Post on 05-Feb-2016
description
The Broad Iron Line Profile ofXTE J1650-500
DOM WALTON
IoA, Cambridge, UK
In collaboration with
Rubens Reis, Ed Cackett, Jon Miller and Andy Fabian
Berlin: 2011
BLACK HOLE ACCRETION
Dom Walton
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Berlin: 2011
AGN SPECTRA
1H 0707-495 - Zoghbi et al. (2010)
(see also Fabian et al. 2004, Boller et al. 2002, etc.)
Dom Walton Berlin: 2011
BLACK HOLE ACCRETION
Dom Walton
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Berlin: 2011
DISC REFLECTION
Dom Walton
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Berlin: 2011
RELATIVISTIC EFFECTS
Dom Walton
Characterising the reflection component is one way in which we can measure BH spin
Fabian et al. (2000)
Berlin: 2011
BLACK HOLE BINARIES
Spectra obtained from Galactic black hole binaries (BHBs) show the same primary continuum components as AGN:
Many also display broad excesses at ~6 keV
BHBs are brighter due to their proximity, so any absorption features can be well constrained
Thermal emission (accretion disc, low energy)
Comptonised emission (corona, high energy)
Dom Walton Berlin: 2011
XTE J1650-500
Dom Walton
2001 outburst observed by XMM (burst mode, x1) and BeppoSAX (x3)
Displays a broad excess at ~6 keV, independent of Comptonised continuum model:
Gaussian: σ = 1.2 ± 0.2 keV Laor: R
in = 1.5 ± 0.1 R
G
Berlin: 2011
XTE J1650-500
Dom Walton
2001 outburst observed by XMM (burst mode, x1) and BeppoSAX (x3)
Displays a broad excess at ~6 keV, independent of Comptonised continuum model:
Note residual instrumental features at ~1.8 and 2.2 keV
Gaussian: σ = 1.2 ± 0.2 keV Laor: R
in = 1.5 ± 0.1 R
G
Berlin: 2011
DISC REFLECTION MODEL
REFBHB (Ross & Fabian, 2007); Rin ~ 2 R
G
Dom Walton
- Powerlaw- Relativistic disc reflection (incl. thermal continuum)
Berlin: 2011
SOFT RESIDUALS
Soft residuals at ~0.8 keV persist. Possible astrophysical origins:
Comparison with burst mode Crab data shows similar residuals, so likely to be systematic
Doesn't effect inner radius obtained (always ~2 RG)
• Additional reflected OVIII emission and/or Neon absorption in the ISM
• Local ionised absorption (disc wind)
Dom Walton Berlin: 2011
INSTRUMENTAL EFFECTS
Dom Walton
Comparison with contemporaneous BeppoSAX MECS data (obtained ~1 day prior to XMM observation):
The line profile is independent of detector type (MECS detectors are gas based)
Profile is not significantly modified by instrumental effects
There are claims the line profiles obtained could be broadened and skewed by instrumental effects, e.g. pile-up, charge transfer inefficiency.
Berlin: 2011
COMPTON BROADENING
Dom Walton
Electron temperature (~6 keV) and optical depth (~1) required to broaden the line in the corona are not consistent with those found for the continuum
Also expect the line centroid energy to increase by ~0.35 keV, but E
G < 6.5 keV
Compton broadening in the disc is self-consistently included in REFBHB
'Windline' models run into problems with the mass outflow rates required
Berlin: 2011
LINE PROFILE EVOLUTION
Dom Walton
Latter two BeppoSAX observations were obtained later in the evolution of the outburst
Line profiles obtained do not show significant deviations from early BeppoSAX and XMM observations
This is not consistent with the expected behaviour for scenarios dominated by electron scattering
Berlin: 2011
XTE J1650-500 SPIN
0.84 ≤ a* ≤ 0.98 (90% confidence)
Dom Walton Berlin: 2011
MCG -6-30-15
Seyfert 1.2 AGN, 350 ks XMM observation taken in 2001
Spectrum complicated by a warm absorber, accounted for by the model of Chiang & Fabian (2011)
Also displays a broad excess at ~6 keV
Dom Walton
Absorption model includes:
Fast, highly ionised component 2 slow, lower ionisation components Iron-L dust absorption
Berlin: 2011
LINE PROFILES
Dom Walton Berlin: 2011
LINE PROFILES
Dom Walton Berlin: 2011
COMMON ORIGIN
As the excesses at ~6 keV broad iron lines observed in AGN and BHBs are similar, we would like to find a common physical origin for them.
Absorption does not (usually) significantly modify the spectra of BHBs
Reflection from the inner accretion disc is the only viable common interpretation
Dom Walton Berlin: 2011
SUMMARY
Dom Walton
The BHB XTE J1650-500 displays a broad iron line profile (see also earlier works by Miller+ 2002, 2009, Miniutti+ 2005)
The line profile requires that the emission arises in the regions of strong gravity close to the black hole, and is similar to those seen in AGN
As BHBs provide an unobscured view of the accretion flow, relativistic disc reflection must be a fundamental process in the disc-corona geometry
Comparison with BHBs therefore provides a strong argument in favour of the presence of relativistic disc reflection in AGN
Berlin: 2011
EPFAST
Dom Walton
EPFAST attempts to correct for the features at ~2 keV; applies an energy independent correction
CTI is energy dependent (CTI ~ E-0.5); EPFAST over-corrects at iron K energies
EPFAST
Berlin: 2011