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In this paper, the implications of string Swampland criteria for a dark energy-dominated universe, where we have a deviation from the cold dark matter model, will be discussed. In particular, we have considered two models. One of them is one parameter model, while the second one has been crafted to reveal the dynamics in the deviation. The analysis has been obtained through the use of Gaussian processes (GPs) and H(z) expansion rate data (a 30-point sample deduced from a differential age method and a 10- point sample obtained from the radial BAO method). We learned that the tension with the Swampland criteria still will survive as in the cases of the models where dark matter is cold. In the analysis besides mentioned 40-point H(z) data, we used the latest values of H0 reported by the Planck and Hubble missions to reveal possible solutions for the H0 tension problem. Finally, the constraints on the neutrino generation number have been obtained revealing interesting results to be discussed yet. This and various related questions have been left to be discussed in forthcoming papers. [ABSTRACT FROM AUTHOR]

The chemical composition of the shell of a neutron star (SNS) at high temperatures and densities is discussed in this paper. A model for nucleosynthesis is proposed based on the approximation of nuclear statistical equilibrium (NSE). The dependence of the results of the nucleosynthesis on the parameters of the medium in a static approximation is studied. The results of this paper are qualitatively similar to earlier work by other authors. It is shown that the proposed model provides a fair description of the abundance of nuclei even in the static approximation. [ABSTRACT FROM AUTHOR]

This paper poses the problem of studying the role of large-scale electric currents propagating in the upper layers of the solar atmosphere in processes of coronal heating of the sun. For detecting and calculating the magnitude of the large-scale electric current, data on the distribution of the components of the magnetic field vector in the photosphere provided by the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO) were used. Photoheliograms of the sun's corona in the ultraviolet radiation channels at 131, 171, 193, and 211 Å provided by the Atmospheric Imaging Assembly (AIA/SDO) were used to estimate the temperature in the corona above active regions (ARs). The dynamics of the large-scale current and the average temperature in 9 regions with different levels of flare activity of the corona above the ARs have been studied and charts of the spatial distribution of the temperature in the corona above the ARs have been constructed. The following results have been obtained: 1. Heating of the coronal matter owing to ohmic dissipation of large-scale electric currents proceeds in a stationary regime. 2. The increase in the average temperature in the corona above an AR during solar flares to < log T ¯ > = 6.3 - 6.5 (2.0-3.2 MK) is caused, not only by heating of coronal structures by large-scale electric currents, but also by other processes at coronal elevations. 3. For the NOAA 11899 and 12494 regions a reduction in the average temperature of the corona to < log T ¯ > = 5.7 (0.5-0.6 MK) was observed with a simultaneous drop in the values of the large-scale electric current to zero. These observations indicate that the mechanism for heating of the corona by ohmic dissipation of electric currents is shut off at zero values (within the computational errors) of the large-scale electric current. 4. In the NOAA regions 12192 and 12371, when constructing charts of the temperature distribution in the corona outside flare events, hot structures with temperatures ≥ 10 MK were observed outside the flare events which appear to mark the location of the channel of a large-scale electric current at coronal elevations. For the NOAA region 12192 this assumption is confirmed by a numerical simulation carried out in 2016. [ABSTRACT FROM AUTHOR]

The well known results of the theory of classical gaseous polytropes are presented in the framework of an integral approach where the standard Lane-Emden differential equation for a spherically symmetric gravitating mass is examined via its equivalent in the form of a nonlinear integral Volterra equation of the 2nd kind. It is shown that the inverse Laplace transform of the Lane-Emden equation for polytropes with an index of n=5 (Schuster model) is a recurrence relation for Bessel functions of the first kind. The invariance of the nonlinear integral Volterra equation with respect to homological transformations is shown, as well as the possibility of obtaining singular solutions under certain conditions. It is also shown that for whole integral and half integral polytrope indices, this equation is equivalent to a multidimensional integral equation, and finding the expansion of the Emden function in a power series of the dimensionless distance ξ from the center of the polytrope is equivalent to finding the Neumann series and the iterated nuclei in the Fredholm theory. Approximations of the Emden functions in closed form and their applicability to various astrophysical objects will be presented and discussed in the second part of this paper. Polytropes of other geometries and dimensionalities are not considered here. [ABSTRACT FROM AUTHOR]

