The Burst Alert Telescope ( BAT ) onboard Swift detected bright emission from 15–195 keV from the source SWIFT J0746.3+2548 ( J0746 in the following ) , identified with the optically-faint ( R \sim 19 ) , z =2.979 quasar SDSS J074625.87+244901.2 .
Here we present Swift and multiwavelength observations of this source .
The X-ray emission from J0746 is variable on timescales of hours to weeks in 0.5–8 keV and of a few months in 15–195 keV , but there is no accompanying spectral variability in the 0.5–8 keV band .
There is a suggestion that the BAT spectrum , initially very hard ( photon index \Gamma \sim 0.7 ) , steepened to \Gamma \sim 1.3 in a few months , together with a decrease of the 15–195 keV flux by a factor \sim 2 .
The 0.5–8 keV continuum is well described by a power law with \Gamma \sim 1.3 , and spectral flattening below 1 keV .
The latter can be described with a column density in excess of the Galactic value with intrinsic column density N _ { H } ^ { z } \sim 10 ^ { 22 } cm ^ { -2 } , or with a flatter power law , implying a sharp ( \Delta \Gamma \buildrel > \over { \sim } 1 ) break across 16 keV in the quasar ’ s rest-frame .
The Spectral Energy Distribution of J0746 is double-humped , with the first component peaking at IR wavelengths and the second component at MeV energies .
These properties suggest that J0746 is a a blazar with high gamma-ray luminosity and low peak energy ( MeV ) stretching the blazar sequence to an extreme .