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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 | Discovery of very high energy gamma-ray emission from the BL Lacertae object H 2356-309 with the HESS Cherenkov telescopes

The H Collaboration (2006)

Discovery of very high energy gamma-ray emission from the BL Lacertae object H 2356-309 with the HESS Cherenkov telescopes

aap, 455:461-466.

The extreme synchrotron BL Lac object H 2356-309, located at a redshift of z = 0.165, was observed from June to December 2004 with a total exposure of ≈40 h live-time with the HESS (High Energy Stereoscopic System) array of atmospheric-Cherenkov telescopes (ACTs). Analysis of this data set yields, for the first time, a strong excess of 453 gamma-rays (10 standard deviations above background) from H 2356-309, corresponding to an observed integral flux above 200 GeV of I(>200 GeV) = (4.1 ± 0.5) × 10^-12 cm^-2 s^-1 (statistical error only). The differential energy spectrum of the source between 200 GeV and 1.3 TeV is well-described by a power law with a normalisation (at 1 TeV) of N^0 = (4.1 ± 0.5) × 10^-13 cm^-2 s^-1 TeV^-1 and a photon index of Gamma = 3.09 ± 0.24_stat ± 0.10_sys. H 2356-309 is one of the most distant BL Lac objects detected at very-high-energy gamma-rays so far. Results from simultaneous observations from ROTSE-III (optical), RXTE (X-rays) and NRT (radio) are also included and used together with the HESS data to constrain a single-zone homogeneous synchrotron self-Compton (SSC) model. This model provides an adequate fit to the HESS data when using a reasonable set of model parameters.

Provided by the SAO/NASA Astrophysics Data System