Published data from 25 papers published between 1995 and 2017 are used to find the effective temperatures and surface acceleration of gravity for 100 RR Lyrae variables in the galactic field with known chemical composition. The atmospheric parameters of almost half the stars in our list were determined in two or more papers. The mean-weighted values of the parameters are calculated for these stars. The values of Teff and logg for almost all the stars studied here lie within the theoretically calculated range where highly evolved stars turn out to be variable. The convergence of the various determinations of the corresponding parameters is analyzed. It is concluded that the values of the effective temperatures and acceleration of gravity for these RR Lyrae variables are highly reliable. [ABSTRACT FROM AUTHOR]

This paper studies the motion of a light signal and a test particle in the field of an infinite flat slab in terms of the general theory of relativity. The two cases of an external solution for a gravitational field in a vacuum corresponding to Rindler and Taub metrics are examined. The time of the motion and the path traveled by a particle before it stops are determined. It is shown that in the Taub geometry, as opposed to a light signal, a material particle does not reach a singularity. The minimum distance from the singularity is determined as a function of the particle energy. Results in terms of the special theory of relativity are given for comparison. [ABSTRACT FROM AUTHOR]

Galaxies' spectral energy distribution has been explored through the use of spectral synthesis codes, and these techniques have been essential in identifying many aspects of the current galaxy evolution model. Most of the spectral synthesis codes that have been developed so far are solely stellar and assume a negligible nebular contribution to the overall continuum. FADO (Fitting Analysis using Differential Evolution Optimisation) is the first spectral synthesis code to fit self-consistently stellar and nebular components. Diagnostic diagrams are powerful tools for classifying galaxies based on the emission line ratio of collisionally excited lines such as [OIII] λ 5007, [NII] λ 6584, [SII] λ 6716, 6731, [OI] λ 6300, and the Balmer recombination lines such as Hα, Hβ. This paper explores the impact of including nebular components on diagnostic diagrams. We investigated the results of the application of FADO to the Sloan Digital Sky Survey Data Release 8 using the data analysed by MPA-JHU, the Max Planck Institute for Astrophysics, and Johns Hopkins University. We found that in all diagnostic diagrams, the fluxes for FADO are higher than those for MPA-JHU; the difference is significant compared to the error in the flux measurement. FADO overestimates the flux ratio of all three diagnostic diagrams over MPA-JHU, but the overestimation is comparable with the line flux ratio errors. The results indicate that the inclusion of a nebular continuum is very important when fitting the spectral energy distribution as it increases the fluxes of all galaxies. However, there is a mild impact from the inclusion of nebular component analysis in the diagnostic diagrams used to classify the ionisation state of galaxies' interstellar medium. [ABSTRACT FROM AUTHOR]

In the present paper, we obtained the first orbital solution for the newly discovered W UMa systems: GSC 3983-0544 and GSC 4502-1040. We used the most recent version of the Wilson-Devinney code to model the light curves of the two systems. The spectral type of the components of the two systems was adopted and the accepted solutions revealed some absolute parameters, which enable us to draw a preliminary picture of their evolutionary status. [ABSTRACT FROM AUTHOR]

MRK 421 is a giant elliptical galaxy in the Ursa Major constellation whose core has all the properties of a BL Lac object. It manifests a high activity and variability from the radio to gamma-ray ranges on time scales from a few hours to more than 10 years. MRK 421 has a large companion— a spiral, probably, also active galaxy (MRK 421-5). This paper presents the results of an analysis of observations (in the V, R, and I bands) as part of a joint Latvian-Ukrainian project for study of the variability of bright AGN. In addition, the light curves of MRK 421 from the AAVSO data base (American Association of Variable Star Observers) are analyzed to confirm the results of periodogram analysis. Ultimately, over the time interval studied here, MRK 421 is suspected of having a cyclical variability with a characteristic time in the range of 9.3-13.4 days determined by two different methods (approximation of the data by sinusoids and the CLEANest method), which is confirmed by an analysis of longer observations of MRK 421 in the V band (with AAVSO data). The longer variability of MRK 421 was also analyzed. It was found that in the V, R, and I light curves from AAVSO the maxima of the LS-periodograms correspond to periods of 1.6-1.7 years. This is close to earlier results from an analysis of historical light curves of MRK 421 obtained by other authors. The AAVSO data also indicate the presence in MRK 421 of a longer cycle of brightness variation with a characteristic time of 20-30 years. [ABSTRACT FROM AUTHOR]

