Fermi observation of blazars and implications for the origin of gamma-rays
by
Prof.Juri Poutanen(University of Oulu)
→
Europe/Stockholm
FA31
FA31
Description
GeV spectra of the brightest blazars detected by the Fermi Gamma-ray Space Telescope cannot be described by a simple power law model.
A much better description is obtained with a broken power law, with the break energies of a few GeV.
We show that the sharpness and the position of the breaks can be well reproduced by absorption of gamma-rays via
photon--photon pair production on He II Lyman recombination continuum and lines.
This implies that the blazar zone lies inside the region of the highest ionization of the broad-line region (BLR)
within a light-year from a super-massive black hole.
The observations of gamma-ray spectral breaks open
a way of studying the BLR photon field in the extreme-UV/soft X-rays,
which are otherwise hidden from our view.