Microquasars

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Microquasars

• Yoshihiro Ueda
• Kyoto University

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Astrophysical Jetunresolved issues in BH
accretion

• Dynamics of the accretion and outflow as a
  function of mass accretion rate
• Crucial for understanding the accretion history
  of the universe (growth of supermassive black
  holes) and formation of the large scale structure
  (e.g., heating source stopping the cooling flow
  in clusters of galaxies)
• Formation mechanism of relativistic jets
• Jet power exeeds the luminosity from the acretion
  disc
• Energy source gravitational energy
• The physical process for the energy transfer is
  mistery (radiation pressure driven? magnetic
  pressure driven?)
• Common physics that can be normalized by BH mass
• AGN vs Galactic BHs

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Microquasars(originally, Galactic black hole
binaries with relativitic jet)

• Microquasars (BH mass 10 M? )
• 10-6 times quasars (106-9 M? )
• X-ray bright
• varies on short timescale
• Ideal Laboratory for studying the relation
  between accretion disc and jet

70
Accretion disk ?X-rays Jet ?Radio
- Infrared
Multi-wavelength approach is important!
Mirabel Dodriguez (1998)
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Examples of microquasars (including neutron star
binaries)
BH binaries jet velocity GRS
1915105 V 0.92-0.98c GRO J1655-40 V
0.92c XTE J1550-564 Vapp gt 2 c
1E1740.7-2942 V0.27c Cyg X-1
Vgt0.3c
All BHCs in the Low State NS binaries Cir
X-1 Vappgt15c Sco X-1
V0.5c BH or NS ? SS433
V0.26c Cyg X-3 V0.3c
C J. Orosz
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X-ray State of black holes
ex. Cyg X-1 (ASCA, RXTE, CGRO OSSE)
Gierlinski1999, MNRAS, 309, 496
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State as a function of accretion rate
Slim disc (opt. thick ADAF) at mgtgt1

• When accretion rate is high
• optically thick disc (standard disc) extends to
  the innermost stable orbit
• strong soft X-rays (blackbody like)
• When accretion rate is low
• ADAF hot corona
• strong hard X-ray emission via Comtonisation
  (power law)

(soft state)
(hard state)
Esin 1997, ApJ, 489, 865
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The microquasar GRS 1915105

• An X-ray Nova detected by the GRANAT satellite
  (Castro-Tirado 1992) persistent since then
• The first superluminal source in our Galaxy
  (1994, 1997)
• Jet intrinsic velocity 0.92-0.98 c
• inclination 70
• (Mirabel Rodriguez 1994)
• Black hole
• MX 14 ? 4 M? (Greiner 2001)
• ? black hole
• Peculiar time variability in X-rays
• gt13 patterns (Belloni 2000)
• due to thermal instability in the inner part of
  the disc under high mass accretion rate?

Mirabel Rodriguez (1994)
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A
X-ray Variability Pattern (Belloni 2000)
B
B
A
A
B
C
C
C
C
1000 sec
A
State B
A
C
C
B
B
HR1
A
C
State C
Transition between 3 basic states
State A
HR2
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Typical SED of GRS 1915105 (VHS)
(YU 2002)
Synchrotron from Jet
Comptonization
I ??0
Multi Color Disk
Companion
Reflection component
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Jet from GRS1915105
Dhawan 2000, ApJ, 543, 373
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YU 2008
2005 Oct Multiwavelength Campaign
20
40
60
Hours since 16 Oct 05 (UT)
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X-ray State (Oscillation)

• Class ?(State C? State A (soft dip) ?State C)

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YU 2008
Near IR (Subaru)
Ks mag
10 minutes
X-rays (Suzaku)
Count Rate
RelativeTime (Hours)
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Repeated Jet from GRS 1915105
Mirabel 1998

• Flux peaks later at longer wavelength radio flare
  delays by 15 minutes
• Synchrotron emission from an expanding region
  (e.g., van der Laan 1966)

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Repeated Jet from GRS 1915105
YU (2002)

• Time delay of the IR flare from the time of X-ray
  state transition by 5-30 minutes
• Flare in Jet occurs at far from the BH (1AU)
• internal shock?
• Time variability of 1 minunte constrains the size
  of flare to lt0.1AU evidence for collimation

X rays
IR
40 minutes
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Indication to disc-Jet connection

• Radio/IR flares occurs with state transition of
  the accretion disc, sometimes with 0-30 minutes
  delay.
• The wavelength dependent profile is qualitatively
  consistent with an expansion as a jet.
• Transition from the hard state to the soft
  state triggers the ejection of plasma. The
  ejected material will flare up by shock,
  probably with slower jet emitted previously (see
  Fender2004). This can cause significant time
  delay between ejection and flare, the latter
  can occur at far from the black hole (r1e12-13
  cm).

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Transient Jet from Cyg X-1

• Relativistic Jets are common phenomena in stellar
  mass BH
• Ejection at transition to the soft state ?

Fender 2006
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Compact Jets in the Low/Hard State

• Persistent jet detected from BHs in the Low/Hard
  State and Very High State (i.e., related to hot
  corona)
• Quench in the High/Soft State (ie. standard
  accretion disc)
• Flat spectrum optically thick synchrotron
  emission from partially self-absorbed jet

Cyg X-1 (Stirling)
1E1740.7-2942 (Fender2001)
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Summary Jet from microquasars

• ( the numbers are for the case of GRS 1915105)
• Large flare with superluminal motion
• S 1 Jy (optically thin)
• time scale rise 1 day, decay months
• Pjetgt5x1038 erg s-1
• Repeated flare in the oscillation state (so far
  only from GRS 1915105)
• S10-300 mJy
• time scale 20 minutes hours
• Pjetgt1038 erg s-1
• Compact jet in the low/hard state or very high
  state
• S1-50 mJy (optically thick)
• Persistent
• X-ray spectra strong Comptonization by hot
  corona Radiatively Inefficient Accretion Flow
  Trancated accretion disc?

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Prospects for VSOP-2

• Microquasars radio quiet (mostly lt100 mJy)
• Increased sensitivity compared with HALCA makes
  these objects as targets of space VLBI for the
  first time!
• Case of GRS 1915105 (_at_12.5 kpc)
• size 0.04 mas 0.5 AU (2e6 Rs for a 14 Mo BH)
• veloicty vc 0.6 mas/hour
• (cf. similar for SS 433 v0.26c _at_ 5 kpc)
• Integration withinlt10 minutes is required to
  fully utilize the VSOP-2 resolution (0.1 mas)
• snap shot mode to constrain (at least) one
  dimensional spatial information

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VSOP-2 imaging the compact jet

• Persistent jet in the low/hard or very high
  state full 2 dimensional images can be obtained
  with 0.5 AU resolution
• How well is the jet collimated?
• Any features (knots) or smooth?
• Measure polarization to constrain the geometry of
  magnetic field (so far not successful)
• Key information to understand the accretion flow
  in the RIAF mode

Dhawan 2000
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VSOP-2 imaging the transient jets

• Directly measure the position of flare to test
  the internal shock scenario at 10 AU from the
  BH?
• Evolution of jet structure in the very early
  phase estimate of the true jet power (E/?t)
• TOO upon detection of state transition in
  X-rays (monitor by e.g., MAXI)

30 mas resolution (VLA or MERLIN)
Fender 1999
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Summary

• Microquasars provide us with the unique
  opportunity to investigate the relation between
  accretion flow and relativistic jet
• VSOP-2 can make new science in resolving the jet
  structure in microquasars both in the radio flare
  and persistent states
• Multiwavelength approach (in particular with
  X-ray observations) is crucial.