Measuring the black hole spin of GX 339-4: A systematic look at its very high and low/hard state.

1
Measuring the black hole spin of GX 339-4 A
systematic look at its very high and low/hard
state.
Rubens ReisInstitute of Astronomy - Cambridge
In collaboration with Andy Fabian, Randy Ross,
Giovanni Miniutti, Jon Miller and Chris Reynolds
2
Constraining the spin of GX 339-4
Black holes (BH) can be characterised by two
observable parameters Mass and spin Over 20
stellar mass BH binaries have known mass
(Remillard McClintock 2006) With XMM-Newton
we can now obtain precise spin for these systems

3
Constraining the spin of GX 339-4
Introduction Geometry
An artist's view of an X-ray binary (GX 339-4?)
from far, far away... Mass gt 6.0 solar
mass (Hynes et al. 2003)? Spin ???
PLC
RDC
rin
And a modest sketch of the region close to the
black hole
rout
Prograde rotation
4
Constraining the spin of GX 339-4
Introduction Spectral Components
Thermal or Very High state (VHS)?
Figure adapted from Zdziarski Gierlinski 2004
Quasi-thermal blackbody emission from accretion
disc. Fluxdisc 75. Powerlaw possibly due to
Compton upscattering of soft disc photons in a
hot thermal/nonthermal corona. Hard X-ray source
illuminates the disc and gives rise to Compton
reflection and Fe Ka fluorescence (amongst other
things).
5
Constraining the spin of GX 339-4
Introduction Spectral Components
... and similarly in the Low Hard state (LHS)?
Figure adapted from Zdziarski Gierlinski 2004
Quasi-thermal emission from accretion disc
decreases to Fluxdisc 20. Contribution from
Comptonisation increases and a cut-off between
100-200 keV is now present. The Fe Ka
fluorescence line is now narrower and more
distinct.
6
Constraining the spin of GX 339-4
Introduction
Fe Ka line and reflection behaviour in extreme
gravity
An intrinsically narrow emission line shows a
double-peak profile from annuli in a
non-relativistic Newtonian disc. Transverse
Doppler shift makes the profile redder and
beaming enhances the blue peak. Closer to the
black hole the overall profile is shifted to the
red side and the blue peak is reduced.
Figure from Fabian et al. 2000
7
Constraining the spin of GX 339-4
Introduction
Fe Ka line and reflection behaviour in extreme
gravity
An intrinsically narrow emission line shows a
double-peak profile from annuli in a
non-relativistic Newtonian disc. Transverse
Doppler shift makes the profile redder and
beaming enhances the blue peak. Closer to the
black hole the overall profile is shifted to the
red side and the blue peak is reduced. In the
inner regions of an accretion disc the resulting
Fe Ka line profile is highly skewed and broad
(Fabian et al. 1989).
Figure from Fabian et al. 2000
These effects are important for ALL of the
reflection signatures and not limited to the Fe
Ka line profile.
8
Constraining the spin of GX 339-4
Model Spin from standard assumption
The effect gravity has on the reflection profile
becomes more prominent the closer the emission is
to the event horizon (Fabian et al.
1989).
rms
Figure adapted from Bardeen et al. 1972
The radius of the innermost stable circular orbit
Rms depends on the spin. (Bardeen et al. 1972).
9
Constraining the spin of GX 339-4
Model Spin from standard assumption
The effect gravity has on the reflection profile
becomes more prominent the closer the emission is
to the event horizon (Fabian et al.
1989).
rms
Figure adapted from Bardeen et al. 1972
The radius of the innermost stable circular orbit
Rms depends on the spin. (Bardeen et al. 1972).
Fit the reflection, obtain rin rms
SPIN
10
Constraining the spin of GX 339-4
Model Self-consistent reflection

• The X-ray spectrum of black hole binaries (BHB)
  in the thermal/VHS have usually been fitted with
  a combination of
• an ionised disc reflection component,
• Laor relativistic line (Laor 1991) and
• a multicolour disc blackbody (usually diskbb,
  Mitsuda et al. 1984).

