A5101464358- Astrophysical Phenomena and Observations
- Astrophysics and Cosmic Phenomena
- Gamma-ray bursts and supernovae
- Pulsars and Gravitational Waves Research
- Astronomical Observations and Instrumentation
- Galaxies: Formation, Evolution, Phenomena
- Solar and Space Plasma Dynamics
- High-pressure geophysics and materials
- Mechanics and Biomechanics Studies
- Brain Tumor Detection and Classification
- Stellar, planetary, and galactic studies
- Information and Cyber Security
- Internet Traffic Analysis and Secure E-voting
- Astrophysics and Star Formation Studies
- Astronomy and Astrophysical Research
- Astro and Planetary Science
- Geophysics and Gravity Measurements
- Network Security and Intrusion Detection
- Particle Accelerators and Free-Electron Lasers
- Blockchain Technology Applications and Security
- Metaheuristic Optimization Algorithms Research
- Advanced Research in Science and Engineering
- VLSI and FPGA Design Techniques
- Digital and Cyber Forensics
- Information Technology Governance and Strategy
Indian Space Research Organisation
2010-2024
Galgotias University
2024
National Institute of Technology Karnataka
2019-2023
Sardar Vallabhbhai National Institute of Technology Surat
2023
Norwegian University of Science and Technology
2017-2018
Ko-Aks (Norway)
2017
Atal Bihari Vajpayee Indian Institute of Information Technology and Management
2012
Jadavpur University
2012
Tata Institute of Fundamental Research
2007-2011
KTH Royal Institute of Technology
2011
Motivation: The above-ground tissues of higher plants are generated from a small region cells situated at the plant apex called shoot apical meristem. An important genetic control circuit modulating size Arabidopsis thaliana meristem is feed-back network between CLAVATA3 and WUSCHEL genes. Although expression patterns for these genes do not overlap, activity both necessary sufficient (when expressed ectopically) induction expression. However, upregulation in conjunction with receptor kinase...
We present the results of Target Opportunity (ToO) observations made with AstroSat newly discovered black hole binary MAXI J1535-571. detect prominent C-type Quasi-periodic Oscillations (QPOs) frequencies varying from 1.85 Hz to 2.88 Hz, along distinct harmonics in all observations. note that while fundamental QPO is seen 3 - 50 keV energy band, harmonic not significant above ~ 35 keV. The were hard intermediate state, as state transitions observed by and Swift. attempt spectral modelling...
ABSTRACT We present a detailed spectro-polarimetric study of black hole X-ray binary 4U 1630−47 during its 2022 outburst with IXPE and NICER observations. The source is observed in disc dominated thermal state (kTin ≈ 1.4 keV) clear detection absorption features at 6.69 ± 0.01 keV 6.97 from both as well spectra, likely indicating coupling disc-wind. A significant degree polarization (PD) $= 8.33\pm 0.17~{{\ \rm per\ cent}}$ angle (PA) =17.78° 0.60° the energy range 2 − 8 are measured IXPE....
We have carried out the first spectro-polarimetric study of bright NS-LMXB GX 9+9 using IXPE and AstroSat observations. report a significant detection polarization $1.7\pm 0.4\%$ over $2-8$ keV energy band, with angle $63^{\circ}\pm 7^{\circ}$. The is found to be energy-dependent, $3\sigma$ degree consistent null in $2-4$ keV, $3.2\%$ $4-8$ keV. Typical spectra seen NS-LMXBs, we find that combination soft thermal emission from accretion disc Comptonized component optically thick corona...
ABSTRACT We report the results of AstroSat observations GRS 1915+105 obtained using 100 ks Guaranteed Time during soft state. The colour–colour diagram indicates a variability class δ with detection high-frequency quasi-periodic oscillation (HFQPO) in power density spectra. HFQPO is seen to vary frequency range 67.96–70.62 Hz percentage rms ∼0.83–1.90 per cent and significance varying from 1.63 7.75. energy dependent spectra show that features are dominant only 6–25 keV band. broad-band...
We present an in-depth spectral and timing analysis of the Black Hole binary 4U 1630-472 during 2016 2018 outbursts as observed by \textit{AstroSat} \textit{MAXI}. The extensive coverage with \textit{MAXI} is used to obtain Hardness Intensity Diagram (HID). source follows a `c'-shaped profile in agreement earlier findings. Based on HIDs previous outbursts, we attempt track evolution `super'-outburst `mini'-outbursts. model broadband energy spectra ($0.7-20.0$ keV) observations both using...
