Precise multi-color CCD-derived photometric data were obtained from EH Cnc at two sites during 2010, 2014 and 2018 wherein each epoch used a different instrument. This has provided a unique opportunity to investigate parameter uncertainty following Roche modeling of light curves optimized by differential corrections using the Wilson–Devinney code. Furthermore, new radial velocity data from EH Cnc presented

Every day, large number of meteoroids enter the Earth’s atmosphere and deposit their mass either in atomic form or in ionic form depending on whether it has undergone ablation or fragmentation. The heavier meteoroids undergo fragmentation while the lighter ones are more prone to ablate. In this paper, we would like to speculate meteoroid stream structure of Leonid meteor shower based on fragmenting

In this study, we investigated the time-independent dynamics (disc structure, forces and torques) of a quasi-Keplerian disc around a millisecond pulsar (MSP) with an internal dynamo. We considered the disc around a MSP to be divided into the inner, middle and outer regions. By assuming that the disc matter flows in a quasi-Keplerian motion, we derived analytical equations for a complete structure (temperature

Classical Cepheid and RR Lyrae variables are radially pulsating stars that trace young and old-age stellar populations, respectively. These classical pulsating stars are the most sensitive probes for the precision stellar astrophysics and the extragalactic distance measurements. Despite their extensive use as standard candles thanks to their well-defined Period–Luminosity relations, distance measurements

Quasars are ideal targets to use for astrometric calibration of large scale astronomical surveys as they have negligible proper motion and parallax. The forthcoming 4-m International Liquid Mirror Telescope (ILMT) will survey the sky that covers a width of about 27\(^\prime \). To carry out astrometric calibration of the ILMT observations, we aimed to compile a list of quasars with accurate equatorial

For the propagation of a shock (blast) in a self-gravitating perfect gas in case of spherical and cylindrical symmetry, an approximate analytical solution is investigated. The shock wave is considered to be a strong one, with the ratio \( \left( {\frac{C}{{V_{S} }}} \right)^{2} \) to be a small quantity, where \( c \) is the sound speed in an undisturbed medium and \( V_{S} \) is the shock wave velocity

In our effort to decipher the words and identify the stars as cited in the text Sarvasiddhāntarāja by Nityānanda of 15th century, we have found that most of the stars near the ecliptic belt are easily identifiable. The coordinate system used is Dhruvaka and Vikṣepa, which differ from the currently used ecliptic longitude–latitude and Right Ascension–declination coordinates. Most of the stars studied

The effect of intense solar flares on total electron content (TEC) variability during the declining phase of solar cycle-24 is studied at the low-latitude station at Varanasi, India (Geog. Lat. 25.31° N, Geog. Long. 82.97° E, Geomag. Lat. 16.54° N, Geomag. Long. 157.09° E). In the present paper, we have chosen the intense solar flares that occurred during 9–13 March 2015, 1–2 January 2016, 12–14 February

The significance increase of the plasma temperature from the solar photosphere to the corona up to 1MK is still unresolved. One of the candidates for this issue is waves and instabilities in the solar plasma. It was suggested that the energy of these waves could heat the solar atmosphere to transition-region (TR) and corona. Despite many recent kind of researches about waves in the various solar dynamic

From a report based on an independent investigation by a senior fellow of the Academy, we find that there is evidence of academic misconduct in the paper titled, “Numerical simulation of inertial alfven waves to study localized structures and spectral index in auroral region” by Bheem Singh Jatav.

Star sensor (SS) is one of the most critical instrument on-board a spacecraft when it comes to attitude determination and control. Capability of providing precise attitude information makes it even more important for high resolution imaging satellite with stringent pointing requirements. At the same time, these instruments are highly sensitive to bright objects like Sun and Earth Albedo. In this paper

The stellar spectral data taken by LAMOST (Large Sky Area Multi-Object Fiber Spectroscopic Telescope) include multiple types, some of which that fall between two spectral classes, namely boundary spectra. Due to the massive and high dimensional nature of spectra data, it will take a lot of time and energy to cluster these spectra by manual operation alone. To address this problem, a new clustering

