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We present synthetic Doppler maps of gaseous flows in binary IP Peg based on the results of 3D gasdynamical simulations. Using of gasdynamical calculations alongside with the Doppler tomography technique permits us to identify the main features of the flow on the Doppler maps without solution of an ill-posed inverse problem. Comparison of synthetic tomograms with observations shows that in quiescence there are two zones of high emission: a shock wave on the edge of the stream from L1 caused by the interaction of the gas of circumbinary envelope and the stream, and the dense region in a apoastron of quasi-elliptical accretion disk. A single arm of the spiral shock and the stream itself give a minor input to the total brightness. During outburst the accretion disk dominates, and the most emitive regions are the two arms of the spiral shock.

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Photometric observations of the low-mass X-ray binary system A0620-00=V616 Mon are performed in the optical (unfiltered light, λ eff ≈ 6400Å) and the near-infrared J and K-bands. The mean system flux, the orbital light curve shape and the flickering amplitude dependences on wavelength are examined in the λλ6400 − 22000Å range for two activity stages of the system which remains in quiescence.In 2015-16 the A0620-00 system was observed to be in passive stage (according to the terminology of Cantrell et al., 2008) exhibiting the regular orbital light curve with a relatively low flickering level.In less than 230 days in 2016-17 the system switched into active stage: its mean brightness increased by ∼ 0.2 − 0.3 mag in all the studied bands, the orbital light curve experienced drastic changes while the flickering amplitude increased more than twice both in the optical and in the infrared.The regular orbital light curves of A0620-00 were modelled within two frameworks, namely assuming existence of "cold" spots on the optical companion surface and without those. These models allow for a good fit of observed orbital light curves both in passive and in active stages. A close correlation between the luminosity of accretion disc, "hotline" and the flickering amplitude is established.The absolute fluxes having been calibrated and corrected for the interstellar extinction, the dependence of the mean square flickering amplitude (in fluxes) is computed as a function of wavelength in the λλ6400 − 22000Å range.In active stage, the observed flickering amplitude decreases as a function of wavelength over the whole studied range and may be adequately represented by a single dependence ∆F fl ∼ λ −2 which corresponds to the thermal free-free emission of optically thin high-temperature plasma.In passive stage, the ∆F fl value behaves like ∆F fl ∼ λ −4 in the short wavelength range of λλ6400 − 12500Å that corresponds to the thermal radiation of optically thick high-temperature plasma. In the long-wave domain λλ12500 − 22000Å the flickering amplitude dependence is flat: ∆F fl ∼ const which may imply existence of a synchrotron component of the relativistic jets emission.The ∆F fl dependence on the mean system flux in K-filter is shallower than corresponding relations for the filter J and for the optical range.The above mentioned flickering features let us propose that the mechanism responsible for flickering includes at least two components: thermal and, apparently, synchrotron, that agrees with the recent discovery of the variable linear polarization of the infrared system emission (Russell et al., 2016).