Sandip K. Chakrabarti
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View article: Study of attitude and rotation period of scientific payload using stratospheric small balloon missions
Study of attitude and rotation period of scientific payload using stratospheric small balloon missions Open
View article: Prediction of Rainfall, Maximum and Minimum Temperature in Summer Monsoon Months Using Artificial Neural Network
Prediction of Rainfall, Maximum and Minimum Temperature in Summer Monsoon Months Using Artificial Neural Network Open
Artificial neural networks (ANNs), are computer based mathematical processing systems inspired by the biological neural networks on which the animals brain works and is being used by state of the art computer technology for faster computin…
View article: Viscous Transonic Accretion Flows in Kerr Black Hole Geometry
Viscous Transonic Accretion Flows in Kerr Black Hole Geometry Open
We study viscous transonic accretion flows in vertical equilibrium in Kerr geometry. We employ the pseudo-Kerr formalism that accurately describes transonic flows around Kerr black holes and is applicable for modeling observational data. W…
View article: Unravelling the Asphericities in the Explosion and Multifaceted Circumstellar Matter of SN 2023ixf
Unravelling the Asphericities in the Explosion and Multifaceted Circumstellar Matter of SN 2023ixf Open
We present a detailed investigation of photometric, spectroscopic, and polarimetric observations of the Type II SN 2023ixf. Earlier studies have provided compelling evidence for a delayed shock breakout from a confined dense circumstellar …
View article: Viscous Transonic Accretion Flows in Kerr Black Hole Geometry
Viscous Transonic Accretion Flows in Kerr Black Hole Geometry Open
We study viscous transonic accretion flows in vertical equilibrium in Kerr geometry. We employ the pseudo-Kerr formalism which accurately describes transonic flows around Kerr black holes and is applicable for modelling observational data.…
View article: Effective potential approach to study hydrodynamics and particle dynamics in Kerr geometry
Effective potential approach to study hydrodynamics and particle dynamics in Kerr geometry Open
We derive the exact form of effective potential in Kerr geometry from the general relativistic radial momentum equation. The effective potential accurately mimics the general relativistic features, over the entire range of the spin paramet…
View article: Accretion properties of a low-mass active galactic nucleus: UGC 6728
Accretion properties of a low-mass active galactic nucleus: UGC 6728 Open
We present a comprehensive analysis of approximately 15 years (2006–2021) of X-ray observations of UGC 6728, a low-mass bare AGN, for the first time. Our study encompasses both spectral and temporal aspects of this source. The spectral pro…
View article: Unravelling the asphericities in the explosion and multi-faceted circumstellar matter of SN 2023ixf
Unravelling the asphericities in the explosion and multi-faceted circumstellar matter of SN 2023ixf Open
We present a detailed investigation of photometric, spectroscopic, and polarimetric observations of the Type II SN 2023ixf. Earlier studies have provided compelling evidence for a delayed shock breakout from a confined dense circumstellar …
View article: Study of Secondary Cosmic Rays and Astronomical X-Ray Sources using Small Stratospheric Balloons
Study of Secondary Cosmic Rays and Astronomical X-Ray Sources using Small Stratospheric Balloons Open
The X-ray sources of the universe are extraterrestrial in nature which emit X-ray photons. The closest strong X-ray source is the Sun, which is followed by various compact sources such as neutron stars, black holes, the Crab pulsar, etc. I…
View article: Accretion Flow Properties of EXO 1846-031 during Its Multi-peaked Outburst after Long Quiescence
Accretion Flow Properties of EXO 1846-031 during Its Multi-peaked Outburst after Long Quiescence Open
