2009 East Asia VLBI Workshop (2009 March 18-20, Seoul)

Multi-frequency Timing and Rapid Spectral Evolution of MicroquasarsSoon-Wook Kim Astrophysics Research Group,International Center for Astrophysics, Korea Astronomy and Space Science Institute

What is Microquasar ?NS(~1.4M) / BH (>3.2M) Relativistic Jets: 0.99c perpendicular to the disk planeaccretion disk(, , , , , ,)mass accretion 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 multi-component jetsCompanion Star108-1013 km1011-1012cm>1038(M/M)erg/s=LEDDTth~1012K1016-1019 gram of Hydrogen per second

Quasar vs. Micro-Quasar[Mirabel & Rodriguez (1988)] 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 micro-scale: 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.

Accretion and High Energy Radiation Processes in Relativistic Compact ObjectsSynchrotron Self-Compton (SSC) with boosting ~TeV photonsShockRelativistic Jet (v~0.99c)JetCorona or RIAF ? (109-1012K)(107K)(>1011, >1014 km) arournd ~10 & >106 MStrong Magnetic Fields (1015G)Shock : TeV Hot SpotSynchrotron RadiationIonization ofCompton & inverse Comptoncosmic raysMass transfer from companion(thermally unstable) 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 1.49-22.5 GHzVLA 22 GHzVLBA 1.6 GHz, 30.4 arcsecVLA 1.49 GHzCGRO/BATSE 20-100kev50 daysMicroquasars 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-3Unlike 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.Cygnus X-3500 daysUnlike 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.GRS 1915+105200 days

Proposal: Timing and Multi-Frequency SpectraFacility of simultaneous, multi-frequency observation is a unique property of KVN !

Spectral Evolution of Cyg X-3 and Simultaneous, Multi-frequency Detection of KVN[Trushkin, RATAN website]April 1-13April 17-May 8Spectral 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.Spectral slope is fastly evolved from negative, flat to positive, even within a week or two. The cause for turnover is in dispute.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 Jetsin Cyg X-3

Imaging Jets: KVN, VERA & Other VLBIsVLBA+VLAVLBAEVNJVNVERA (J.S. Kims talk)KVN?KVN+VERA=?# baselines: 4(4-1)/2=127(7-1)/2=243(3-1)/2=3+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 !KVN+EAVN=?

Microquasars as a Key Science for KVN:Summary & ConclusionImaging jets with KVN may not be possible; hence, the collaboration with east asia VLBI facilities are demanding.KVNs 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.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 !