Utilizing a range of techniques including multi-band light curves,softness ratio analysis,structure functions,rms spectra,cross-correlation functions,and ratios of spectra from different intervals,we present a compreh...Utilizing a range of techniques including multi-band light curves,softness ratio analysis,structure functions,rms spectra,cross-correlation functions,and ratios of spectra from different intervals,we present a comprehensive study of the complex X-ray spectral variability in Seyfert 1 galaxy Ark 120,through re-analyzing its six XMMNewton observations taken between 2003 and 2014.We find a clear“softer-when-brighter”trend in the 2-10 keV power-law component over long timescales,with this trend being timescale dependent,as it is much weaker on shorter timescales,similar to that previously detected in NGC 4051.Notably,a rare“harder-when-brighter”trend is observed during one exposure,indicating dynamic changes in the spectral variability behavior of the power-law component.This exceptional exposure,with the spectral variability indeed marked by a power-law pivoting at an unusually low energy of~2 keV,suggests intricate variations in the thermal Comptonization processes within the corona.Furthermore,when the data below 2 keV are included,we identify that the soft excess component adds significant complexity to the spectral variability,such as evidenced by a transition from“harder-when-brighter”to“softer-when-brighter”during another single exposure.Such extra complexity arises because the variability of the soft excess sometimes follows and sometimes does not follow the changes in the power-law component.Our findings underscore the necessity of applying multiple analytic techniques to fully capture the multifaceted spectral variability of AGNs.展开更多
基金supported by the National Natural Science Foundation of China (NSFC,grant Nos.12033006,12192221,and 123B2042)the Cyrus Chun Ying Tang Foundationsfunded by ESA Member States and NASA
文摘Utilizing a range of techniques including multi-band light curves,softness ratio analysis,structure functions,rms spectra,cross-correlation functions,and ratios of spectra from different intervals,we present a comprehensive study of the complex X-ray spectral variability in Seyfert 1 galaxy Ark 120,through re-analyzing its six XMMNewton observations taken between 2003 and 2014.We find a clear“softer-when-brighter”trend in the 2-10 keV power-law component over long timescales,with this trend being timescale dependent,as it is much weaker on shorter timescales,similar to that previously detected in NGC 4051.Notably,a rare“harder-when-brighter”trend is observed during one exposure,indicating dynamic changes in the spectral variability behavior of the power-law component.This exceptional exposure,with the spectral variability indeed marked by a power-law pivoting at an unusually low energy of~2 keV,suggests intricate variations in the thermal Comptonization processes within the corona.Furthermore,when the data below 2 keV are included,we identify that the soft excess component adds significant complexity to the spectral variability,such as evidenced by a transition from“harder-when-brighter”to“softer-when-brighter”during another single exposure.Such extra complexity arises because the variability of the soft excess sometimes follows and sometimes does not follow the changes in the power-law component.Our findings underscore the necessity of applying multiple analytic techniques to fully capture the multifaceted spectral variability of AGNs.
