H.E.S.S. discovery of very high energy gamma-ray emission from PKS 0625-354
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY(2018)
摘要
PKS 0625-354 (z=0.055) was observed with the four H.E.S.S. telescopes in 2012 during 5.5 hours. The source was detected above an energy threshold of 200 GeV at a significance level of 6.1σ. No significant variability is found in these observations. The source is well described with a power-law spectrum with photon index Γ =2.84 ± 0.50_stat± 0.10_syst and normalization (at E_0=1.0 TeV) N_0(E_0)=(0.58 ± 0.22_stat± 0.12_syst)×10^-12 TeV^-1cm^-2s^-1. Multi-wavelength data collected with Fermi-LAT, Swift-XRT, Swift-UVOT, ATOM and WISE are also analysed. Significant variability is observed only in the Fermi-LAT γ-ray and Swift-XRT X-ray energy bands. Having a good multi-wavelength coverage from radio to very high energy, we performed a broadband modelling from two types of emission scenarios. The results from a one zone lepto-hadronic, and a multi-zone leptonic models are compared and discussed. On the grounds of energetics, our analysis favours a leptonic multi-zone model. Models associated to the X-ray variability constraint supports previous results suggesting a BL Lac nature of PKS 0625-354, with, however, a large-scale jet structure typical of a radio galaxy.
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关键词
radiation mechanisms: non-thermal,galaxies: active,galaxies: individual: PKS 0625-354,galaxies: jets,gamma-rays: galaxies
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