We present the study of dynamical status of the globular cluster NGC 1851. A combination of multi-wavelength space and ground-based data sets are used for the present analysis. In order to select the genuine cluster members, we used the astro-photometric data available from HST and GAIA-DR2 catalogs. The BSS radial distribution of the cluster is plotted from the center of the cluster to the outskirts

In this work, the effects of extensive air showers (EASs) were described by estimating the lateral distribution function (LDF) at very high energies of various cosmic-ray particles. The LDF simulation was performed using the air shower extended simulation (AIRES) system version 2.8.4a. LDF was simulated for charged particles such as pair production, muons, and all charged particles at very high energies

We present the results from the multi-wavelength monitoring observations of the Narrow-Line Seyfert 1 galaxy Mrk 335 with AstroSat. We analysed both the X-ray (SXT and LAXPC) and UV (UVIT) data of the source at two epochs, separated by \(\sim\)18 days. The source was in a low flux state during the observations, and the X-ray spectra were found to be harder than usual. The presence of soft X-ray excess

We present an ultra-violet study of two nearby dwarf irregular galaxies WLM and IC 2574, using the Far-UV and Near-UV data from the Ultra-Violet Imaging Telescope (UVIT). We used the F148W band Far-UV images and identified 180 and 782 young star-forming clumps in WLM and IC 2574, respectively. The identified clumps have sizes between 7–30 pc in WLM and 26–150 pc in IC 2574. We noticed more prominent

AstroSat/UVIT carries two gratings in the FUV channel and a single grating in the NUV channel. These gratings are useful for low resolution, slitless spectroscopy in the far and near UV bands of a variety of cosmic sources such as hot stars, interacting binaries, active galactic nuclei, etc. We present calibration of these gratings using observations of UV standards NGC 40 and HZ 4. We perform wavelength

We review the basic definitions and properties of trapped surfaces and discuss them in the context of Kerr–Vaidya line element. Our study shows that the apparent horizon does not exist in general for axisymmetric space–times. The reason being the surface at which the null tangent vectors are geodesics and the surface at which the expansion of such vectors vanishes do not coincide. The calculation of

We present the UV photometry of the old open cluster NGC188 obtained using images acquired with Ultraviolet Imaging Telescope (UVIT) on board the AstroSat satellite, in two far-UV (FUV) and one near-UV (NUV) filters. UVIT data is utilised in combination with optical photometric data to construct the optical and UV colour-magnitude diagrams (CMDs). In the FUV images, we detect only hot and bright blue

We report the discovery of a bright, compact ultraviolet source at a projected separation of 1.1 kpc from the known active galactic nucleus (AGN) in Mrk 766 based on AstroSat/UVIT observations. We perform radial profile analysis and derive the UV flux almost free from the nearby contaminating sources. The new source is about 2.5 and 5.6 times fainter than the AGN in the far and near UV bands. The two

AstroSat, India’s first observatory class satellite, operates as a proposal based observatory. AstroSat carries five science payloads capable of simultaneous observations in a broad energy band. In this article, we will summarize the science operations of AstroSat, AstroSat user distribution, user support available for AstroSat users and publications related to AstroSat and AstroSat data.

Ultra Violet Imaging Telescope (UVIT) is one of the 5 instruments on AstroSat satellite, which was launched on September 28, 2015. UVIT was designed to make images with a resolution of \(< 1.8''\), simultaneously in two ultraviolet channels: Far Ultraviolet (130–180 nm) and Near Ultraviolet (200–300 nm). Images are also made in visible region (320–550 nm) for tracking drifts in pointing. The shortest

The origins of X-ray and radio emissions during an X-ray binary outburst are comparatively better understood than those of ultraviolet, optical and infrared radiation. This is because multiple competing mechanisms – emission from intrinsic and irradiated disk, secondary star emission, synchrotron emission from jet and/or non-thermal electron cloud, etc – peak in these mid-energy ranges. Ascertaining