Brain tumors are extreme and doubtlessly fatal sicknesses, early correct analysis critical to enhance affected person effects. Magnetic resonance imaging, or MRI, is an tool for detection screening of mind cancer. tumor has turn out be more in recent years due the combination system gaining knowledge (ML) convolutional neural network (CNN).This paper offers a focused use A complete evaluate CNN-ML methods on How awful lot ML-CNN-based strategies identification Effective most appropriate...
We present the first spectro-polarimetric study of bright atoll source GX 9+1, using simultaneous Imaging X-ray Polarimetry Explorer (IXPE), and Neutron star Interior Composition (NICER) observations. The was observed to remain in soft state, with no changes state throughout observation period. does not show significant polarization 2-8 keV energy range. However, a (3.3 sigma) detected 2-3 range, degree 3.3 +/- 0.8% angle 11 7 deg. used spectra from NICER (0.6 - keV) IXPE (2-8 spectral...
Background -Risk Analysis is an integral part of management practice and essential element good corporate governance.There are many risk analysis methods available today, it a tedious task for organization (particularly small mid-scale company) to choose the proper method.Problem -Although tools in this domain, very few inventories do exist that structured according set common properties.There main determine which one use.Contribution -The objective review paper provide researchers, four...
We study the spectral and temporal characteristics of source GS 2023$+$338 (V404 Cyg) during initial phase its June 2015 outburst, over energy range 0.5 - 150 keV. This is first detailed this based on {\it SWIFT} observations, being reported. Based our analysis, we understand that existed in hard, intermediate soft states. find evolution parameters, hardness intensity diagram rms-intensity are not similar to those observed for most outbursting black hole sources. also observe presence weak...
ABSTRACT In this paper, we performed a spectro-polarimetric analysis of the transient NS-LMXB XTE J1701−462 using IXPE, NICER, and NuSTAR data during its 2022 outburst. We report significant detection energy-dependent polarization in X-ray signal from source on September 29 2–4, 4–8, 2–8 keV energy bands with degree 3.9 ± 0.3, 5.5 0.6, 4.5 0.4 per cent, respectively. The angle overall band was ∼143° 2°. spectra were modelled combination thermal emission an accretion disc, Comptonized hot...
In this paper, we attempt to find out the `spectro-temporal' characteristics during jet ejection, of several outbursting Galactic black hole sources based on RXTE-PCA/HEXTE data in energy band 2 - 100 keV. We present results detailed analysis these rising phase their outburst, whenever simultaneous or near-simultaneous X-ray and Radio observations are `available'. that before peak radio flare (transient jet) a few (in addition those reported earlier) exhibit `local' softening within soft...
We investigate the X-ray variability characteristics of hard selected AGNs (based on Swift/BAT data) in soft band using RXTE/ASM data. The uncertainties involved individual dwell measurements ASM are critically examined and a method is developed to combine large number dwells with appropriate error propagation derive long duration flux (greater than 10 days). also provide general prescription estimate errors derived from rms values unequally spaced Though for sources not very high...
Abstract We perform comprehensive temporal and spectral analysis of the newly discovered X-ray transient MAXI J1803–298 using an AstroSat target opportunity observation on 2021 May 11 during its outburst. The source was found to be in hard-intermediate state. detect type C quasi-periodic oscillations (QPOs) at frequencies ∼5.4 ∼6.3 Hz along with a subharmonic ∼2.8 3–15 keV band. frequency fractional rms amplitude QPO 15–30 band are higher than those find soft lags ∼3.8 ∼6.8 ms for respective...
We investigate the accretion disk geometry in Galactic black hole sources by measuring time delay between soft and hard X-ray emissions. Similar to recent discoveries of anti-correlated lags Cyg X-3 GRS 1915+105, we find that X-rays are with a significant lag another source: XTE J1550-564. also existence pivoting model independent spectrum during these observations. time-resolved spectral parameters variation is consistent idea truncated disk. The QPO frequency, which measure size disk, too...
