We report a study of the color-magnitude diagram (CMD) of globular cluster SL 506, which shows extended main sequence turn-off (eMSTO). The CMD is derived from deep F450W (B) and F555W (V) images of Hubble Space Telescope/Wide Field Planetary Camera 2 (HST/WFPC2). We reproduce the CMD via simple stellar population including the combination of rotational stars and binaries, and composite stellar population

Low beta plasma system is chosen for the study of low frequency electromagnetic Shear Alfvén waves exhibiting dynamical charging of micron/sub micron size dust particles. A semi classical Quantum Hydrodynamic Model (QHD) is employed which includes the quantum effects for plasma electrons in the terms of statistical degenerate pressure, Landau quantization, exchange-correlation potential, and tunneling

Correction to: Astrophys Space Sci (2018) 363:31 https://doi.org/10.1007/s10509-018-3251-z The first author’s third affiliation was missing in the original publication.

In the present communication, we investigated flat Friedmann-Lemaître-Robertson-Walker mathematical model of universe in \(f (R,T )\) theory of gravity with bulk viscous fluid as a source of energy. A system of modified field equations with cosmological constant has been solved by considering time-dependent deceleration parameter (DP) (Mishra et al. in Eur. Phys. J. Plus 127:137, 2012). Suitable assumption

This is the first report of coupled noble gases (He, Ne, Ar, Kr and Xe) and nitrogen isotopic results in metal separates from the ordinary chondrites Katol (L6), Itawa Bhopji (L3-5) and Portales Valley (H6). Noble gas elemental ratios (corrected for cosmogenic) in the metal separates are mixture of several components, Q-gas, air and solar wind. The chondritic metal shows new nitrogen isotopic data

In this paper, we have examined the Rényi holographic dark energy (RHDE) model in the framework of an isotropic and spatially homogeneous flat FLRW (Friedmann-Lemaître-Robertson-Walker) Universe by considering different values of parameter \(\delta \), where the infrared cut-off is taken care by the Hubble horizon. We examined the RHDE model through the analysis of the growth rate of perturbations

We present medium resolution (1000) K-band spectra of 12 post-AGB candidates and related stars. For several objects in our sample, these spectra were obtained for the first time. The Br\(\gamma \) line in emission is detected in seven objects indicating the onset of photo-ionization in these objects. Four objects show the presence of an He i line. We detect H2 emission line in the spectra of IRAS 06556+1623

The property of dark energy, which is predicted as the physical reason for the accelerated expansion of the present universe and the coincidence problem by which are suppressed many dark energy models are two of the most difficult problems in modern cosmology. From the Wilkinson Microwave Anisotropy Probe (WMAP) the dark energy contributes about 73% of the total energy of the present universe. Also

Based on the detected spin periods (\(P\)) and inferred magnetic field strengths (\(B\)) by the cyclotron resonance scattering features, we analyze the \(B-P\) properties of Be/X-ray Pulsars (BeXPs). We find that the \(P\) distribution of BeXPs exhibits a bimodal feature separated at \(P\sim 40\) s, where the average spin period of the BeXPs with \(P>40\) s (\(\langle P\rangle \sim 267\) s) is larger

Locally-rotationally-symmetric Bianchi-I space-time model is studied with constant Hubble parameter in \(f(R,T)=R+2\lambda T\) gravity. Although a single (primary) matter source is considered, an additional matter source appears due to the coupling between matter and \(f(R,T)\) gravity. The constraints are obtained for a realistic cosmological scenario. The solutions are also extended to the case of

The Global Positioning System (GPS) applications are highly vulnerable to the ionospheric space weather effects. Modelling and forecasting the ionospheric effects such as time delays for GPS signals are important for real time alerts of space weather effects on GPS services. In the present work, the performance of Neural Networks (NN) model is compared with International Reference Ionosphere (IRI)

The measurement of thermal neutrons generated by cosmic ray extensive air showers (EAS) on the Earth’s surface provides a new method for studying the composition and energy of cosmic rays with energy in the so-called “knee” region. Given the success of the PRISMA-YBJ array, a new type of thermal neutron detector array was installed at the high-altitude cosmic ray observatory in Yangbajing, Tibet. The