The structure of our Galaxy has been studied from ultraviolet (UV) star counts obtained with the Ultra-Violet Imaging Telescope (UVIT) on board the AstroSat satellite, in Far-UV (FUV) and Near-UV (NUV) bands. The F154W (BaF2) and N263M (NUVB4) filters were used in the FUV and NUV bands, respectively. The point sources are separated from the extra-galactic sources of UVIT observations using infrared

The ground data processing, archival and dissemination of the science data for India’s first multi wavelength astronomical spacecraft, AstroSat is carried out from Indian Space Science Data Centre (ISSDC). The proposals submitted by users worldwide are grouped into observations and are observed in multiple orbit segments. Large volume of data in various configurations from different payloads and the

The Large Area Proportional Counter (LAXPC) instruments onboard the AstroSat Observatory has observed the X-ray binary system Her X-1 during AstroSAT observing sessions AO2, AO3 and TO2. These include observations while Her X-1 is in different stages of its 35 day cycle: Low State, Turn-On to Main High State, peak of Main High State and early decline of Main High State. These observations also include

With its large effective area at hard X-rays, high time resolution and having co-aligned other instruments, AstroSat/LAXPC was designed to usher in a new era in rapid variability studies and wide spectral band measurements of the X-ray binaries. Over the last five years, the instrument has successfully achieved to a significant extent these Science goals. In the coming years, it is poised to make more

The Cadmium–Zinc–Telluride (CZT) Imager on board AstroSat is a hard X-ray imaging spectrometer operating in the energy range of 20–100 keV. It also acts as an open hard X-ray monitor above 100 keV capable of detecting transient events like the Gamma-ray Bursts (GRBs). Additionally, the instrument has the sensitivity to measure hard X-ray polarization in the energy range of 100–400 keV for bright on-axis

We present the detection of type C quasi-periodic oscillation (QPO) along with upper harmonic at respective frequencies of \(\sim \)0.6 Hz and \(\sim \)1.2 Hz in the single AstroSat observation taken during the 2016 outburst of the low-mass black hole X-ray binary H 1743-322. These frequencies are found to be shifted by \(\sim \)0.4 Hz for the QPO and \(\sim \)0.8 Hz for the upper harmonic with respect

We present far ultraviolet (FUV) observations of globular cluster NGC 4147 using three FUV filters, BaF\(_2\) (F154W), sapphire (F169M), and silica (F172M) of Ultra-Violet Imaging Telescope (UVIT) on-board the AstroSat satellite. We confirmed the cluster membership of the UVIT observed sources using proper motions from Gaia data release 2 (GAIA DR2). We identified 37 blue horizontal branch stars (BHBs)

We present imaging and photometric studies of the radio galaxy NGC 1316 (Fornax A) using high spatial resolution near-ultraviolet (NUV) and far-ultraviolet (FUV) imaging telescopes of the first Indian multi-wavelength space observatory AstroSat. The residual maps of UV emission obtained from the subtraction of smooth models witness peculiar features within the central few kpc (1–2 kpc) region. The

We have written a reference manual to use JUDE (Jayant’s UVIT Data Explorer) data pipeline software for processing and reducing the Ultraviolet Imaging Telescope (UVIT) Level 1 data into event lists and images—Level 2 data. The JUDE pipeline is written in the GNU Data Language (GDL) and released as an open-source which may be freely used and modified. GDL was chosen because it is an interpreted language

The Large Area X-ray Proportional Counter (LAXPC) instrument on-board AstroSat has three nominally identical detectors for timing and spectral studies in the energy range of 3–80 keV. The performance of these detectors during the five years after the launch of AstroSat is described. Currently, only one of the detector is working nominally. The variation in pressure, energy resolution, gain and background

We present the results obtained from timing and spectral studies of Be/X-ray binary pulsar EXO 2030+375 using observations with the Large Area Xenon Proportional Counters and Soft X-ray Telescope of AstroSat, at various phases of its Type-I outbursts in 2016, 2018, and 2020. The pulsar was faint during these observations as compared to earlier observations with other observatories. At the lowest luminosity