We revisit here a possibility of generation of gravitational wave (GW) bursts due to a very quick change in the quadrupole moment (QM) of a deformed spheroidal pulsar as a result of crustquake. Since it was originally proposed as a possible explanation for sudden spin-up (glitch) of pulsars, the occurrence of crustquake and its various consequences have been studied and discussed quite often in the

We present a CCD photometric survey for the search of variable stars in four open clusters namely Berkeley 69, King 5, King 7 and Berkeley 20. The time series observations were carried out for 1 and/or 2 nights for each of the clusters in the year 1998, which have led to identify nineteen variable stars in these clusters. Out of these 19 variable stars, five stars show \(\delta \) Scuti-like variability

The work is the study of Bianchi type-I models with holographic dark energy in the framework of \( f(R) \) theory of gravitation. The exact solutions of the field equations are deduced by considering the exponential and power-law volumetric expansion. Various physical and kinematical properties of the models are discussed. In addition to make our interpretation more clear for that we have taken the

We studied dust acoustic solitary waves (DASW) in a five component cometary plasma by deriving the Kadomstev–Petiashvili (KP) equation. The five components consist of two components of electrons described by kappa distributions with different temperatures and spectral indices, a lighter (hydrogen) and a heavier (oxygen) ion component, both ion components are described by Maxwellian distributions. Dust

Analysis of spectropolarimetric observations of two circular sunspots located close to disk centre in H\({\alpha }\) (6562.8 Å) and Fe i (6569.22 Å) is presented in this paper. The corresponding active region numbers are NOAA 10940 and NOAA 10941 referred to as AR1 and AR2, respectively. The vector magnetic field at the photosphere is derived through inversion of Stokes profiles of Fe i under Milne–Eddington

Ongoing research on pulsar timing array (PTA) to detect gravitational radiation is reviewed. Here, we discuss the use of millisecond pulsars as a gravitational wave detector, the sources of gravitational radiation detectable by PTAs and the current status of PTA experiments pointing out the future possibilities.

We study the distributions of \(\gamma \)-ray properties of a sample of \(\gamma \)-ray loud blazars taken from the third catalogue of blazars detected by Fermi-Large Area Telescope (Fermi-LAT). We compute the \(\gamma \)-ray dominance (\(D_{\mathrm {g}}\)) of the sample which includes 415 flat spectrum radio quasars (FSRQs) and 535 BL Lacertae objects (BL Lacs). We find that BL Lacs and FSRQs are

The study of the solar energetic particle events (SEPs) and their association with solar flares and other activities are very crucial to understand the space weather. Keeping this in view, here we present the study of SEPs (intensity \(\ge 10\) pfu) during the solar cycles 21–24 (1976–2017) in \(> 10\) MeV energy channels associated with solar flares. For our analysis, we have used the data from different

Archival Vilnius CCD photometric observations are presented for the heavily reddened star cluster Melotte 105, resulting in colour-magnitude diagrams and spectral class estimates. There is considerable lack of agreement between studies for reddening, age and distance for this cluster explaining why the archival data are being made available by this paper. The derived reddening \(E(B-V)=0.34\pm 0.04\)

In view of the negative results from various dark matter detection experiments, we propose alternate models by postulating a minimal field strength (minimal curvature) and also a minimal acceleration. These postulates lead to modified Newtonian dynamics, modified Newtonian gravity, and modified relativistic gravity. Through these postulates, we show that the observed flat rotation curves of galaxies

A simulation of the radiation field inside a habitable module (a diameter of 6 m and length of 12 m) of a spacecraft generated by isotropic Galactic Cosmic Radiation (GCR) in deep interplanetary space is carried out for minimum and maximum solar activity using the FLUKA code. Protons, alpha-particles, deuterons, \(^{\mathrm {3}}\)He, and nuclei with \({Z} > 2\) are considered as primary GCR irradiating

Solar flare activity is characterized by different classification systems, both in optical and X-ray ranges. The most generally accepted classifications of solar flares describe important parameters of flares such as the maximum of brightness of the flare in the optical range – \(H_{\alpha }\) flare class (change from F to B), area of the flare in \(H_{\alpha }\) (change from S for areas less than

