observations of black holestanaka et al ’95 – iwasawa et al ’96 - guainazzi et al ’99 –...
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Observations of Black Holes
AC Fabian Institute of Astronomy
University of CambridgeUK
“True” color image0.5-2.0 keV 2.0-4.0 keV 4.0-8.0 keV
1.945 MsACIS-I
exposure
503 point sources6 extended sources
(447 arcmin2 )
20 observations spanning 27 months
HDF-N
Bauer et al. (2002)
Alexander et al. (2003)Still photon limited near the aim point
Accretion Discs• Viscosity causes angular momentum to flow out
while mass flows in.• Viscosity due to Magneto-Rotational Instability.• For radiatively efficient, optically thick discs, flux
emitted proportional to 1/r3
• So most emission from smallest radii• Energy dissipated within disc emitted as quasi-
blackbody emission from surface• Magnetic energy dissipated above disc creates
high temperature corona (and/or jet)• Hot coronal electrons rapidly Compton scatter
softer disc BB photons into a powerlaw spectrum seen as X-ray continuum
Blaes et al 01
3C273 Hubeny et al 00
BB flux from disks- Not straightforward!
ULX in NGC1313 Miller et al 03
L ⇒T4
MillerFabianMiller 2004
Accretion modes
• Radiatively Efficient accretion (Shakura & Sunyaev 83, Pringle 81) is responsible for most BH growth
• When accretion rate below about α2
of Eddington rate then hot, optically thin, radiatively inefficient, solution is possible (Yi & Narayan 95, Rees+82)
Adiabatic accretion Stone, Pringle & Begelman 01
Computations of radiatively efficient disks much more difficult
X-ray Binary
Masses from binary orbit
Kepler’s law gives the mass function
Inclination can be found/constrained from eclipses or ellipsoidal variations of optical companion
Charles & Coein
Lewin & van den Heuvel2005 CUP
QPO in GRS J1655-40Strohmayer ApJ 2001
Do QPO reflect Keplerian frequencies?
Types of AGN• Most (90%) are radio-quiet• Divided into unobscured
(NH<1022) – Type I objects and obscured – Type II
• Obscured objects may outnumber unobscured ones 5:1 at low z (some of obscuration is a torus, but most is probably messy)
• Fraction of Type II quasars is an ongoing quest
NGC1068
Active Galactic Nuclei
M84 HST
M106 Miyoshi et al 1995
Black hole mass vs stellar bulge velocity dispersion
Accretion makes massive black holes
• Number density of quasars peaked at z~2 at ~1000 times present density
• Integrated light of quasars + obscured AGN makes present BH density if accretion efficiency ~0.1
2)1(1.0 cz •+= ρε Soltan 82
AGN Reverberation
Woo & Urry 02
T
pEdd
cGMmL
σπ4
=
AGN variability can be extreme, particularly in X-ray band, the peak is 1e45 erg/s
Clues from spectra and variability
• X-ray ‘reflection’ gives important clues in the spectrum
• Variability timescales and spectral changes show different spectral components
• Powerful method for mass measurement is reverberation
NGC4395
Rapid variabilityin AGN
MCG-6-30-15
Emission dominated by innermost regions
Orbital frequency at 10rs
Cyg X-1 low state (Uttley+05)
PSD
f P(f)Log-normal fit
Schwarzschild
Kerr
Fabian+89, Laor 90…Dovciak+04; Beckwith+Done05
Reflection from photoionized matter(Ross & Fabian 93, 04)
Also see Young+, Nayakshin+, Ballantyne+, Rozanska+, Dumont+
Vary spectral index
Add relativistic blurring
Soft excess – broad iron line – Compton hump
Very Broad Line ⇒Spinning BH
Tanaka+ Iwasawa+ Wilms+ Fabian+
Lockman Hole800 ks XMM-Newton observationHasinger
Streblyanskaya et al 2004
Broad Line ⇒Probably spinning BHs
Stacked spectra of 53 Type I AGN Streblyanska et al (2005)
Galactic Black Hole GX339-4
Very Broad Line ⇒spinning BH
Miller+
XTE J1650-500 from BeppoSAX(G. Miniutti)
Assumption: measurements of rms determine (or constrain) a
Schwarzschild
Kerr
Iron line extending below 4 keV generally implies a spinning Kerr BH (spin parameter from rms )(mag field caveat on ISCO: Gammie, Krolik…)
520 ks Chandra HEG observation of MCG-6-30-15Young et al 2005 (in press)
compared with XMM-Newton spectrum
Constrains absorption by highly ionized species
Implies that absorption models for red wing do NOT work
XMM-Newton observations of MCG-6-30-15 in the 2-10 keVband
Wilms et al 2002; Fabian et al 2002; Vaughan et al 2002; Fabian & Vaughan 2002; Ballantyne et al 2003; Reynolds et al 2003; Vaughan & Fabian 2004
Understanding the spectral behaviour
How does it vary?
