Résumé
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 = 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.