Probing the strong (stationary) gravitational field of ... · Probing the strong (stationary)...

Probing the strong (stationary) gravitational field of accreting black holes with X-ray observations

Luigi Stella – INAF-OAR, Astronomical Observatory of Rome

Black holes Gravitational Waves and Spacetime Singularities

Specola Vaticana – May 2017

Tests of General Relativity with binary millisecond radiopulsars:

RELATIVISTIC EFFECTS ARE SMALL PERTURBATIONS

Near the event horizon relativistic effects are large !

ASTROPHYSICS NEAR BLACK HOLES: STRONG FIELD EFFECTS

•! Innermost Stable Circular Orbit •! Orbital motion near ISCO •! Orbital and epicyclic frequencies •! Frame dragging, light deflection, Shapiro effect

ASTROPHYSICAL IMPACT

•! Black hole masses and spins •! Accretion physics •! AGN feedback •! Relativistic jets

deflection, Shapiro effect

X-RAY DIAGNOSTICS: •! Strong field motions:

orbital & epicyclic •! Spectral/timing/polarimetry

•! Reverberation •! Doppler tomography

STRONG GRAVITY IN STATIONARY SPACETIMES (COMPLEMENTARY TO DYNAMICAL SPACETIMES OF GWS SOURCES)

Accre%ngBlackHoles

StellarmassBlackHolesinX-raybinariesSupermassiveBlackHolesinnucleiofac%veGalaxies(AGN)-Accre%on-releasedenergyleadstopowerfulX-rayemissionfromtheinnermostdiskregions-X-rayfluxisoEenveryvariableandspectraarecomplex

General relativity predicted velocity and redshift map of the accretion disk

Accreting stellar mass Black Hole

Line profile integrated over entire flow encodes: -! Strong field relativistic effect: Doppler shifts and boosting,

gravitational redshift, strong field lensing, black hole spin -! Observed in both Active Galactic Nuclei and X-ray binaries Moreover: X-ray polarimetry diagnostics of accretion disk

Fe-line diagnostics


Fe-lines from accretion disks around supermassive black

holes in AGNs -  Strong field relativistic effect:

Doppler shifts and boosting, gravitational redshift, strong field lensing

-  Observed in manyActive Galactic

Nuclei and X-ray binaries

Line profile black hole spin Probing of strong field effects (~few Rs) MCG 6-30-15: - Kerr BH required to fit line profile

MGC 6-30-15 XMM

Nandra et al. '98

F$#6()#.+A(G$5H(*3&$((9#.I*$/(((((((((((((((((((((((((((((!<?/(((((((((((((((((((((((((((((((((((((((((((((((((((45#+6()3&+#3$/((

Nandra et al. '98

JKGL(H3",5.M(2$$%&'(5(N.2$(!O(P$(N./+(

Nandra et al. '98

Probing strong gravitational fields with Quasi Periodic Oscillations (QPOs) Strong Field Diagnostic: Fast variability and

Quasi Periodic Oscillations Accreting neutron stars Accreting black hole candidates

Sco X-1

10 100 1000 Frequency

!"#$%&'()*+'&#,-."/'+.,&%$01203'45%+,6)%",*'7#)85)%2.)0'$7'6$1$%'.%'0"#$%&'&#,-."/'

Inhomogeneities in inner disk

Q(R.(7*+",(C.*$(B31C(+SR(TUOV((WQU(-X(.#731+*((;#$Y8$&"6(

Z0[K(

9)%)#.2'6$+)*'7$#'':.&:)#'7#)85)%2/';<='


Stellar mass BH / RXTE

!"(

!#

!r !rr

Fundamental Frequencies of Particle Motion

5(\93"6"*3"(N$/.&+&"$(>I=$A(#@((5(N$*+%:3/%"(]#$"$//3.&^(&.A+*(+&A(9$#3+/1#.&(>:+#3+7*$(#@((((((

!#

General relativity:rg !GM / c2 j ! Jc /GM 2

!" = GM / r3 / 2# (1+ j(rg / r)3/2 )

! r2 =!"

2 (1" 6(rg / r)+ 8 j(rg / r)3/2 " 3 j2 (rg / r)2 )

!$2 =!"

2 (1" 4 j(rg / r)3/2 + 3 j2 (rg / r)2 )

General relativity:rgrgr !GMGMG / c2 j ! JcJcJ /GMGMG 2

!" = GMGMG / r3 / 2# (1+ j(rgrgr / r)3/2 )

! r2 =!"

