Clues from microquasars to the origin of radio-loudness of quasars
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We analysed the long-term variability of four microquasars (GRS 1915+105, Cyg X-1, Cyg X-3, and Sco X-1) in radio and X rays. The results of our analysis indicate the existence of two distinct modes of energy output, which we refer to as the `coupled' mode and the `flaring' mode. The coupled mode is responsible for mildly fluctuating, flat-spectrum radio emission, coupled with the X-ray emission; the flaring mode produces powerful, steep-spectrum radio flares, with no significant counterpart in X rays. We find that the fraction of time spent by a typical microquasar in the flaring mode is similar to the fraction of quasars that are radio-loud. This is consistent with the hypothesis that radio-loudness of quasars is a function of the epoch at which the source is observed.
5 pages, 2 figures. Accepted for publication in the proceedings of the "VI Microquasar Workshop: Microquasars and Beyond" (September 18-22, 2006 Como, Italy). Available from pos.sissa.it
5 pages, 2 figures. Accepted for publication in the proceedings of the "VI Microquasar Workshop: Microquasars and Beyond" (September 18-22, 2006 Como, Italy). Available from pos.sissa.it