The discovery of γ - ray emitting Seyfert galaxies has opened a new unified scheme of active galactic nuclei (AGN) in which jetted Seyfert galaxies are viewed as young counterparts of radio loud AGN. In this paper, we investigate the relationship between gamma-ray (γ - ray) properties of jetted Seyfert galaxies and those of traditionally radio galaxies, radio quasars and BL Lac objects. Results show that jetted Seyfert galaxies appear as low luminosity tail of the radio loud AGNs on the luminosity redshift (Lγ – z) plane, indicating an evolutionary link between them. Nevertheless, narrow-line Seyfert galaxies (NLS1s) do not share similar characteristics with Seyfert galaxies as they possess higher luminosities and redshift than Seyfert galaxies, suggestive that NLS1s are more evolved sources. Analyses of γ – ray and radio core-dominance show that for each subclass of jetted AGN, the beaming angle is wider for radio than for γ - ray emissions. While Seyferts and radio galaxies, on average, have similar low inclination to the line of sight, NLS1 objects have orientations similar to quasars and BL Lacs. There is a significant correlation (r ~ 0.7) between the γ - ray core dominance and γ - ray luminosity. The results are consistent with the revised unification scheme and suggests that NLS1s are highly beamed sources whose parent populations can be found among the regular Seyferts and/or radio galaxies [ABSTRACT FROM AUTHOR]

In this paper, we have investigated the Bianchi-type V cosmological model which is spatially homogeneous and anisotropic in presence of bulk viscous fluid containing one-dimensional cosmic string. We have obtained the exact solutions of highly non-linear differential field equations considering the power-law volumetric expansion of the universe and f (T) = T formalism. Some physical and kinematical properties of the constructed model have been discussed and presented graphically and it is interesting to note that the resultant model resembles the recent observational data. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to study the Kaluza-Klein universe in the context of the f (R, T) gravity theory using magnetized strange quark matter (MSQM). To obtain exact solutions of field equations, we assume two types of volumetric expansion: power law and exponential law volumetric expansions. The violation of energy conditions has been studied. The physical and geometrical properties of the examined model have also been investigated thoroughly. [ABSTRACT FROM AUTHOR]

Kantowski-Sachs perfect fluid cosmological model is explored in modified gravity with functional form f (R, T) = f1(R) + f2 (T) where R is Ricci scalar and T is the trace of energymomentum tensor. With this functional form, three different cases have been formulated, namely negative and positive powers of curvature, logarithmic curvature and exponential curvature given by f1 (R) = R + γ R2 – μ4 / R, f1(R) = R+ v ln(τR) and f1(R) = R+ κe–ιR respectively, and for all these three cases, f2 (T) = λT, here γ,λ,μ,v,τ,κ and ι are constants. While solving the field equations, two constraints i) Expansion scalar is proportional to shear scalar ii) Hyperbolic scale factor are used. By using these conditions the required optimum solutions are obtained. The physical parameters are calculated and geometrical parameters of three cases are analysed against redshift z with the help of pictorial representation. In the context of f (R, T) gravity energy conditions are discussed with the help of pressure and energy density. If strong energy condition is positive the gravity should be attractive but in our model it is negative. It means that cosmic acceleration is due to antigravity, whereas NEC and DEC are fulfilled. The perturbation technique is used to test the stability of the background solutions of the obtained models. The inferences obtained from this paper are in persistent with the present cosmological observations and the model represents an accelerating universe. [ABSTRACT FROM AUTHOR]

In the blazar catalog BZCAT the objects are divided into 4 types: BZB, BZQ, BZG, and BZU. In this paper BZG objects are studied in order to determine their physical nature. Of the 274 BZG objects, 150 have optical spectra in the SDSS spectroscopic catalog, for which a detailed spectral classification has been carried out. A radio study showed that these objects mostly (69%) have a flat radio spectrum with a spectral index less than ±0.5. Quasars predominate among these kinds of radio spectra. However, with increasing distance, on the average the radio spectrum becomes steeper. [ABSTRACT FROM AUTHOR]

