Title: A physical model of the broadband continuum of AGN and its implications for the UV/X relation and optical variability Show Chinese title

Title: 活动星系核宽带连续谱的物理模型及其对紫外/ X射线关系和光学变异性的影响

Abstract: We develop a new spectral model for the broadband spectral energy distribution (SED) of Active Galactic Nuclei (AGN). This includes an outer standard disc, an inner warm Comptonising region to produce the soft X-ray excess and a hot corona. We tie these together energetically by assuming Novikov-Thorne emissivity, and use this to define a size scale for the hard X-ray corona as equal to the radius where the remaining accretion energy down to the black hole can power the observed X-ray emission. We test this on three AGN with well defined SEDs as well as on larger samples to show that the average hard X-ray luminosity is always approximately a few percent of the Eddington luminosity across a large range of Eddington ratio. As a consequence, the radial size scale required for gravity to power the X-ray corona has to decrease with increasing Eddington fraction. For the first time we hardwire this into the spectral models, and set the hard X-ray spectral index self consistently from the ratio of the hard X-ray luminosity to intercepted seed photon luminosity from the disc. This matches the observed correlation of steeper spectral index with increasing Eddington ratio, as well as reproducing the observed tight UV/X relation of quasars. We also include the reprocessed emission produced by the hot inner flow illuminating the warm Comptonisation and standard disc regions and show that this predicts a decreasing amount of optical variability with increasing Eddington ratio as observed, though additional processes may also be required to explain the observed optical variability. Show Chinese abstract

Abstract: 我们开发了一种新的光谱模型，用于活动星系核（AGN）的宽带能谱能量分布（SED）。该模型包括一个外部标准盘、一个内部温暖的康普顿化区域以产生软X射线过量以及一个高温日冕。我们通过假设Novikov-Thorne辐射率将这些部分在能量上联系起来，并利用这一点定义硬X射线日冕的尺度等于剩余吸积能到黑洞时能够提供观测到的X射线发射的半径。我们在三个具有明确SED的AGN以及更大样本上测试了这一模型，显示平均硬X射线亮度始终大约是爱丁顿亮度的百分之几，跨越广泛的爱丁顿比范围。因此，重力为X射线日冕提供能量所需的径向尺度必须随着爱丁顿分数的增加而减小。首次我们将这一点硬性纳入光谱模型，并从硬X射线亮度与来自盘的截获种子光子亮度之比自洽地确定硬X射线光谱指数。这与观测到的较陡光谱指数随爱丁顿比增加的关联一致，并且重现了类星体中紧密的UV/X关系。我们还包含了由热内流照亮温暖康普顿化和标准盘区域所产生的再处理发射，并表明这预测了光学变异性随着爱丁顿比增加而减少，这是被观测到的现象，尽管可能还需要其他过程来解释观测到的光学变异性。