Since the late 1990’s observations of type Ia Supernova, our universe is predicted to experience a late time cosmic acceleration. Theoretical support to this observation were intended to be built via proposition of a hypothetical fluid which staying inside the universe exerts negative pressure. Cosmologists have prescribed many candidates for this exotic fluid so far. In this alley, a popular method

The Widefield ASKAP L-band Legacy All-sky Blind surveY (wallaby) is a next-generation survey of neutral hydrogen (H i) in the Local Universe. It uses the widefield, high-resolution capability of the Australian Square Kilometer Array Pathfinder (ASKAP), a radio interferometer consisting of \(36 \times12\)-m dishes equipped with Phased-Array Feeds (PAFs), located in an extremely radio-quiet zone in Western

In the framework of the gravitational theory based on Lyra geometry and the general theory of relativity, we study Bianchi type I cosmological model in the presence of viscous fluid. A discussion about the suitability of the Sen equations as field equations in Lyra geometry is given. A clear physical meaning for the time component of the displacement vector, introduced in the Sen field equations used

The ionospheric medium is the primary source of error for signals from the Global Positioning System (GPS) satellites. Modeling ionospheric effects is one of the main challenges in developing accurate and reliable services for Space-Based Augmentation Systems. The Mapping Function (MF) and the estimation of the model coefficients are an essential parameter in the aspects of ionospheric modeling. In

With the widespread availability of ground and space-based global navigation satellite system (GNSS) observables, continuous and long-term explorations of ionospheric variations have been made possible worldwide or on regional basis with improved accuracy. The Formosa Satellite Mission#3/Constellation Observing System for Meteorology, Ionosphere, and Climate (FORMOSAT-3/COSMIC) mission has a huge database

Strange Nuggets are believed to be among the relics of the early universe. They appear as dark matter due to their low charge-to-mass ratio. Their distribution is believed to be the same as that of dark matter. As such, they could be accreted by high magnetic field objects and their collisions with pulsars are inevitable. Pulsar glitches are commonly seen as sudden spin-ups in pulsar frequency. It

Two dozens of different mass galaxies observed at distances less than 10 Mpc from the Local Group are organized in the elongated structure known as the Sculptor Filament. We use recent Hubble Space Telescope data on local galaxies to study the dynamical structure and evolutionary trends of the filament. An N-body computer model, which reproduces its observed kinematics, is constructed under the assumption

This work aims to study the influence of the rotation of the galaxy which it is modelled as a bi-symmetrical potential consists of a two-dimensional harmonic oscillator with quartic perturbing terms on some dynamics aspects for the problem of the motion of stars. We prove analytically the non-integrability of the motion (i.e., the motion is chaotic) when the parameters meet certain conditions. Poincaré

The plasma motion in the dissipative layer of a flowing high beta plasma is studied. The linearized magnetohydrodynamic (MHD) equations are used to study the plasma motion. Using the perturbation method presented by Ruderman (2009) the solution of equations of motion are determined. The effect of the plasma flow is to change the distance between the slow and Alfvénic resonant points as well as the

It is known that the solar radio flux is strongly correlated to the sunspot cycle and that the flux is nearly the same at every minimum. If 64 sfu is taken as the baseline for all cycles, then we can calculate the proxy sunspot number from the flux, and vice versa. Furthermore, we find that the fitted adjusted flux divided by the fitted sunspot number gives a strong marker for the start of Solar Cycle

We calculated the median parallaxes for 47 OB associations including at least 10 stars with known Gaia DR2 parallaxes. A comparison between trigonometric and photometric parallaxes of OB associations reveals a zero-point offset of \(\Delta \varpi=-0.11\pm0.04\) mas indicating that Gaia DR2 parallaxes are, on average, underestimated and the distances derived from them are overestimated. The correction

We present new H i data of the dwarf galaxy KK 69, obtained with the Giant Metrewave Radio Telescope (GMRT) with a signal-to-noise ratio almost double previous observations. We carried out a Gaussian spectral decomposition and stacking methods to identify the cold neutral medium (CNM) and the warm neutral medium (WNM) of the H i gas. We found that 30% of the total H i gas, which corresponds to a mass

