High energy properties of PKS 1830-211

Abstract

We report on an analysis of X- and g-ray observations of PKS 1830-211, a gravitational-lensed high-redshift quasar, based on the long-term campaigns carried out by INTEGRAL and COMPTEL. The INTEGRAL data currently available present a 33σ significance detection in the 20-100 keV band, while the COMPTEL 6-years data provide a 5.2σ significance detection in the 1-3 MeV energy band. At hard X-rays, INTEGRAL and supplementary SWIFT observations show flux variability on timescales of months. At g-rays, the source shows persistent emission over years. The hard X-ray spectrum is well represented by a power-law model, with Γ ∼ 1.3 in the 20-250 keV band. This photon index is well consistent with the previous report of G ∼ 1.3 obtained at E > 3.5 keV from the best fit of XMM-Newton data with a broken power law model. The joint XMM-Newton/INTEGRAL spectrum presented here is fitted with a broken power-law model and the parameters are refined compared to the previous. The results show that the photon index changes from ∼ 1.0 to ∼ 1.3 at a break energy of ∼ 4 keV At MeV energies, the spectrum softens to G ∼ 2.2. These results, together with the EGRET measurement at E ≥ 100 MeV, constitute a broad-band spectrum containing the peak of the power output at MeV energies, similar to most high-luminosity g-ray blazars. The measured spectral characterstics are then discussed in the framework of the gravitational lens effects.