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We report the Fermi Large Area Telescope (LAT) detection of twovery-high-energy (VHE, E>100 GeV) gamma-ray photons from the directionalvicinity of the distant (redshift, z = 1.1) blazar PKS 0426-380. The nullhypothesis that both the 134 and 122 GeV photons originate from unrelatedsources can be rejected at the 5.5 sigma confidence level. We therefore claimthat at least one of the two VHE photons is securely associated with theblazar, making PKS 0426-380 the most distant VHE emitter known to date. Theresults are in agreement with the most recent Fermi-LAT constraints on theExtragalactic Background Light (EBL) intensity, which imply a $z \simeq 1$horizon for $\simeq$ 100 GeV photons. The LAT detection of the two VHEgamma-rays coincided roughly with flaring states of the source, although we didnot find an exact correspondence between the VHE photon arrival times and theflux maxima at lower gamma-ray energies. Modeling the gamma-ray continuum ofPKS 0426-380 with daily bins revealed a significant spectral hardening aroundthe time of detection of the first VHE event (LAT photon index \Gamma\ $\simeq$1.4) but on the other hand no pronounced spectral changes near the detectiontime of the second one. This combination implies a rather complex variabilitypattern of the source in gamma rays during the flaring epochs. An additionalflat component is possibly present above several tens of GeV in theEBL-corrected Fermi-LAT spectrum accumulated over the ~8-month high state.

Fermi Large Area Telescope Detection of Two Very-High-Energy (E>100 GeV) Gamma-ray Photons from the z = 1.1 Blazar PKS 0426-380