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
R ISCO/rg vs Spin parameter a
*
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
EXOSAT
Barr et al.
broad
Tenma
Kitamoto et al.
narrow
Gas scintillation prop. counter: best energy resolution at that time
Rest frame
@6.4 keV
Iron K-Line profile
near a black hole
Newtonian
Fabian et al. 1989
Special Relativity:
Beaming and
Transverse Doppler
General Relativity:
Gravitational
Redshift
Disk Emissivity
nobs/nem
by Armitage & Reynolds
SPIN
MCG-6-30-15 (z=0.008)
Broad Fe-K line first
observed with ASCA
Tanaka, Fabian et al 1994
(z=0.008)
Flux (photons
Broad Fe-K Line from the AGN MCG-6-30-15
first observed with ASCA
Energy (keV)
Tanaka, Fabian et al. (1995)
MCG-6-30-15
Red wing due to large
gravitational redshift
implying BH rapidly spinning
a > 0.98
*
SＵＺＡＫＵ
Broad Fe K-Lines observed with ASCA
K. Nandra
Broad Fe K-Lines in Galactic BHBs
Cyg X-1 (XMM)
(JMM 02, 06)
GRS 1915+105 (CXO)
XTE J1550-564 (ASCA)
(JMM 04)
(JMM 04)
GX 339-4 (CXO)
(JMM 04)
XTE J1650-500 (XMM)
GRO J1655-40 (ASCA)
(JMM 02)
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.
Partial Covering
Compton-thick partial coverer may
mimic a broad line
「すざく」
HXD
海老沢 天文月報 p445, vol.103, 2010
Patchy Absorber
taken from Dewangan 2011
Partial Covering
Compton-thick partial coverer may
mimic a broad line
「すざく」
HXD
海老沢 天文月報 p445, vol.103, 2010
A convincing case exists. 1H0707-495
Ｎarrow Ｌine Ｓeyfert １
Optical properties:
_____narrow H lines: FWHM Hß<2000 km/s
_____relatively weak [O III]l5007
_____strong FeII emission
X-ray properties:
power law: photon index > 2.0
_____significant soft excess
_____rapid & large-amplitude variation
considered to be relatively low mass &
high Eddington ratio
_____steep
1H0707-495 time variability
Gallo et al. 2004
Examples of NLS1
Deep edge, Strong
soft comp.
Γ = 2.4
Edge: 7.1 keV
（Boller et al. 2002）
Γ = 2.5
Edge: 8.2 keV
（Boller et al. 2003）
“Partial Covering” fit to
two NLS1 spectra
Note the absence of
narrow Fe-K line
Soft Excesses
kT：100～150 eV
Over mass range of
orders of magnitude
Crummy+05 22 PG QSO +12 Seyf1
Excludes accretion disk origin !
three
Reflection from photoionized disk
(Ross & Fabian 93, 04)
Fe-K line must
be present !
Also see Young+, Nayakshin+, Ballantyne+, Rozanska+, Dumont+
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