We present the results of observations of blazar PKS 1510 - 089 with the Herschel Space Observatory PACS and SPIRE instruments , together with multiwavelength data from Fermi /LAT , Swift , SMARTS and SMA .
The source was found in a quiet state , and its far-infrared spectrum is consistent with a power-law with a spectral index of \alpha \simeq 0.7 .
Our Herschel observations were preceded by two ‘ orphan ’ gamma-ray flares .
The near-infrared data reveal the high-energy cut-off in the main synchrotron component , which can not be associated with the main gamma-ray component in a one-zone leptonic model .
This is because in such a model the luminosity ratio of the External-Compton and synchrotron components is tightly related to the frequency ratio of these components , and in this particular case an unrealistically high energy density of the external radiation would be implied .
Therefore , we consider a well-constrained two-zone blazar model to interpret the entire dataset .
In this framework , the observed infrared emission is associated with the synchrotron component produced in the hot-dust region at the supra-pc scale , while the gamma-ray emission is associated with the External-Compton component produced in the broad-line region at the sub-pc scale .
In addition , the optical/UV emission is associated with the accretion disk thermal emission , with the accretion disk corona likely contributing to the X-ray emission .