We report the discovery of a quasi-periodic oscillation (QPO) at 642 mHz in an XMM–Newton observation ultraluminous X-ray source (ULX) IC 342 X-1. The QPO has centroid νQPO = ± 20 mHz, coherence factor Q 11.6 and amplitude (rms) 4.1 per cent with significance 3.6σ. energy dependence study shows that is stronger range 0.3–5.0 keV. A subsequent (6 d later) does not show any signature power-density spectrum. broad-band spectra (0.3–40.0 keV) obtained by quasi-simultaneous observations NuSTAR...
ABSTRACT We present the first results of extragalactic black hole (BH) X-ray binaries LMC X-1 and X-3 using all archival legacy observations by AstroSat during period 2016–2020. Broad-band energy spectra (0.5–20 keV) both sources obtained from Soft Telescope Large Area Proportional Counter on-board are characterized strong thermal disc blackbody component (kTin ∼ 1keV, $f_{\mathrm{ disc}}\gt 79{{\ \rm per\ cent}}$) along with a steep power-law (Γ 2.4–3.2). Bolometric luminosity varies...
We present a detailed spectral and timing analysis of Cygnus X-1 with multi-epoch observations, during $2016$ to $2019$, by SXT LAXPC on-board AstroSat. model the spectra in broad energy range $0.5\!-\!70.0\,\rm{keV}$ study evolution properties while transited from hard state an extreme soft via intermediate states 2017. Simultaneous features are also examined modelling power density $3.0\!-\!50.0\,\rm{keV}$ . find that high-soft made AstroSat on Oct $24,\,2017$ (MJD $58050$), spectrum...
We present a comprehensive study of GRS 1915+105 in wide energy band ($0.5-60$ keV) using AstroSat observations during the period $2016-2019$. The MAXI X-ray lightcurve source shows rise and decay profiles similar to canonical outbursting black holes. However, does not follow exemplary 'q'-diagram Hardness-Intensity Diagram (HID). Model independent analysis lightcurves suggests that displays various types variability classes ($\delta,\chi,\rho,\kappa,\omega$ $\gamma$). also report possible...
In this letter, we develop a model formalism to study the structure of relativistic, viscous, optically thin, advective accretion flow around rotating black hole in presence radiative coolings. We use examine physical parameters Ultra-luminous X-ray sources (ULXs), namely mass ($M_{\rm BH}$), spin ($a_{\rm k}$) and rate (${\dot m}$), respectively. While doing this, adopt recently developed effective potential mimic spacetime geometry holes. solve governing equations obtain shock induced...
ABSTRACT We present a comprehensive spectrotemporal analysis of five ultraluminous X-ray sources (ULXs) with central object likely being black hole, using archival XMM–Newton observations. These sources, namely NGC1313 X−1, NGC5408 X-1, NGC6946 M82 and IC342 reveal short-term variability fractional variance 1.42$-27.28~{{\ \rm per\ cent}}\, $ exhibit Quasi-periodic Oscillations (QPOs) frequency νQPO ∼ 8−667 mHz. Long-term evolution ULXs energy spectra (0.3–10 keV; excluding X−1) are...
Data from {\it Chandra} observations of thirty nearby galaxies were analyzed and 365 X-ray point sources chosen whose spectra not contaminated by excessive diffuse emission affected photon pile up. The these fitted using two spectral models (an absorbed power-law a disk blackbody) to ascertain the dependence estimated parameters on model used. It was found that cumulative luminosity function depends choice model, especially for luminosities $> 10^{40}$ ergs/s. In accordance with previous...
We present the results obtained by a detailed study of extragalactic Z source LMC X-2, using broad-band Suzaku data and large (∼750 ks) set with proportional counter array (PCA) onboard Rossi X-ray Timing Experiment (RXTE). The PCA allow complete spectral evolution along horizontal, normal flaring branches track. Comparison previous studies shows that details (like variation Comptonizing electron temperature) are similar to those GX 17+2 but unlike Cyg X-2 349+2. This suggests sources...
IGR J17091--3624 is a transient galactic black hole which has distinct quasi-periodic variability known as `heartbeat', similar to the one observed in GRS 1915+105. In this paper, we report results of $\sim 125$ ks \textit{AstroSat} observations source during 2016 outburst. For first time double peaked QPO (DPQ) detected few segments with difference $\delta f ~\sim12$ mHz between two peaks. The nature DPQ was studied based on hardness ratios and using static well dynamic power spectrum....