The flat-spectrum radio quasar PKS 1441+25 at a redshift of z = 0.940 is detected between 40 and 250 GeV with a significance of 25.5 \sigma using the MAGIC telescopes .
Together with the gravitationally lensed blazar QSO B0218+357 ( z = 0.944 ) , PKS 1441+25 is the most distant very high energy ( VHE ) blazar detected to date .
The observations were triggered by an outburst in 2015 April seen at GeV energies with the Large Area Telescope on board Fermi .
Multi-wavelength observations suggest a subdivision of the high state into two distinct flux states .
In the band covered by MAGIC , the variability time scale is estimated to be 6.4 \pm 1.9 days .
Modeling the broadband spectral energy distribution with an external Compton model , the location of the emitting region is understood as originating in the jet outside the broad line region ( BLR ) during the period of high activity , while being partially within the BLR during the period of low ( typical ) activity .
The observed VHE spectrum during the highest activity is used to probe the extragalactic background light at an unprecedented distance scale for ground-based gamma-ray astronomy .