In the elliptic restricted three-body problem framework, periodic orbits are multi-revolution (MR) orbits. In the conventional approach to design an MR orbit, the circular halo orbit initial conditions are used with continuation on eccentricity and by dividing the whole orbit into multiple segments. An alternative scheme based on differential evolution is developed which avoids the continuation on

The present investigation considers the effect of small perturbations given in the Coriolis and centrifugal forces on the location and stability of the equilibrium points in the Robe’s circular restricted three-body problem with non-spherical primary bodies. The felicitous equations of motion of \(m_3\) are obtained by taking into account the shapes of primaries \(m_1\) and \(m_2\), the full buoyancy

Recently, Alzain proposed a modified inertial formalism of modified Newtonian dynamics (MOND), wherein Galiliean invariance is violated and new Lorentz transformation properties from an inertial to an accelerated frames are posited. Milgrom’s acceleration constant is then found to be invariant under the aegis of these new space-time coordinate transformations. In this model, a modified equation of

Dynamical aspects of an anisotropic cosmological model are investigated in an extended gravity theory. A hybrid scale factor is employed to investigate the cosmic dynamics. The hybrid scale factor simulates a cosmic transit behaviour from a decelerated phase of expansion to an accelerated phase. The parameters of the hybrid scale factors have been constrained from the cosmic transit behaviour and the

In the present work, turbulence generation due to the dynamic evolution of magnetic islands is investigated. The role of ambient magnetic field in the evolution of magnetic islands and turbulence generation is also investigated. The origin of magnetic islands lies in the fact that reconnection takes place in thin current sheets which becomes unstable and leads to the formation of magnetic islands.

In this article, a historical overview of the development of the Periodic Table has been sketched. After Mendeleev published his Periodic Table in 1869, 55 more elements have been discovered. Of these 55 elements, 35 are radioactive; most of them never existed on Earth earlier. The excitement of the discovery of these unstable elements has been emphasized in this article. In conclusion, the dynamicity

We give a brief overview of the current status of important nuclear physics inputs, like reaction rates, in hydrostatic and explosive nucleosynthesis. Recently, it has been proposed that exotic neutron-rich nuclei play an important role even in the formation of heavy elements via the r-process. The main problems here are identification, abundance estimation of seed nuclei in these processes, and their

The large fraction of carbon-enhanced metal-poor (CEMP) stars at lower metallicities makes them an interesting class of objects to be probed further in greater detail. They show different abundance patterns of neutron-capture elements and based on that CEMP stars are further divided into four categories. Abundances of C, N and O, along with other elements, are required to understand the different nucleosynthetic

The overabundance of lithium in low-mass red giants has been a topic of interest for over four decades. Low-mass stars are expected to destroy lithium gradually throughout their lifetimes. Against this expectation, about \(1\%\) of red giants in the Galaxy show anomalously large Li which, in the literature, are known as lithium-rich giants. The advent of large-scale stellar surveys (LAMOST, GALAH, Kepler

Orbital decay mechanisms argue that double white dwarf mergers are inevitable, but extremely rare. Whilst some mergers result in explosions, the survivors re-ignite helium and burn brightly for tens of thousands or millions of years. Candidate survivors include extreme helium stars, R CrB variables and various classes of helium-rich subluminous star. Nuclear waste on the survivors’ surfaces provides

The blue straggler stars (BSSs) are main-sequence (MS) stars, which have evaded stellar evolution by acquiring mass while on the MS. The detection of extremely low mass (ELM) white dwarf (WD) companions to two BSSs and one yellow straggler star (YSS) from our earlier study using UVIT/AstroSat, as well as WD companions to main-sequence stars (known as blue lurkers) suggest a good fraction of post-mass

The surface chemical compositions of a large fraction of carbon-enhanced metal-poor (CEMP) stars, the so-called CEMP-r/s stars, are known to exhibit enhancement of both s-process and r-process elements. For these stars, the heavy-element abundances cannot be explained either by s-process or r-process nucleosynthesis alone, as the production sites of s-process and r-process elements are very different

We present an on-going project consisting of analysis of a sample of twenty-five metal-poor stars, most of them carbon-enriched and thus tagged carbon-enhanced metal-poor (CEMP) stars, observed with the high-resolution HERMES spectrograph mounted on the Mercator telescope (La Palma), the UVES spectrograph on VLT (ESO Chile), or the HIRES spectrograph on KECK (Hawaii). This sample consists of CEMP-s

The chemical evolution of galaxies is governed by the chemical yields from stars, especially from Asymptotic Giant Branch (AGB) stars. This underlines the importance of understanding how AGB stars produce their elements by obtaining accurate stellar nucleosynthetic yields. Although AGB nucleosynthesis has general validity, critical uncertainties (such as the treatment of convective-driven mixing processes

The availability of multi-wavelength observations and parallaxes from the space missions and very comprehensive models of AGB evolution that include the accretion of matter from the circumbinary disc have strongly impacted our understanding of these enigmatic objects. The important developments made in the recent times are summarized here. The revised estimates of luminosities (derived from better-defined

