arXiv subjects

Sunanda

Publications and source records attributed to Sunanda.

4 recordsLinked to original sources

arXiv2023

Time-lag in hadronic channel: to explore delayed VHE-flare of 3C 279

On 28 January 2018, the High Energy Stereoscopic System (H.E.S.S.) reported a significant very-high-energy (VHE) gamma-ray activity, occurring nearly 11 days after the high-energy (HE) gamma-ray flare observed by \textit{Fermi}-LAT from the blazar 3C 279. It has long been considered a candidate site for accelerating particles to ultra-high energies (UHE) and producing subsequent secondaries. Such an event can be crucial to explore the different phenomena of secondary production from the UHEs and viable to understand the energetics of the sources. Our study finds that the multi-wavelength flare, spanning UV, optical, X-rays, and HE gamma rays, originates from leptonic emissions, whereas the delayed VHE activity by proton synchrotron emission within the source, results from the extended duration of particle acceleration. To explain the prolonged electromagnetic emission, our model requires a magnetic field luminosity (L$'_B$) $6.1 \times 10^{43}$ erg/sec, a proton luminosity (L$'_{p}$) $1.2\times 10^{46}$ erg/sec in the jet frame.

astro-ph.HE↗

arXiv2023

Generalized Linear Models of T$_{90}$-T$_{50}$ relation to classify GRBs

Gamma-ray bursts (GRBs) can be classified with their linearly dependent parameters alongside the standard $T_{90}$ distribution. The Generalized linear mixture model(GLM) identifies the number of linear dependencies in a two-parameter space. Classically, GRBs are classified into two classes by the presence of bimodality in the histogram of T$_{90}$. However, additional classes and sub-classes of GRBs are fascinating topics to explore. In this work, we investigate the GRBs classes in the $ T_{90} {-}T_{50}$ plane using the Generalized Linear Models(GLM) for Fermi GBM and BATSE catalogs. This study shows five linear features for the Fermi GBM catalog and four linear features for the BATSE catalog, directing towards the possibility of more than two GRB classes.

astro-ph.HE↗

arXiv2022

Proton Synchrotron, an explanation for possible extended VHE gamma-ray activity of TXS 0506+056 in 2017

TXS 0506+056, a source of the extreme energy neutrino event, IceCube-170922A, was observed on 22 September 2017. The Fermi-LAT detector reported high energy (HE) $\gamma$-ray flare between 100 MeV and 100 GeV starting from 15 September 2017 from this source. Several attempts to trace the very high energy (VHE) gamma-ray counterparts around the IceCube-170922A resulted in no success. Only after 28 September, the Major Atmospheric Gamma-ray Imaging Cherenkov (MAGIC) telescopes observed the first VHE gamma-rays from the blazar above 100 GeV. The $\sim$ 41 hr survey resulted in VHE-$\gamma$ ray activity till 31 October 2017. Here we propose the extended GeV $\gamma-$rays can be explained by taking two production channels, electron synchrotron self Compton and proton synchrotron for HE and VHE emissions, respectively. The 45 days of VHE emission from the peak of the HE-flare can be explained with $ {L_p'}{\simeq}10^{47}$ erg/sec in the jet frame and magnetic field of 2.4 G, consistent with the ${L}_{Edd}$ for a blackhole mass $5\times 10^{9} {M}_\odot$

astro-ph.HE↗

arXiv2022

Implications of photon-ALP oscillations in the extragalactic neutrino source TXS 0506+056 at sub-PeV energies

Photon-axion-like particle (ALP) oscillations result in the survival of gamma rays from distant sources above TeV energies. Studies of events observed by CAST, Fermi-LAT, and IACT have constrained the ALP parameters. We investigate the effect of photon-ALP oscillations on the gamma-ray spectra of the first extragalactic neutrino source, TXS 0506+056, for observations by Fermi-LAT and MAGIC around the IC170922-A alert. We obtain a constraint on the ALP coupling parameter $g_{a\gamma} < 5 \times 10^{-11}$ GeV$^{-1}$ with 95% C.L. when focusing on the ALP mass range 0.1 neV $\le$ $m_a$ $\le$ 1000 neV. Importantly, we study the implications of ALP-$\gamma$ oscillations on the counterpart $\gamma$ rays of the sub-PeV neutrinos observed from TXS 0506+056. We also show the diffuse $\gamma$-ray fluxes and observabilities from flat-spectrum radio quasars, high-synchrotron peaked sources, and low-intermediate-synchrotron peaked sources, assuming similar gamma-ray emissions as that from TXS 0506+056.

astro-ph.HE↗