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X-ray spectroscopy of bright Seyfert 2s: The importance of the 10-100 keV spectrum
Guido RisalitiINAF - Arcetri Observatory, Italy
&Harvard-Smithsonian Center for Astrophysics
- One Case study: XMM observations of NGC 1365- Time-resolved NH variability: current limits- The impact of Simbol-X
Outline
NGC 1365: The best laboratory to investigate the absorber in obscured AGN
Hard X-ray observations:
ASCA (1995) 40 ksBeppoSAX (1997) 30 ks Chandra (Dec 2002) 15 ksXMM 1 (Jan 2003) 17 ksXMM 2 (Jan 2003) 10 ksXMM 3 (Aug 2003) 15 ks XMM 4 (Jan 2004) 60 ksXMM 5 (Aug 2004) 60 ks
Chandra (Apr 2006):6 x 15 ks
(Risaliti et al. 2007, ApJ 659, L11)
NGC 1365: Two XMM long observations
Spectral analysis of XMM long observations2. Relativistic Iron Line
One of the best cases, only (?) strong case in high NH sources
Disappearing in obscured spectrum --> within 1014 from the center
Intra-day NH variations XMM 4: 60 ks
New analysis: -10 time intervals, 6 ks each-Constant continuum + (a) free NH for each spectrum (b) two NH (the same for all spectra) and free covering factor of NH2
Short-time column density variability
T = 25 ksD ~ 3x1013 cm
NH1=1.1x1023 cm-2
NH2=3.0x1023 cm-2
Only) other know case: NGC 4151 observation with BeppoSAX
Puccetti et al. 2007
Simbol-X simulations:
T = 6 ksec
NH=2x1023 cm-2
E(NH) ~ 20%
E(NH) ~ 6%
XMM (var. cont.):
E(NH) ~ 6%XMM (const cont.):
Conclusions
- Short timescale (~5-10 ksec) column denisty variability may be common in Seyfert Galaxies
-Resolving the NH variability is crucial to understand the structure of the circumnuclear absorber AND to obtain a correct fit of the other spectral components
-High quality 10-50 keV spectra needed to unambigously detect NH variability: Simbol-X capable to completely remove degeneracy between spectral parameters in bright Seyfert Galaxies