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

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

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