Multiwavelength Observations of the Powerful Gamma-ray Quasar PKS 1510-089: Clues on the Jet Composition - AstrophysicsReport as inadecuate

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Abstract: We present the results from a multiwavelength campaign of the powerfulGamma-ray quasar PKS 1510-089. This campaign commenced with a deep Suzakuobservation lasting three days for a total exposure time of 120 ks, andcontinued with Swift monitoring over 18 days. Besides Swift observations, thecampaign included ground-based optical and radio data, and yielded aquasi-simultaneous broad-band spectral energy distribution from 10^9 Hz to10^{19} Hz. The Suzaku observation provided a high S-N X-ray spectrum, which iswell represented by an extremely hard power-law with photon index Gamma ~ 1.2,augmented by a soft component apparent below 1 keV, which is well described bya black-body model with temperature kT ~ 0.2 keV. Monitoring by Suzaku revealedtemporal variability which is different between the low and high energy bands,again suggesting the presence of a second, variable component in addition tothe primary power-law emission.We model the broadband spectrum of PKS 1510-089assuming that the high energy spectral component results from Comptonization ofinfrared radiation produced by hot dust located in the surrounding moleculartorus. In the adopted internal shock scenario, the derived model parametersimply that the power of the jet is dominated by protons but with a number ofelectrons-positrons exceeding a number of protons by a factor ~10. We also findthat inhomogeneities responsible for the shock formation, prior to thecollision may produce bulk-Compton radiation which can explain the observedsoft X-ray excess and possible excess at ~18 keV. We note, however, that thebulk-Compton interpretation is not unique, and the observed soft excess couldarise as well via some other processes discussed briefly in the text.

Author: J.Kataoka, G.Madejski, M.Sikora, P.Roming, M.M.Chester, D.Grupe, Y.Tsubuku, R.Sato, N.Kawai, G.Tosti, D.Impiombato, Y.Y.Kovalev,


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