Accretion is a common physical process in the Universe, playing a crucial role in galactic and extra-galactic astronomy. Accretion can be studied in detail by looking at black holes and neutron stars in low-mass X-ray binaries (LMXBs), where changes occur on timescales favorable for human studies. X-ray observations of these systems during the last decade have revealed that accretion proceeds via various accretion states. Optical and near-infrared (OIR) emission was thought to originate from thermal reprocessing of the X-ray emission by the accretion disc. Recent spectral and timing multiwavelength studies are, however, challenging this classical scenario. The new studies show that a relativistic outflow in the form of a jet plays an important role in the accretion process. Key to these new works are fast, high signal-to-noise OIR observations. However, these new studies are not systematic in the sense that only a few accretion states and sources have been covered. The proposed project would provide the systematic study by determining the origin of the multiwavelength emission via a spectral and fast variability study covering all the accretion states observed in both neutron stars and black holes. To this end I have gathered an extensive database of simultaneous, high time-resolution X-ray, optical and near-infrared observations, and the host is a leading institute in new radio facilities like LOFAR and MeerKAT, which will provide guaranteed data to the project.
Both spectral and timing analysis tools will be applied to the data set. For the interpretation I will use two numerical codes that will allow me to interpret the simultaneous high time resolution X-ray and OIR data.
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