Lepto$-$Hadronic Origin of $\gamma$-ray Outbursts of 3C 279
  The blazar 3C 279 exhibited a giant $\gamma$-ray outburst in 2013 December and 2014 April. Apart from the very fast $\gamma$-ray flux variability, the spectral nature of the flares were also found to vary significantly between these two flaring events. A prominent curvature in the $\gamma$-ray spectrum was noticed in 2014 April flare, on the other hand, the 2013 December displayed an extreme hardening of the spectrum. These observations, thus, put strong constraints on our understanding of the underlying particle acceleration mechanisms. 
Vaidehi S. Paliya, Chris Diltz, Markus Bottcher, C. S. Stalin, and   David Buckley
astro-ph.HE