Astronomy and Astrophysics – Astrophysics
Scientific paper
2007-06-07
Astrophys.J.666:817-827,2007
Astronomy and Astrophysics
Astrophysics
Accepted for publication by ApJ, 6/6/07
Scientific paper
10.1086/520763
We present a detailed analysis of XMM-Newton EPIC-pn data for the Seyfert-1 galaxy NGC 4593. We discuss the X-ray spectral properties of this source as well as its variations with time. The 0.5-10 keV spectrum shows significant complexity beyond a simple power-law form, with clear evidence existing for a "soft excess" as well as absorption by highly ionized plasma (a warm absorber) within the central engine of this active galactic nucleus. We show that the soft excess is best described as originating from thermal Comptonization by plasma that is appreciably cooler than the primary X-ray emitting plasma; we find that the form of the soft excess cannot be reproduced adequately by reflection from an ionized accretion disk. The only measurable deviation from the power-law continuum in the hard spectrum comes from the presence of cold and ionized fluorescent iron-K emission lines at 6.4 and 6.97 keV, respectively. While constraints on the ionized iron line are weak, the cold line is found to be narrow at CCD-resolution with a flux that does not track the temporal changes in the underlying continuum, implying an origin in the outer radii of the accretion disk or the putative molecular torus of Seyfert unification schemes. The X-ray continuum itself varies on all accessible time scales. We detect a ~230-second time-lag between soft and hard EPIC-pn bands that, if interpreted as scattering timescales within a Comptonizing disk corona, can be used to constrain the physical size of the primary X-ray source to a characteristic length scale of ~2 gravitational radii. Taken together, the small implied coronal size and the large implied iron line emitting region indicate a departure from the current picture of a "typical" AGN geometry.
Brenneman Laura W.
Kaiser Mary Elizabeth
Reynolds Chris S.
Wilms Joern
No associations
LandOfFree
An X-ray Spectral Analysis of the Central Regions of NGC 4593 does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with An X-ray Spectral Analysis of the Central Regions of NGC 4593, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and An X-ray Spectral Analysis of the Central Regions of NGC 4593 will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-652143