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