MHD shock waves and discontinuities are often observed in the solar wind. We studied a strong shock wave event on 7 June 2014, during a solar maximum. The properties of forward shock are investigated and all physical parameters of interplanetary shock are analyzed. The upstream parameters, such as Alfven velocity and sound speed are calculated, and the angle (\({\theta }\)) between the upstream magnetic

The paper deals with the dynamics of particles which are on the surface of the cometary nucleus. The key point is to research the behavior of the particles as a result of local sublimation. Generally, we can describe three mechanisms related to the particles behavior. Relatively small particles (of the order of micrometers) are ejected into the atmosphere of the comet due to sublimation. Slightly larger

The propagation of cylindrical shock wave in rotational axisymmetric perfect gas under isothermal flow condition with azimuthal magnetic field is investigated. Distributions of gas dynamical quantities are discussed. The density, magnetic pressure, azimuthal fluid velocity and axial fluid velocity are assumed to be varying according to power law with distance from the axis of symmetry in the undisturbed

Indian siddhāntic texts are well known for their indigenous approach to solutions of problems in astronomy which also speaks of their expertise in mathematics. The text Sūryasiddhānta is considered as an authority and we come across a number of texts as commentaries on this text. They range from 8th Century CE to 19th century CE. The study of the stars that have been listed in the text appears relatively

We present results of the first time observations of whistlers during day time (sunrise) on 4th January 2017 at 01 UT (\(\hbox {UT} + 5.30 = \hbox {IST}\)) at Indian low latitude ground station Varanasi (geomag. lat. \(14{^{\circ }}55^\prime \hbox {N}\), geomag. long. \(153{^{\circ }}54^\prime \hbox { E}\), L.1.078). The main goal of analysis is to study the propagation characteristic of the observed

The propagation of cylindrical ionizing shock waves in a self-gravitating ideal gas with axial magnetic field is investigated. The density and magnetic pressure are assumed to be varying according to power law with distance in the undisturbed medium. Approximate analytical solutions are obtained by expanding the flow variables in power series. The zeroth order and first order approximate solutions

In this paper, the neutral particle trajectory around a rotating black hole in the four-dimensional Kerr space–time is studied. The equation of motion is derived by using the Kerr metric within the slowly rotating and weak-field limit. The stability conditions of the orbital motion of the neutral particle are deduced. For small amplitude of motion, the approximate solutions of the resulting differential

Dynamical models for dark energy are an alternative to the cosmological constant. It is important to investigate properties of perturbations in these models and go beyond the smooth FRLW cosmology. This allows us to distinguish different dark energy models with the same expansion history. For this, one often needs the potential for a particular expansion history. We study how such potentials can be

We investigate the astronomical almanacs of the Manchukuo state, which lasted for 14 years, from 1932 to 1945. We examine their contents and analyze the accuracy of the time data by using the almanacs for the years from 1933 to 1945. We find that the calendar of the Qing dynasty in China, Shixianshu, provided the name of the almanac. In addition, the reference location of the time data was Xinjing

In standard cosmologies, dark energy interacts only gravitationally with dark matter. An extension to this picture is interacting quintessence (IQ) model where scalar field coupled directly to cold dark matter. The percentage deviation is studied in IQ model with respect to \(\Lambda \)CDM for varied values of the interacting parameter W. We investigated the effect of interaction on matter, kaiser

About \(\sim \)200 radio pulsars have been observed to exhibit nulling episodes – short and long. We find that the nulling fraction of a pulsar does not have any obvious correlation with any of the intrinsic pulsar parameters. It also appears that the phenomenon of nulling may be preferentially experienced by pulsars with emission coming predominantly from the polar cap region, and also having extremely

This review summarizes recent studies of the cold neutral hydrogen gas associated with galaxies probed via the HI 21-cm absorption line. HI 21-cm absorption against background radio-loud quasars is a powerful tool to study the neutral gas distribution and kinematics in foreground galaxies from kilo-parsec to parsec scales. At low redshifts (\(z<0.4\)), it has been used to characterize the distribution