Type Ia supernovae are the result of explosive thermonuclear burning in CO white dwarfs. The progenitors of the Ia supernovae are white dwarfs in an interacting binary system. The donor companion is either a degenerate star (white dwarf) or a non-degenerate star (e.g. red giant). Recurrent novae are interacting binaries with a massive white dwarf accreting from either a main sequence, slightly evolved

The cosmic origin of fluorine, the ninth element of the periodic table, is still under debate. The reason for this fact is the large difficulties in observing stellar diagnostic lines, which can be used for the determination of the fluorine abundance in stars. Here we discuss some recent work on the chemical evolution of fluorine in the Milky Way and discuss the main contributors to the cosmic budget

The article presents the consolidated results drawn from the chemical composition studies of Reddy et al. (2012, 2013, 2015, 2016) and Reddy & Lambert (2019), who through the high-dispersion echelle spectra (\(R = 60000\)) of red giant members in a large sample of Galactic open clusters (OCs), derived stellar parameters and chemical abundances for 24 elements by either line equivalent widths or synthetic

All the elements heavier than Fe are produced either by the slow (-s) or rapid (-r) neutron-capture process. The neutron density prevailing in the stellar sites is one of the major factors that determines the type of neutron-capture processes. We present the results based on the estimates of corrected value of absolute carbon abundance, [C/N] ratio, carbon isotopic ratio and [hs/ls] ratio obtained

The origin and evolution of hydrogen-deficient stars are not yet adequately understood. Their chemical peculiarities, along with hydrogen-deficiency, makes them stand out from the rest and sheds light on their possible origin. Severe fluorine enrichment (of the order of 800–8000) is one such characteristic feature of a class of hydrogen deficient stars, mainly the RCBs (R Coronae Borealis stars) and

This communication is a summary of our measurements of cross sections and astrophysical S-factors for radiative proton capture on deuteron. The measurements are a part of a new program to study light-ion induced nuclear capture and inelastic scattering reactions relevant to nucleosynthesis and astrophysics. We are primarily interested in the capture reactions relevant to primordial or Big Bang Nucleosynthesis

The Sun provides a standard reference against which we compare the chemical abundances found anywhere else in the Universe. Nevertheless, there is not a unique ‘solar’ composition, since the chemical abundances found in the solar interior, the photosphere, the upper atmosphere, or the solar wind, are not exactly the same. The composition of the solar photosphere, usually preferred as a reference, changes

Understanding nucleosynthesis in and evolution of asymptotic giant branch (AGB) stars is of primary importance as these stars are the main producers of some of the key elements in the Universe. They are the predominant sites for slow-neutron-capture nucleosynthesis (s-process). The exact physical conditions and nucleosynthetic processes occurring in the interior of AGB stars are not clearly understood

We present the results obtained from the UV photometry of the globular cluster NGC 1261 using far-UV (FUV) and near-UV (NUV) images acquired with the Ultraviolet Imaging Telescope (UVIT) on-board the AstroSat satellite. We utilized the UVIT data combined with HST, GAIA, and ground-based optical photometric data to construct the different UV colour-magnitude diagrams (CMDs). We detected blue HB (BHB)

The 3.6-meter Indo–Belgian Devasthal optical telescope (DOT) has been used for optical and near-infrared (NIR) observations of celestial objects. The telescope has detected stars of \(B = 24.5\pm 0.2, R = 24.6\pm 0.12\) and \( g =25.2\pm 0.2\) mag in exposure times of 1200, 4320 and 3600 s respectively. In one hour of exposure time, a distant galaxy of 24.3 ± 0.2 mag and point sources of \(\sim \)25

In this work, the helium-enhancement (He-enhancement) in the lithium-rich (Li-rich) K-giant HD 77361 is investigated using the strengths of the MgH band and the Mg i lines. The detailed abundance analysis and also the synthesis of the MgH band and the Mg i lines has been carried out for HD 77361. One would expect, within uncertainities, same Mg abundance from both the MgH and Mg i lines. But, we found

A toy model of a graviton is explored by considering the minimum amount of information gravitons could carry. The total entropy of the universe is calculated and compared to estimates from super massive black holes and massive models of the graviton. The running cosmological constant is calculated using the entropy relation previously computed and compared to its experimentally accepted value. Both

Sunspot prediction is an important task for space weather and solar physics. Traditional point forecast may not be sufficiently satisfactory and reliable. To quantify the uncertainty of point prediction, a hybrid interval prediction model has been proposed for sunspot forecasting. Three major steps are taken: (1) the complementary ensemble empirical mode decomposition (CEEMD), to decompose the sunspot

We review the Baňados–Teitelboim–Zanelli (BTZ) black hole solution in connection with the spinning string solution. We find a new exact solution, which can be related to the (2 + 1)-dimensional spinning point particle solution. There is no need for a cosmological constant, and so the solution can be up-lifted to (3 + 1) dimensions. The exact solution in a conformally invariant gravity model, where

High resolution infrared imaging observations of the young planetary nebulae (PNe) NGC 7027 and BD +30° 3639, taken with the newly installed TIFR near infrared camera-II (TIRCAM2) on 3.6 m Devasthal optical telescope (DOT), ARIES, Nainital, are being reported. The images are acquired in J, H, K, polycyclic aromatic hydrocarbon (PAH) and narrow-band L (nbL) filters. The observations show emission from

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