论文标题
类星体PDS 456中的弹性X射线电晕
The flaring X-ray corona in the quasar PDS 456
论文作者
论文摘要
提出了对变量的新快速监测观察结果，即射电 - 定价类星体PDS 456。 2018年9月捕获了一个明亮的X射线耀斑，通量增加了4倍，时间尺度为2天。从光线交叉参数中，推断出冠状大小约为30个重力半径，黑洞质量为$ 10^{9} {\ rm M} _ {\ odot} $，总耀斑能量超过$ 10^{51} $ erg。 X射线发射的硬化伴随着耀斑，光子指数从$γ= 2.2 $降低到$γ= 1.7 $，然后再次返回。耀斑是在X射线电晕中产生的，缺乏与恒定吸积率一致的任何光学或紫外线变异性。同时进行了XMM-Newton和Nustar观察结果，在耀斑峰值和下降阶段，$ 1-3美元。这些在明亮，裸露的状态下捕获了PDS 456，没有圆盘吸收功能显而易见。硬X射线频谱显示出高能滚动，其E折叠能量为$ e _ {\ rm fold} = 51^{+11} _ { - 8} $ kev。推导的冠状温度为$ kt = 13 $ keV，是任何AGN和PDS 456中最酷的冠状温度之一，远低于X射线电晕的预测对歼灭线。当耀斑之后的淡淡时，光谱变异性变得更加柔和，与冷却X射线冠的模型一致。另外，非热组件的增加可能有助于硬X射线耀斑光谱。
New Swift monitoring observations of the variable, radio-quiet quasar, PDS 456, are presented. A bright X-ray flare was captured in September 2018, the flux increasing by a factor of 4 and with a doubling time-scale of 2 days. From the light crossing argument, the coronal size is inferred to be about 30 gravitational radii for a black hole mass of $10^{9} {\rm M}_{\odot}$ and the total flare energy exceeds $10^{51}$ erg. A hardening of the X-ray emission accompanied the flare, with the photon index decreasing from $Γ=2.2$ to $Γ=1.7$ and back again. The flare is produced in the X-ray corona, the lack of any optical or UV variability being consistent with a constant accretion rate. Simultaneous XMM-Newton and NuSTAR observations were performed, $1-3$ days after the flare peak and during the decline phase. These caught PDS 456 in a bright, bare state, where no disc wind absorption features are apparent. The hard X-ray spectrum shows a high energy roll-over, with an e-folding energy of $E_{\rm fold}=51^{+11}_{-8}$ keV. The deduced coronal temperature, of $kT=13$ keV, is one of the coolest measured in any AGN and PDS 456 lies well below the predicted pair annihilation line in X-ray corona. The spectral variability, becoming softer when fainter following the flare, is consistent with models of cooling X-ray coronae. Alternatively, an increase in a non-thermal component could contribute towards the hard X-ray flare spectrum.