The magnetosphere and ionosphere have a crucial interaction during severe geomagnetic storms. The Global Navigation Satellite System (GNSS) provides high-quality ionospheric observations with high temporal and spatial resolution, is generally preferred to investigate the ionospheric variation. In this study, the storm-time ionospheric response of the June 2015 severe storm (Dstmin = −208 nT) was investigated

Considering the dark matter as self-gravitating Bose-Einstein condensate in a gravito-chemical equilibrium state, we have studied the light trajectory through the halo. Found that depending on the initial direction cosine of the light ray, there are three types of trajectories: (a) the refracted light i.e. light which can refracts away from the halo to the out side, (b) the trapped light i.e. light

High-energy neutrinos present the ultimate signature for a cosmic ray accelerator. Galactic sources responsible for acceleration of cosmic ray up to the knee in cosmic ray spectrum will provide a guaranteed, albeit subdominant, contribution to the high-energy cosmic neutrino flux. In this review, we discuss the the prospects for identification of high-energy neutrinos from sources of the very high

The effects of dust temperature and radiative heat-loss functions on the instability of selfgravitating homogeneous viscoelastic dusty plasma have been studied using the modified GH model. A general dispersion relation representing the dust temperature, radiative heat-loss functions, magnetic field, thermal conductivity and relaxation time parameters are obtained using the normal mode analysis method

Relative drifts between different species or particle populations are characteristic to solar plasma outflows, e.g., in the fast streams of the solar winds, coronal mass ejections and interplanetary shocks. This paper characterizes the dispersion and stability of the low-beta alpha/proton drifts in the absence of any intrinsic thermal anisotropies, which are usually invoked in order to stimulate various

Radiative capture \(p + {}^{13}\mathrm{C}\rightarrow {}^{14}\mathrm{N}+\gamma \) at energies bearing astrophysical consequences is one of the important processes in the CNO cycle. We focus on the possibility of describing the main contribution to the total cross section of the radiative capture process in the framework of the single-particle potential model without separation into direct and resonant

Motivated by a successful prediction on the peak of solar cycle 24 (81.7, comparable to the observed 81.9, Du in Astrophys. Space Sci. 338:9, 2012), based on the logarithmic relationship between the maximum amplitude (\(R_{ \mathrm{m}}\)) of a solar cycle and the preceding minimum \(aa\) geomagnetic index (\(aa_{\mathrm{min}}\)), we perform a prediction on the peak of the upcoming cycle 25 using the

The manuscript presents the dynamics of Tsallis holographic dark energy (THDE) and Rényi holographic dark energy (RHDE) prescribed by a non-linear interaction in the FRW spacetime and for a scale factor evolving with a composite power law-exponential (hybrid) form. To construct the energy densities of these holographic dark energy models, I assume the Hubble cutoff to be the IR limit. I find that the

We analyzed the BVR photometry of the comets 63P/Wild 1 and C/2012 K1 (PANSTARRS) obtained between March 2013 and May 2014, with 0.20-m to 2.0-m aperture telescopes installed in Australia, Europa and USA. We have found R-band nuclear magnitudes \(H_{0}=16.3\pm 0.6\) and \(12.52 \pm 0.02\) for 63P and K1 comets. Admitting a geometric albedo equal to 0.04, the nuclei have a radius equal to \(1.5\pm 0

This paper deals with the photogravitational circular restricted three-body problem, including the effect of circular cluster of material points. The parametric evolution of the position of equilibrium points and the existence of a different number of equilibrium points are illustrated using graphs. A detailed investigation to find out the influence of the radiation pressure \(q\), mass ratio \(\mu

The Earth’s central plasma sheet plays an important role in mass and energy transport in the whole magnetosphere. Here, we first present a new approach, i.e., an Artificial Neural Network (ANN) model, to investigate the electron number fluxes in the central plasma sheet. With the time series of 8 solar wind/geomagnetic indices and spatial locations as inputs, the model has been trained, validated,

