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Science 23 June 2006:
Vol. 312. no. 5781, p. 1712
DOI: 10.1126/science.312.5781.1712b
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Microquasars are binary star systems with twin radio-emitting jets that resemble those of quasars, albeit on smaller scales. Radiation from these jets arises from particles moving at relativistic speeds in high magnetic fields, but little is known about the jets' composition or how they are formed. Albert et al. (p. 1771, published online 18 May; see the Perspective by Mirabel) have used the Major Atmospheric Gamma-ray Imaging Cherenkov (MAGIC) telescope to monitor monthly variations caused by very high energy gamma rays (>100 gigaelectron volts) from a microquasar. A comparison of the phases of the gamma-ray variability with those of radio waves and x-rays shows that the gamma-ray emission peak does not coincide with the time when the two stars are closest to one another, which suggests that there is a strong orbital modulation of the emission processes. Further analysis of the emission favors an underlying leptonic over a hadronic process.




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