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A NICER Look at the ‘Changing Look’ Seyfert NGC 2992

Presentation #106.42 in the session “AGN (Poster)”.

Published onApr 01, 2022
A NICER Look at the ‘Changing Look’ Seyfert NGC 2992

NGC 2992 is a Seyfert galaxy that varies by more than a factor of 10 in X-ray flux as seen with RXTE, Swift, and now NICER monitoring campaigns. It is one of the few known “changing look” Seyferts, and it has historically varied between types 1.5 and 2, with dramatic variability being seen in the Fe K band. A single joint XMM-Newton/NuSTAR observation that was specifically targeted at an extremely bright state in fact has claimed variability in the relativistically broadened component of the Fe line. In this work, we consider a series of NICER monitoring observations taken over two, several month periods that themselves were separated by a several month period. The large effective area, and good spectral resolution of NICER allows us to decompose the spectra into two components: a rapidly varying component associated with the near-horizon spectrum, and a relatively steady component, associated with the distant ‘torus’. Our models indicate that this latter component, especially the Fe edge, in fact comprises the bulk of the Fe line region emission, with relatively small contributions from the relativistic component. The lack of variation of the ‘torus’ component on month time scales, along with prior Chandra-HETG measurements of the width of the narrow component of the Fe line, places lower limits on the ‘torus’ distance. Clear variation in the narrow component of the Fe line over year long time scales, however, places upper limits on this ‘torus’ distance. By separating out the ‘torus’ emission, we are able to more clearly describe the intrinsic variations from the near-horizon components of the spectrum, and discuss evidence for variations in the absorption of this component as a function of inner-region luminosity. Although not simultaneous with our NICER studies, we show that the NuSTAR spectra are consistent with the models that we apply to the NICER spectra.


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