We are considering the spacetime described by the metric proposed by Mannheim and Kazanas. The effective potential and the circular orbits are discussed. The rotational velocity derived from the geodesics equation agrees with the observed flat galactic rotation curves. Finally, solutions to the Gordon equation for massless bosons evolving in this spacetime are obtained in terms of Heun general functions

In this paper Robe-finite straight segment model is analyzed under the effects of viscosity and perturbations in the Coriolis and centrifugal forces. We have taken the first primary \(P_{1}\) as a rigid spherical shell \(m_{1}\) filled with viscous, homogeneous incompressible fluid of density \(\rho _{1}\), and the second primary \(P_{2}\) as a finite straight segment of length \(2l\). A third body

The comparative analysis of measured and modelled Vertical Total Electron Content (VTEC) in low, mid and high latitude assists in the correction of Global Positioning System (GPS) measurements. In this study, we compare VTEC from GPS and International Reference Ionosphere (IRI) models (2007, 2012 and 2016) over mid latitude Sukkur (Lat \(27.7^{\circ}~\text{N}\), Long \(68.8^{\circ}~\text{E}\)) region

It is shown that the solar wind interaction with dusty plasma in planetary magnetospheres gives rise to electrostatic instabilities and solitary structures. Non-Maxwellian electrons increase the growth rate of shear flow instability and reduce the amplitude of solitary pulses formed by the modified dust ion acoustic wave (mDIAW) in nonlinear regime. Dust number density plays the similar role. The kappa

In this paper, we use the distributions of two-component radio emissions to investigate the consequences of relativistic beaming on the unified scheme of blazar populations and radio galaxies. Our results show remarkable continuity in the distributions of source luminosities (radio core and extended luminosities, \(L_{C}\) and \(L_{E}\) respectively as well as \(\gamma \)-ray luminosity \(L_{\gamma

We present for the first time the X-ray luminosity function of short gamma-ray bursts (sGRBs) estimated from 22 Fermi sGRBs. We find that the cumulative distribution of X-ray emission at rest frame 200 s is well described by a broken power law function, which is \(\phi (L_{\mathrm{X,0}})\propto L_{\mathrm{X,0}}^{-0.20\pm 0.04}\) for dim bursts and \(\phi (L_{\mathrm{X,0}})\propto L_{\mathrm{X,0}}^{-1

With outer space being speculated as the source of handedness in molecules of biological importance, there is a great need to explore the gas-phase stereoinversion in molecules under the conditions akin to interstellar medium. In this work, quantum-mechanical computations are performed to trace the pathways for gas-phase stereoinversion in isoleucine, an amino acid with two chiral centres. Contrary

We examined the behaviour of blazar OJ 287 based on 12 year observation data in optic, UV, X-ray, and gamma ray. The optical, UV, and X-ray data of OJ 287 were obtained from Swift archive, which provide more or less simultaneous optical–X-ray observations, while gamma ray data were obtained from Fermi archive. The occurrence of outburst episode in 2007 can be confirmed in Swift/UVOT data. In addition

Extreme high-energy peaked BL Lac objects (EHBLs) are an emerging class of blazars with exceptional spectral properties, e.g., enhanced emission in the hard X-ray region and a hard spectrum at very high \(\gamma \)-ray energies. Currently, no suitable model exists to explain the high-energy radiation mechanism of EHBLs. Here we apply a new model of the emission process to describe the Spectral Energy

Our present study involves the strange stars model in the framework of \(f(R,T)\) theory of gravitation. We have taken a linear function of the Ricci scalar \(R\) and the trace \(T\) of the stress-energy tensor \(T_{\mu\nu}\) for the expression of \(f(R,T)\), i.e., \(f(R,T)=R+ 2 \gamma T \) to obtain the proposed model, where \(\gamma \) is a coupling constant. Moreover, to solve the hydrostatic equilibrium

Artificial Light pollution (AL) in Turkey and in Turkish observatories between 2012–2020 have been studied using the archival data of Visible Infrared Imaging Radiometer Suite (VIIRS) instrument. The astroGIS database has been used in processing the data (astrogis.org) Aksaker et al. (2020a). The total energy released to space from Turkey increased by 80% in 2019 with respect to 2012. In the span of

