Understanding X-ray Reflection in AGN
Dan WilkinsInstitute of AstronomyUniversity of Cambridge
Athena Science Workshop, Garching, June 2011
1. Detailed X-ray observations of AGN
2. Emissivity profiles
• Determination from observations
3. Theoretical modelling
• What can we learn?
4. 1H 0707-495 – a change of ‘state’
5. The way ahead – Athena
Outline
2
10.5 2 5104
103
2×10
45×
104
2×10
35×
103
keV
2 (Ph
oton
s cm
2 s1 k
eV1 )
Energy (keV)
1H 0707 495
X-ray Spectra
3
• High quality X-ray spectra
• XMM-Newton EPIC pn
• Power law continuum
• Disc reflection
• Reverberation lags
• Further evidence for reflection
• Constrain characteristic sizes
...and Timing
4
Zoghbi+09, Zoghbi+11
‘Lamppost’ Model
5
PLC
RDC
X-ray source in corona around BHIC scattering of seed photons
Reflection from accretion discatomic lines/absorption imprinted (reflionx)
Emissivity Profile
6
• Reflected power per unit area from disc
• Flux received at point on disc falls off with distance from X-ray source
1e-05
0.0001
0.001
0.01
0.1
1
10
0.1 1 10 100r
Emissivity Profile
6
• Reflected power per unit area from disc
• Flux received at point on disc falls off with distance from X-ray source
F ∝ 1d2
=1
r2 + h2
d
h
• e.g. Euclidean space
r
Emissivity Profile - So What?
7
• Depends on
• Source location/height
• Source extent
• Source/disc geometry
1 100.5 2 5
01
23
45
ratio
Energy (keV)
• Narrow emission line in disc frame
• To observer, broadened by relativistic effects:• Doppler shift/beaming• Gravitational redshift
• Function of emission radius
Broadened Emission Lines
8
105
050
010
00
norm
aliz
ed c
ount
s s
1 keV
1
Energy (keV)
Broadened Emission Lines
9
• Line profiles different from successive radii
• Total line is sum (integral) over disc
• Photon count from each annulus
• Get emissivity from photon counts from successive reflionx annuli (divided by projected area)
Emissivity from Broad Lines
10
F0(ν0) =�
T (re, g)redre�(re)
N(r) ∝ A(r)�(r)
Wilkins & Fabian 2011
! = 3.3
! = 6
" /
arbi
trar
y u
nits
10#10
10#9
10#8
10#7
10#6
10#5
10#4
10#3
0.01
r / RG
1 10 100
! = 0
! = 7.8
" /
arbi
trar
y u
nits
10#12
10#9
10#6
10#3
r / RG
1 10 100
1H 0707-495 Emissivity Profile
11
3-10 keV 3-5 keV
• General relativistic ray tracing
• GPU code
• Isotropic point source above the disc plane
• Trace rays from source until they hit disc plane
• Emissivity – number of photons hitting disc per unit area
12
Modelling X-ray PropagationWilkins & Fabian, in prep.
100 101 102 10310 4
10 2
100
102
104
106
108
r / rg
/ ar
bitra
ry u
nits
h = 1.235 rgh = 3 rgh = 5 rgh = 10 rgh = 15 rgh = 20 rgh = 25 rg
rs
Theoretical Emissivity Profiles (1)
13
StationaryAxialSource
100 101 102 10310 1
100
101
102
103
104
105
106
107
r / rg
/ ar
bitra
ry u
nits
x = 1.235 rgx = 3 rgx = 5 rgx = 10 rgx = 15 rgx = 20 rgx = 25 rg
!"
"
Theoretical Emissivity Profiles (2)
14
‘Co-rotating’Ring Source(h = 5rg)
• Follow time of rays, e.g. from disc to observer
Understanding Reverberation
15
• Understand observed emissivity profile in terms of General Relativity
• Simple model produces observed effects
• Constrain X-ray source parameters
• Low height (timing & steep inner emissivity) – 2rg
• Extended to ~20rg (outer break radius)
Consequences
16
1 100.5 2 5
104
103
0.01
0.1
1
norm
aliz
ed c
ount
s s1 k
eV1
Energy (keV)
1H 0707-495 in January 2011
17
Fabian, Wilkins et al, in prep.
XMM NewtonEPIC pn
January 2008January 2011
1 100.5 2 5
104
103
0.01
0.1
1
norm
aliz
ed c
ount
s s1 k
eV1
Energy (keV)
100 101 102 10310!10
10!8
10!6
10!4
10!2
100
r / rg
! / a
rbitr
ary u
nits
January 2011January 2008
1H 0707-495 in January 2011
17
Fabian, Wilkins et al, in prep.
XMM NewtonEPIC pn
January 2008January 2011
! /
arb
itrar
y un
its
10"3
1
106
r / rg
1 10 100
h = 1.235 rg
h = 1.5 rg
h = 2 rg
h = 10 rg
h = 5 rg
Pho
ton
Fra
ctio
n
0
0.2
0.4
0.6
0.8
Source Height / rg
1 10 100
• Compact source, close to axis at h ~ 1.5rg
A change to the source?
18
DiscEscape
• Line profiles – detail on red wing
• Constraints on inner emissivity profile
• Source properties
The Future with Athena
19
XMM Newton Athena
Collecting area @ 6 keV 0.08 m2 0.5 m2
Spectral Resolution (FWHM) @ 6 keV
150 eV (EPIC pn) 3 eV (XMS)
Timing ~300 μs (timing mode)
100 μs (WFI)
• Detailed analysis of X-ray spectra and timing reveals accretion disc emissivity profile
• Systematic theoretical modelling
• Understand observed spectra (and variability)
• Observed profiles explained by GR
• Constraints on source properties
• Era of precision X-ray measurements and understanding the physics of these sources...
Conclusions
20