We study the recent outburst of the black hole candidate EXO 1846-031, which went into an outburst in 2019 after almost 34 yr in quiescence. We use archival data from the Swift/XRT, MAXI/GSC, NICER/XTI, and NuSTAR/FPM satellites/instrument…
View article: The accretion properties of a low-mass Active Galactic Nucleus: UGC 6728
The accretion properties of a low-mass Active Galactic Nucleus: UGC 6728 Open
We present a comprehensive analysis of approximately $15$ years ($2006-2021$) of X-ray observations of UGC~6728, a low-mass bare AGN, for the first time. Our study encompasses both spectral and temporal aspects of this source. The spectral…
View article: Survey of Bare Active Galactic Nuclei in the Local Universe (z < 0.2). I. On the Origin of Soft Excess
Survey of Bare Active Galactic Nuclei in the Local Universe (z < 0.2). I. On the Origin of Soft Excess Open
We analyze a sample of 21 “bare” Seyfert 1 active galactic nuclei, a subclass of Seyfert 1 galaxies, with intrinsic absorption N H ∼ 10 20 cm −2 , in the local Universe ( z < 0.2) using XMM-Newton and Swift/XRT observations. The luminositi…
View article: Survey of Bare Active Galactic Nuclei in the local universe (z < 0.2): I. On the origin of Soft-Excess
Survey of Bare Active Galactic Nuclei in the local universe (z < 0.2): I. On the origin of Soft-Excess Open
We analyse a sample of 21 `bare' Seyfert~1 Active Galactic Nuclei (AGNs), a sub-class of Seyfert~1s, with intrinsic absorption $\mathrm{N_{H}} \sim 10^{20}~ \mathrm{cm}^{-2}$, in the local universe (z $<$ 0.2) using {\it XMM-Newton} and {\…
View article: Accretion Flow Properties of EXO 1846-031 During its Multi-Peaked Outburst After Long Quiescence
Accretion Flow Properties of EXO 1846-031 During its Multi-Peaked Outburst After Long Quiescence Open
We study the recent outburst of the black hole candidate EXO 1846-031 which went into an outburst in 2019 after almost 34 years in quiescence. We use archival data from Swift/XRT, MAXI/GSC, NICER/XTI and NuSTAR/FPM satellites/instruments t…
View article: Study of accretion flows around an ultraluminous X-ray source M82 X-1 using NuSTAR data
Study of accretion flows around an ultraluminous X-ray source M82 X-1 using NuSTAR data Open
We study the spectral properties and accretion flow behavior of an ultraluminous X-ray source M82\,X-1 using {\it NuSTAR} observations. We use the physical two component advective flow (TCAF) model to fit the data and to derive the accreti…
View article: Diagnostic study of geomagnetic storm-induced ionospheric changes over very low-frequency signal propagation paths in the mid-latitude D region
Diagnostic study of geomagnetic storm-induced ionospheric changes over very low-frequency signal propagation paths in the mid-latitude D region Open
We performed a diagnostic study of geomagnetic storm-induced disturbances that are coupled to the mid-latitude D region by quantifying the propagation characteristics of very low-frequency (VLF) radio signals from transmitters located in C…
View article: Understanding accretion flow properties of black hole candidates after implementation of the TCAF solution in XSPEC
Understanding accretion flow properties of black hole candidates after implementation of the TCAF solution in XSPEC Open
View article: Flux and spectral variability of Mrk 421 during its moderate activity state using<i>NuSTAR</i>: Possible accretion disc contribution?
Flux and spectral variability of Mrk 421 during its moderate activity state using<i>NuSTAR</i>: Possible accretion disc contribution? Open
Context. The X-ray emission in BL Lac objects is believed to be dominated by synchrotron emission from their relativistic jets. However, when the jet emission is not strong, one could expect signatures of X-ray emission from inverse Compto…
View article: Flux and spectral variability of Mrk 421 during its moderate activity state using NuSTAR: Possible accretion disc contribution?
