Editing X-ray binary (section)

== Microquasar ==
[[Image:Ss433 art big.gif|250px|thumb|Artist's impression of the microquasar [[SS 433]].]]
A '''microquasar''' (or radio emitting X-ray binary) is the smaller cousin of a [[quasar]].  Microquasars are named after quasars, as they have some common characteristics: strong and variable radio emission, often resolvable as a pair of radio jets, and an [[accretion disk]] surrounding a [[compact object]] which is either a [[black hole]] or a [[neutron star]]. In quasars, the black hole is supermassive (millions of [[solar mass]]es); in microquasars, the mass of the compact object is only a few solar masses. In microquasars, the accreted mass comes from a normal star, and the accretion disk is very luminous in the optical and [[X-ray]] regions. Microquasars are sometimes called ''radio-jet X-ray binaries'' to distinguish them from other X-ray binaries. A part of the radio emission comes from [[relativistic jet]]s, often showing apparent [[superluminal motion]].<ref>{{Cite journal |last1=Mirabel |first1=I. F. |last2=Rodríguez |first2=L. F. |date=1994-09-01 |title=A superluminal source in the Galaxy |url=https://ui.adsabs.harvard.edu/abs/1994Natur.371...46M |journal=Nature |volume=371 |issue=6492 |pages=46–48 |doi=10.1038/371046a0 |bibcode=1994Natur.371...46M |s2cid=4347263 |issn=0028-0836}}</ref>

Microquasars are very important for the study of [[relativistic jet]]s. The jets are formed close to the compact object, and timescales near the compact object are proportional to the mass of the compact object. Therefore, ordinary quasars take centuries to go through variations a microquasar experiences in one day.

Noteworthy microquasars include [[SS 433]], in which atomic emission lines are visible from both jets; [[GRS 1915+105]], with an especially high jet velocity and the very bright [[Cygnus X-1]], detected up to the High Energy [[gamma rays]] (E > 60 MeV). Extremely high energies of particles emitting in the VHE band might be explained by several mechanisms of particle acceleration (see [[Fermi acceleration]] and [[Centrifugal mechanism of acceleration]]).