论文标题
磁通分辨的X射线光谱中的隐藏偏见
Hidden biases in flux-resolved X-ray spectroscopy
论文作者
论文摘要
通量分辨的X射线光谱被广泛采用，以研究各种通量水平之间目标的光谱变化。在许多情况下，它是通过水平将单个光曲线分为多个通量水平的，具有一定的计数率阈值。在这项工作中，我们指出，这种方法中存在两个隐藏的偏见，可能会影响特定情况下的光谱分析。首先是，当光曲线箱中源计数的泊松波动与内在变化相比不可忽略时，这种方法将过分（低（低）状态的固有平均通量水平过高（低）状态。第二个偏见是，当背景计数速率的泊松波动不可忽略时，高（低）状态的背景光谱将被低估（过度估计），从而产生偏置的光谱拟合参数。例如，我们以Nustar光谱为例来说明偏见的影响，尤其是如何偏向AGN中的冠状温度的测量值。我们提出了一种玩具方法来评估此类偏见的重要性，并在必要时为它们纠正。
Flux-resolved X-ray spectroscopy is widely adopted to investigate the spectral variation of a target between various flux levels. In many cases it is done through horizontally splitting a single light curve into multiple flux levels with certain count rate threshold(s). In this work we point out there are two hidden biases in this approach which could affect the spectral analyses under particular circumstances. The first is that, when Poisson fluctuations of the source counts in light curve bins are non-negligible compared with the intrinsic variation, this approach would over-estimate (under-estimate) the intrinsic average flux level of the high (low) state. The second bias is that, when the Poisson fluctuations of the background count rate is non-negligible, the background spectrum of the high (low) state would be under-estimated (over-estimated), thus yielding biased spectral fitting parameters. We take NuSTAR spectra for example to illustrate the effects of the biases, and particularly, how the measurements of the coronal temperature in AGNs would be biased. We present a toy method to assess the significance of such biases, and approaches to correct for them when necessary.
