(News & views on the paper by Lü et al. RAA, 2015, vol.15, 617-622)
News and Views on "Extending the correlation of LR - LX to gamma-ray bursts"
(School of Astronomy and Space Science, Nanjing University, Nanjing 210093, China)
Understanding phenomena associated with astrophysical systems that occur on different scales is important for finding common physical mechanisms that operate in them. The correlation between the radio luminosity (LR) and X-ray luminosity (LX) was firstly found in active cool stars (Güdel & Benz 1993). Following studies showed that M dwarfs, solar flares, late-type stars (Benz & Güdel 1994), Galactic black holes (Gallo et al. 2003) and active galactic nuclei (Merloni et al. 2003; Falcke et al. 2004) also have similar distributions of radio and X-ray luminosity.
However, the physical origin of this correlation and its relationship with the physical properties of the source are mysterious. There are at least two possible explanations for the origin of this correlation in black hole systems. The first explanation is that the radio and X-ray emission from sources that have a black hole is attributed to synchrotron emission from a jet in the jet-dominant state. Because the radio and X-rays emissions are powered by the jet, a tight correlation between them could be expected. On the other hand, X-ray emission may originate from the accretion flow, but the radio emission is produced by the relativistic jet. In addition, the accretion flow and jet are strongly coupled, so that the radio and X-ray luminosity are correlated.
Lü et al. (2015) extend the LR-LX correlation to gamma-ray bursts (GRBs), which are the most energetic explosions in the Universe, and find that GRBs also follow the same LR-LX correlation. Although these astrophysical phenomena occur at different scales, they still have common features that exhibit similar properties. Black hole sources may have essentially the same physical origin. This work can inspire people to search for similar properties that occur in astrophysical phenomena at different scales.
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