FERMI/LARGE AREA TELESCOPE DISCOVERY OF GAMMA-RAY EMISSION FROM A RELATIVISTIC JET IN THE NARROW-LINE QUASAR PMN J0948+0022
- Space Science Division, Naval Research Laboratory, Washington, DC 20375 (United States)
- W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States)
- Oskar Klein Centre for Cosmo Particle Physics, AlbaNova, SE-106 91 Stockholm (Sweden)
- Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, I-56127 Pisa (Italy)
- Laboratoire AIM, CEA-IRFU/CNRS/Universite Paris Diderot, Service d'Astrophysique, CEA Saclay, F-91191 Gif sur Yvette (France)
- Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, I-34127 Trieste (Italy)
- Istituto Nazionale di Fisica Nucleare, Sezione di Padova, I-35131 Padova (Italy)
- Department of Physics, Center for Cosmology and Astro-Particle Physics, Ohio State University, Columbus, OH 43210 (United States)
- Istituto Nazionale di Fisica Nucleare, Sezione di Perugia, I-06123 Perugia (Italy)
- Dipartimento di Fisica 'M. Merlin' dell'Universita e del Politecnico di Bari, I-70126 Bari (Italy)
We report the discovery by the Large Area Telescope (LAT) onboard the Fermi Gamma-Ray Space Telescope of high-energy {gamma}-ray emission from the peculiar quasar PMN J0948+0022 (z = 0.5846). The optical spectrum of this object exhibits rather narrow H{beta} (FWHM(H{beta}) {approx}1500 km s{sup -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 {gamma}-ray observations are presented. Both radio and {gamma}-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 {gamma}-ray spectrum measured by Fermi are similar to those of more powerful Flat-Spectrum Radio Quasars (FSRQs). A comparison of the radio and {gamma}-ray characteristics of PMN J0948+0022 with the other blazars detected by LAT shows that this source has a relatively low radio and {gamma}-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 and 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.
- OSTI ID:
- 21333759
- Journal Information:
- Astrophysical Journal, Vol. 699, Issue 2; Other Information: DOI: 10.1088/0004-637X/699/2/976; Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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