Relativistically Broad Iron K-Lines of AGN “ Probing BH spin ”
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Transcript of Relativistically Broad Iron K-Lines of AGN “ Probing BH spin ”
Relativistically Broad Iron K-Lines of AGN
“ Probing BH spin ”
Y. Tanaka
June 22, 2011 @ICRR
Black Holes are Very Simple• Mass: M
• Spin: J = a*GM2/c (0 < a* < 1)
• (Electric Charge: Q)
But to measure these quantities is not simple
Two feasible methods for estimating spin:
1. Determine R ISCO of an accretion disk applicable to stellar-mass BH in the soft (X-ray) state. Mass, Distance, Inclination optically determined.
2. Relativistically broad Fe-K line Fe-K line near BH is broadened redward due to Doppler effect and gravitational redshift (depends on a ). *
X-ray spectra of BH binaries in the “soft state” Multicolor blackbody disk (MCD) model (Ginga)
Determine RISCO based on the MCD model
Based on the MCD model, corresponds to RISCO
Spins of several BH in binaries estimated (McClintock et al 2011)
R ISCO/rg vs Spin parameter a *R
Black Holes are Very Simple• Mass: M
• Spin: J = a*GM2/c (0 < a* < 1)
• (Electric Charge: Q)
But to measure these quantities is not simple
Two feasible methods:
1. Determine R ISCO of an accretion disk applicable to stellar-mass BH in the soft (X-ray) state. Mass, Distance, Inclination optically determined.
2. Relativistically broad Fe-K line Fe-K line near BH is broadened redward due to Doppler effect and gravitational redshift (depends on a ). *
“Broad Iron Line” story initiated in 1985 Cyg X-1
Tenma Kitamoto et al.EXOSAT Barr et al.
broad narrow
Gas scintillation prop. counter: best energy resolution at that time
obs/em
Rest frame @6.4 keV
Newtonian
Special Relativity: Beaming and Transverse Doppler
General Relativity: Gravitational Redshift
Disk Emissivity
by Armitage & Reynolds
Fabian et al. 1989
Iron K-Line profile near a black hole
SPIN
Maximal
Kerr
MCG-6-30-15 (z=0.008)
Broad Fe-K line first observed with ASCA
Tanaka, Fabian et al 1994
Energy (keV)
Flu
x
(ph
oto
ns
Broad Fe-K Line from the AGN MCG-6-30-15 (z=0.008) first observed with ASCA
Tanaka, Fabian et al. (1995)
S UZAKUMCG-6-30-15
Red wing due to large gravitational redshiftimplying BH rapidly
spinning
a > 0.98*
Broad Fe K-Lines observed with ASCA
K. Nandra
Broad Fe K-Lines in Galactic BHBs
GX 339-4 (CXO)
GRS 1915+105 (CXO)
XTE J1650-500 (XMM)
Cyg X-1 (XMM) XTE J1550-564 (ASCA)
GRO J1655-40 (ASCA)
(JMM 02, 06)
(JMM 04)
(JMM 02)
(JMM 04)
(JMM 04)
Broad Fe line in ~ 20 systems: [J.Miller]
Fe K emission line
• Most prominent feature in X-ray spectrum of reprocessed (reflected) emission from surrounding matter (accretion disk, torus ?)
• Relativistic broad line is the result of strong gravitational field near the central BH
• Probing the spin of BH, in particular SMBH
• But the reality of the Relativistic Broad Line is still subject of debate !
because the line profile is sensitive to the underlying continuum. Fixing the correct continuum is not straightforward.
海老沢 天文月報 p445, vol.103, 2010
Partial Covering
HXD
Compton-thick partial coverer may mimic a broad line 「すざ
く」
Patchy Absorber
taken from Dewangan 2011
海老沢 天文月報 p445, vol.103, 2010
Partial Covering
HXD
Compton-thick partial coverer may mimic a broad line 「すざ
く」
N arrow L ine S eyfert 1
Optical properties: _____narrow H lines: FWHM Hß<2000 km/s _____relatively weak [O III]5007 _____strong FeII emission
X-ray properties: _____steep power law: photon index > 2.0 _____significant soft excess _____rapid & large-amplitude variation
considered to be relatively low mass & high Eddington ratio
A convincing case exists. 1H0707-495
1H0707-495 time variability
Gallo et al. 2004
Γ = 2.4
Edge: 7.1 keV
Γ = 2.5
Edge: 8.2 keV
( Boller et al. 2002 )
( Boller et al. 2003 )
Deep edge, Strong soft comp.
Examples of NLS1
“Partial Covering” fit to two NLS1 spectra
Note the absence of narrow Fe-K line
Crummy+05 22 PG QSO +12 Seyf1
Sof t Excesses
Over mass range of three orders of magnitude
kT : 100 ~ 150 eV
Excludes accretion disk origin !
Reflection from photoionized disk(Ross & Fabian 93, 04)
Also see Young+, Nayakshin+, Ballantyne+, Rozanska+, Dumont+
Fe-K line must be present !
XMM RGS Spectrum of the Soft Excess ____________________of 1H0707
Fe-L
Blustin & Fabian 09
Ratio to the PL + BB model
a > 0.98*
Remaining Issues
• Why not all AGN show broad lines?• How to determine the correct continuum ?• Black hole spin: tend to be high ( too few sample yet)
• NLS1: show distinct differences from BLS1 ______strong soft excess ______steep power-law ______lack of narrow Fe K-line ______high Fe abundance
Strong light bending close to BH
Martocchia & Matt, Miniutti & Fabian