6 citations · 6 across the 15 of their papers we have counts for
16 papers
Short-timescale X-ray variability of the blazar 1ES 1959+650 observed with AstroSat/SXT
Sikandar Akbar, Zahir Shah
We analyse the AstroSat Soft X-ray Telescope (SXT) observation of the high-synchrotron-peaked blazar 1ES 1959+650 taken on 2023 September 2, which covers 362 ks with about 95 ks of…
Probing the High-Energy Emission of the VHE-emitting Changing-Look Blazar B2 1420+32
Anjum Peer, Zahir Shah, Sikandar Akbar +2
We present a multi-wavelength temporal and spectral study of the changing-look blazar B2~1420+32 using \emph{Fermi}-LAT, \emph{Swift}-XRT, and \emph{Swift}-UVOT data from MJD~58818…
Exploring the Transitional Parameter Space of Blazars using Gamma-ray and X-ray Population Diagnostics
Zahoor Malik, Sikandar Akbar, Zahir Shah +1
We investigate the -ray and X-ray population properties of changing-look blazars (CLBs) using sources from the Fourth \textit{Fermi} LAT Source Catalog Data Release 4 (4FGL-DR4)…
Advance warning of -ray blazar flares from \textit{Fermi}-LAT light curves: a strictly causal machine-learning backtest
Zahir Shah, Sikandar Akbar
Long-term \textit{Fermi}-LAT monitoring makes it possible to ask whether a blazar light curve shows signs of an upcoming flare before the flare becomes obvious in the -ray emiss…
Indication of gamma-Ray Quasi-periodicity in GB6 J1037+5711 from Multi-technique Timing Analysis
Zahoor Malik, Sikandar Akbar, Zahir Shah +1
We report the indication of a long-term quasi-periodic oscillation (QPO) in the -ray emission of the BL Lac object 4FGL J1037.7+5711 (GB6 J1037+5711) using more than 17 years of…
Characterizing Short-Timescale Optical Variability in Non-blazar Active Galactic Nucleus PKS~052136 Using TESS
Sikandar Akbar, Zahir Shah
We present a systematic analysis of high-cadence optical light curves of the non-blazar AGN PKS~052136 obtained with \textit{TESS} across three sectors: Sectors~5 and~6 (Cycle~1…
A Possible Short-Timescale Optical Quasi-Periodic Oscillation in PKS\,080507 from High-Cadence TESS Observations
Sikandar Akbar, Zahir Shah, Athar A. Dar +1
We present a timing analysis of the high-cadence optical light curve of the high-redshift flat-spectrum radio quasar PKS\,080507 obtained during \textit{TESS} Sector~34 (MJD~=~5…
Broadband Variability Analysis of FSRQ PKS\,0402-362 with Indications of Quasi-Periodic Modulation
Zeeshan Nazir, Sikandar Akbar, Zahir Shah +2
We present a comprehensive temporal and spectral study of the flat-spectrum radio quasar PKS~0402362 using \textit{Fermi}-LAT/Swift-XRT/UVOT observations spanning from MJD 54686…
A multi-technique search for year-scale -ray quasi-periodic modulation in the high-redshift FSRQ PKS~205247
Sikandar Akbar
We investigate year-scale quasi-periodic oscillations in the -ray emission of the high-redshift flat-spectrum radio quasar PKS~205247 using monthly binned \emph{Fermi}-LAT da…
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…
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,…
Comprehensive Variability Analysis of Blazars Using Fermi Light Curves Across Multiple Timescales
Zahir Shah, Athar A. Dar, Sikandar Akbar +8
In this study, we conducted a systematic analysis of long-term Fermi-LAT γ-ray data for a sample of blazars, including FSRQs, BL\,Lacs, and BCUs, to investigate their -ray varia…
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…
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…
Probing Broadband Spectral Energy Distribution and Variability of Mrk\,501 in the low flux state
Javaid Tantry, Zahir Shah, Ranjeev Misra +2
We conducted a multi-wavelength analysis of the blazar Mrk\,501, utilizing observations from \emph{Astro}Sat (SXT, LAXPC), \emph{Swift-UVOT}, and \emph{Fermi-LAT} during the period…
Insights into the Long-Term Flaring Events of Blazar PKS 0805-07: A Multi-Wavelength Analysis over the 2009-2023 Period
Sikandar A. Dar, Zahir Shah, Ranjeev Misra +1
We conducted a comprehensive temporal and spectral study of the FSRQ PKS 0805-07 by using the broadband observations from the Fermi-LAT and Swift-XRT/UVOT instruments over the peri…