In this work, we establish a model of holographic dark energy interacting with dark matter in flat Friedmann-Lemaitre-Robertson-Walker (FLRW) universe and test this model with observational data of Type-Ia supernovae (SNeIa), baryon acoustic oscillation (BAO), cosmic microwave background (CMB) anisotropy and Hubble parameter \(H(z)\). Next we obtain the deceleration parameter and the coincidence parameter

It is now well established that Coronal Mass Ejections (CMEs) may produce shocks in near Sun and interplanetary medium. A Type-II radio burst is characterized by shock and associated emission with very slow frequency drift rate (∼0.1 MHz/sec). A CME driven shock and their velocity, acceleration/deceleration signature can be observed by a Type-II solar radio burst which drifts with the shock speed and

We present the cosmological model of a bouncing universe with causal fluid in the universe. The dissipative effects of the causal cosmic fluid is probed with both truncated Israel–Stewart theory and full Israel–Stewart theory. The following classes of non-vanishing scale factors of bouncing cosmology are considered with a viscous fluid: (i) the power-law bouncing model, (ii) the exponential bouncing

We study the solar flare of July 19, 2000 of M6.4/3N class, which occurred in the active region NOAA 9087. Echelle Zeeman spectrograms of this flare were obtained with the horizontal solar telescope of the Astronomical Observatory of Taras Shevchenko National University of Kyiv. Physical conditions were compared for two times corresponding to the pre-peak and peak phases of the flare in area of a small

The nonlinear dynamics of an elliptic restricted three-body system with perturbations such as radiation and albedo are studied in this paper. The effects of different perturbation parameters on the nonlinear dynamic behavior of the third-body are analyzed through the system’s bifurcation diagram. The second- and third-order approximate periodic solutions near the collinear libration points in the plane

We investigate the problem of determining the shape of a rotating celestial object – e.g., a comet or an asteroid – under its own gravitational field. More specifically, we consider an object symmetric with respect to one axis – such as a dumbbell – that rotates around a second axis perpendicular to the symmetry axis. We assume that the object can be modeled as an incompressible fluid of constant mass

In order to support the analysis of potential long-term trends in the Sun’s variability and trace the WRR ground calibration ratio to the measurement on the satellite. We established the total solar irradiance (TSI) calibration model in orbit for the new generation of solar radiation monitor on the FY-3E satellite. First, we measured the non-equivalence of the instrument, and the air to vacuum ratio

In this work, we examine a spherically symmetric compact body with isotropic pressure profile. In this context we obtain a new class of exact solutions of Einstein-Maxwell field equation for compact stars with uniform charged distributions on the basis of Pseudo-spheroidal space-time with a particular form of electric field intensity and the metric potential \(g_{11}\). Taking these two parameters

We remind that the “ring down” features observed in the LIGO gravitational waves (GW) resulted from trembling of “photon spheres” (\(R_{\mathit{photon}}=3M\), by using units \(G=c=1\)) of newly formed compact objects and not from the trembling of their event horizons (EH) \(R=2M\) (Cardoso et al. 2016). Further, the tentative evidence for late time “echoes” in GWs might be signatures of horizonless

Coronal mass ejections (CMEs) largely influence the space weather and cause geomagnetic perturbations. Hence, the statistical studies pertaining to the occurrence of CMEs over the solar cycles and their consequence at the near-Earth region are extremely important. For an in-depth understanding, such studies need to be carried out considering various observational aspects of CMEs. With this motivation

A dynamical model has been developed to envisage the star formation scenario in filamentary molecular clouds. In the present work a double well potential has been considered to find the number of stable stationary points as the origin of field star, binary stars or stellar associations. It is found that low density structure can lead to the formation of field stars while an intermediate density structure

The formation of a temporary third radiation belt in the slot region of Earth’s magnetosphere was reported (Baker et al. in Science 340:186-190, 2013a) from the early data of the radiation belt storm probes (RBSP) mission. The cumulative flux of relativistic electrons in L = 3-3.5 for the third radiation belt of that study is calculated here and defined as threshold flux (TF) (105 cm−2 s−1 sr−1 MeV−1)