Iwasawa+ Shih+ Fabian+ Vaughan+ Uttley+ Reynolds+
Spectral changes seen in 10 flux slices
Difference spectrum: (High flux)-(Low flux)
is a power-law modified by absorption
1 keV 10 keV
So we know which large scale features are due to absorption
Schematic picture of the two-component model
Variable power-law
Stable reflection-dominated component
Summary of MCG-6-30-15 observations:1. The broad Fe line
A broad Fe line is present in all flux states
Fe line red wing suggests a rotating Kerr black hole
Fabian et al 02
Tanaka et al ’95 – Iwasawa et al ’96 - Guainazzi et al ’99 – Wilms et al 01 – Fabian et al 02 …
Summary of MCG-6-30-15 observations:1. The broad Fe line
A broad Fe line is present in all flux states
Fe line red wing suggests a rotating Kerr black holeTanaka et al ’95 – Iwasawa et al ’96 - Guainazzi et al ’99 – Wilms et al 01 – Fabian et al 02 …
A steep emissivity profile is implied ( β > 3 ) possibly in the form of a broken power-law
The emissivity suggests the presence of a centrallyconcentrated primary source of hard X-rays
KevinRauchJHU
Light bending model in Kerr spacetime
Miniutti et al 03; Miniutti & Fabian 04; earlier work by Matt et al
PLC
Fe line
PLC and Fe line variability induced by light bendingwhen an intrinsically constant source changes height
hs
Small h = low PLC fluxLarge h = high PLC flux
The Fe line varies with much smaller amplitude
Continuum
Fe li
ne
MCG-6-30-15
model prediction
more details on the model:GM et al, 2003, MNRAS 344 L22GM & Fabian, 04GM et al, 04
Low flux results from Reynolds et al
XTE J1650-500 during outburst
Rossi +05
Is it absorption or a line?
Laor line fit
Boller+04; Fabian+04
1H0707
Variability
RMS fractional variability spectrum
0
1
2
3
4
5
6
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6
0.3-
1 ke
V c
ount
s / s
1-5 keV counts / s
0
1
2
3
4
5
6
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6
0.3-
1 ke
V c
ount
s / s
1-5 keV counts / s
0
1
2
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4
5
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0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6
0.3-
1 ke
V c
ount
s / s
1-5 keV counts / s
RD
C
PLC
Conclusions• Detailed observations reveal properties
of radiatively efficient accreting BH • Some involve both
– strong gravitational redshift– and light bending
• indicating that much of the reflection and thus primary emission is occurring within a few gravitational radii of the event horizon
• Good evidence from several objects that BH is spinning (Kerr solution necessary)
Additional material
Accretion text:Frank, King
& Rayne, CUP
This text is for
reference only
Viscosity from MRI instability
Radio-loud objects• Many parts of the
spectrum are dominated by power-law jetted emission
(synchrotron or SSC)
Jets often relativistic (and some show superluminal motion)
Some X-ray jets
Cen A
Gallo, Fender & Pooley 03Jetted components in BHC?
Fender et al 04
Outburst of Galactic BH Transient