  The blazar PKS 1510-089 is an example of flat spectrum radio quasars.
High-energy emissions from this class of objects are believed to have been
produced by inverse Compton radiation with seed photons originating from the
broad line region. In such a paradigm, a lack of very high-energy emissions is
expected because of the Klein-Nishina effect and strong absorption in the broad
line region. Recent detection of at least three such blazars by Cherenkov
telescopes has forced a revision of our understanding of these objects. We have
aimed to model the observed spectral energy distribution of PKS 1510-089 from
the high-energy flares in March 2009, during which very high-energy emission
were also detected by H.E.S.S. We have applied the single-zone internal shock
scenario to reproduce the multiwavelength spectrum of PKS~1510-089. We have
followed the evolution of the electrons as they propagate along the jet and
emit synchrotron and inverse Compton radiation. We have considered two sources
of external photons: the dusty torus and the broad line region. We have also
examined the effects of the gamma-gamma absorption of the high-energy photons
both in the AGN environment (the broad line region and the dusty torus), as
well as while traveling over cosmological distances: the extragalactic
background light. We have successfully modeled the observed spectrum of PKS
1510-089. In our model, the highest energy emission is the result of the
Comptonization of the infrared photons from the dusty torus, thus avoiding
Klein-Nishina regime, while the bulk of the emissions in the GeV range may
still be dominated by the Comptonization of radiation coming from the broad
line region.