We study the geo-effectiveness of high-speed streams (HSS) detected during the consecutive eight years (2009 - 2016) period of solar cycle 24. These HSS are of different speeds and durations. During their passage, solar wind plasma and magnetic field parameters are also not similar. We utilize solar wind plasma and magnetic field parameters during the HSS passage in addition to two geomagnetic indices

In the present paper, the relation between the CMEs and their linked solar flares is examined during the entire solar cycle 23. During this solar cycle and under certain temporal and spatial conditions, 521 CMEs linked with solar flares are selected. These selected CMEs are separated into two groups according to their time of detection, 254 Before Flare-ECME events (BF-CMEs) and 267 After Flare–ECME

Low-energy bi-impulsive Earth-Moon transfers are investigated by using periodic orbits. Two Earth-Moon transfer design strategies in the CR3BP are proposed, termed direct and indirect design strategy. In the direct design strategy, periodic orbits which approach both vicinities of the Earth and Moon are selected as candidate periodic orbits, which can provide an initial guess of bi-impulsive Earth-Moon

We present the star formation rates (SFRs) of galaxies with redshifts of 0 < \(z\) < 6 and cosmic star formation rate densities as a function of redshift. The SFRs for the galaxies at infrared emission have been investigated for 1752 sources from the Spitzer 70 μm observations of the Spitzer COSMOS Legacy survey and the various surveys in the literature. Analyzing the SFRs of these objects provides

Open clusters (OCs) are important objects in exploring the structure and history of the Milky Way. Large amount of sky survey data can be used to detect OCs. However, analyzing these data manually has become a bottleneck of OC identification. This study proposes a multi-scale density feature learning (MSDFL), which includes the open cluster kernel density map to visualize the features of OCs; and open

There exists a small but statistically significant north–south asymmetry in most of the solar activity indices and it has important implications on the solar dynamo mechanism. Here we analyzed the daily sunspot-group data reported by the Greenwich Photoheliographic Results (GPR) during the period 1874–1976, Debrecen Photoheligraphic Data (DPD) during the period 1977–2017, and the revised Version-2

In this article, we examine the solution for expanding cosmology, which imitates properties similar to an interplay of dark matter and dark energy. The effective fluid of this toy model may behaves like dust matter at early epoch and as a cosmological constant at later epoch. Also, for this solution, the cosmological parameters are calculated and the model is able to explain dynamical universe evolution

Binary systems of Population III can evolve to microquasars when one of the stars collapses into a black hole. When the compact object accretes matter at a rate greater than the Eddington rate, powerful jets and winds driven by strong radiation pressure should form. We investigate the structure of the jet-wind system for a model of Population III microquasar on scales beyond the jet-wind formation

The supermassive black hole at the Galactic Centre is surrounded by the so-called Circumnuclear Disc (CND) with a sharp inner edge at 1.5 pc. Both its outer extent and the total mass contained within it are somewhat unknown making it difficult to conclude on its long term stability. In this work we report the results of our simulations for the orbital evolution of the CND taking into account its warped

In this work, we compiled a sample of 1172 4FGL blazars with available spectral information and broadband intensities to the study the spectral indices. Based on this sample, we studied the correlations of spectral indices, and further studied BCU classification by using multi-band spectral indices. Among these sources, there are 196 BCUs, we manage to classify these sources into either FSRQs or BL

This paper describes a novel homotopy method to compute fuel-optimal trajectories starting from a time-optimal solution. The time-optimal problem is proposed to serve as a gateway for solving the minimum thrust problem. Homotopy is used to link the original low-thrust fuel-optimal problem with the minimum thrust problem. Two new variables are introduced in the dynamic model. The first is a logarithm

We study the transient modulation of galactic cosmic rays (GCRs) due to coronal mass ejections (CMEs) and their associated structures detected during most part of solar cycle 24. The interplanetary counterpart of CMEs (ICMEs), while propagating in the interplanetary space, may be associated with the shock/sheath region. An ICME may (or may not) be the so-called magnetic cloud. Using the method of superposed-epoch

We consider the nonlinear ion acoustic wave induced by orbiting charged space debris objects in the plasma environment generated at the Low Earth Orbital (LEO) region. The generated nonlinear ion acoustic wave is shown to be governed by a forced Korteweg-de Vries (fKdV) equation with the forcing function dependent on the charged space debris function. For a specific relationship between the forcing

