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New constraints on accretion
from fast optical and X-ray
timing of X-ray binaries
Poshak Gandhi (RIKEN)
Martin DurantAndy FabianJulien Malzac
Jon MillerTariq Shahbaz
Kazuo MakishimaVik DhillonTom MarshHenk Spruit
What is the source of the optical power of X-ray binaries?
GX 339-4 ESO (2008) / L. Calçada
Optical and X-ray simultaneous timing
u’
(Gandhi+10 submitted)
(CC
F)
2.5 s
GX 339-4 : 2007 low/hard state
+VLT RXTE
PCA
New fast red component in CCF?
r’
g’
u’
u’
g’
r’
(Gandhi+10 submitted)
(CC
F)
2.5 s
GX 339-4 : 2007 low/hard state
+VLT RXTE
PCA
Sub-second X-O Cross Correlation Function (CCF)
Avera
ge
Optical Lag (seconds) (Gandhi+ 2008)
150 ms
50 ms
r’r’r’
GX 339-4 : 2007 low/hard state
+VLT RXTE
PCA
ULTRACAM:ultra-fast, triple-beam CCD camera
High-speed light-weight camera
Frame-transfer CCDs withnegligible dead-time
Speeds ~ 500 frames / sec
3 simultaneous optical filters
Absolute timing ~ 1 ms
http://www.shef.ac.uk/physics/people/vdhillon/ultracam/
ug
r / i / z
ULT
RA
CA
M @
VLT
Speedy optical variability
Swift J1753.5-0127
GX 339-4
de
ΔT
=50 m
sΔ
T=
39 m
sU
LT
RA
CA
M
Anim
atio
ns: b
insim
Speedy optical variations in X-ray binaries
(XTE J1118+480: Kanbach et al. 2001)
(V404 Cyg: Uemura+02)
(GX 339-4: Motch+82)
mag
1s
0.5 s
Swift J1753.5-0127: Durant et al. 2008
XTE J1118+480:Kanbach et al. 2001
GX 339-4: Gandhi et al . 2008
Asymmetric and complex optical/X-ray cross-correlation functions in the low/hard state
Rapid variability origin?:
Simple reprocessing models
All X-ray data: RXTE PCA
1. Small time delayA
vera
ge
Optical Lag (seconds) (Gandhi+ 2008)
150 ms
Swift J1753.5-0127: Durant et al. 2008
XTE J1118+480:Kanbach et al. 2001
GX 339-4: Gandhi et al . 2008
2. Anti-correlation
All X-ray data: RXTE PCA
3. Small optical coherence times
X-rays (PCA)
Optical(r’,g’,u’)
Optical ACFs narrower than X-ray ACF for two sources
Lag (s)
Auto Correlation Function(Poisson corrected)
Optical
(white)
X-rays (PCA)
GX 339-4 XTE J1118+480
How much reprocessing is expected?(v
an P
arad
ijs&
McC
linto
ck 1
99
4)
All sources in low/hard state with
LX/LEdd<~0.01
(Gan
dh
i+2
01
0, D
ura
nt+
10
)
Speedy optical variability: scales and power
• Fastest flares have timescales <~ 20-50 ms.
=> R <~ 104 km <~ 103 RG
• Brightness temperature
=> TB >~ 107 K
Models for XTE J1118+480
“The physical origin of the
variability
Is likely to be complicated.”
• Merloni+00 Magnetic corona
• Esin+01 Advection flow (ADAF)
• Markoff+01 Pure jet
• Malzac+04 Magnetic‘reservoir’jet/corona
• Yuan+05 ADAF+jet
• …
Optical (cyclo)synchrotron.
Interaction between components.
CCFs characteristic times =>interacting components
150 ms
X-ray coronal flares lead to reordering of jet poloidal field
(~ tens x tdynamical ~ 100 ms; Livio+03; Malzac+04)
Ima
ge cred
it: Pu
nsly+
09
(Gandhi+2008)
CCFs characteristic times =>interacting components
150 ms
Jet /
Outflow
Schem
atic ca
rtoo
n
Disk
Propagation of perturbations : from disc/corona to jet
(150 ms 50 RG @ Alvenic speed, or 5000 RG @ lightspeed)
(Gan
dh
i+2
00
8, 2
01
0)
B field dissipation anti-correlation
150 ms
Jet /
Outflow
Schem
atic ca
rtoo
n
Disk
Release of coronal B energy density
optical cyclosynchrotron
(Gandhi+2008)
Optical power spectra
reminiscent of X-rays
(Gandhi 2009)
X-ray: PCAOptical: Either
r’ or g’ or white
Broad band optical noiseand QPO
r’
g’
u’
X-ray PCA
(Gandhi+10 submitted)GX 339-4 : 2007 low/hard state
Optical QPO quite “stable” in GX 339-4
(Motch+83)white light
(Motch+83)Ariel data
(Steiman-Cameron+97)
(Gandhi+10): PCA(Gandhi+10):
r’, g’
(Motch+85)
Optical X-ray
Fre
q x
Po
wer
(arb
itra
ry)
cf. also Uttley talk: 100s QPO
Anything
special
about
these
binaries?
Swift J1753.5-0127
XTE J1118+480
GX 339-4
V4641 Sgr
(J. O
ros
z)
(Durant+10, in prep)
X-r
ay :
Op
tica
l Cro
ss-C
orr
ela
tio
n F
un
ctio
n (
CC
F)
Optical Delay (s)
Neutron star binaries?
Fast optical timing constraints• Optical timing complementary constraints to X-
ray timing.
(Gandhi 2009)
Flux-dependent variability
(Gandhi 2009, Uttley et al. 2001…2005)
R.M.S. variability amplitude increases with flux=> Argues against additive shot noise
Fast optical timing constraints• Optical timing complementary constraints to X-
ray timing.
• How “close in” can optical timing take us?
(Gandhi 2009)
Summary
• Rapid optical flaring in
low/hard state observations
of several binaries.
• Optical not reprocessed simply.
• Complex CCF
=> jet/corona/disk interaction.
• Optical timing gives
independent constraints on
inner accretion processes.