2 (1" 6(rgrgr / r)+ 8 j(rgrgr / r)3/2 " 3 j2 (rgrgr / r)2 )

!$2 =!"

2 (1" 4 j(rgrgr / r)3/2 + 3 j2 (rgrgr / r)2 )

Stellar mass BH / RXTE

Periastron Precession Frequency: !per

# Frequency !#

Relativistic Precession Model

Nodal Precession Frequency: !nod $

_]K/(;#.2(1C$(1#+&/3$&1()-(73&+#6(<NK(`abQQ5WU^(N4L\(A+1+(

!"−! !"" !"! !"#!"−!

!""

!"!

!"#

!"$

%&'()*+,-./-012*3456

+,-./-012*3456

*

*

+,-./-012*(7*89:;<+,-./-012*(7*84&,=5&0

>-?)-,=(0*+,-./-012@-,=(A7,&0*?,-1-AA=&0*+,-./-012%&'()*+,-./-012:=B/)7(0-&/A*C@<A<DA-,E-'*@F>*D,&('*1&B?&0-07A

$" #" !" ** ** ** ** *G ** ** **8('=/A*38H6

>R.c+($1(+*(dUaV@(

5! N$*+%:3/%"(9#$"$//3.&(2.A$*(I1/(A+1+(B$**(+&A('3:$/(((((((RT(QOVa(eS5(UOUf(R.((>;#.2(.9%"+*(RT(QOW(eS5(UOV(R.@((((((((+g(T(UOdhU(eS5(UOUUV((

100 101

101

Pow

er s

pect

ral d

ensi

ty

Frequency (Hz)

200 300 400 500 600 700800

1.84

1.86

1.88

1.9

1.92

Pow

er s

pect

ral d

ensi

ty

Frequency (Hz)

<DA-,E-'*@F>*D,&('*1&B?&0-07A<DA-,E-'*@F>*D,&('*1&B?&0-07A<DA-,E-'*@F>*D,&('*1&B?&0-07A<DA-,E-'*@F>*D,&('*1&B?&0-07A0328*1+&$.8/(_]K/(

PROBING SPACETIME AND MATTER UNDER EXTREME CONDITIONS

QUU(

aUUU(

dUUU(

WUUU(

iUUU(

abUUU(

VdUUU(

bWUUU(

adiUUU(

ahbQ( ahfQ( ahiQ( ahhQ( dUUQ( dUaQ( dUdQ( dUVQ(

UHURU 1970-1973, 800 cm2, X-ray sky, accreting X-ray pulsars HEAO-1 1977-1979, A2: 400-800 cm2, variability and eclipses EINSTEIN 1978-1981, MPC: 670 cm2, extend number of known sources EXOSAT 1983-1986, ME: 1600 cm2, QPOs in LMXB GINGA 1987-1991, LAC: 4000 cm2, transient BHCs RossiXTE 1995-2012, PCA: 2000-6000 cm2, kHz QPOs, fast BH QPOs, AMXP ASTROSAT 2015- : LAXPC: 6000 cm2 at 6 keV

TIMING Proportional Counters, 1.2 keV FWHM @ 6 keV

"2d(

6$+#(

!(0-KNL(-Z0LKNj(KG(LZRZ?<(Z?(LZR\(

F$#6(J+#'$(+#$+((/9$"1#+*5%23&'^(

03*3".&(P#3E(P$1$"1.#/(kdUU($F(Gl-R(m(b(,$F(

POSSIBLE MISSION APPROACHES

LOFT Large Observatory For x-ray Timing

(ESA)

eXTP enhanced X-ray Timing and Polarization mission (CAS)

Large Observatory For x-ray Timing Large Observatory For x-ray Timing (ESA) (ESA) (ESA)

Large Observatory For x-ray Timing (ESA)

Bright sources: Large Collimated Area

Weak/soft sources: Collimated + Focused Area

POSSIBLE MISSION APPROACHES

LOFT Large Observatory For x-ray Timing

(ESA)

eXTP enhanced X-ray Timing and Polarization mission (CAS)

