Fundamental and Applied X-ray Astrophysics

• We have enhanced a method of modeling atmospheres of neutron stars heated by streams of fast ions. The model gives an opportunity to increase precision of measurements of masses and radii of neutron stars.
• We have enhanced a method of modeling spectrums of radiation of fast-spinning neutron stars. We have modified a method of determining fundamental parameters of neutron stars by spectral evolution of thermonuclear flashes at their surfaces at the glow decreases stage. A new method has been developed for direct approximation of obtained spectrums with models of neutron star atmospheres and a procedure for interpolation of model spectrums.
• A method for analysis of fast variability of X-ray pulsars has been proposed and tested. The technique allows to use qualities of ensembles of pulses and to determine the phases in which nonstochastic variability is observed.
• A software package has developed for complex simultaneous analysis of shared characteristics (cross-correlations, power spectrums, coherence, temporal delays) from data coming from several X-ray channels.
• Several dozens of pulsars have been selected that can be observed in the X-ray part of the electromagnetic spectrum. Using data from the NICER observatory we have conducted analysis of eight «candidates» that are optimally suited for usage as reference sources for X-ray navigation systems.
• Requirements on X-ray detectors for research of neutron stars and navigation using X-ray pulsars have been formulated. Main parameters of such sensors have been determined.
• Our researchers formulated and investigated feasibility of requirements on thermal regime systems of X-ray detectors designed for researching neutron stars and navigation systems using X-ray pulsars installed on spacecraft functioning in Low Earth Orbit and highly elliptical orbits.
• A topology of main IP blocks for an application-specific integrated circuit (ASIC) comprising the spectrometric route of a future X-ray detector. We have optimized the topology of IP blocks and assembled them into a single SDDASIC3 circuit. Compliance of the topology with rules of design has been checked and a project of the ASIC has been prepared for production.
• A draft of the structure of an X-ray radiation detector based on a matrix of silicon drift detectors has been developed. It uses the developed ASIC and is aimed at solving fundamental and applied problems of astrophysics

Collaborations:

University of Tübingen (Germany), Leiden University (the Netherlands), University of Turku (Finland), International Space Science Institute (Switzerland), Stockholm University (Sweden), Xiangtan University (China PR): joint research.