Issue |
A&A
Volume 548, December 2012
|
|
---|---|---|
Article Number | A106 | |
Number of page(s) | 14 | |
Section | Extragalactic astronomy | |
DOI | https://doi.org/10.1051/0004-6361/201220225 | |
Published online | 30 November 2012 |
Radio-to-γ-ray monitoring of the narrow-line Seyfert 1 galaxy PMN J0948 + 0022 from 2008 to 2011⋆,⋆⋆
1 INAF – Osservatorio Astronomico di Brera, via E. Bianchi 46,
23807 Merate ( LC), Italy
e-mail: luigi.foschini@brera.inaf.it
2
Max-Planck-Institut für Radioastronomie,
Auf dem Hügel 69, 53121
Bonn,
Germany
3
Cahill Center for Astronomy & Astrophysics, Caltech,
1200 E. California Blvd, Pasadena, CA
91125,
USA
4
Aalto University Metsähovi Radio Observatory,
Metsähovintie 114, 02540
Kylmälä,
Finland
5
Department of Physics, Purdue University,
West Lafayette, IN
47907,
USA
6
Department of Astronomy and Physics, Saint Mary’s
University, 923 Robie Street,
Halifax, NS
B3H 3C3,
Canada
7
Department of Natural Sciences, Shawnee State
University, 940 2nd
Street, Portsmouth,
OH
45662,
USA
8
National Astronomical Observatory of Japan,
2-21-1 Osawa, Mitaka, 181-8588
Tokyo,
Japan
9
Crimean Astrophysical Observatory, 98409
Nauchny, Crimea,
Ukraine
10
Pulkovo Observatory, 196140
St. Petersburg,
Russia
11
NASA Goddard Space Flight Center, Greenbelt, MD
20771,
USA
12
ITPA, Universität Würzburg, Campus Hubland Nord, Emil-Fischer-Str. 31,
97074
Würzburg,
Germany
13
ISDC Data Centre for Astrophysics, Chemin d’Ecogia
16, 1290
Versoix,
Switzerland
14
Instituto Nacional de Astrofísica, Óptica y Electrónica, Tonantzintla,
72840
Puebla,
Mexico
15
Department of Astronomy & Astrophysics, Pennsylvania
State University, University
Park, PA
16802,
USA
16
INAF – Istituto di Radioastronomia, via Gobetti 101,
40129
Bologna,
Italy
17
Astro Space Center of the Lebedev Physical
Institute, Profsoyuznaya
84/32, 117997
Moscow,
Russia
18
Instituto de Radioastronomía Milimétrica (IRAM),
Avenida Divina Pastora 7, Local
20, 18012
Granada,
Spain
19
SISSA, via Bonomea 265, 34136
Trieste,
Italy
20
Institute of Space and Astronautical Science,
JAXA, 3-1-1 Yoshinodai, Sagamihara,
229-8510
Kanagawa,
Japan
Received: 14 August 2012
Accepted: 24 September 2012
We present more than three years of observations at different frequencies, from radio to high-energy γ-rays, of the Narrow-Line Seyfert 1 (NLS1) Galaxy PMN J0948 + 0022 (z = 0.585). This source is the first NLS1 detected at energies above 100 MeV and therefore can be considered the prototype of this emerging new class of γ-ray emitting active galactic nuclei (AGN). The observations performed from 2008 August 1 to 2011 December 31 confirmed that PMN J0948 + 0022 generates a powerful relativistic jet, which is able to develop an isotropic luminosity at γ-rays of the order of 1048 erg s-1, at the level ofpowerful quasars. The evolution of the radiation emission of this source in 2009 and 2010 followed the canonical expectations of relativistic jets with correlated multiwavelength variability (γ-rays followed by radio emission after a few months), but it was difficult to retrieve a similar pattern in the light curves of 2011. The comparison of γ-ray spectra before and including 2011 data suggested that there was a softening of the high-energy spectral slope. We selected five specific epochs to be studied by modelling the broad-band spectrum, which are characterised by an outburst at γ-rays or very low/high flux at other wavelengths. The observed variability can largely be explained by changes in the injected power, the bulk Lorentz factor of the jet, or the electron spectrum. The characteristic time scale of doubling/halving flux ranges from a few days to a few months, depending on the frequency and the sampling rate. The shortest doubling time scale at γ-rays is 2.3 ± 0.5 days. These small values underline the need of highly sampled multiwavelength campaigns to better understand the physics of these sources.
Key words: galaxies: jets / galaxies: Seyfert / gamma rays: galaxies / galaxies: individual: PMN J0948+0022
Appendix A is available in electronic form at http://www.aanda.org
Data displayed in Figs. A.1–A.3 are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/548/A106
© ESO, 2012
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