In this paper we study the bulk viscous cosmology by considering modified Chaplygin gas in the framework of \((2+1)\)-dimensional spacetime. For this we consider various form of bulk viscosity coefficient \(\zeta \) and then obtain the physical parameters energy density \(\rho \), Hubble and deceleration parameters, H and q, respectively. Finally we discuss the stability of the model by using the speed

This article reviews our current understanding about \(\gamma \)-ray detected narrow-line Seyfert 1 (\(\gamma \)-NLSy1) galaxies. The detection with the Large Area Telescope onboard Fermi Gamma-ray Space Telescope has provided the strongest evidence for the presence of closely aligned relativistic jet in these intriguing active galactic nuclei (AGN) and opened up a realm to explore the physical conditions

In this study, the irreversible thermodynamics of the universe in the framework of f(R) gravity has been studied following standard Eckart theory of non-equilibrium thermodynamics. For a spatially flat universe, validity of GSLT and thermodynamic equilibrium have been examined both for apparent and event horizon as bounding horizons.The general result has been verified for exponential models of f(R)

We present a new class of closed-form solutions to the Einstein–Maxwell system of equations for a static spherically symmetric anisotropic star in the presence of an electric field by generalizing earlier approaches. The field equations are integrated by specifying the form of the electric field, anisotropic factor, and one of the gravitational potentials which are physically reasonable. We regain

A revised catalogue of Galactic supernova remnants (SNRs) is presented, along with some simple statistics of their properties. Six new SNRs have been added to the catalogue since the previous published version from 2014, and six entries have been removed, as they have been identified as H ii regions, leaving the number of entries in the catalogue at 294. Some simple statistics of the remnants in the

We present an ultra-violet (UV) study of the galaxy NGC 300 using GALEX far-UV (FUV) and near-UV (NUV) observations. We studied the nature of UV emission in the galaxy and correlated it with optical, H I and mid-infrared (3.6 \(\mu \)m) wavelengths. Our study identified extended features in the outer disk, with the UV disk extending up to a radius of 12 kpc (\({>}2R_{25}\)). We estimated the FUV and

In this paper, we investigate the stability properties of soft gluons in SIBYLL 2.1 with reference to its original version 1.7 that corresponds to hadronic hard interactions. In order to investigate the stability structures, we classify the regions of the gluon density fluctuations in its double leading logarithmic approximation and its equivalent description as the fractional power law. In the parameter

The open clusters NGC 2323 and NGC 2539 have been analysed using CCD \(U\!B\!V\!(R\!I)_{KC}\) photometric data, observed at the San Pedro Mártir Observatory. Cluster memberships have been determined with the proper motion and parallax measures from the GaiaDR2 astrometric data release. Photometric metal and heavy element abundances have been obtained as \(([M/H],\;Z) = (-0.10,~0.012)\) (NGC 2323) and

Isolated millisecond pulsars (IMSPs) are a topic of academic contention. There are various models to explain their formation. We explore the formation of IMSP via quark novae (QN). During this formation process, low-mass X-ray binaries (LMXBs) are disrupted when the mass of the neutron star (NS) reaches \(1.8M_\odot \). Using population synthesis, this work estimates that the galactic birthrate of

Tilted Bianchi type-III cosmological model filled with perfect fluid is investigated in f(R, T) theory of gravity, where R is the Ricci scalar and T is the trace of stress energy momentum tensor. Here we study the class of \(f(R, T) = R + 2f(T)\). To decipher the solutions of field equations, we used time power-law form of a metric potential C, i.e. \( C=t^m\), where m is a positive constant, which

Structural fatigue property of Shanghai 65-m fully-steerable antenna structure is analysed. According to the active fully-steerable working pattern, the typical fatigue stress piece is put forward based on simple sampling and decomposed by real-time rain flow counting algorithms. Subsequently, the fatigue lives of pitch mechanism bearings were computed by miner linear accumulative damage criterion

The chromospheric network extended to the transition region as the solar EUV network disperses at the coronal level. The EUV emission lines from the transition region give information about different atmospheric heights. The network properties have been obtained from the daily spectroscopic data from the Coronal Diagnostic Spectrometer (CDS) on board the Solar and Heliospheric Observatory (SOHO) in

The effect of atmospheric turbulence is gentler at infrared wavelengths than in visible regime. Hence adaptive optics (AO) delivers better performance in the infrared regime. Robotic Adaptive Optics (Robo-AO) is an AO system for medium-sized telescopes jointly built by Caltech, USA and IUCAA, India. It works with minimal overheads and provides good sky coverage in both visible and infrared regime.