Dorado is a nearby (17.69 Mpc) strongly evolving galaxy group in the Southern Hemisphere. We are investigating the star formation in this group. This paper provides a FUV imaging of NGC 1533, IC 2038 and IC 2039, which form a substructure, south west of the Dorado group barycentre. FUV CaF2-1 UVIT-Astrosat images enrich our knowledge of the system provided by GALEX. In conjunction with deep optical

Performance of the Level-2 pipeline, which translates the UVIT data created by the ISRO’s ground segment processing systems (Level-1) into astronomer ready scientific data products, is described. This pipeline has evolved significantly from experiences during the in orbit mission. With time, the detector modules of UVIT developed certain defects which led to occasional corruption of imaging and timing

For the AstroSat 5-Year Special Issue, we present a tutorial on the usage of the CCDLAB Pipeline for UVIT data reduction from Level 1 raw data to completed science images. The tutorial informs us of the unique data-processing requirements for reducing UVIT data, including one unique development borne out of such reduction applicable to the field of astronomy in general in the form of a novel approach

AstroSat Proposal Processing System (APPS) is a mission critical software solution designed and developed by the joint efforts of Indian Space Research Organization and the Inter-University Centre for Astronomy and Astrophysics. It facilitates the participation of global scientific community to submit scientific proposals for observations with India’s first multi-wavelength space observatory. The software

AstroSat is India’s first dedicated multi-wavelength space observatory launched by the Indian Space Research Organisation (ISRO) on 28 September 2015. After launch, the AstroSat Science Support Cell (ASSC) was set up as a joint venture of ISRO and the Inter-University Centre for Astronomy and Astrophysics (IUCAA) with the primary purpose of facilitating the use of AstroSat, both for making observing

AstroSat, India’s first astronomical observatory was launched on 28th September 2015 by PSLV into an orbit of altitude 650 km and 6o inclination. The simultaneous observations made by the payloads allow imaging of celestial source in various wavebands and has resulted in scientific achievements published in various fora. AstroSat is designed to carry 6 (5 +1 auxiliary) astronomy payloads namely, UVIT

AstroSat, a dedicated Space Observatory of India, has completed five successful years of operation in space on 28th September 2020. AstroSat is a quite complex satellite, as it is a multi-wavelength observatory with many scientific instruments. The saga of many agencies, including Indian Space Research Organisation, the lead agency, and many scientists and engineers has resulted in realizing and operating

AstroSat is an astronomical observatory from India which is in a low earth orbit of 650 km altitude with a 6-degree inclination and has been functioning successfully in orbit for the last 5 years. The simultaneous observation by the payloads allows imaging of celestial sources in various wavebands that has resulted in scientific achievements which are published in various forum. Uniqueness of its orbit

Curvit is an open-source Python package that facilitates the creation of light curves from the data collected by the Ultra-Violet Imaging Telescope (UVIT) onboard AstroSat, India’s first multi-wavelength astronomical satellite. The input to Curvit is the calibrated events list generated by the UVIT-Payload Operation Center (UVIT-POC) and made available to the principal investigators through the Indian

AstroSat is India’s first dedicated astronomical observatory in space with multi-wavelength payload on a single platform. It enables simultaneous observations in the desired wavebands. The increase in the number of payloads has also led to an increase in the complexity in space segment design, ground segment design, and mission operation management. Each payload instrument and mainframe has its own

In this review, we explain recent progress made in the Babcock–Leighton dynamo models for the Sun, which have been most successful to explain various properties of the solar cycle. In general, these models are two-dimensional (2D) axisymmetric and the mean-field dynamo equations are solved in the meridional plane of the Sun. Various physical processes (e.g., magnetic buoyancy and Babcock–Leighton mechanism)

Over the last 5 years, UVIT has completed observations of more than 500 proposals with \(\sim 800\) unique pointings. In addition, regular planned monitoring observations have been made and from their analysis various key parameters related to in orbit performance of UVIT have been quantified. The sensitivities of the UV channels have remained steady indicating no effect of potential molecular contamination

