arXiv subjects

Aminabi Thekkoth

Publications and source records attributed to Aminabi Thekkoth.

3 recordsLinked to original sources

arXiv2026

A Rare Gamma-ray Flaring episode of the Narrow-Line Seyfert 1 Galaxy 1H 0323+342

Gamma-ray-emitting narrow-line Seyfert 1 ($γ$-NLSy1) galaxies represent an enigmatic class of active galactic nuclei (AGNs) bridging populations of radio-quiet and radio-loud AGNs. Here we report the multi-wavelength investigation of a rare $γ$-ray flaring episode of an NLSy1 galaxy, 1H 0323+342 ($z=0.063$), using data from Fermi-Large Area Telescope, Swift, and Nuclear Spectroscopic Telescopic Array. The source exhibited a significant enhancement in $γ$-ray flux along with rapid variability on $\sim$sub-hour timescales in both $γ$-ray and hard X-ray wavelengths, hinting that the energy dissipation is happening from a compact region close to the central supermassive black-hole. The time-resolved X-ray spectral study revealed a transition between a jet-dominated and a mixed jet+corona emission state. Reproducing the broadband spectral energy distribution with a one-zone leptonic model suggested that the high-energy emission is mainly produced by external Compton scattering of the accretion disc and broad line region photons. The inferred jet power reaches values of the order of $10^{46}$ erg s$^{-1}$ comparable to those of powerful flat-spectrum radio quasars, suggesting that even low black-hole mass systems can occasionally produce powerful $γ$-ray outbursts.

astro-ph.HE↗

arXiv2024

Gamma-ray variability and multi-wavelength insights into the unprecedented outburst from 4C 31.03

The blazar 4C 31.03 recently underwent a major gamma-ray outburst at the beginning of 2023 after a prolonged quiescent phase. Fermi-LAT reported a daily average flux of 5x10^-6 phs cm^-2 s^-1, which is about 60 times its average value. We investigated this extraordinary outbreak through temporal and multi-wavelength analysis. From the statistical analysis of the gamma-ray lightcurves using Bayesian blocks, we identified 3 epochs of prominent flares. The fastest flux decay during this major outburst was observed within 5.5 +/- 0.7 hours. The highest energy of gamma-ray photons found from the source during the active phase is ~ 82 GeV. Using the transparency of gamma-rays against pair production and light crossing time argument, we could obtain the minimum jet Doppler factor as 17 corresponding to the flaring state.The broadband spectral energy distribution study performed using synchrotron, SSC and EC emission processes supports the external Compton scattering of IR photons as the likely mechanism for the gamma-ray emission from the source. The results of this study suggest the scenario of the emission region in 4C 31.03, being located beyond the Broad-line region from the central blackhole. Long-term gamma-ray flux distribution of 4C 31.03 depicts a double log-normal variability, indicating that two distinct flux states are active in this energy band. The index distribution also reveals a two distinct variability patterns, suggesting that the gamma-ray spectrum can be more precisely described by two photon indices.

astro-ph.HE↗

arXiv2023

Understanding the Broadband Emission Process of 3C 279 through Longterm Spectral Analysis

The long term broadband spectral study of Flat Spectrum Radio Quasars during different flux states has the potential to infer the emission mechanisms and the cause of spectral variations. To scrutinize this, we performed a detailed broadband spectral analysis of 3C 279 using simultaneous Swift-XRT/UVOT and Fermi-LAT observations spanning from August 2008 to June 2022. We also supplement this with the simultaneous NuSTAR observations of the source. The optical/UV, X-ray, and gamma-ray spectra were individually fitted by a power-law to study the long-term variation in the flux and the spectral indices. A combined spectral fit of simultaneous optical/UV and X-ray spectra was also performed to obtain the transition energy at which the spectral energy distribution is minimum. The correlation analysis suggests that the long-term spectral variations of the source are mainly associated with the variations in the low energy index and the break energy of the broken power-law electron distribution which is responsible for the broadband emission. The flux distribution of the source represents a log-normal variability while the gamma-ray flux distribution showed a clear double log-normal behavior. The spectral index distributions were again normal except for gamma-ray which showed a double-Gaussian behavior. This indicates that the log-normal variability of the source may be associated with the normal variations in the spectral index. The broadband spectral fit of the source using synchrotron and inverse Compton processes indicates different emission processes are active at optical/UV, X-ray, and gamma-ray energies.

astro-ph.HE↗