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Many X-ray binaries remain undetected in the mid-infrared, a regime where emission from their compact jets is likely to dominate. Here, we report the detection of the black hole binary GX 339-4 with the Wide-field Infrared Survey Explorer (WISE) during a very bright, hard accretion state in 2010. Combined with a rich contemporaneous multiwavelength dataset, clear spectral curvature is found in the infrared, associated with the peak flux density expected from the compact jet. An optically-thin slope of ~-0.7 and a jet radiative power of >6x10^{35} erg/s (d/8 kpc)^2 are measured. A ~24 h WISE light curve shows dramatic variations in mid-infrared spectral slope on timescales at least as short as the satellite orbital period ~95 mins. There is also significant change during one pair of observations spaced by only 11 s. These variations imply that the spectral break associated with the transition from self-absorbed to optically-thin jet synchrotron radiation must be varying across the full wavelength range of ~3-22 microns that WISE is sensitive to, and more. Based on four-band simultaneous mid-infrared detections, the break lies at ~5x10^{13} Hz in at least two epochs of observation, consistent with a magnetic field B~1.5x10^4 G assuming a single-zone synchrotron emission region. The observed variability implies that either B, or the size of the acceleration zone above the jet base, are being modulated by factors of ~10 on relatively-short timescales.
Galactic black hole binaries produce powerful outflows with emit over almost the entire electromagnetic spectrum. Here, we report the first detection with the Herschel observatory of a variable far-infrared source associated with the compact jets of
Black-hole transients exhibit a correlation between the time lag of hard photons with respect to softer ones and the photon index of the hard X-ray power law. The correlation is not very tight and therefore it is necessary to examine it source by sou
Type-B quasi periodic oscillations (QPOs) in black-hole X-ray binaries (BHXRBs) are a class of low-frequency QPOs that are observed in the soft intermediate state in the rising and the declining phases of an outburst. They are suspected to result fro
We analyze seven NICER and NuSTAR epochs of the black hole X-ray binary GX 339-4 in the hard state during its two most recent hard-only outbursts in 2017 and 2019. These observations cover the 1-100 keV unabsorbed luminosities between 0.3% and 2.1% o
We present results from the first multi-epoch X-ray/IR fast-photometry campaign on the black-hole transient GX 339--4, during its 2015 outburst decay. We studied the evolution of the power spectral densities finding strong differences between the two