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Title: Constraints on the hadronic content of gamma ray bursts

The IceCube High-energy Neutrino Telescope has been collecting data since 2006. Conversely, hundreds of gamma-ray bursts (GRBs) have been detected by the GRB Monitor on board Fermi since its launch in 2008. So far no neutrino event has been associated with a GRB, despite many models predicting the generation of high-energy neutrinos through GRB photon interaction with PeV protons in the GRB jet. We use the non-detection of neutrinos to constrain the hadronic content of GRB jets independent of jet model parameters. Assuming a generic particle spectrum of E {sup –α} with α = 2, we find that the ratio of the energy carried by pions to that in electrons has to be small f {sub π}/f{sub e} ≲ 0.24 at 95% confidence level. A distribution of spectral slopes can lower f {sub π}/f{sub e} by orders of magnitude. Another limit, independent of neutrinos, is obtained if one ascribes the measured Fermi/Large Area Telescope GeV gamma-ray emission to pair-photon cascades of high-energy photons resulting from (the same photon-hadronic interactions and subsequent) neutral pion decays. Based on the generally observed MeV-to-GeV GRB fluence ratio of ≈10, we show that f {sub π}/f{sub e} ≲ 0.3. In some bursts, this ratio ismore » as low as unity, f {sub π}/f{sub e} ≲ 0.03. These findings add to mounting doubts regarding the presence of PeV protons in GRB jets.« less
Authors:
; ;  [1]
  1. Department of Physics, Technion (Israel)
Publication Date:
OSTI Identifier:
22365020
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 793; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; COSMIC GAMMA BURSTS; DETECTION; DISTRIBUTION; ELECTRONS; EMISSION; GAMMA RADIATION; GEV RANGE; INTERACTIONS; JET MODEL; NEUTRINOS; PARTICLE DECAY; PEV RANGE; PHOTONS; PROTONS; SPECTRA; TELESCOPES