Disk-jet connection in microquasars and quasars

There are many X-ray sources (microquasars) in our Galaxy which show spectacular variability in radiation from radio wavelengths to hard X-ray wave bands. Superluminal motion is observed in these microquasars which are binary systems containing black holes as the compact objects. The microquasars offer a unique opportunity to study the connection between the observed radio jets and the accretion disks which is thought to be present in distant Quasars. Attempts have been made to relate the changes in X-ray emission from the accretion disk with the amount of matter ejected from the system. The oscillations observed in radio wave-bands appear to have a direct connection to the dips observed in X-rays. In microquasars, such as GRS 1915+105, superluminal radio-emitting features appear and propagate along the jet shortly after sudden decrease in X-ray flux (dips). Although there is some debate whether these oscillations observed in radio are associated with X-ray soft dips or hard dips, the connection between the radio jets and the accretion disk events (X-ray) are qualitatively established.

The connection in the X-ray emission and the superluminal radio jets was established for AGNs. Three years of monitoring the X-ray and radio emission of the galaxy 3C120, X-ray dips of durations about ~ 1 month appeared in the X-ray light curve along with the detection of superluminal knots in radio wave bands. It is observed that dips in X-ray emission are followed by ejections of bright superluminal radio blobs which is seen in Galactic microquasars. Hence, the model which explains the disk-jet connection in microquasars is in a position to explain that in distant quasars. It is, therefore, interesting to query all other properties of microquasars such as the presence of accretion disk, spectral behavior of the source during the dips which causes radio flares etc. in AGNs or quasars, for which multi wavelength observations are required. It is also useful to compare the timing and spectral properties of 3C120 with those in microquasars during the observed dips and non-dips in X-ray light curves and the associated radio properties.

We have conducted a large international multiwavelength campaign of GRS 1915+105 in 2005 October by taking the opportunity of the Suzaku (recently launched Japanese X-ray satellite) observation. Simultaneous observations were carried out with the Suzaku, INTEGRAL, RXTE, Swift, Spitzer, and ground observatories including the VLA, ATCA, Nancay, Ryle, RATAN, Subaru, ESO/NTT, and REM. During the campaign epoch GRS 1915+105 was found to be in a very active phase, showing dramatic ``oscillation'' in the X-ray light curve with an intense flux (1 to 3 Crab in the 2-10 keV band). A preliminary analysis of the Suzaku observation shows the variable nature of the iron K emission and absorption line features in the oscillation and stable states of the source. This simultaneous observation will provide enough information in understanding the the physics of disk-jet connection in the system which is a big mystery in astrophysics.

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