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2009 East Asia VLBI Workshop (2009 March 18-20, Seoul)
Multi-frequency Timing and
Rapid Spectral Evolution of
Microquasars
Soon-Wook Kim
Astrophysics Research Group,
International Center for Astrophysics,
Korea Astronomy and Space Science Institute
Relativistic Jets:
≤0.99c
perpendicular to
the disk plane
What is Microquasar ?
>1038(M/M⊙)
•
erg/s=LEDD
NS(~1.4M⊙) /
BH (>3.2M⊙)
Tth~1012K
X-ray Binaries: BH/NS + disk + normal star
• micro-quasars: collimated bipolar, relativistic
jet-emitting X-ray binaries
• ≥ 10 BHB & ≥ 2-3 NS (?) microuqasars ;
~30 BH candidate microquasars with multicomponent jets
1011-1012cm
accretion disk
108-1013 km
mass accretion
1016-1019 gram of
Hydrogen per second
Companion Star
(褐色矮星, 準矮星, 主系列星,
準巨星, 巨星, 超巨星,白色矮星)
Quasar vs. “Micro”-Quasar
• Quasars and microquasars share
common phenomena: flares,
relativistic jets, red shifted emission
lines, & leptonic/hadronic variabilities.
• Microquasars are micro-scale to
quasars in BH mass, disk size, radio
jet dimension, luminosity & distance.
Furthermore, variability time scale (i.e.,
viscous, thermal or dynamic time
scale) is also approximately microscale: taking much shorter time scale
to monitor a complete limit cycle of
variability, perhaps tens of years,
shorter than human lifetime, vs.
millions of years.
[Mirabel & Rodriguez (1988)]
Accretion and High Energy Radiation Processes in Relativistic Compact Objects
cosmic rays
Shock : TeV Hot Spot
Relativistic Jet (v~0.99c)
Synchrotron Self-Compton (SSC)
with boosting ⇒ ~TeV photons
Strong Magnetic Fields (≤1015G)
Synchrotron Radiation
Compton & inverse Compton
Ionization of
(107K)
Mass transfer
from companion
(thermally unstable)
Shock
Corona or RIAF ?
(109-1012K)
(>1011, >1014 km)
arournd ~10 & >106 M⊙
Jet
• Microquasars radiate photons over all EM wavebands, from radio to gamma-rays, and is
also a promising candidates for muon & neutrino sources, produced by almost all possible
astrophysical radiation processes.
• In addition to drastic spectral changes & timing with broad time scales, microquasars
show discrete ejection events detectable in the radio. However, the exact nature of the
ejected material and mechanism for such “microquasar phenomena” are yet to be
unraveled.
Microquasar Phenomena
Jet Events during Outburst in GRO J1655-40 (XRNV Sco 1994)
VLA 22 GHz
CGRO/BATSE 20-100kev
VLBA 1.6 GHz,
30.4 arcsec
VLA 1.49 GHz
50 days
VLA 1.49-22.5 GHz
Microquasars typically display superluminal jets, accompanied with months
to a year-long outburst (flare), recurring irregularly, every few to tens of
years (or even a century ?)
Unusual Frequent “Flares” in GRS 1915+105 & Cyg X-3
GRS 1915+105
Cygnus X-3
500 days
Unlike typical transients with recurrence
time of up to tens of years, GRS
1915+105 and Cyg X-3 are flaring as
frequent as ~ hrs to days, much more
chances for detection, and fluctuating
as short as millisecond. These are also
radio bright, enough to detect with KVN.
200 days
Unlike well-studied GRS 1915+105,
Cyg X-3 has been poorly explored,
although > 50 outbursts with
peaks > 1 Jy have been observed
since the 1st detection of 1972
“giant flare”, as high as 20 Jy.
Proposal:
Timing and
Multi-Frequency Spectra
Facility of simultaneous,
multi-frequency observation
is a unique property of KVN !
[Trushkin, RATAN website]
Spectral Evolution of Cyg X-3 and Simultaneous,
Multi-frequency Detection of KVN
April 1-13
April 17-May 8
Spectral slope is fastly evolved
from negative, flat to positive,
even within a week or two. The
cause for turnover is in dispute.
Spectral change in microquasars,
e.g., Cyg X-3 here, is very dramatic
& much faster time than that in
AGNs. The spectral evolution should
be studied together with more
complicated X-ray spectra.
Therefore, the study of time-evolving spectral
index through simultaneous, multi-frequency
observations with KVN will provide important clues
to solve the microquasar phenomena as a whole !
Timing & Imaging Jets
in Cyg X-3
Imaging Jets: KVN, VERA & Other VLBIs
VLBA+VLA
EVN
VERA
KVN?
(J.S. Kim’s talk)
+
# baselines:
4(4-1)/2=12
3(3-1)/2=3
JVN
KVN+VERA=?
VLBA
7(7-1)/2=24
KVN+EAVN=?
To study jet features of Cyg X-3, VERA itself is not enough, nor with KVN.
Therefore, observations of KVN-VERA, and other combinations of East Asia
VLBI facilities, are necessary in particular for imaging !
Microquasars as a Key Science for KVN:
Summary & Conclusion
(1)Imaging jets with KVN may not be possible; hence, the collaboration
with east asia VLBI facilities are demanding.
(2)KVN’s unique facility of the simultaneous, multi-frequency
observation is idealistic for studying dramatic and rapid change of
spectra, containing at least five evolutionary stages, together with the
correlation to more than 15 different X-ray states and QPOs.
(3)Timing, spectra and imaging of microquasars are very complicated,
and, in most cases, the physical origin of such “microquasar
phenomena” is in dispute, or even unsolved. Microquasars have
fingerprints different from a source to another, in spite of a handful
of similarities discovered. So, story of microquasars is never-ending !