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arXiv 1609.04845astro-ph.HE
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gamma-ray窄线塞弗特1星系PKS 1502+036的觉醒

The awakening of the gamma-ray narrow-Line Seyfert 1 galaxy PKS 1502+036

F. D'Ammando, M. Orienti, J. Finke, T. Hovatta, M. Giroletti, W. Max-Moerbeck, T. J. Pearson, A. C. S. Readhead, R. A. Reeves, J. L. Richards

摘要:

经过一段长时间的低活动期后,费米望远镜上的大面积望远镜(LAT)在2015年探测到了窄线塞弗特1 PKS 1502+036(z=0.4089)的伽马射线耀斑。在2015年12月20日,该源达到了0.1-300 GeV波段的日峰值通量,(93)$\pm$ 10 $^{-8}$ ph cm $^{-2}$ s $^{-1}$,获得的通量为(237 $\pm$ 71)$\times$ 10 $^{-8}$ ph cm $^{-2}$ s $^{-1}$(3小时时标),其对应于(7.3 $\pm$ 2.1)$\times$ 10 $^{47}$ erg/s的各向同性光度。伽马射线耀斑并没有伴随着显著的光谱变化。我们报告了2008年8月至2016年3月期间Fermi-LAT,Swift,XMM-Newton,Catalina Real-Time Transient Survey和Owens Valley Radio Observatory(OVRO)对PKS 1502+036的多波长射电到伽马射线观测。2015年12月22日,斯威夫特在光学、紫外线和X射线中观察到活动增加。OVRO 15 GHz光变曲线在2016年1月12日达到了从该源观测到的最高通量密度,表明伽马射线和15 GHz发射峰值之间有大约三周的延迟。这表明伽马射线发射区位于宽线区之外。我们比较了平均活度态和耀斑态的光谱能量分布。这两个SED,与高能量凸块建模为外部康普顿组件与种子光子从尘埃环,可以通过改变电子分布参数以及磁场。在平均状态下,盘发射的拟合将黑洞质量限制在低于10个$^8$太阳质量的值。源的SED、高能发射机制和伽马射线性质类似于平谱射电类星体。

英文摘要:

After a long low-activity period, a gamma-ray flare from the narrow-line Seyfert 1 PKS 1502+036 (z=0.4089) was detected by the Large Area Telescope (LAT) on board Fermi in 2015. On 2015 December 20 the source reached a daily peak flux, in the 0.1-300 GeV band, of (93 $\pm$ 19) $\times$10$^{-8}$ ph cm$^{-2}$ s$^{-1}$, attaining a flux of (237 $\pm$ 71) $\times$10$^{-8}$ ph cm$^{-2}$ s$^{-1}$ on 3-hr time-scales, which corresponds to an isotropic luminosity of (7.3 $\pm$ 2.1) $\times$10$^{47}$ erg/s. The gamma-ray flare was not accompanied by significant spectral changes. We report on multi-wavelength radio-to-gamma-ray observations of PKS 1502+036 during 2008 August-2016 March by Fermi-LAT, Swift, XMM-Newton, Catalina Real-Time Transient Survey, and the Owens Valley Radio Observatory (OVRO). An increase in activity was observed on 2015 December 22 by Swift in optical, UV, and X-rays. The OVRO 15 GHz light curve reached the highest flux density observed from this source on 2016 January 12, indicating a delay of about three weeks between the gamma-ray and 15 GHz emission peaks. This suggests that the gamma-ray emitting region is located beyond the broad line region. We compared the spectral energy distribution (SED) of an average activity state with that of the flaring state. The two SED, with the high-energy bump modelled as an external Compton component with seed photons from a dust torus, could be fitted by changing the electron distribution parameters as well as the magnetic field. The fit of the disc emission during the average state constrains the black hole mass to values lower than 10$^8$ solar masses. The SED, high-energy emission mechanisms, and gamma-ray properties of the source resemble those of a flat spectrum radio quasar.

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