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Recently, white dwarf stars have found a new use in the fundamental physics community. Many prospective theories of the fundamental interactions of Nature allow traditional constants, like the fine structure constant $\alpha$, to vary in…
This paper reviews the physics of stars, the type, structure, evolution and stability. Simple thermodynamics and statistical mechanics are used to show the inner working of white dwarf and neutron stars. The major concentration of the paper…
The mean white dwarf (WD) mass in the Galactic bulge cataclysmic variables (CVs) was measured by applying the the shock temperature-WD mass correlation of magnetic cataclysmic variables (mCVs) to the Galactic Bulge X-ray Emission (GBXE)…
The spectral and photometric studies of the cataclysmic variable Gaia 19cwm (or ZTF19aamkwxk) have been performed. Based on the analysis of long-term variability, it is concluded that the object belongs to WZ Sge type stars. The light…
Over the last decade or so, we have been developing the possible existence of highly magnetized white dwarfs with analytical stellar structure models. While the primary aim was to explain the nature of the peculiar overluminous type Ia…
Precise measurements of neutron star observables (such as mass and radius) allow one to constrain the equations of state for supranuclear matter and develop a stronger understanding of nuclear physics. The Neutron star Interior Composition…
Neutron star$-$white dwarf (NSWD) binaries are one of the most abundant sources of gravitational waves (GW) in the Milky Way. These GW sources are the evolutionary products of primordial binaries that experienced many processes of binary…
Recent theoretical and observational progress has substantially improved the definition of the lower main sequence and established a new basis for a comparison of main sequence stars and the secondaries in CVs. The evolutionary sequences of…
We compare the distribution in position and velocity of nearby stars from the Gaia DR2 radial velocity sample with predictions of current theories for spirals in disc galaxies. Although the rich substructure in velocity space contains the…
We estimated the contribution of binary systems to the velocity dispersion inside OB-associations derived from Gaia DR2 proper motions. The maximum contribution to the velocity dispersion is given by the systems with the period of…
The origin of ultra-wide massive binaries (orbital separations $10^3-2\times 10^5$~AU) and their properties are not well characterized nor understood. Here we use the second Gaia data release to search for wide astrometric companions to…
We present a brief overview of the theory of stellar winds with a strong emphasis on the radiation-driven outflows from massive stars. The resulting implications for the evolution and fate of massive stars are also discussed. Furthermore,…
We analyze the coupling between the internal degrees of freedom of neutron stars in a close binary, and the stars' orbital motion. Our analysis is based on the method of matched asymptotic expansions and is valid to all orders in the…
Accretion discs are fundamental to much of astronomy. They can occur around stars both young and old, around compact objects they provide a window into the extremes of physics, and around supermassive black holes in galaxy centres they…
We use the results from recent computations of updated non-linear convective pulsating models to constrain the distance modulus of Galactic globular clusters through the observed periods of first overtone RRc pulsators. The resulting…
Precise measurements of neutron star (NS) velocities provide critical clues to the supernova physics and evolution of binary systems. Based on Gaia Data Release 2 (DR2), we selected a sample of 24 young (<3 Myr) pulsars with precise…
Mass transfer from an evolved donor star to its binary companion is a standard feature of stellar evolution in binaries. In wide binaries, the companion star captures some of the mass ejected in a wind by the primary star. The captured…
The ESA Gaia mission provides a unique time-domain survey for more than 1.6 billion sources with G ~ 21 mag. We showcase stellar variability across the Galactic colour-absolute magnitude diagram (CaMD), focusing on pulsating, eruptive, and…
Binary stars play a crucial role in our understanding of the formation and evolution of star clusters and their stellar populations. We use Gaia Data Release 3 to homogeneously analyze 78 Galactic open clusters and the unresolved binary…
Several recent studies have shown that very wide binary stars can potentially provide an interesting test for modified-gravity theories which attempt to emulate dark matter; these systems should be almost Newtonian according to standard…