The well-known Lane–Emden equation plays an important role in describing some phenomena in mathematical physics and astrophysics. Recently, a new type of this equation with fractional order derivative in the Caputo sense has been introduced. In this paper, two computational schemes based on collocation method with operational matrices of orthonormal Bernstein polynomials are presented to obtain numerical

We present a process for thermal forming of thin glass panels of borosilicate glass to produce mirror segments for X-ray telescope optics. The mirror segments are required to be shaped in a parabolic and hyperbolic shape in accordance with Wolter-I type design of X-ray telescope optics. Thermal forming of glass is a low-cost method to produce light-weight mirror segments. The process makes use of a

The main motive of this investigation is to study the behavior of cosmological model in the presence of matter and a modified holographic Ricci dark energy for homogeneous hypersurface in the scalar tensor theory of gravitation, proposed by Saez–Ballester (Phys. Lett. A, 113, 467 (1986)). The hybrid expansion law (Akarsu et al., JCAP, 01, 022 (2014)) has been used to get a determinate solution. The

This paper comprises the comparative study of the behavior of CRI with geomagnetic storms, southward component of IMF, i.e. \({\vert }{} { Bz}{\vert }\), IMF B, solar wind speed (V) and \(V\cdot {\vert }{} { Bz}{\vert }\) for two consecutive odd solar cycles 21 (1976–1985) and 23 (1996–2008). Our examination arrived at an interesting result that the strongest decrement in CRI occurs around the same

The increase in the number of researchers coupled with the ease of publishing and distribution of scientific papers (due to technological advancements) has resulted in a dramatic increase in astronomy literature. This has likely led to the predicament that the body of the literature is too large for traditional human consumption and that related and crucial knowledge is not discovered by researchers

This paper discusses the influence of light pollution of the night sky on the conditions of visibility of astronomical objects such as planets, stars and comets. This phenomenon has a huge impact on the observability of astronomical objects, especially in cities, where the brightness of the sky makes it difficult or even impossible to conduct astronomical observations. The main purpose of this article

We have investigated the spatially homogeneous and isotropic Friedmann–Robertson–Walker (FRW) universe filled with barotropic fluid and dark energy in the framework of the Brans–Dicke theory of gravitation. Here we have discussed three models: (i) law of variation for Hubble’s parameter, which leads to a constant value of deceleration parameter, (ii) hybrid expansion law model, and (iii) special form

Based on Shannon entropy transfer estimation technique and Stanford’s solar global magnetic field harmonic coefficients, several new facts about solar magnetic modes have been found. The entropy transferring between most of the modes has been subjected to a steady modulation with a period near 72 solar rotations (5.38 years). As a rule, the amplitudes of entropy transferring modulation were less or

This article follows a simpler approach (Siddiqui et al. 2011, Chin. Phys. Lett. 28, 050401) using foliation’s concept with virtual displacement of hyper-surfaces near the event horizon to derive the first law of black hole thermodynamics for the Kerr black hole spacetime.

In this work we have proposed a non-canonical model of exponential harmonic field as dark energy in FRW universe. In this context, we have studied the inflationnary parameters in presence of power law potential. The analysis showed that observational data have been confirmed for quadratic and cubic potentials. In addition, deceleration parameter have been examined by associating to that dark energy

We present new radio observations of the massive and X-ray luminous galaxy cluster MACS J0417.5–1154, at 1.387 GHz and 18 GHz, from the Giant Metrewave Radio Telescope (GMRT) and the Australia Telescope Compact Array (ATCA) respectively. We estimate diffuse emission in the central region of the cluster at 1.387 GHz and 18 GHz. We combine these data with previously published results and present the