap, 470:475-489.

Context: The blazar 1ES 1101-232 was observed with the High Energy Stereoscopic System (HESS) of Atmospheric Cherenkov Telescopes (ACT) in 2004 and 2005, for a live time of 43 h. VHE (E > 10^11 eV) gamma-rays were detected for the first time from this object. Aims: VHE observations of blazars are used to investigate the inner parts of the blazar jets, and also to study the extragalactic background light (EBL) in the near-infrared band. Methods: Observations in 2005 were conducted in a multiwavelength campaign, together with the RXTE satellite and optical observations. In 2004, simultaneous observations with XMM-Newton were obtained. Results: 1ES 1101-232 was detected with HESS with an excess of 649 photons, at a significance of 10sigma. The measured VHE gamma-ray flux amounts to dN/dE = (5.63 ± 0.89) × 10^-13 (E/TeV)^-(2.94±0.20) cm^-2 s^-1 TeV^-1, above a spectral energy threshold of 225 GeV. No significant variation of the VHE gamma-ray flux on any time scale was found. 1ES 1101-232 exhibits a very hard spectrum, and at a redshift of z = 0.186, is the blazar with the highest confirmed redshift detected in VHE gamma-rays so far. Conclusions: The data allow the construction of truly simultaneous spectral energy distributions of the source, from the optical to the VHE band. Using an EBL model with nu F^nu = 14 nWm^-2 sr^-1 at 1.5 mum as presented in Aharonian et al. (2006a) suggests an intrinsic VHE power output peak of the source at above 3 TeV.

Provided by the SAO/NASA Astrophysics Data System