2010A&A...514A..69Z

The active galaxy PKS 0208-512, detected at lower energies by COMPTEL, has been claimed to be a MeV blazar from EGRET. We report on the most recent emINTEGRAL observations of the blazar PKS 0208-512, which are supplemented by emSwift ToO observations. The high energy X-ray and γ-ray emission of PKS 0208-512 during August-December 2008 has been studied using 682ks of INTEGRAL guest observer time and ∼56ks of emSwift/XRT observations. These data were collected during the decay of a γ-ray flare observed by emFermi/LAT. At X-ray energies (0.2-10keV) PKS 0208-512 is significantly detected by emSwift/XRT, showing a power-law spectrum with a photon index of ∼1.64. Its X-ray luminosity varied by roughly 30% during one month. At hard X-/soft γ-ray energies PKS 0208-512 shows a marginally significant (∼3.2σ) emission in the 0.5-1MeV band when combining all emINTEGRAL/SPI data. Non-detections at energies below and above this band by emINTEGRAL/SPI may indicate intrinsic excess emission. If this possible excess is produced by the blazar, one possible explanation could be that its jet consists of an abundant electron-positron plasma, which may lead to the emission of an annihilation radiation feature. Assuming this scenario, we estimate physical parameters of the jet of PKS 0208-512.