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Evolution of the 2021 Outburst of GX 339-4 with AstroSat
Vaibhav Sharma, Ranjeev Misra, J S Yadav +2
We present a comprehensive study of the 2021 outburst of GX 339-4 using AstroSat observations in the hard-intermediate (HIMS) and soft-intermediate states (SIMS). Spectral and timi…
Spectral State Switching in Mrk 421: Results from the AstroSat LAXPC/SXT Observations
Sikandar Akbar, Zahir Shah, Ranjeev Misra +1
We carried a detailed time and flux resolved X-ray spectral analysis of the high-synchrotron-peaked blazar Mrk\,421 using simultaneous LAXPC20 and SXT observations. The 100\,s binn…
Multiwavelength spectral and temporal analysis of VHE Blazar 1ES 1959+650: Tracing emission mechanisms across flux states
Peer Anjum, Athar A. Dar, Zahir Shah +2
The high-synchrotron-peaked BL Lac object 1ES\,1959+650 exhibited pronounced activity between MJD~60310 -- 60603, including a very high energy (VHE) detection reported by LHAASO. T…
Synchrotron radiation from NGC 470 HLX1 - a hidden hyperluminous accreting neutron star?
Tanuman Ghosh, Shiv Sethi, Gulab Chand Dewangan +3
We present the first broadband spectral analysis of NGC 470 HLX1, a hyperluminous X-ray source that exhibits significant flux variability over different epochs. We investigate the…
The strong Fe K line and spin of the black-hole X-ray binary MAXI J1631-479
Andrzej A. Zdziarski, Swadesh Chand, Gulab Dewangan +5
We study the transient black hole binary MAXI J1631--479 in its soft spectral state observed simultaneously by the NICER and NuSTAR instruments. Its puzzling feature is the presenc…
Probing the Origin of X-ray Flares in the Low-Hard State of GRS 1915+105 Using AstroSat and NuSTAR
Shahzada Akhter, Sajad Boked, Bari Maqbool +2
We performed a detailed time-resolved spectral study of GRS 1915+105 during its low-flux rebrightening phase using the broadband capabilities of AstroSat and NuSTAR in May-June 201…
Probing the energy-dependent temporal nature of MAXI J1803-298 with AstroSat and NICER
Arbind Pradhan, Akash Garg, Ranjeev Misra +1
We performed the spectral and temporal analysis of MAXI J1803-298 using AstroSat/LAXPC and NICER observations taken in May 2021 during the initial phase of the outburst. We found t…
Quasi-Periodic Oscillations due to radiative feedback mechanism between the disc and corona
Akash Garg, Ranjeev Misra, Somasri Sen
Compact object systems exhibit Quasi-Periodic Oscillations (QPOs) as revealed by peaked features in their power density spectra. It has been known that stochastic variations in the…
Spectral evolution of GX 17+2 using AstroSat and NICER observations
Sree Bhattacherjee, Ranjeev Misra, Biplob Sarkar +3
We study the spectral evolution of the Z-track source GX 17+2 using AstroSat and NICER observations taken between 2016 and 2020. The AstroSat observations cover the period when the…
Indication for Dual Periodic Signatures in PKS 0805-07 from Multi-technique Time Series Analysis
Sikandar Akbar, Zahir Shah, Ranjeev Misra +2
We report the identification of two statistically significant quasi-periodic oscillations in the weekly binned -ray light curve of the flat-spectrum radio quasar PKS 080507,…
Statistical Insights into Flux and Photon Index Distributions of VHE FSRQs from Fermi-LAT Observations
Zahoor Malik, Sikandar Akbar, Zahir Shah +8
This study examines the flux and photon index distributions of 11 Very High Energy (VHE) Flat Spectrum Radio Quasars (FSRQs) using over 16 years of Fermi-LAT -ray data. The dist…
Astrophysics with Compact Objects: An Indian Perspective, Present Status and Future Vision
Manjari Bagchi, Prasanta Bera, Aru Beri +18
Astrophysical compact objects, viz., white dwarfs, neutron stars, and black holes, are the remnants of stellar deaths at the end of their life cycles. They are ideal testbeds for v…
Spectral Analysis of Cyg X-3 using simultaneous AstroSat and Insight-HXMT Observations
Suraj K. Chaurasia, Gitika Mall, Ruchika Dhaka +2
We present the results from the spectral analysis of Cygnus X-3 using simultaneous data from AstroSat and Insight-HXMT during its soft state. A pure reflection spectrum, including…
QPO signatures of disk restoration after type-I X-ray bursts from 4U~1636536
Suchismito Chattopadhyay, Jaiverdhan Chauhan, Ranjeev Misra +4
Type--I thermonuclear bursts (TNBs) from neutron star low-mass X-ray binaries (NS LMXBs) originate on the neutron star's surface from the unstable burning of the accreted material.…
Spectral-timing analysis of the kilohertz quasi-periodic oscillations and constraints on the mass of the neutron star in 4U 1636-536 using AstroSat observations
Suchismito Chattopadhyay, Soma Mandal, Ranjeev Misra
Kilohertz quasi-periodic oscillations (kHz QPOs) are believed to originate from the orbital timescales of the inner accretion flow, reflecting the dynamics of the innermost disk re…
Discovery of a new flaring class in GRS 1915+105 using AstroSat
Ruchika Dhaka, JS Yadav, Ranjeev Misra +1
Highly variable Black Hole X-ray Binary (BHXB) GRS~1915+105 has shown many flaring classes when the source oscillates between the High Soft state (HS) and the Hard Intermediate sta…
Modelling the energy dependent X-ray variability of Mrk 335
K. Akhila, Ranjeev Misra, Rathin Sarma +2
We present a technique which predicts the energy dependent fractional r.m.s for linear correlated variations of a pair of spectral parameters and apply it to an XMM-Newton observat…
Thermal Conduction and Thermal-Driven Winds in Magnetized Viscous Accretion Disk Dynamics
Biplob Sarkar, Indu Kalpa Dihingia, Ranjeev Misra
This paper investigates the effects of saturated thermal conduction (TC) and thermal-driven winds (TDWs) on magnetized advection-dominated accretion onto a rotating black hole (BH)…
Probing Spectral Evolution and Intrinsic Variability of Mkn\,421: A Multi-Epoch AstroSat Study of X-ray Spectra
Sikandar Akbar, Zahir Shah, Ranjeev Misra +2
Our study presents a time-resolved X-ray spectral analysis of Mkn 421, using AstroSat observations taken during different epochs between 2016 and 2019. The variability of the sourc…