We study the effect of the Bumblebee deviation parameter \(l\) on galactic scale by means of Relative Time Delay (RTD) caused by frame dragging effect. While weak field solar system tests have been fairly accurately measured leading to an exceedingly tiny upper limit \(l\leq10^{-13}\), measurements on the large astrophysical scale are yet unavailable, so we decided to keep \(l\) neither too tiny nor

The gravitational-wave signal GW190814 involves a compact object with mass \((2.50-2.67)~{\mathrm{M}}_{\odot }\) within the so-called low mass gap. As yet, a general consensus on its nature, being a black hole, a neutron star or an exotic star, has not been achieved. We investigate the possibility this compact object to be an anisotropic neutron star. Anisotropies in a neutron star core arise naturally

This study aims to examine the dynamics of flat Friedmann-Lemaitre-Robertson-Walker (FLRW) model of universe with time varying cosmological constant \(\Lambda (t)\) in Brans-Dicke theory of gravity. The authors find a solution of the field equations using simple parametrization of scale factor \(a(t)\) i.e. \(a(t)=\exp \{(\alpha t+\beta )^{p}\}\), and power law relation between \(a(t)\) and Brans-Dicke

By expanding the perturbation function of tesseral harmonic \(J_{22}\) term of the earth’s non spherical gravitation, it is found that there is a term \(\cos 2\Omega _{e}\) related to the rotation of the earth. The period of the term is half a day, and the coefficient includes the factor \(\sin ^{2}i\) related to the orbital inclination angle. For the low polar orbit satellite with orbit inclination

We employ a perturbative analysis to study the evolution of large-scale peculiar velocity fields within the framework of Newtonian gravity and then compare our results to those of the corresponding relativistic treatment. In so doing, we use the same mathematical formalism and apply the same physical approach. This facilitates a direct and transparent comparison between the two treatments. Our study

In this paper, the prediction model for ionospheric total electron content (TEC) based on Long Short-Term Memory (LSTM) deep learning network and its performance are discussed. The input parameters of the model are previous values of daily TEC, solar radio flux at 10.7 cm parameter of 81 day moving average (\(\overline{F107\_81}\)), sunspot number (SSN), geomagnetic Kp index, and disturbance storm

This paper presents a statistical analysis of soft X-ray flares during the period January 1986 to June 2017 covering the last three solar cycles (SCs) 22, 23, and 24. We have analyzed the distribution of flare number, the relationship between the occurrence rate of soft X-ray flares and solar activity, and the duration of different intensity class (B, C, M, and X) solar flares during the period of

We present new observations of the reconnection outflow jet obtained from the crossing of a solar wind reconnection exhaust by the Wind spacecraft on 5 March 2001. The outflow jet is characterized by a bifurcated configuration, which is different from typical reconnection exhausts. The two outflow jets are mainly distributed in the region close to the exhaust boundaries. Between the two jets, the bulging

The Mücket-Treder-type potential was initially introduced to explain the discrepancy between Mercury’s observed perihelion advance and the computed value based on Newton’s law, but it can also be used for many astronomical situations as, for instance, the study of the very eccentric cometary orbits in the neighborhood of the Sun. In this paper we tackle the two-body problem in the Mücket-Treder post-Newtonian

Metallicities of the Milky Way globular cluster (GC) system are interpreted within the framework of a closed box model of chemical evolution. Model age-metallicity relations normalised to the Sun are compared with an observed age-metallicity relation constructed from literature data for the Galactic globular clusters and solar neighbourhood dwarf stars. One branch of the GC age-metallicity relation

This paper presents different families of transfers from Low Lunar Orbit to Distant Retrograde Orbits in the Earth-Moon system and analyzes their characteristics from the perspective of velocity increment requirement, transfer time, and sensitivity to small perturbations. Initially, families of transfer trajectories in the Circular Restricted Three-Body Problem are found by the predictor-corrector

Two parameters such as magnetic fields near the light cylinder \(B_{lc} \) and rates of rotational energy losses \(\frac{dE}{dt} \) for 1795 radio pulsars without high energy emission (R), 52 radio loud gamma-ray pulsars (\(\gamma\)+R), 33 radio quiet gamma-ray pulsars (\(\gamma\)) and 61 radio loud X-ray pulsars (X+R) are compared with each other in this work. Pulsars with registered X-ray and gamma-ray