Several kinds of instabilities are often observed in the solar wind. Langmuir waves have been observed using wideband plasma wave measurements on several spacecrafts such as the Galileo spacecraft. We studied the Langmuir wave instability event in the solar wind on 10 December 1990, during a solar maximum. On this date, highly structured bursts and Langmuir waves have been observed by the Galileo spacecraft

AstroSat has completed 5 years of successful in-orbit operation on 28 September 2020. AstroSat is ISRO’s first Indian multi-wavelength satellite operating as a space Observatory. It is the only satellite which can simultaneously observe in the Far UV and a wide X-ray band from 0.3 to 80 keV using different instruments. This astronomy mission was conceived, following the success of several piggy back

The Soft X-ray Telescope (SXT) aboard the AstroSat satellite is the first Indian X-ray telescope in space. It is a modest size X-ray telescope with a charge coupled device (CCD) camera in the focal plane, which provides X-ray images in the \(\sim \)0.3–8.0 keV band. A forte of SXT is in providing undistorted spectra of relatively bright X-ray sources, in which it excels over some current large CCD-based

Recently, quasi-periodic propagating disturbances have been detected frequently in different structures of the solar corona. These propagating disturbances are interpreted as slow magnetoacoustic waves. They may be responsible for longitudinal intensity oscillations in coronal structures. The purpose of this study is to investigate the features of propagating disturbances in two different types of

A “Nova” refer to close binary systems, where outbursts occur on the white dwarf surface due to thermonuclear runaway. Numerical simulations of nova explosions have shown that the accreted envelopes attain peak temperature of about \(4 \times 10^{8}\) K. The temperature remains at the peak value for about several hundred seconds; this allows nuclear reactions to take place in the ejecta. Theoretical

Most of the large galaxies host a supermassive black hole, but their origin is still not well understood. In this paper, we look at a possible connection between the gravitational binding energies of large galaxies, etc., and the masses of their central black holes. Using this relation (between the gravitational binding energy of the host structure and the black hole energy), we argue why globular

A near-infrared photometer based on an InGaAs PIN photodiode and the filter set recommended by Infrared Working Group (IRWG) have been designed and built. It is mounted on the 1-m Carl–Zeiss telescope at the Vainu Bappu Observatory (VBO) in Kavalur, India. The main science goal is to observe bright sources (< 5 magnitude) in the iZ, iJ and iH photometric bands. A discussion of the instrument and on-telescope

We obtained three new full BVRI light curves for two eclipsing binaries V1094 Her and MT Cas on nine nights from 2015 to 2018 using two optical telescopes. We analysed the orbital period variations using all available light curve minima, seven of which were from our work. For V1094 Her, we found that there is a cyclic variation overlaying a continuous period decrease. The cyclic variation of V1094

Dynamical behavior of ion-acoustic waves (IAWs) is explored in magnetized Auroral zone plasma comprising ions and two-temperature electrons. Employing reductive perturbation technique (RPT), Kadomtsev–Petviashvili (KP) and modified KP (mKP) equations are derived. By considering a typical set of parameters for the Auroral zone, all probable phase plots for unperturbed and perturbed dynamical systems

Studying solar filaments can help in understanding the distribution of large-scale field in the solar atmosphere and provide useful insights into the nature of the solar magnetic field. Recently, the National Astronomical Observatory of the Chinese Academy of Sciences has collected huge volumes of data about solar filaments from several international observing stations for nearly 100 years. Designing

Investigation of the relationship between ionospheric scintillations and equatorial spread F (ESF) during adverse space weather conditions is of paramount significance for developing ionospheric scintillation mitigation strategies for Global Navigation Satellite System (GNSS) receivers. In this paper, we present correlation analysis between equatorial spread F (ESF) and L-band amplitude scintillations

The estimation of the main parameters of star clusters is a very important target in astrophysical studies. Many of the open clusters listed in known catalogs have insufficient astrometric parameters. Improving the observations and analysis methods proved that some of them are asterisms and not true clusters. The most important aspect of using the GAIA DR2 survey lies in the positions, parallax and

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