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

Constraining the spin of GX 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

Introduction: Geometry 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 r in r out Prograde rotation Constraining the spin of GX PLC RDC

Introduction: Spectral Components Thermal or Very High state (VHS) ‏ Quasi-thermal blackbody emission from accretion disc. Flux disc ≥ 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). Constraining the spin of GX Figure adapted from Zdziarski & Gierlinski 2004

Introduction: Spectral Components... and similarly in the Low Hard state (LHS) ‏ Quasi-thermal emission from accretion disc decreases to Flux disc ≤ 20%. Contribution from Comptonisation increases and a cut-off between keV is now present. The Fe Kα fluorescence line is now narrower and more distinct. Constraining the spin of GX Figure adapted from Zdziarski & Gierlinski 2004

Introduction: Fe Kα line and reflection behaviour in extreme gravity Constraining the spin of GX 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: Fe Kα line and reflection behaviour in extreme gravity Constraining the spin of GX Figure from Fabian et al 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: Spin from standard assumption Constraining the spin of GX 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 R ms depends on the spin. (Bardeen et al. 1972). Figure adapted from Bardeen et al r ms

Model: Spin from standard assumption Constraining the spin of GX 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 r ms Fit the reflection, obtain r in = r ms SPIN The radius of the innermost stable circular orbit R ms depends on the spin. (Bardeen et al. 1972).

Constraining the spin of GX 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 Constraining the spin of GX Mid-plane kT BB H = half-thickness of disc F disc Emergent flux Disc surface, Г T = 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

Constraining the spin of GX Results: Fits 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 χ 2 /υ = / 2031 (1.1)‏ Log(ξ) ≈ 3.1 ( ξ in ergs cm s -1 )‏ r in = r g Constraining the spin of GX Results: Fits with reflection model VHS. Model assuming a broken power- law emissivity profile (R break = 4.9 r g ) ‏ χ 2 /υ = / 1653 (1.35)‏ Log(ξ) ≈ 4.2 ( ξ in ergs cm s -1 )‏ r in = 2.03 ± 0.03 r g

Constraining the spin of GX Results: Broadband fits with reflection model VHS. Model assuming a broken power- law emissivity profile (R break = 4.9 r g ) ‏ χ 2 /υ = / 1718 (1.48)‏ LHS. χ 2 /υ = /2095 (1.11)‏ Log(ξ) ≈ 3.1 ( ξ in ergs cm s -1 )‏

Constraining the spin of GX Results: Different disc ionisation... VHS LHS

r in = r g (90% confidence)‏ Constraining the spin of GX Results:... Similar disc geometry r in = 2.03 ± 0.03 r g (90% confidence)‏ VHS LHS Assume r in = r ms

Constraining the spin of GX Results:... Similar spin parameter VHS LHS

Constraining the spin of GX Results:... Similar spin parameter VHS LHS

Constraining the spin of GX Results:... Similar spin parameter VHS LHS Spin: ± 0.01 (statistical)

Constraining the spin of GX Recent work on Suzaku data of GX 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

Constraining the spin of GX 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 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 to be: ± 0.01 (statistical) ± 0.01 (systematic) ‏

Constraining the spin of GX 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

Constraining the spin of GX 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 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 to be: ± 0.01 (statistical) ± 0.01 (systematic) ‏