IGR J12319–0749: evidence for another extreme blazar found with INTEGRAL

We report on the identification of a new soft gamma-ray source, IGR J12319–0749, detected with the IBIS imager on board the INTEGRAL satellite. The source, which has an observed 20−100 keV flux of ∼8.3 × 10−12 erg cm−2 s−1, is spatially coincident with an active galactic nucleus (AGN) at redshift z = 3.12. The broad-band continuum, obtained by combining XRT and IBIS data, is flat (Γ = 1.3) with evidence for a spectral break around 25 keV (100 keV in the source restframe). X-ray observations indicate flux variability, which is also supported by a comparison with a previous ROSAT measurement. IGR J12319–0749 is also a radio-emitting object likely characterised by a flat spectrum and high radio loudness; optically it is a broad-line emitting object with a massive black hole (2.8 × 109 solar masses) at its centre. The source spectral energy distribution is similar to another high-redshift blazar, 225155+2217 at z = 3.668: both objects are bright, with a high accretion disk luminosity and a Compton peak located in the hard X-ray/soft gamma-ray band. IGR J12319–0749 is likely the second-most distant blazar detected so far by INTEGRAL.