X-ray variability of the Narrow Line Seyfert 1 Galaxy PKS 0558-504
X-ray variability of the Narrow Line Seyfert 1 Galaxy PKS 0558-504
复制标题
窄线 Seyfert 1 Galaxy PKS 0558-504 的 X 射线变异性
DOI：
10.1051/0004-6361:20031705
复制
发表时间：
2003
影响因子：
6.5
通讯作者：
E. Ferrero
中科院分区：
文献类型：
--
作者：
W. Brinkmann;P. Arévalo;M. Gliozzi;E. Ferrero
我们目前的结果，从几个XMM牛顿观测射电响亮窄线塞弗特1星系（NLS 1）PKS 0558-504。我们发现了强而持久的X射线变化的证据，无论是在短期和长期的时间尺度。在2小时的短时间尺度上，源平滑地变化15-20%;在相对较短的曝光中，无法解决2倍的长期变化：我们发现源大多处于“低”状态，11个观测中有2个处于“高”状态。X射线耀斑似乎是周期性的，其时间尺度为~24 k s，如果将其解释为圆盘中的开普勒时间尺度，则将发射区域置于最后一个稳定轨道之外。PKS 0558-504的X射线谱可以很好地拟合两个康普顿化分量，一个在中等温度（kT ~ 4.5 keV）和光学深度$\tau \sim 2$，另一个在高温（kT $\ga $50 keV）和低光学深度（$\tau \la 1.0$）。 然而，由于康普顿化模型的固有简并性，这些参数会产生很大的误差。源的通量变化仅由较冷分量的变化引起，热分量的参数与BLS 1星系的参数非常相似，保持不变。所有的结果都很好地符合NLS 1星系是低质量物体的图片，从一个非常活跃的磁动力吸积盘日冕发射X射线的爱丁顿率接近吸积。
We present results from several XMM-Newton observations of the radio-loud Narrow-line Seyfert 1 galaxy (NLS1) PKS 0558-504. We find evidence for strong and persistent X-ray variability, both on short and long time-scales. On short time scales of $\ga$2 hours the source varies smoothly by 15-20%; long-term variations by a factor $\ga$2 could not be resolved in the relatively short exposures: we find the source mostly in a “low” state, in 2 out of the 11 observations in a “high state”. X-ray flares seem to be recurrent with a time scale of ~24 ks which, if interpreted as the Keplerian time scale in the disc, would place the emission region just outside the last stable orbit. The X-ray spectrum of PKS 0558-504 can be well fitted by two Comptonization components, one at moderate temperatures of kT ~ 4.5 keV and optical depths of $\tau \sim 2$, the other at high temperatures ( kT $\ga$ 50 keV) and low optical depths ($\tau \la 1.0$). These parameters are, however, subject to large errors due to the inherent degeneracy of the Comptonization models. Flux variations of the source are caused by changes of the colder component only, the hot component with parameters very similar to those of BLS1 galaxies, stays constant. All results fit nicely the picture that NLS1 galaxies are lower mass objects, accreting close to the Eddington rate emitting X-rays from a very active magnetically powered accretion disc corona.