H.E.S.S. discovery of very high energy γ-ray emission from PKS 0625−354
Date
2018Author
Abdalla, H.
Barnard, M.
Davids, I.D.
Garrigoux, T.
Ivascenko, A.
Pekeur, N.W.
Seyffert, A.S.
Spanier, F.
Sushch, I.
Van der Walt, D.J.
Van Rensburg, C.
Venter, C.
Wadiasingh, Z.
H.E.S.S. Collaboration
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PKS 0625−354 (z = 0.055) was observed with the four High Energy Stereoscopic System (H.E.S.S.) telescopes in 2012 during 5.5 h. 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 ± 0.50stat ± 0.10syst and normalization (at E0 = 1.0 TeV) N0(E0) = (0.58 ± 0.22stat ± 0.12syst) × 10−12 TeV−1 cm−2 s−1. Multiwavelength 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 multiwavelength coverage from radio to very high energy, we performed a broad-band modelling from two types of emission scenarios. The results from a one zone lepto-hadronic and a multizone leptonic models are compared and discussed. On the grounds of energetics, our analysis favours a leptonic multizone model. Models associated to the X-ray variability constraint support previous results, suggesting a BL Lac nature of PKS 0625−354 with, however, a large-scale jet structure typical of a radio galaxy
URI
http://hdl.handle.net/10394/30942https://doi.org/10.1093/mnras/sty439
https://academic.oup.com/mnras/article/476/3/4187/4880460