1. Multi-epoch X-ray observations of Seyfert 1 galaxies
Luigi Gallo
Saint Mary’s University
Thanks to a long list of collaborators!
The X-ray Universe
Granada, 27 May 2008
Luigi Gallo

2. Case 1: 1H0707-495 First discovery of a sharp spectral drop in a NLS1.
2000 XMM-Newton, Boller et al (2002)
First discovery of a sharp
spectral drop in a NLS1.
Several models to describe the
single-epoch spectra (Boller et al.
2002; Fabian et al. 2002;
Tanaka et al 2004; Done et al. 2008;
Sobolewska & Done 2008…..)
More information is needed.
The X-ray Universe
Granada, 27 May 2008
Luigi Gallo

3. Drop structure changes within 2 years
Case 1: 1H
Gallo et al. (2004)
Drop structure changes within 2 years
Can still be described by multiple models but becomes more challenging (Gallo et al. 2004; Fabian et al. 2004)
2002
2000
The X-ray Universe
Granada, 27 May 2008
Luigi Gallo

4. Case 1: 1H0707-495 2007 observations < 2 days
Drop structure changes on scales of at least 2 days!
Drop depth appears to depend on continuum flux.
~ 30 days
~ 15 days
The X-ray Universe
Granada, 27 May 2008
Luigi Gallo

5. Level of complexity depends on X-ray weakness
Gallo 2006
Strateva et al. (2005)
aox-Luv relation
No 2-10 keV complexity
(i.e. power law)
2-10 keV complexity
Need to catch objects in
low-X-ray flux state
The X-ray Universe
Granada, 27 May 2008
Luigi Gallo

6. 1H : Recap
-- New data shows that the drop structure is changing on
rapid time scales (days). Starts to challenge some
models.
-- Several models can describe single-epoch observations.
With more data, these models can be scrutinized better
and probably eliminated.
The X-ray Universe
Granada, 27 May 2008
Luigi Gallo

7. Case 2: I Zw 1 (pre XMM) “modest” variability
-- steep spectrum (~2.4),
but weak soft excess
-- notable intrinsic cold
absorption
-- strong, broad and ionised
Fe K emission
The X-ray Universe
Granada, 27 May 2008
Luigi Gallo

8. 2002 XMM-Newton observations
Case 2: I Zw 1
2002 XMM-Newton observations
(Gallo et al. 2004)
-- steep spectrum
-- weak soft excess
-- intrinsic neutral (5-101020 cm-2)
and ionised absorption
-- broad, ionised Fe K emission
The X-ray Universe
Granada, 27 May 2008
Luigi Gallo

9. 2002 XMM-Newton observations
Case 2: I Zw 1
2002 XMM-Newton observations
(Gallo et al. 2004)
-- steep spectrum
-- weak soft excess
-- intrinsic neutral (5-101020 cm-2)
and ionised absorption
-- broad, ionised Fe K emission
-- multiple emission lines?
-- narrow 6.4 keV (from torus?)
plus broad-ish, ionised line
The X-ray Universe
Granada, 27 May 2008
Luigi Gallo

10. 2002 XMM-Newton observations
Case 2: I Zw 1
2002 XMM-Newton observations
(Gallo et al. 2004)
-- modest amplitude flare concentrated at high energies
-- spectral variability due to power law
normalisation fluctuations
The X-ray Universe
Granada, 27 May 2008
Luigi Gallo

11. 2005 XMM-Newton observation
Average spectral properties
(Gallo et al. 2007a)
2005 spectrum
-- flux diminished since 2002
-- steep spectrum (as always)
-- intensity of soft excess increases
-- intrinsic neutral absorption
diminishes (1.51020 cm-2)
-- changes in the ionised absorber
(see Costantini et al. 2007)
-- broad, ionised Fe K emission
seems unchanged -- likely emitted
from ~ rg
-- no 6.4 keV emission line
2002
2005
The X-ray Universe
Granada, 27 May 2008
Luigi Gallo

12. 2005 XMM-Newton observation
Average spectral properties
(Gallo et al. 2007a)
2005
2002
2005
 the same 2-component model fits mean continuum in 2002 and 2005 well,
but requires different relative contributions to the keV band
The X-ray Universe
Granada, 27 May 2008
Luigi Gallo

13. Re-examining the Fe line in 2002
The X-ray Universe
Granada, 27 May 2008
Luigi Gallo

14. Re-examining the Fe line in 2002
The X-ray Universe
Granada, 27 May 2008
Luigi Gallo

15. Re-examining the Fe line in 2002
Black: 2-12 keV continuum
-- ionised line does not respond to hard
continuum flare
-- redder component arises during the flare
The X-ray Universe
Granada, 27 May 2008
Luigi Gallo

16. Distinct modes of variability
(Gallo et al. 2007b)
pre-dip
post-dip
flux-correlated
spectral variability
change in ff-plot
pre-dip spectral
hardening
onset of hard
X-ray lag
rms changes pre-
and post-dip
 pre-dip: variability from changes in spectral shape
post-dip: variability from changes in normalisation
The X-ray Universe
Granada, 27 May 2008
Luigi Gallo

17. I Zw 1: Recap -- mean spectrum at two epochs separated by 3 years
can be described by a 2-component model (modified
by a warm absorber)
-- broad, ionised Fe K originates from ~ 40 rg
-- transient Fe K emission originates much closer
and its flux is correlated with a hard X-ray flare
-- change in the mode of variability occurs on dynamical
timescales
The X-ray Universe
Granada, 27 May 2008
Luigi Gallo

18. Thank you! Why do we need multi-epoch observations of AGN?
* multi-epoch observations are necessary
to understand the whole story
- what is changing?
- how fast are things changing?
- accurately constrain what is NOT
changing (e.g. inclination, abundances)
* catching AGN/NLS1 in a low X-ray flux
state reveals the nature of the complexity
--> can potentially distinguish
absorption/reflection
Thank you!
The X-ray Universe
Granada, 27 May 2008
Luigi Gallo

19. The X-ray Universe
Granada, 27 May 2008
Luigi Gallo

20. The X-ray Universe
Granada, 27 May 2008
Luigi Gallo

21. Summary Thank you! Multi-epoch observations of AGN are needed to
constrain the physics in the X-ray region
1H : new data shows variations in the drop
structure on much more rapid times
scales then previously seen
(in progress….)
I Zw 1: both observations “may” be understood if the
corona exists in two states:
(1) one centrally located and rapidly variable
(2) the other: more constant and distant
-- several other objects not discussed, come see me if
interested (e.g. Mrk 335, IRAS , UGC 3973)
Thank you!
The X-ray Universe
Granada, 27 May 2008
Luigi Gallo