Wuppertal 2015 – wissenschaftliches Programm

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T: Fachverband Teilchenphysik

T 27: Gammaastronomie II

T 27.1: Vortrag

Montag, 9. März 2015, 16:45–17:00, I.13.71 (HS 28)

Observation of the distant blazar PG1553+113 with Fermi and H.E.S.S. — Stephen Fegan, Berrie Giebels, Mathieu de Naurois, •Johannes King, and David Sanchez — Laboratoire Leprince-Ringuet, Palaiseau, France

High-frequency peaked BL Lac objects are primary targets and the bulk of extragalactic sources detected in the TeV range, and the AGN PG1553+113 belongs to this class. In the High Energy (HE) range, PG1553+113 exhibits a hard spectrum (Γ∼ 1.6). The TeV spectrum, however, is among the softer ones (Γ∼ 4.5) making this object the source with the sharpest break between the HE and TeV range ever detected.

An updated analysis of the Fermi data with a larger data set of 5 years, from 2008 August 4 to 2013 August 4 (MJD54682.0-56508.0) and improved reconstruction software is presented in this talk. The HE spectrum of PG1553+113 is fitted best by a log-parabola model. By correcting an estimated intrinsic power law spectrum for absorption due to the extragalactic background light (EBL), an estimation of the redshift of PG1553+113 can be made using also archival spectra in the Very High Energy (VHE) range. The found redshift can be considered as an upper limit and is in agreement with other measurements.