Measuring the black hole spin of GX 339-4: A systematic look at its very high and low/hard state. Rubens Reis Institute of Astronomy - Cambridge In collaboration

Measuring the black hole spin of Measuring the black hole spin of GX 339-4: A systematic look at its GX 339-4: A systematic look at its

very high and low/hard state.very high and low/hard state.

Rubens ReisRubens ReisInstitute of Astronomy - CambridgeInstitute of Astronomy - Cambridge

In collaboration with Andy Fabian, Randy Ross, Giovanni Miniutti, Jon Miller and Chris Reynolds

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 With XMM-Newton we can now obtain precise spin for these systems spin for these systems

IntroductionIntroduction: : GeometryGeometry

An artist's view of an X-ray binary (GX 339-4?) from far, far away...

Mass > 6.0 solar mass(Hynes et al. 2003)

Spin ???

And a modest sketch of the region close to the black hole

rin

rout

Prograde rotation


PLC

RDC

IntroductionIntroduction: : Spectral ComponentsSpectral Components

Thermal or Very High state (VHS)

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 Kα fluorescence (amongst other things).


Figure adapted from Zdziarski & Gierlinski 2004

IntroductionIntroduction: : Spectral ComponentsSpectral Components

... and similarly in the Low Hard state (LHS)

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 Kα fluorescence line is now narrower and more distinct.


Figure adapted from Zdziarski & Gierlinski 2004

Introduction:Introduction: Fe Kα 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

Introduction:Introduction: Fe Kα line and reflection behaviour in extreme gravity


Figure from Fabian et al. 2000

These effects are important for ALL of the reflection signatures and not limited to the Fe Kα line profile.

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 Kα line profile is highly skewed and broad (Fabian et al. 1989).

Model:Model: Spin from standard assumptionSpin 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).

The radius of the innermost stable circular orbit Rms depends on the spin. (Bardeen et al. 1972).

Figure adapted from Bardeen et al. 1972

rms

Model:Model: Spin from standard assumptionSpin 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).

Figure adapted from Bardeen et al. 1972

rms

Fit the reflection, obtain rFit the reflection, obtain rinin = r = r

ms ms SPINSPIN

The radius of the innermost stable circular orbit Rms depends on the spin. (Bardeen et al. 1972).


Model: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).

Model:Model: Self-consistent reflection


Mid-plane kTBB

H = half-thickness of discFdisc

Emergent flux

Disc surface, ГT = 10

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


Results:Results: Fits with simple modelFits with simple model

Simple model consisting of power-law and diskbb

The broad Fe Kα line and in the case of the VHS the Kα edge is clearly seem.

LHS. Fitted with reflection model above 2 keV.

Ignored thermal emission

χ2/υ = 2242.5 / 2031 (1.1)

Log(ξ) ≈ 3.1 ( ξ in ergs cm s-1 )

rin = r

g

Constraining the spin of GX 339-4Results:Results: Fits with reflection Fits with reflection

modelmodel VHS. Model assuming a broken power-law emissivity profile (Rbreak

= 4.9 rg )

χ2/υ = 2237.8/ 1653 (1.35)


rin = 2.03 ± 0.03 r

g

0.170.102.08


Results:Results: Broadband fits with reflection modelBroadband fits with reflection model

VHS. Model assuming a broken power-law emissivity profile (Rbreak

= 4.9 rg )

χ2/υ = 2549.3/ 1718 (1.48)

LHS.

χ2/υ = 2316.6 /2095 (1.11)



Results:Results: Different disc ionisation...Different disc ionisation... VHS LHS

rin = r

g (90% confidence)


Results:Results: ......Similar disc geometrySimilar disc geometry

rin = 2.03 ± 0.03 r

g (90% confidence)

VHS LHS

0.170.102.08

Assume rAssume rinin = r = r

msms


Results:Results: ......Similar spin parameterSimilar spin parameter

VHS

LHS



VHS

LHS



VHS

LHS

Spin:0.935 ± 0.01 (statistical)


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


Summary: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:



Future work: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


Summary: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:


Documents

Measuring the black hole spin of GX 339-4: A systematic look at its very high and low/hard state. Rubens Reis Institute of Astronomy - Cambridge In collaboration