NUSTAR and XMM-Newton Spectroscopy of Ark 564

Abstract

Ark 564 is a Narrow line Seyfert 1 that has been well observed in the 0.3-10 keV X-ray band. It has also been previously observed in the 3-50 keV band in a previous analysis using 200 ks NuSTAR observational data [24], which has revealed features such as a steep spectrum, strong soft excess, an iron K emission line, and dramatic variability. We conduct a detailed analysis combining this 2015 NuSTAR observation with another 2 NuSTAR observations, one for 400 ks, and a shorter one for 38 ks, both collected in 2018. We also include 2 ~114 ks XMM-Newton observations that overlap with the 400 ks NuSTAR observation to span the whole 0.3-50 keV energy range. We perform spectral analysis of both the NuSTAR and the NuSTAR+XMM- Newton data to test whether previously observed features are still displayed. We find that the best fit model requires a relativistic reflection component, although the current state of available models still needs to be improved on to understand the physical picture of these sources. We also examine the root mean square (RMS) spectra of the observations and find that the current models underestimate the variability of the soft excess, which could imply a higher variable reflection component or an additional variable soft excess component.