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Fermi/Large Area Telescope Discovery of Gamma-Ray Emission from a Relativistic Jet in the Narrow-Line Quasar PMN J0948+0022
Stockholm University, Faculty of Science, Department of Astronomy.
Stockholm University, Faculty of Science, Department of Physics.
Stockholm University, Faculty of Science, Department of Physics.
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2009 (English)In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 699, no 2, 976-984 p.Article in journal (Refereed) Published
Abstract [en]

We report the discovery by the Large Area Telescope (LAT) onboard the Fermi Gamma-Ray Space Telescope of high-energy γ-ray emission from the peculiar quasar PMN J0948+0022 (z = 0.5846). The optical spectrum of this object exhibits rather narrow Hβ (FWHM(Hβ) ~1500 km s–1), weak forbidden lines, and is therefore classified as a narrow-line type I quasar. This class of objects is thought to have relatively small black hole mass and to accrete at a high Eddington ratio. The radio loudness and variability of the compact radio core indicate the presence of a relativistic jet. Quasi-simultaneous radio/optical/X-ray and γ-ray observations are presented. Both radio and γ-ray emissions (observed over five months) are strongly variable. The simultaneous optical and X-ray data from Swift show a blue continuum attributed to the accretion disk and a hard X-ray spectrum attributed to the jet. The resulting broadband spectral energy distribution (SED) and, in particular, the γ-ray spectrum measured by Fermi are similar to those of more powerful Flat-Spectrum Radio Quasars (FSRQs). A comparison of the radio and γ-ray characteristics of PMN J0948+0022 with the other blazars detected by LAT shows that this source has a relatively low radio and γ-ray power with respect to other FSRQs. The physical parameters obtained from modeling the SED also fall at the low power end of the FSRQ parameter region discussed in Celotti & Ghisellini. We suggest that the similarity of the SED of PMN J0948+0022 to that of more massive and more powerful quasars can be understood in a scenario in which the SED properties depend on the Eddington ratio rather than on the absolute power.

Place, publisher, year, edition, pages
2009. Vol. 699, no 2, 976-984 p.
Keyword [en]
galaxies: active, gamma rays: observations, quasars: individual: PMN J0948+0022
National Category
Astronomy, Astrophysics and Cosmology Astronomy, Astrophysics and Cosmology
Research subject
URN: urn:nbn:se:su:diva-28883DOI: 10.1088/0004-637X/699/2/976ISI: 000267401500008OAI: diva2:227529
Available from: 2009-07-15 Created: 2009-07-15 Last updated: 2011-02-15Bibliographically approved

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