Bright sources: Large Collimated Area

Weak/soft sources: Collimated + Focused Area

8.5m2

3.4m2

1m2 0.6m2

018A6(9C+/$(+99#.:$A(R+#"C(dUaf(



Line profile integrated over entire flow encodes: -! Strong field relativistic effect: Doppler shifts and boosting,

gravitational redshift, strong field lensing, black hole spin -! Observed in both Active Galactic Nuclei and X-ray binaries Moreover: X-ray polarimetry diagnostics of accretion disk

Fe-line diagnostics


eXTP-LAD simulation of black hole X-ray binary 4ks integration a* = 0.967±0.003

De Rosa


!"#$%&'()*+'&#,-."/'+.,&%$01203'45%+,6)%",*'7#)85)%2.)0'$7'6$1$%'.%'0"#$%&'&#,-."/'


BH in XRB / RXTE BH in XRB / RXTE eXTP:LAD 7 x S/N

Q(R.(7*+",(C.*$(B31C(+SR(TUOV((WQU(-X(.#731+*((;#$Y8$&"6(

Z0[K(

9)%)#.2'6$+)*'7$#'':.&:)#'7#)85)%2/';<='


a*=0.7

a*=0.6 m = 7.1

600

500

400

Hz

300 400 500

m = 7.3

Orbital frequency

L323&'(A3+'&./%"/^(#$*+%:3/%"($93"6"*3"(2.%.&((

0 1 2 3 4 TIME (ksec)

400

0

800

1200

X-ray flux (Crab)

Hz Orbital and epicyclic frequencies

0.9

1.0

1.1

•! Precisely measure orbital and epicyclic frequencies at each radius

•! Compare to GR predictions •! Measure black hole mass and spin

to < 0.3 % precision

JKGL(

09$"1#+*5L323&'(A3+'&./%"/((P.99*$#(1.2.'#+9C6^(.#731+*(2.%.&(3&(!<?/(

rout

rin

rsp

G=TV2[#+7n(\lTVU($Fn(+TUOQn(#3&Ta#'n(#.81TaUU#'n((>?@AB'CDE'>05%F',?DGBADGE'

JKGL^(b(9C+/$/(>aOQ(,/($+"C@(((1B.("6"*$/(

Orbiting spot: XMM observations of NGC3516

De Rosa

Reprocessed radiation from the disk

N$9#."$//$A(/9$"1#82

(

P3/,(#$9#."$//3&'(((

C.1(".&%&882(/.8#"$(

5 10 20 50 keV

G$5*3&$(

In addition to the iron line and reflection continuum, the absorbed flux is reradiated by the disc as thermal blackbody radiation

[6'(45a(

Spectral - Timing diagnostics

1C$#2+*(A3/,(

o1(

P3/,(#$:$#7$#+%.&((!"#$(C.1(".&%&882(( F+#3+7*$(C.1(

".&%&882(/.8#"$(

•! Probe disk velocity/redshift map as radiation fronts propagate over the disk

•! Relativistic effects as a function of absolute radius (e.g. km)

Reverberation: energy resolved light echoes

Uttley

1C$#2+*(A3/,(

o1(

P3/,(#$:$#7$#+%.&((!"#$(C.1(".&%&882(

F+#3+7*$(C.1(".&%&882(/.8#"$(".&%&882(/.8#"$(

10 FA + 40LAD

In addition to the iron line and reflection continuum, the absorbed flux is reradiated by the disc as thermal blackbody radiation eXTP can study all three components simultaneously!

•! Frame dragging: central hot torus precesses •! Hard radiation sweeps around over disk •! Reflection line profile varies periodically •! eXTP tracks the line profile, probing the disk

velocity and redshift map

Ingram

G#+2$(A#+''3&'(&.A+*(9#$"$//3.&^(*.B(;#$Y(_]K/(((Precessing hot torus: reverberation

! " #! #" $!

%!!!

&!!!

'−()*+,

(-./0123

3

4-52+637

89:#;#"<#!"

Frame dragging nodal precession: timing (low freq. QPO) diagnostics

Z&'#+2(

H 1743-322 – XMM

Frame dragging nodal precession: timing-spectral (Fe-line) diagnostics

!"# $" #"

"%&

!!%$

'()*+

,-.'/0123.45

6789:;

< = & !"

!!%"#

'()*+

,-.'/0123.45

>??−6.@)+-

Z&'#+2(

H 1743-322

timing-spectral (Fe-line) diagnostics

# $" #"!"# $" #"!"

"%&

!!%$

'()*+

,-.'/0123.45

6789:;

< = & !"