In the present paper, we report the photometric and spectroscopic observations of the pulsating star BL Cam obtained by the 1.88 m telescope at the Kottamia astronomical observatory (KAO). Fourier analysis of the light curves indicates one frequency, 25.14427 c/d, with harmonics 51.112 c/d, 33.388 c/d, and 17.72464 c/d. The frequency of 31-32 c/d reported in the literature is not detected in our data except for one close to 33.3882934 c/d. A total of 55 new times of maximum light have been presented. A new value of (1/P) dP/dt is estimated using the O-C diagram based on all newly obtained times of maximum light combined with those taken from the literature, assuming the periods are decreasing and changing smoothly. Using model atmosphere analysis, we computed the effective temperature and surface gravity as Teff = 7625 ± 300 K and logg = 4.30 ± 0.37. The bolometric magnitude Mbol = 2.335, radius R = 1.69 R⨀, luminosity L = 0.957 L⨀, the mass M = 1.68M⨀, and pulsation constant Q = 0.025 days. Locations of the star on the M-R and M-L diagrams indicate that it is close to the ZAMS track and is an unevolved star. [ABSTRACT FROM AUTHOR]

Simple analytic formulas are obtained for the equatorial radius and relative rotation velocity of a star as functions of its absolute and relative angular momentum as a Huygens-Roche figure. The results are compared with numerical simulations of the structure of rotating stars and it is shown that the analytic model considered here is sufficient for describing the corresponding parameters. [ABSTRACT FROM AUTHOR]

This paper analyzes spectral observations of spicules in the helium D3 line obtained at the Abastumani Observatory (Georgia).with a 53-cm eclipse-free coronagraph. It is concluded that the changes in the Doppler (radial) velocities and half-widths of the D-3 lines are in antiphase. The maxima of the periods of the oscillations of the Doppler velocities coincide with the minima of the oscillations of the half-width of D3. [ABSTRACT FROM AUTHOR]

In this paper, we have studied Friedmann-Robertson-Walker space-time in the presence of domain walls in the framework of f(G) theory of gravitation. We propose the generalization of linearly varying deceleration parameter. It is observed that the universe is accelerating and expanding. The values of state finder parameters are close to ΛCDM model. Some physical parameters of the obtained models are discussed in detail. [ABSTRACT FROM AUTHOR]

The orbits of visual binary systems still attract the interest of many working groups in astronomy. These orbits are the most important and reliable sources of stellar masses. In the present paper, we computed the orbits and dynamical masses of some visual binaries using an independent code. We used the Kowalsky method to compute the geometrical elements, while the dynamical elements (the orbital period and the time of periastron passage) were computed by implementing the double areal constant. We used the developed code to calculate the orbits for four visual binaries: WDS J02262+3428, WDS J14310-0548, WDS J17466-0354, and WDS J12422+2622. We introduce a new orbit for the neglected visual binary WDS J17466-0354 and modified the orbits for the remaining three binaries. Using Gaia DR2 parallaxes, we computed the total and individual dynamical masses of the systems. Comparing the adopted masses with those derived from the mass-spectral type relation revealed good agreement. [ABSTRACT FROM AUTHOR]

The mass spectra of astronomical objects of various kinds are compared: cosmic dust, asteroids, planets, stars, star clusters, galaxies, and galactic clusters. The authors have previously noted a similarity in the (initial) mass functions for relatively massive objects (stars, galaxies, galactic clusters). In this paper the range of masses of astronomical objects is extended to the limit and covers roughly 68 orders of magnitude. It is confirmed that the initial mass spectra of objects in ensembles formed by fragmentation (a fast process) may, in a first approximation in a statistically significant range be represented by a basis (reference) function dN / dM ∞ M-2, where dN is the number of objects in a range [M, M+dM] of masses. The significance of this function is the probability density of formation of objects, which total mass in a range [d ln M] of masses is independent of the mass M or, in other words, reduces to the absence of a distinct mass scale. The physical reasons determining the deviation of the initial mass functions from the reference function are discussed briefly. It is noted that the mass spectra in ensembles of objects formed by mergers (coagulation in the case of dust), i.e., in a relatively slow evolutionary process, can also be of a form close a reference function. The main reason for this universality lies in the random character of the processes of formation and evolution of these ensembles of astronomical objects. [ABSTRACT FROM AUTHOR]