This study aims to predict daily ionospheric Total Electron Content (TEC) using Gaussian Process Regression (GPR) model and Multiple Linear Regression (MLR). In this case, daily TEC values from 2015 to 2017 of two Global Navigation Satellite System (GNSS) stations were collected in Turkey. The performance of the GPR model was compared with the classical MLR model using Taylor diagrams and relative

We discuss Tsallis holographic dark energy (THDE) model in higher dimension. An interacting dark energy model is proposed with Generalized Chaplygin Gas (GCG) in the framework of Compact Kaluza-Klein gravity. It is shown that a stable configuration can be found in the present epoch which is also compatible with the observed value of the density parameter. It is noted that dark energy (DE) might have

We have studied alpha attractor cosmology with exponential harmonic fields and reheating phase after inflation. The results show that, for large limit of alpha, the inflationary parameters of the used model confirm the observational data. For exponential harmonic fields, we have obtained constraints on reheating parameters. It arises that for these fields, reheating can last longer than canonical and

A one-step hybrid block method which is applied for solving Lane-Emden second-order singular differential equations arising in astrophysics is developed. The present technique is obtained by considering three intra-step nodal points, which are chosen appropriately in order to get optimized errors of the main formulas approximating the solution and the first derivative at the final position of the block

Recent studies showed that observations of line emission from shocks in YSO jets require a substantial amount of ionization of the pre-shock matter. Photoionization from X-ray emitted close to the central source may be responsible for the initial ionization fraction. The aim of our work is to study the effect of X-ray photoionization, coming from the vicinity of the central star, on the ionization

Under the premise that the current observations of the cosmic microwave background radiation set a very stringent limit to the anisotropy of the universe, we consider an anisotropic model in the presence of a barotropic perfect fluid and a homogeneous scalar field, which transits to a flat FRW cosmology for late times in a dust epoch, presenting an accelerated volume expansion. Furthermore, the scalar

Samples of red giant branch (RGB) stars have been compiled from the literature for seven moving groups, and searches made for both GALEX FUV and Johnson \(\mathit{BV}\) photometry. It has been possible to derive a colour index \((\mathit{FUV}-B)\) for many giants, which has been combined with \(B-V\) to give a two-colour diagram for each kinematic group. In addition, analogous data have been gleaned

In this paper we deal with the Tsallis holographic dark energy from a dynamical system approach. Here we assume the Hubble horizon as an infra red cutoff. We consider the cosmic evolution of the model in noninteracting, linearly, sign changeable and nonlinearly interacting cases. The analysis includes an autonomous system of equations and then we analyze the related phase spaces. We find that for a

This article is devoted to the study of the dynamical aspects of the perfect fluid cosmological model in the presence of an attractive massive scalar field in an axially symmetric Bianchi type-I space time in Lyra (Math. Z. 54:52, 1951) geometry. An exact cosmological model is presented by solving Einstein field equations using physically valid conditions. We have evaluated all the dynamical and geometrical

The ESA-Gaia satellite is regularly producing Alerts on objects where photometric variability has been detected after several passages over the same region of the sky. The physical nature of these objects has often to be determined with the help of complementary observations from ground-based facilities. We have compared the list of Gaia Alerts (from the beginning in 2014 to Nov. 1st, 2018) with archival

A theoretical and numerical study on amplitude modulated positron-acoustic waves (PAWs) in a magnetized four-component space plasma (containing immobile positive ions, inertial cold positrons, and inertia-less hot electrons and positrons following Cairn’s non-thermal distribution function) has been carried out. The reductive perturbation method have been applied to derive the corresponding nonlinear

We review the observational properties and possible carriers of the 21 and 30 μm features seen in the spectra of evolved carbon-rich objects. The 30 μm feature is generally taken to be due to MgS, possibly in combination with other sulfides. It is commonly assumed that the sulfides coat grains of SiC or amorphous carbon, but it remains unclear if coated grains can produce the observed feature given

Ion-scale magnetic flux ropes have been observed in the reconnection diffusion region. In this paper, we show a typical ion-scale flux rope observed by the Magnetospheric Multiscale spacecraft at the subsolar magnetopause. The most intriguing feature of this flux rope is that the rapid variations of electron density are correlated with the changes of electron temperature and pitch angle distribution

