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: ≤0.99cperpendicular to the disk plane What is Microquasar ? >1038(M/M⊙)erg/s=LEDD • 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 jets NS(~1.4M⊙) / BH (>3.2M⊙) Tth~1012K accretion disk 1011-1012cm 108-1013 km mass accretion Companion Star 1016-1019 gram of Hydrogen per second (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 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. [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 Mass transfer from companion Ionization of (107K) (thermally unstable) (>1011, >1014 km) arournd ~10 & >106 M⊙ Corona or RIAF ? (109-1012K) Shock 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.
Jet Events duringOutburst in GRO J1655-40 (XRNV Sco 1994) CGRO/BATSE 20-100kev VLA 22 GHz VLBA 1.6 GHz, 30.4 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 Spectral slope is fastly evolved from negative, flat to positive, even within a week or two. The cause for turnover is in dispute. April 17-May 8 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 !
Imaging Jets: KVN, VERA & Other VLBIs EVN VLBA+VLA VERA (J.S. Kim’s talk) KVN? + # baselines: 4(4-1)/2=12 3(3-1)/2=3 JVN KVN+VERA=? 7(7-1)/2=24 VLBA 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 • Imaging jets with KVN may not be possible; hence, the collaboration with east asia VLBI facilities are demanding. • 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. • 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 !