11
Constraining the spin of GX 339-4
Model Self-consistent reflection

• The X-ray spectrum of black hole binaries (BHB)
  in the thermal/VHS have usually been fitted with
  a combination of
• an ionised disc reflection component,
• Laor relativistic line (Laor 1991) and
• a multicolour disc blackbody (usually diskbb,
  Mitsuda et al. 1984).
• We employed the self-consistent reflection model
  developed by Ross Fabian (2007) where blackbody
  radiation entering the accretion disc surface
  from below is implicitly included.

Illuminating flux from disc corona
Emergent flux
Disc surface, ?T 10
H half-thickness of disc
Fdisc
Mid-plane kTBB
12
Constraining the spin of GX 339-4
Results Fits with simple model
Simple model consisting of power-law and
diskbb
The broad Fe Ka line and in the case of the VHS
the Ka edge is clearly seem.
13
Constraining the spin of GX 339-4
Results Fits with reflection model
VHS. Model assuming a broken power-law emissivity
profile (Rbreak 4.9 rg )? ?2/? 2237.8/ 1653
(1.35)? Log(?) 4.2 ( ? in ergs cm s-1 )? rin
2.03 0.03 rg

• LHS. Fitted with reflection model above 2 keV.
• Ignored thermal emission
• ?2/? 2242.5 / 2031 (1.1)?
• Log(?) 3.1 ( ? in ergs cm s-1 )?
• rin rg

14
Constraining the spin of GX 339-4
Results Broadband fits with reflection model
VHS. Model assuming a broken power-law emissivity
profile (Rbreak 4.9 rg )? ?2/? 2549.3/ 1718
(1.48)?

• LHS.
• ?2/? 2316.6 /2095 (1.11)?
• Log(?) 3.1 ( ? in ergs cm s-1 )?

15
Constraining the spin of GX 339-4
Results Different disc ionisation...
VHS LHS
16
Constraining the spin of GX 339-4
Results ...Similar disc geometry
VHS LHS
rin rg (90 confidence)?
rin 2.03 0.03 rg (90 confidence)?
Assume rin rms
17
Constraining the spin of GX 339-4
Results ...Similar spin parameter
VHS
LHS
18
Constraining the spin of GX 339-4
Results ...Similar spin parameter
VHS
LHS
19
Constraining the spin of GX 339-4
Results ...Similar spin parameter
VHS
LHS
Spin 0.935 0.01 (statistical)
20
Constraining the spin of GX 339-4
Recent work on Suzaku data of GX 339-4 in the
intermediate state (Miller et al. 2008) resulted
in a spin parameter of 0.93 0.01
(statistical) 0.04 (systematic)?
Figure from Miller et al. 2008
21
Constraining the spin of GX 339-4
Summary

• The obvious differences in the spectra of the
  two states are due to differences in the
  ionisation state of the disc ( Ross Fabian
  1993)?
• For the VHS, it is particularly important to
  use a reflection model that fully accounts for
  the effects of Compton scattering.
• The spin parameter in GX 339-4 was found to be
  the same in both low hard and very high spectral
  states
• With XMM-Newton we were able for the first time
  to measure the spin of a stellar mass black hole
  to a high level of accuracy in two distinct
  states.

Using a self-consistent reflection model we were
able to infer the spin parameter of GX 339-4 to
be 0.935 0.01 (statistical) 0.01
(systematic)?
22
Constraining the spin of GX 339-4
Future work
Measure spin in AGN using reflection model
PI A.C.Fabian et al.
Explain the rapid and complex variability in the
frame-work of reflection
23
Constraining the spin of GX 339-4
Summary

• The obvious differences in the spectra of the
  two states are due to differences in the
  ionisation state of the disc ( Ross Fabian
  1993)?
• For the VHS, it is particularly important to
  use a reflection model that fully accounts for
  the effects of Compton scattering.
• The spin parameter in GX 339-4 was found to be
  the same in both low hard and very high spectral
  states
• With XMM-Newton we were able for the first time
  to measure the spin of a stellar mass black hole
  to a high level of accuracy in two distinct
  states.

Using a self-consistent reflection model we were
able to infer the spin parameter of GX 339-4 to
be 0.935 0.01 (statistical) 0.01
(systematic)?