In this paper, a broad examination of the N-S asymmetry of daily sunspot numbers during the period January 1992 to March 2020 has been performed, examining its statistical significance and looking for the short term periodicity of daily sunspot numbers using the Fast Fourier Transform (FFT) during solar cycle 22 (1 January 1986 to 27 August 1996), cycle 23 (28 August 1996 to 10 December 2008) and cycle 24 (11 December 2008 to 31 March 2020). The present study indicates that sunspot number activity dominates in the southern hemisphere during the solar cycles 22 and 23, while during the solar cycle 24, the sunspot number becomes dominant in the northern hemisphere. It is also revealed that the magnitude of sunspot number activity for solar cycle 23 is more prominent in both the northern and southern hemispheres than in solar cycles 22 and 24. The power spectrum of daily sunspot numbers shows several significant periodicities in a wide range between 26 days and 83 days. We discuss the possible explanations of the observed periodicities and north-south asymmetry of the daily sunspot number in light of previous results and existing techniques. [ABSTRACT FROM AUTHOR]

The masses of supermassive black holes and the (parent) galaxies containing them are related approximately by MBH ~ 0.002 M*. This indicates their close interaction during the process of their joint evolution. However, the large spread in the observed masses around this relation and, in particular, the considerably larger value, by an order of magnitude, of this mass ratio in the early universe (z > 6) observed in recent years indicates that the character of their interaction may vary significantly as they evolve. This circumstance requires a reliable observational determination of the ratios of the masses of the black holes, stellar populations, and interstellar gas in galaxies at large redshifts when these cannot be measured directly. In this paper a simple description illustrating this possibility is proposed. The features of the spectra of galaxies containing growing black holes and a forming stellar population are examined. A set of models with variations in the masses of the black hole, stellar population, and interstellar gas is used to illustrate the feasibility of finding the ratio of their masses using multiwavelength spectra: far infrared, submillimeter, and X-ray. [ABSTRACT FROM AUTHOR]

In this paper, two efficient computational algorithms based on Rational and Exponential Bessel (RB and EB) functions are compared to solve several well-known classes of nonlinear Lane-Emden type models. The problems, which are define in some models of non-Newtonian fluid mechanics and mathematical physics, are nonlinear ordinary differential equations of second-order over the semi-infinite interval and have a singularity at x = 0. The nonlinear Lane-Emden equations are converted to a sequence of linear differential equations by utilizing the quasilinearization method (QLM), and then these linear equations are solved by RB and EB collocation methods. Afterwards, the obtained results are compared with the solution of other methods to demonstrate the efficiency and applicability of the proposed methods. [ABSTRACT FROM AUTHOR]

In the second part of this paper we derive the final formulas for calculating the azimuthal average of the frequency redistribution functions (RF), for direction, and polarization for Compton scattering in plane stationary media. The azimuthal averages of the most singular term of the RF are expressed in terms of elliptical integrals of the first kind. Examples of averaging are given. [ABSTRACT FROM AUTHOR]

The possibility of invoking a fractional Poisson distribution (fractional Poisson process) in statistical studies of flashing objects is discussed. [ABSTRACT FROM AUTHOR]

Some controversial results that arise in the problem of the scattering of gravitational objects are analyzed in this paper. First, the approach leading to possible use of the approximation of pairwise (binary) collisions in the theory of scattering in plasmas and in gravitational systems is examined. It is stressed that this possibility is not a consequence of neglecting long-range (distant) collisions. Next, results obtained for the number of scattering events of a test particle in an infinite gravitational medium with a fixed velocity change are discussed. The conclusion that the function describing the number of particle collisions is divergent is shown to be incorrect. This is because the finite time duration of collisions with large impact parameters is neglected. In concluding, we show that the previously proposed variant of a modified Holtsmark distribution is erroneous. [ABSTRACT FROM AUTHOR]

The problem of asynchronous rotation of massive stars in close binary systems is investigated in this paper. A massive star with twice the sun's mass, a convective core, and an external radiative transfer zone (envelope) is examined. The model takes into account the influence of the companion on the star. It is assumed that the tidal flow is dissipated through radiative viscosity. The asynchrony of massive stars is explained by pseudosynchronization and differential rotation of the star. [ABSTRACT FROM AUTHOR]

