The three basic ingredients - a spinning compact object , an accretion disc and a collimated relativistic jet - make microquasars a galactic scaled-down version of the radio-loud AGN .
That explains the large interest attributed to this new class of objects , which up to now consists of less than 20 members .
Microquasars belong to the much larger class of X-ray binary systems , where there exists a compact object together with its X-ray emitting accretion disc , but the relativistic jet is missing .
When does an X-ray binary system evolve into a microquasar ?
Ideal for studying such kind of a transition is the periodic microquasar LS I +61 ^ { \circ } 303 formed by a compact object accreting from the equatorial wind of a Be star and with more than one event of super-critical accretion and ejection along the eccentric orbit .
For ejections at periastron passage the relativistic electrons suffer severe inverse Compton losses by upscattering the UV photons of the Be star at high energy : At periastron passage Gamma-ray emission has been observed , whereas radio outbursts have never been observed in 20 years of radio flux monitoring .
For ejections displaced from periastron passage the losses are less severe and radio outbursts are observed .
The radio emission mapped on scales from a few AU to hundreds of AU shows a double-sided relativistic ( \beta = 0.6 c ) S-shaped jet , similar to the well-known precessing jet of \object SS 433 .