!!%"#

'()*+

,-.'/0123.45

>??−6.@)+-

H 1743-322 GRS 1915+105

eXTP

,-.'/0123.45,-.'/0123.45,-.'/0123.45

Ro=20Rg, a=0.98

].*+#3X+%.&(.;(9#."$//3&'(3&&$#((1.#8/((

5(9.*+#3X+%.&(A$'#$$(+&A(+&'*$(+M$"1$A(76(/1#.&'(I$*A(*3'C1(7$&A3&'(5(9#$"$//3.&("C+&'$/('$.2$1#6(+&A(1C8/(2.A8*+1$/(9.*+#3X+%.&(

Z&'#+2(

Frame Dragging: timing-polarisation diagnostics

Frame dragging: eXTP polarization measurements

Only eXTP can study frame dragging through the combination of Timing-Spectral-Polarimetry

Z&'#+2(

COMPLEMENTARY TO GRAVITATIONAL WAVE EXPERIMENTS: LOFT/EXTP PROBE STATIONARY SPACETIMES

Accretion in strong field gravity: mass range

X-ray binary system

Active galactic nucleus

Stellar mass black hole (or neutron star) Strongly curved spacetime. (1016 times Solar)

Supermassive black hole Weakly curved spacetime (~Solar)

X-ray diagnostics cover a very wide mass range in uniform setting

((((((;+"1.#(aUad(3&("8#:+18#$(

((((((

L$/1S".&/1#+3&(+*1$#&+%:$(1C$.#3$/(.;('#+:316(1C+1(A3M$#(;#.2(<N(.&*6(3&(1C$(/1#.&'(I$*A(#$'32$n(1C#.8'C(45#+6(A3+'&./%"/(*3,$(G$5*3&$/(+&A(_]K/((;+"1.#(aUQ(3&(I$*A(

/1#$&'1C(Maselli

-! Test (or constrain) gravity theories that differ from GR in the strong field/high curvature regime”

•! Bottom-up approach: parametrised spacetime (PPK-type) but in strong field

•! Top-down approach: 1st principle modifications of GR (e.g. quadratic curvature term coupled to a scalar field)

Fundamental frequencies in Einstein Dilaton Gauss Bonnet:

Maselli +

JKGL(

01#.&'(I$*A('#+:316(#$/$+#"C^(/6&$#'6(+&A(".29*$2$&1+#316(

!A:+&"$A(JZ<KSF3#'.(/1$**+#(2+//(2$#'$#/(

\:$&1(C.#3X.&((1$*$/".9$^(((9C.1.&((((('$.A$/3"/(

!",1$%,#/'0H,2)16)0' I/%,6.2'0H,2)16)0'

!"#$%&*/'25#-)+'0H,2)16)0'J0")**,#'6,00''K*,2L':$*)0M'

N),L*/'25#-)+'0H,2)16)0'J05H)#6,00.-)''K*,2L':$*)0M'

JKGLS($4L]S0LNK)\54(/1$**+#(2+//()-/((((((((

JKGLS$4L]S(0LNK)\54(/89$#5(2+//3:$()-/(

!H,2)16)03'

JZ0!n(]L!(/89$#2+//3:$((2$#'$#/(

0*3'C1*6(A6&+23"(S(&$+#*6(/1+%.&+#6(/9+"$%2$/^(5! 0H!(2/(#+A3.(98*/+#(0'#!g(5! $JZ0!(\RN(3&/93#+*/(

PROBING SPACETIME AND MATTER UNDER EXTREME CONDITIONS

LOFT AND DENSE MATTER - SUMMARY

LOFT •! measures both M and R.

•! minimises statistical error with its large effective area.

•! minimises systematic error with complementary methods and same source cross-checks.

•! relies only on known

sources to deliver the required number of data points.

No other mission does this.

LOFT WILL MEASURE THE EOS OF DENSE MATTER, PROVIDING UNIQUE INSIGHT INTO THE PHYSICS OF THE STRONG FORCE.

Conclusions •  X-ray timing, spectral and spectral/timing diagnostics of accreting black holes will allow us to:

-  verify key predictions of GR in the strong field regime -  test or constrain some alternative theories of gravity

•  Very high throughput combined with good spectral resolution is required: different missions are being studied, LOFT, eXTP and STROBE-X

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