In this paper, we investigated the thermodynamic properties of strange quark matter using the Nambu-Jona-Lasinio (NJL) model at finite temperatures where we considered the dynamical mass as the effective interaction between quarks. By considering the pressure of strange quark matter (SQM) at finite temperatures, we showed that the equation of state of this system gets stiffer with increasing temperature. In addition, we investigated the energy conditions and stability of the equation of state and showed that the equation of state of SQM satisfies the conditions of stability. Finally, we computed the structure properties of hot strange quark stars (SQS) including the gravitational mass, radius, Schwarzschild radius, average density, compactness, and gravitational redshift. Our calculations showed that in this model, the maximum mass and radius of SQS increase with increasing temperature. Furthermore it was shown that the average density of SQS is greater than the normal nuclear density, and it is an increasing function of temperature. We also discussed the temperature dependence of the maximum gravitational mass calculated by different methods. [ABSTRACT FROM AUTHOR]

This is the last of a series of papers devoted to the application of group theoretical methods for astrophysical radiative transfer problems. The superdeterminant of the supermatrix-operators of the composition and translation groups for inhomogeneous absorbing and scattering media of finite thickness is proved to equal unity. The feasibility of applying a group approach for determining the statistical average quantities describing radiative diffusion is demonstrated. A variational principle is used for the diffusion of radiation in homogeneous media, a formulation of Hamilton's principle is given, and the corresponding Lagrangians and conservation law are found. Examples are given of two parameter composition groups introduced for nonstationary radiative transfer problems and problems involving the diffusion of radiation in turbulent media. [ABSTRACT FROM AUTHOR]

Ambartsumian’s paradigm for the creation of galaxies owing to the decay of denser matter is examined. The roots of this concept can be found in the very earliest papers of Ambartsumian on quantum fields and the structure of atomic nuclei. In the early 1930’s his papers contained new ideas regarding the ejection by one physical object of another which had not originally existed inside the first. The basic observational data which served as the basis for the final formulation of the new concept are described. Special attention is devoted to those objects and phenomena, which, upon further study, have confirmed the validity of Ambartsumian’s reasoning and arguments. It is noted that the discovery of Hubble expansion’s acceleration of the universe opened up new possibilities for the interpretation of activity phenomena in terms of Ambartsumian’s concept. The further extension of this concept is discussed and it is suggested that the major result of this approach should be the proof of the existence of galaxies of all ages within a finite volume of space. [ABSTRACT FROM AUTHOR]

Diagnostics for the rarefied plasmas in gaseous nebulae are reviewed, beginning with the pioneering papers of V. A. Ambartsumian. These papers, as well as the diagnostic techniques which have been developed on the basis of ideas contained in them, are discussed. Diagnostic techniques for homogeneous, as well as inhomogeneous, plasmas are described. [ABSTRACT FROM AUTHOR]

This paper is devoted to a determination of the statistical mean quantities describing spectral line radiation of dynamically active stochastic and multicomponent atmospheres. The lines in LTE are considered so that the effects of multiple scattering can be neglected. Two types of problem are discussed. In the first it is assumed that the realization of one or another type of nonthermal motion depends on the type of structural element and in the other this type of dependence is absent, i.e., it is supposed that the assumed random values of the velocity are distributed according to a law that is common to all the components. Particular attention is paid to a determination of the relative mean square deviation of the intensity of the observed radiation. It appears that the distinctive feature of the relative mean square deviation of the radiation in a line formed in a dynamically active stochastic atmosphere is local “spikes” (maxima) in the wings of the line. The theoretical results in this paper are compared with spectral observations of quiescent solar prominences obtained in framework of the SOHO space mission. [ABSTRACT FROM AUTHOR]

The problem of finding statistical averages which characterize the radiation field in a semi-infinite atmosphere has been discussed by the author in a series of papers. In this paper some of the results obtained there are generalized to media of finite optical thickness. The average number of scattering events undergone by a photon during its random walk in an atmosphere and the average time required for this are determined. Three different types of averages are considered, depending on the photon characteristics over which the averages are taken. Special attention is devoted to the asymptotic behavior of these quantities for media with large optical depths taking the influence of continuum absorption into account. [ABSTRACT FROM AUTHOR]

The limiting mass of cold white dwarfs was first calculated by E. Stoner in an approximate model of a uniform star and was soon reduced by ~20% in papers by S. Chandrasekhar and L. D. Landau based on an exact solution of the equations for the stellar equilibrium. Here we examine uniform models of white dwarfs taking general relativity effects and the influence of finite temperature into account. Solutions are obtained in the form of finite analytic formulas and, for masses differing by no more than ~20% from the exact solutions, found by numerical integration of the differential equations for the stellar equilibrium. [ABSTRACT FROM AUTHOR]