In this paper, we present the multi-wavelength study of a high level of solar activity during which a single active region produced multiple flares/CMEs. According to the sunspot observations, the current solar cycle 24 manifest to be less intense in comparison with the previous recent sunspot cycles. In the course of the current sunspot cycle 24, several small and large sunspot groups have produced

This work presents an analytical approach for studying the cosmological 21cm background signal from the Dark Ages (DA) and subsequent Epoch of Reionization (EoR). We simulate differential observations of a galaxy cluster to demonstrate how these epochs can be studied with a specific form of the Sunyaev-Zel’dovich Effect called the SZE-21cm. This work produces simulated maps of the SZE-21cm and shows

The coincidental detection of the gravitational wave event GW 170817 and the gamma-ray burst GRB 170817A marked the advent of multi-messenger astronomy and represented a milestone in the study of GRBs. Significant progress in this field is expected in the coming years with the increased sensitivity of gravitational waves detectors and the launch of new facilities for the high-energy survey of the sky

The regional ionospheric models are successful in capturing the variability of ionosphere with the inclusion of local ground-based GPS observations and location dependent ionospheric dynamics. In this context, there is a need to develop regional ionospheric maps that aids in improving the consistency of global models. In this paper, an attempt is made to understand the potentiality of multi-instrument

We investigate whether certain extra-solar multi-planet systems simultaneously follow the scaling and spacing rules of the angular-momentum-deficit model. The masses and semi-major axes of exoplanets in ten multi-planet systems are considered. It is found that GJ 667C, HD 215152, HD 40307, and Kepler-79 systems are currently close to configurations of the angular-momentum-deficit model. In a gas-poor

Impacts of solar flare vary at different parts of the lower ionosphere depending on it’s proximity to the direct exposure of incoming solar radiation. The quantitative analysis of this phenomena can be attributed to ‘solar zenith angle (\(\chi (t)\))’ profile over ionosphere. We numerically solve the ‘electron continuity equation’ to obtain the lower ionospheric electron density profile (\(N_{e}(t)\))

Despite that the tricarbon monosulfide (C3S) is among the first sulfur-containing carbon-chain molecules to be detected in the interstellar medium, no studies focused on the determination of its collisional rates. These rate coefficients are essential to estimate the abundance of C3S in the interstellar medium. Computations of the C3S(\(^{1}\Sigma^{+}\)) downward rate coefficients, induced by collision

The global features of the modulation of galactic cosmic ray protons and helium nuclei in a very quiet heliosphere are studied with a comprehensive, three-dimensional, drift model and compared to proton and helium observations measured by PAMELA from 2006 to 2009. Combined with accurate very local interstellar spectra (VLIS) for protons and helium nuclei, this provides the opportunity to study in detail

We demonstrate a technique to generate new class of exact solutions to the Einstein-Maxwell system describing a static spherically symmetric relativistic star with anisotropic matter distribution. An interesting feature of the new class of solutions is that one can easily switch off the electric and/or anisotropic effects in this formulation. Consequently, we show that a plethora of well known stellar

This paper explores and analyzes a set of solutions describing the interior structure of relativistic compact stellar structures with variable cosmological constant \(\Lambda (r)\). We consider the solution of Krori–Barua space-time to a static spherical symmetric metric. Furthermore, we match our interior stellar structure with the exterior Schwarzschild geometry to determine the values of the constants

This paper presents the performance of the latest version of the International Reference Ionosphere (IRI-2016) model for estimating the Total Electron Content (TEC) variations in the mid-latitudinal Turkish regions during low solar activity years (2015–2018). Moreover, TEC is estimated from dual-frequency Global Navigation Satellite System (GNSS) receivers operating in different regions of Turkey:

We study the luminosity function of long gamma-ray bursts (LGRBs) using the peak flux obtained from three LGRB samples with known redshifts: (a) a sample of 251 LGRBs from the Swift/BAT satellite/instrument; (b) a sample of 37 LGRBs from the Fermi/GBM telescope; (c) a sample of 152 GRBs from the Konus-Wind instrument. For the Swift/BAT and Fermi/GBM samples, we use data available on the Swift Burst