Nayantara Gupta

High-energy neutrinos from the gravitational wave event GW150914 possibly associated with a short gamma-ray burst

High-energy neutrinos (HEN) and gravitational waves (GW) can probe astrophysical sources in addition to electromagnetic observations. Multimessenger studies can reveal the nature of the sources, which may not be discerned from one type of signal alone. We discuss HEN emission in connection with the Advanced Laser Interferometer Gravitational-Wave Observatory event GW150914, which could be associated with a short gamma-ray burst detected by the Fermi Gamma-Ray Burst Monitor 0.4 s after the GW event and within localization uncertainty of the GW event. We calculate HEN flux from this short gamma-ray burst, GW150914-GBM, and show that nondetection of a high-energy starting event by the IceCube Neutrino Observatory can constrain the total isotropic-equivalent jet energy of this short burst to be less than

pγ interactions in Galactic jets as a plausible origin of the positron excess

3\ifmmode\times\else\texttimes\fi{}{10}^{52}\text{ }\text{ }\mathrm{erg}

PROTON SYNCHROTRON RADIATION FROM EXTENDED JETS OF PKS 0637–752 AND 3C 273

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Possible proton synchrotron origin of X-ray and gamma-ray emission in large-scale jet of 3C 273

The positron flux measured near Earth shows a rise with energy beyond 30 GeV. We show that this rise may be compatible with the production of positrons in

Long-term Study of the Light Curve of PKS 1510-089 in GeV Energies

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Constraints on Proton Synchrotron Origin of Very High Energy Gamma Rays from the Extended Jet of AP Librae

interactions in the jets of microquasars.

Photo-disintegration of heavy nuclei at the core of Cen A

Recently, the IC/CMB X-ray mechanism has been strongly disfavoured for 3C 273 and PKS 0637-752 since the anomalously hard and steady gamma-ray emission predicted by such models violates the observational results from Fermi-LAT. Here we propose the proton synchrotron origin of the X ray-gamma ray flux from the knots of PKS 0637-752 with a reasonable budget in luminosity, by considering synchrotron radiation from an accelerated proton population. Moreover, for the source 3C 273, some of the optical data points could not be explained by electron synchrotron (Meyer et al. 2015), which we have included in our updated proton synchrotron model. We also show that TeV emission from large scale quasar jets in principle, can arise from proton synchrotron, which we discuss in the context of knot wk8.9 of PKS 0637-752.

Fermi-Large Area Telescope Observations of the Brightest Gamma-Ray Flare Ever Detected from CTA 102

The large scale jet of quasar 3C 273 has been observed in radio to

Constraining the halo size from possible density profiles of hydrogen gas of Milky Way Galaxy

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Cosmic ray antiprotons from nearby cosmic accelerators

ray frequencies. Earlier the X-ray emission from knot A of this jet has been explained with inverse Compton scattering of the cosmic microwave background radiations by the shock accelerated relativistic electrons in the jet. More recently it has been shown that this mechanism overproduces the gamma ray flux at GeV energy and violates the observational results from Fermi LAT. We have considered the synchrotron emission from a broken power law spectrum of accelerated protons in the jet to explain the observed X-ray to