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活动星系核XMM-NuSTAR光谱的联合分析

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XMM-Newton望远镜近期发布的技术说明指出NuSTAR望远镜与XMM-Newton EPIC设备之间存在一显著的校准问题,并提供了一种对EPIC有效面积的经验性改正方法.为了定量刻画这种校准问题给联合分析XMM-NuSTAR光谱带来的偏差并确认相应改正方法的有效性,在本工作中我们针对包含 44 个X射线明亮的活动星系核的 104 次观测对开展了NuSTAR和XMM EPIC-pn光谱的联合拟合.所抽取的XMM-NuSTAR光谱具有绝对的同时性(通过合并两个设备的GTI文件),以避免活动星系核快速光谱光变带来的影响.在改正之前,EPIC-pn的光谱比相应的NuSTAR光谱系统性的硬(∆Γ~0.1),因此在联合拟合时导致了显著被低估的截断能量Ecut及反射成分强度R.我们确认了经验性改正非常有效,很好地消除了Γ,Ecut及R的最佳拟合值的偏差.因此,我们呼吁社群在联合拟合XMM-NuSTAR光谱时应用此改正;不过需要注意此改正仅对 3-12 keV的数据有效,因此在使用软X射线波段数据时不适用.此外,我们展示了由于匹配两个设备的GTI会导致NuSTAR净曝光时间的严重损失,联合拟合相对于只利用NuSTAR数据在许多情况下并没有优势.最后,我们提供了一个过滤XMM-Newton EPIC-pn小窗模式下高背景时间段的技术说明.
On joint analysing XMM-NuSTAR spectra of active galactic nuclei
A recently released XMM-Newton note revealed a significant calibration issue between nuclear spectroscopic telescope array(NuSTAR)and XMM-Newton European Photon Imaging Camera(EPIC)and provided an empirical correc-tion to the EPIC effective area.To quantify the bias caused by the calibration issue in the joint analysis of XMM-NuSTAR spectra and verify the effectiveness of the correction,in this work,we perform joint-fitting of the NuSTAR and EPIC-pn spectra for a large sample of 104 observation pairs of 44 X-ray bright active galactic nuclei(AGN).The spectra were ex-tracted after requiring perfect simultaneity between the XMM-Newton and NuSTAR exposures(merging good time inter-vals(GTIs)from two missions)to avoid bias due to the rapid spectral variability of the AGN.Before the correction,the EPIC-pn spectra are systematically harder than the corresponding NuSTAR spectra by ∆Γ∼0.1,subsequently yielding sig-nificantly underestimated cutoff energy Ecut and the strength of reflection component R when performing joint-fitting.We confirm that the correction is highly effective and can commendably erase the discrepancy in best-fit Γ,Ecut,and R.We thus urge the community to apply the correction when joint-fitting XMM-NuSTAR spectra,but note that the correction is limited to 3-12 keV and therefore not applicable when the soft X-ray band data are included.Besides,we show that as merging GTIs from two missions would cause severe loss of NuSTAR net exposure time,in many cases,joint-fitting yields no advantage compared with utilizing NuSTAR data alone.Finally,We present a technical note on filtering periods of high background flares for XMM-Newton EPIC-pn exposures in the small window(SW)mode.

active galactic nucleiX-ray spectroscopyXMM-NewtonNuSTARcross-calibration issue

康嘉来、王俊贤

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中国科学技术大学天文学系中国科学院星系宇宙学重点实验室,安徽合肥 230026

中国科学技术大学天文与空间科学学院,安徽合肥 230026

活动星系核 X射线光谱学 XMM-Newton望远镜 核光谱望远镜阵列 仪器校准问题

ESA Member StatesNASANational Natural Science Foundation of ChinaNational Natural Science Foundation of ChinaNational Natural Science Foundation of Chinasupport of Cyrus Chun Ying Tang Foundations

1203300612192221123B2042

2024

10.52396/JUSTC-2023-0160

中国科学技术大学学报
中国科学技术大学

中国科学技术大学学报

CSTPCD北大核心
影响因子：0.421
ISSN：0253-2778
年,卷(期)：2024.54(7)