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A few binary systems display High Energy (100 MeV - 100 GeV) and/or Very High Energy (> 100 GeV) gamma-ray emission. These systems also display non-thermal radio emission that can be resolved with long-baseline radio interferometers, revealing the presence of outflows. It is expected that at very low frequencies the synchrotron radio emission covers larger angular scales than has been reported up to now. Here we present preliminary results of the first deep radio observations of the gamma-ray binary LS I +61 303 with LOFAR, which is sensitive to extended structures on arcsecond to arcminute scales.
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Gamma-ray binaries are a subclass of high-mass binary systems whose energy spectrum peaks at high energies (E$gtrsim$100 MeV) and extends to very high energies (E$gtrsim$100 GeV) $gamma$ rays. In this review we summarize properties of well-studied non-transient $gamma$-ray binaries as well as briefly discuss poorly known systems and transient systems hosting a microquasar. We discuss also theoretical models that have been used to describe spectral and timing characteristics of considered systems
Recent ground based and space telescopes that detect high energy photons from a few up to hundreds of gigaelectron volts (GeV) have opened a new window on the universe. However, because of the relatively poor angular resolution of these telescopes, a large fraction of the thousands of sources of gamma-rays observed remains unknown. Compact astrophysical objects are among those high energy sources, and in the Milky Way there is a particular class called Gamma-Ray Binaries.
We review the multiwavelength properties of the few known gamma-ray binaries, focusing on extended emission recently resolved with Chandra. We discuss the implications of these findings for the nature of compact objects and for physical processes operating in these systems.
Gamma-ray emitting binaries (GREBs) are complex systems. Its study became in the last years a major endeavour for the high-energy astrophysics community, both from an observational and a theoretical perspective. Whereas the accumulation of observation time for most Galactic gamma-ray sources is typically leading to highly accurate descriptions of their steady phenomenology, GREBs keep providing exceptions to the rule either through long-term monitoring of known systems or in the discovery of new sources of this class. Moreover, many GREBs have been identified as powerful radio, optical and X-ray emitters, and may significantly contribute as well to the Galactic cosmic-ray sea. Their understanding implies, therefore, solving a puzzle in a broad-band and multi-messenger context. In these proceedings we will summarise our current understanding of GREBs, emphasising the most relevant observational results and reviewing a number of controversial properties.
X-ray binaries stand as the brightest X-ray sources in the galaxy, showing both variable X-ray emission and extreme flares. Some of these systems have been recently discovered to be TeV gamma-ray emitters, with the high energy emission posited as resulting from particle acceleration in relativistic jets or from shocks between pulsar and stellar winds. VERITAS, an array of four 12m imaging atmospheric Cherenkov telescopes has accrued more than 100 hours of observation time on X-ray binaries. Here we present the results of observations on 3A 1954+319, XTE J2012+381, 1A 0620-00, EXO 2030+375, KS 1947+300, SS 433, Cygnus X-1 and Cygnus X-3.
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