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arXiv 1209.5867astro-ph.HEastro-ph.GA
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2008年至2011年窄线Seyfert 1 Galaxy PMN J0948 +0022的无线电至gamma-ray监测

Radio-to-gamma-ray Monitoring of the Narrow-Line Seyfert 1 Galaxy PMN J0948+0022 from 2008 to 2011

L. Foschini, E. Angelakis, L. Fuhrmann, G. Ghisellini, T. Hovatta, A. Lahteenmaki, M. L. Lister, V. Braito, L. Gallo, T. S. Hamilton, M. Kino, S. Komossa, A. B.… 展开作者

L. Foschini, E. Angelakis, L. Fuhrmann, G. Ghisellini, T. Hovatta, A. Lahteenmaki, M. L. Lister, V. Braito, L. Gallo, T. S. Hamilton, M. Kino, S. Komossa, A. B. Pushkarev, D. J. Thompson, O. Tibolla, A. Tramacere, A. Carraminana, L. Carrasco, A. Falcone, M. Giroletti, D. Grupe, Y. Y. Kovalev, T. P. Krichbaum, W. Max-Moerbeck, I. Nestoras, T. J. Pearson, A. Porras, A. C. S. Readhead, E. Recillas, J. L. Richards, D. Riquelme, A. Sievers, J. Tammi, M. Tornikoski, H. Ungerechts, J. A. Zensus, A. Celotti, G. Bonnoli, A. Doi, L. Maraschi, G. Tagliaferri, F. Tavecchio

摘要:

我们提出了三年多的观测在不同的频率,从无线电到高能伽马射线,窄线塞弗特1(NLS 1)星系PMN J 0948 +0022(z=0.585)。这个源是第一个在能量超过100 MeV的情况下探测到的NLS 1,因此可以被认为是这一新兴的新一类伽马射线发射活动星系核(AGN)的原型。从2008年8月1日到2011年12月31日进行的观测证实,PMN J 0948 +0022产生了一个强大的相对论性喷流,能够在伽马射线10^48 erg·s^-1的量级上发展出各向同性的光度,达到强大类星体的水平。在2009年和2010年,这个源的辐射发射的演化遵循相对论喷流的规范预期,具有相关的多波长变化(伽马射线,几个月后无线电发射),但很难在2011年的光变曲线中检索到类似的模式。对比2011年之前和包括2011年数据在内的伽马射线谱,发现高能谱的斜率有所软化。我们选择了五个特定的时期进行研究,通过模拟宽带光谱,其特征是在伽马射线或非常低/高通量在其他波长的爆发。所观察到的变异性可以在很大程度上解释由注入功率的变化,批量洛伦兹因子的射流或电子光谱。通量倍增/减半的特征时间尺度从几天到几个月不等,取决于频率和采样率。伽马射线的最短倍增时间尺度为2.3 ± 0.5天。这些小值强调了高采样多波长活动的必要性,以更好地了解这些源的物理特性。

英文摘要:

We present more than three years of observations at different frequencies, from radio to high-energy gamma-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 gamma-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, able to develop an isotropic luminosity at gamma-rays of the order of 10^48 erg s^-1, at the level of powerful 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 (gamma-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 gamma-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, characterised by an outburst at gamma-rays or very low/high flux at other wavelengths. The observed variability can largely be explained either 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 gamma-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.

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