instabilities. From the comparison of the X-ray color-color diagrams of all observations available until then, they showed that all observations were consistent with this interpretation, with the exception of a few, whose character could not be accounted for. Additional spectral analysis has been presented by Markwardt, Swank & Taam (1999) and Muno, Morgan & Remillard (1999), who analyzed in detail the connection between QPOs and X-ray spectral distribution in GRS 1915+105.

Quasi-periodic variability in the radio and infrared bands has been discovered (Pooley 1995, Pooley & Fender 1997, Fender et al. 1997). Fender et al. (1997) suggested that these oscillations correspond to small ejections of material from the system. Indeed, these oscillations have been found to correlate with the disk-instability as observed in the X-ray band (Pooley & Fender 1997, Eikenberry et al. 1998, Mirabel et al. 1998, Fender & Pooley 1998). This strongly suggests that (some of) the matter from the inner disk is ejected in form of a jet throughout the instability phase.

GRS 1915+105 displays a bewildering variety of variability modes (see Greiner, Morgan & Remillard 1996; Belloni et al. 1997a,b; Chen, Swank & Taam 1997; Nayakshin, Rappaport & Melia 1999, Muno et al. 1999). In this 