This study aims to investigate the effects of the solar activity phases on the magnetospheric processes in relation to daily relativistic electron (\(E>2\) MeV) dynamics at geosynchronous orbit (GEO) during Solar Cycles 23–24. GOES observations indicate that in the descending phase the electron fluxes are seasonally dependent with largest flux in equinoctial periods, relatively high, and 27-day recurrent

The collinear libration point of the Sun-Earth Circular Restricted Three-Body Problem (CR3BP), \(L_{3}\) is located opposite to the Earth with respect to the Sun. Whereas several space missions have been launched to the other two collinear equilibrium points, i.e., \(L_{1}\) and \(L_{2}\), the region around \(L_{3}\) is so far unexploited essentially because of the severe communication limitations

In this paper, we consider a holographic dark energy model driven by the gravitationally induced adiabatic matter creation with constant creation rate. It is assumed that the present accelerating stage is a consequence of the negative pressure describing the irreversible process of gravitational matter creation. Exact solutions are obtained to discuss the evolution of the universe. We obtain the best-fit

Many space agencies are working on solutions for manned operations on the Moon, both on its surface and in cislunar space. In such a scenario, with stable human presence, a launch facility would be needed and launch vehicles could take advantage of the benefits of the lunar environment. In the present paper missions to Earth (to a geostationary orbit) and to Mars (to an areostationary orbit), from

We consider the 3-dimensional space with \(t_{1} = \mbox{constant}\) in a super dense star which is spheroidal. We report a class of static spherically symmetric physically viable models based on a particular actual solution of Einsteins field equations. The models of the class admit densities of the order of \(2 \times 10^{14}~\mbox{gm}\,\mbox{cm}^{-3}\), radii of the order of a few kilometers and

The effect of rotation, porosity and finite ion Larmor radius (FLR) corrections on the gravitational instability and radiative instability of infinite homogeneous plasma has been explored, accounting for the consequences of radiative heat-loss function and thermal conductivity. The general dispersion relation is obtained by means of the normal mode analysis method with the help of appropriate linearized

The petroleum and coal models of the unidentified infrared emissions (UIE), sometimes referred also as unidentified infrared bands (UIBs) has been reviewed mainly based on the work of the authors with the inclusion of unpublished results. It is shown that the petroleum and coal model of the UIE converges and merges quite well with the MAON (Mixed Aromatic Aliphatic Organic Nanoparticles) model of the

A methodology is proposed to design optimal time-fixed impulsive transfers in the vicinity of the L2 libration point of the Earth-Moon system, taking the construction of a space station around the collinear libration points as the background. The approximate analytical expression of motions around the L2 point in the CRTBP is given, and the expression in the ERTBP is derived by linearizing the dynamical

This work investigates the basic features of Nonlinear Ion Acoustic Solitary waves (NIASWs) and their dynamical behaviours in an unmagnetized relativistic collisionless plasma system via the Schamel Korteweg-de Vries (SKdV) equation. Such plasma is composed by the generalized distributed electrons, Boltzmann distributed positrons and relativistic warm ions. The influences of plasma parameters on NIASWs

We have carried out an intensive study of photometric (Kepler Mission) and spectroscopic data on the system Kepler-2 (HAT-P-7A) using the dedicated software WinFitter 6.4. The mean individual data-point error of the normalized flux values for this system is 0.00015, leading to the model’s specification for the mean reference flux to an accuracy of ∼0.5 ppm. This testifies to the remarkably high accuracy

The basic purpose of this communication, is to investigate the dynamical nature of Bianchi type-I universe with perfect fluid content in Sáez-Ballester (SB) theory (Phys. Lett. A 113:467–470, 1986). We got the solution of modified Einstein’s field equations (EFEs) by considering the bilinearly varying deceleration parameter (BVDP) and the gravitational constant \((G)\) as a power function of average

In this paper, a very first use of the \(\kappa \)-deformed Kaniadakis distribution is made in the context of arbitrary amplitude ion-acoustic solitary waves (IASWs) in a magnetized plasma composed of cold fluid ions and non-Maxwellian electrons. The basic equations governing the dynamics of nonlinear structures are reduced to an evolution equation in the form of an energy-balance like equation through