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Register a new userThe July 2010 outburst of the NLS1 PMN J0948+0022
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We report about the multiwavelength campaign on the Narrow-Line Seyfert 1 (NLS1) Galaxy PMN J0948+0022 (z = 0.5846) performed in 2010 July-September and triggered by high activity as measured by Fermi/LAT. The peak luminosity in the 0.1-100 GeV energy band exceeded, for the first time in this type of source, the value of 10^48 erg/s, a level comparable to the most powerful blazars. The comparison of the spectral energy distribution of the NLS1 PMN J0948+0022 with that of a typical blazar - like 3C 273 - shows that the power emitted at gamma rays is extreme.
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We report on a multiwavelength campaign on the radio-loud Narrow-Line Seyfert 1 (NLS1) Galaxy PMN J0948+0022 (z=0.5846) performed in 2010 July-September and triggered by a high-energy gamma-ray outburst observed by the Large Area Telescope (LAT) onboard the Fermi Gamma-ray Space Telescope. The peak flux in the 0.1-100 GeV energy band exceeded, for the first time in this type of source, the value of 10^-6 ph cm^-2 s^-1, corresponding to an observed luminosity of 10^48 erg s^-1. Although the source was too close to the Sun position to organize a densely sampled follow-up, it was possible to gather some multiwavelength data that confirmed the state of high activity across the sampled electromagnetic spectrum. The comparison of the spectral energy distribution of the NLS1 PMN J0948+0022 with that of a typical blazar - like 3C 273 - shows that the power emitted at gamma rays is extreme.
Following the recent discovery of gamma rays from the radio-loud narrow-line Seyfert 1 galaxy PMN J0948+0022 (z=0.5846), we started a multiwavelength campaign from radio to gamma rays, which was carried out between the end of March and the beginning of July 2009. The source displayed activity at all the observed wavelengths: a general decreasing trend from optical to gamma-ray frequencies was followed by an increase of radio emission after less than two months from the peak of the gamma-ray emission. The largest flux change, about a factor of about 4, occurred in the X-ray band. The smallest was at ultraviolet and near-infrared frequencies, where the rate of the detected photons dropped by a factor 1.6-1.9. At optical wavelengths, where the sampling rate was the highest, it was possible to observe day-scale variability, with flux variations up to a factor of about 3. The behavior of PMN J0948+0022 observed in this campaign and the calculated power carried out by its jet in the form of protons, electrons, radiation and magnetic field are quite similar to that of blazars, specifically of flat-spectrum radio quasars. These results confirm the idea that radio-loud narrow-line Seyfert 1 galaxies host relativistic jets with power similar to that of average blazars.
We report on multifrequency observations performed during 2012 December-2013 August of the first narrow-line Seyfert 1 galaxy detected in gamma rays, PMN J0948+0022 ($z$ = 0.5846). A gamma-ray flare was observed by the Large Area Telescope on board Fermi during 2012 December-2013 January, reaching a daily peak flux in the 0.1-100 GeV energy range of (155 $pm$ 31) $times$10$^{-8}$ ph cm$^{-2}$ s$^{-1}$ on 2013 January 1, corresponding to an apparent isotropic luminosity of about 1.5$times$10$^{48}$ erg s$^{-1}$. The gamma-ray flaring period triggered Swift and VERITAS observations in addition to radio and optical monitoring by OVRO, MOJAVE, and CRTS. A strong flare was observed in optical, UV, and X-rays on 2012 December 30, quasi-simultaneously to the gamma-ray flare, reaching a record flux for this source from optical to gamma rays. VERITAS observations at very high energy (E > 100 GeV) during 2013 January 6-17 resulted in an upper limit of F (> 0.2 TeV) < 4.0$times$10$^{-12}$ ph cm$^{-2}$ s$^{-1}$. We compared the spectral energy distribution (SED) of the flaring state in 2013 January with that of an intermediate state observed in 2011. The two SEDs, modelled as synchrotron emission and an external Compton scattering of seed photons from a dust torus, can be modelled by changing both the electron distribution parameters and the magnetic field.
We present a comprehensive analysis of multiple wavelength observational data of the first GeV-selected narrow-line Seyfert 1 galaxy PMN J0948+0022. We derive its lightcurves in the gamma-ray and X-ray bands from the data observed with Fermi/LAT and Swift/XRT, and make the optical and radio lightcurves by collecting the data from the literature. These lightcurves show significant flux variations. With the LAT data we show that this source is analogue to typical flat spectrum radio quasars in the $L_gamma-Gamma_gamma$ plane, where $L_gamma$ and $Gamma_gamma$ are the luminosity and spectral index in the LAT energy band. The gamma-ray flux is correlated with the V-band flux with a lag of ~44 days, and a moderate quasi-periodic oscillation (QPO) with a periodicity of ~490 days observed in the LAT lightcurve. A similar QPO signature is also found in the V-band lightcurve. The gamma-ray flux is not correlated with the radio flux in 15 GHz, and no similar QPO signature is found in a confidence level of 95%. Possible mechanisms of the QPO are discussed. We propose that gravitational wave observations in the future may clarify the current plausible models for the QPO.
We report on radio-to-gamma-ray observations during 2011 May-September of PMN J0948+0022, the first narrow-line Seyfert 1 (NLSy1) galaxy detected in gamma-rays by Fermi-LAT. Strong variability was observed in gamma-rays, with two flaring periods peaking on 2011 June 20 and July 28. The variability observed in optical and near-infrared seems to have no counterpart in gamma-rays. This different behaviour could be related to a bending and inhomogeneous jet or a turbulent extreme multi-cell scenario. The radio spectra showed a variability pattern typical of relativistic jets. The XMM spectrum shows that the emission from the jet dominates above 2 keV, while a soft X-ray excess is evident in the low-energy part of the X-ray spectrum. Models where the soft emission is partly produced by blurred reflection or Comptonisation of the thermal disc emission provide good fits to the data. The X-ray spectral slope is similar to that found in radio-quiet NLSy1, suggesting that a standard accretion disc is present, as expected from the high accretion rate. Except for the soft X-ray excess, unusual in jet-dominated AGNs, PMN J0948+0022 shows all characteristics of the blazar class.
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