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An upper limit on the spin in GX 339-4

An upper limit on the spin in GX 339-4. Mari Kolehmainen & Chris Done Durham University. Determining the BH spin. Currently two methods shape of the Fe line from reflected emission continuum fitting of disc dominated spectra GX 339-4 widely studied in terms of Fe line

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An upper limit on the spin in GX 339-4

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  1. An upper limit on the spin in GX 339-4 Mari Kolehmainen & Chris Done Durham University

  2. Determining the BH spin • Currently two methods • shape of the Fe line from reflected emission • continuum fitting of disc dominated spectra • GX 339-4 widely studied in terms of Fe line • burst mode (non-piled up) spectra give a*= 0.935 with i≈20° (Reis et al. 2008; Miller et al. 2008)

  3. Continuum fitting • Multi-colour disc blackbody • Disc emission ~80 % of the total emission in the disc dominated state • Restricted to stellar-mass BHs as AGNs peak in the UV GX 339-4 log ν f(ν) log ν

  4. GX 339-4 • A lot of RXTE data available • all spectral states observed

  5. Continuum fitting • Luminosity relates to the observed flux via where is the area of the inner disc • constant emitting area, constant disc inner radius GX 339-4 , (Rg=GM/c2)

  6. Continuum fitting • Luminosity relates to the observed flux via where is the area of the inner disc • constant emitting area, constant disc inner radius GX 339-4 , (Rg=GM/c2)

  7. GX 339-4 • Limit parameters from the mass function fM=5.8 ± 0.5M(Hynes et al. 2003) • 5.8 < M< 15 M D > 6 kpc 45°< i < 70° • The inner radius • rin2 >62/(152 cos 45°) gives an upper limit for a*

  8. Correction factors • Disc not accurately described by simple models • stress-free inner boundary condition • colour-temperature correction fcol • relativistic effects • We apply these corrections to the simple models to illustrate the effect on spin

  9. diskbb+thCompml Likely: M= 10 M D= 8 kpc i= 60°

  10. diskbb+thCompml Max spin: M= 15 M D= 6 kpc i= 45°

  11. More physical model for disc • BHSPEC (Davis et al. 2005) • N-T stress-free inner boundary condition • self-consistently calculates fcol and the radiative transfer through each disc annuli • includes all the relativistic corrections

  12. BHSPEC Likely: M= 10 M D= 8 kpc i= 20° i= 40° i= 60°

  13. BHSPEC Likely: M= 10 M D= 8 kpc i= 20° i= 40° i= 60°

  14. BHSPEC Likely: M= 10 M D= 8 kpc i= 20° i= 40° i= 60°

  15. Misaligned disc • Δθ ≈ 20°- 30° • asymmetric supernova (Fragos et al. 2010) Δθ

  16. Upper limit for spin in GX 339-4 a* < 0.9 for any reasonable mass (<15M), distance (>6 kpc) and inclination (i > 45°) Max spin: M= 15 M D= 6 kpc i = 45° ΔΧ2≈65 Lower mass and/or larger distance and/or higher inclination will give lower spin

  17. Conclusions Disc+line Disc Fe line • SN collapse models X✔X (a*≤0.8) • Binary form. models X✔X (i≥45°) - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Fe line? Disc?

  18. Mass function • We constrain limit parameters from the mass function of Hynes et al. (2003): • Inserting M2=0.166 M and Mx=15 M gives i=45° • (Muñoz-Darias et al. 2008) =5.8±0.5M

  19. BHSPEC a*=0 a*=0.7 a*=0.8 a*=0.9

  20. Black hole spin • Specific angular momentum, described as a dimensionless parameter a* • Drags the accretion disc inwards • a* : 0 - 0.998 Rin : 6 - 1.23 Rg

  21. Conclusions • We derive an upper limit of 0.9 for spin in GX 339-4 • Discrepancy between the two methods, Fe line spin higher (and inclination lower) than from continuum fitting • Lower spin from disc spectral fitting seems more likely so Fe line profile probably not yet completely understood

  22. Conclusions • Hard to see how disc spectral fitting is wrong! • L-T4, disc emission dominant, • Fe line spin too high for supernovae collapse models (Gammie et al. 2004) • Inclination too low (big misalignment from orbit) for binary formation models

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