Observing the Fast X-ray Spectral Variability of NLS1 1H1934-063 with XMM-Newton and NuSTAR
Abstract
The most variable active galactic nuclei (AGN), taken together, are a compelling wellspring of interesting accretion-related phenomena. They can exhibit dramatic variability in the X-ray band on a range of timescales down to a few minutes. We present the exemplifying case study of 1H1934-063 (z = 0.0102), a narrow-line Seyfert I (NLS1) that is among the most variable AGN ever observed with XMM-Newton. We present spectral and temporal analyses of a concurrent XMM-Newton and NuSTAR observation taken in 2015 and lasting 120 ks, during which the source exhibited a steep (factor of 1.5) plummet and subsequent full recovery of flux that we explore in detail here. Combined spectral and timing results point to a dramatic change in the continuum on timescales as short as a few ks. Similar to other highly variable Seyfert 1s, this AGN is quite X-ray bright and displays strong reflection spectral features. We find agreement with a change in the continuum, and we rule out absorption as the cause for this dramatic variability observed even at NuSTAR energies. We compare detailed time-resolved spectral fitting with Fourier-based timing analysis in order to constrain coronal geometry, dynamics, and emission/absorption processes dictating the nature of this variability. We also announce the discovery of a Fe-K time lag between the hard X-ray continuum emission (1 - 4 keV) and its relativistically-blurred reflection off the inner accretion flow (0.3 - 1 keV).
- Publication:
-
AAS/High Energy Astrophysics Division #16
- Pub Date:
- August 2017
- Bibcode:
- 2017HEAD...1610644F