Flux and spectral variability of Mrk 421 during its moderate activity state using NuSTAR: Possible accretion disc contribution? Open
The X-ray emission in BL Lac objects is believed to be dominated by synchrotron emission from their relativistic jets. However, when the jet emission is not strong, one could expect signatures of X-ray emission from inverse Compton scatter…
View article: Similarities and differences in accretion flow properties between GRS 1915+105 and IGR J17091-3624: A case study
Similarities and differences in accretion flow properties between GRS 1915+105 and IGR J17091-3624: A case study Open
View article: Seismogenic Anomalies in Atmospheric Gravity Waves as Observed from SABER/TIMED Satellite during Large Earthquakes
Seismogenic Anomalies in Atmospheric Gravity Waves as Observed from SABER/TIMED Satellite during Large Earthquakes Open
Atmospheric disturbances caused by seismic activity are a complex phenomenon. The Lithosphere–Atmosphere–Ionosphere Coupling (LAIC) mechanism gives a detailed idea to understand these processes to study the possible impacts of a forthcomin…
View article: Transonic Accretion and Winds Around Pseudo-Kerr Black Holes And Comparison with General Relativistic Solutions
Transonic Accretion and Winds Around Pseudo-Kerr Black Holes And Comparison with General Relativistic Solutions Open
Spectral and timing properties of accretion flows on a black hole depend on their density and temperature distributions, which in turn come from the underlying dynamics. Thus, an accurate description of the flow which includes hydrodynamic…
View article: Unusual Surface Latent Heat Flux Variations and Their Critical Dynamics Revealed before Strong Earthquakes
Unusual Surface Latent Heat Flux Variations and Their Critical Dynamics Revealed before Strong Earthquakes Open
We focus on the possible thermal channel of the well-known Lithosphere–Atmosphere–Ionosphere Coupling (LAIC) mechanism to identify the behavior of thermal anomalies during and prior to strong seismic events. For this, we investigate the va…
View article: Is There Any Linkage between Interstellar Aldehyde and Alcohol?
Is There Any Linkage between Interstellar Aldehyde and Alcohol? Open
It is speculated that there might be some linkage between interstellar aldehydes and their corresponding alcohols. Here an observational study and astrochemical modeling are coupled together to illustrate the connection between them. The A…
View article: Spectral Signature of Mass Outflow in the Two Component Advective Flow Paradigm
Spectral Signature of Mass Outflow in the Two Component Advective Flow Paradigm Open
Outflows are common in many astrophysical systems. In the Two Component Advective Flow ( TCAF ) paradigm, which is essentially a generalized Bondi flow including rotation, viscosity, and cooling effects, the outflow originates in the hot, …
View article: Comment on angeo-2021-42
Comment on angeo-2021-42 Open
We performed a diagnostic study of geomagnetic storm-induced disturbances that are coupled to the lower ionosphere in mid-latitude D-region using propagation characteristics of VLF radio signals. We characterised the diurnal VLF amplitude …
View article: Long Term Ionospheric VTEC Variation During Solar cycle 24 as Observed from Indian IGS GPS Station
Long Term Ionospheric VTEC Variation During Solar cycle 24 as Observed from Indian IGS GPS Station Open
The International Scientific Research Organization for Science, Engineering and Technology (ISROSET) is a Non-Profit Organization; The ISROSET is dedicated to improvement in academic sectors of Science (Chemistry, Bio-chemistry, Zoology, B…
View article: Pre-Seismic Irregularities during the 2020 Samos (Greece) Earthquake (M = 6.9) as Investigated from Multi-Parameter Approach by Ground and Space-Based Techniques
Pre-Seismic Irregularities during the 2020 Samos (Greece) Earthquake (M = 6.9) as Investigated from Multi-Parameter Approach by Ground and Space-Based Techniques Open
We present a comprehensive analysis of pre-seismic anomalies as computed from the ground and space-based techniques during the recent Samos earthquake in Greece on 30 October 2020, with a magnitude M = 6.9. We proceed with a multi-parametr…
View article: Diagnostic study of geomagnetic storm-induced ionospheric changes over VLF signal propagation paths in mid-latitude D-region
Diagnostic study of geomagnetic storm-induced ionospheric changes over VLF signal propagation paths in mid-latitude D-region Open
We performed a diagnostic study of geomagnetic storm-induced disturbances that are coupled to the lower ionosphere in mid-latitude D-region using propagation characteristics of VLF radio signals. We characterised the diurnal VLF amplitude …
View article: AstroSat observation of non-resonant type-C QPOs in MAXI J1535-571
AstroSat observation of non-resonant type-C QPOs in MAXI J1535-571 Open