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Abstract Gamma-ray flares of blazars may be accompanied by high-energy neutrinos due to interactions of high-energy cosmic rays in the jet with photons, as suggested by the detection of the high-energy neutrino IceCube-170922A during a major gamma-ray flare from blazar TXS 0506+056 at the ∼3σsignificance level. In this work, we present a statistical study of gamma-ray emission from blazars to constrain the contribution of gamma-ray flares to their neutrino output. We construct weekly binned light curves for 145 gamma-ray bright blazars in the Fermi Large Area Telescope Monitored Source List adding TXS 0506+056. We derive the fraction of time spent in the flaring state (flare duty cycle) and the fraction of energy released during each flare from the light curves with a Bayesian blocks algorithm. We find that blazars with lower flare duty cycles and energy fractions are more numerous among our sample. We identify a significant difference in flare duty cycles between blazar subclasses at a significance level of 5%. Then using a general scaling relation for the neutrino and gamma-ray luminosities, with a weighting exponent ofγ= 1.0–2.0, normalized to the quiescent gamma-ray or X-ray flux of each blazar, we evaluate the neutrino energy flux of each gamma-ray flare. The gamma-ray flare distribution indicates that blazar neutrino emission may be dominated by flares forγ≳ 1.5. The neutrino energy fluxes for 1 week and 10 yr bins are compared with the decl.-dependent IceCube sensitivity to constrain the standard neutrino emission models for gamma-ray flares. Finally, we present the upper-limit contribution of blazar gamma-ray flares to the isotropic diffuse neutrino flux.
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Searching for gamma-ray emission from stellar flares
ABSTRACT Flares from magnetically active dwarf stars should produce relativistic particles capable of creating γ-rays. So far, the only isolated main-sequence star besides the Sun to have been detected in γ-rays is TVLM 513−46546. Detecting γ-ray flares from more dwarf stars can improve our understanding of their magnetospheric properties, and could also indicate a diminished likelihood of their planets’ habitability. In this work, we stack data from the Fermi Gamma-ray Space Telescope during a large number of events identified from optical and X-ray flare surveys. We report an upper limit of γ-ray emission from the population of flare stars. Stacking results towards control positions are consistent with a non-detection. We compare these results to observed solar γ-ray flares and against a model of emission from neutral pion decay. The upper limit is consistent with solar flares when scaled to the flare energies and distances of the target stars. As with solar flares, the neutral pion decay mechanism for γ-ray production is also consistent with these results.
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- Award ID(s):
- 2219090
- PAR ID:
- 10513043
- Publisher / Repository:
- Oxford University Press
- Date Published:
- Journal Name:
- Monthly Notices of the Royal Astronomical Society
- Volume:
- 531
- Issue:
- 3
- ISSN:
- 0035-8711
- Format(s):
- Medium: X Size: p. 3215-3221
- Size(s):
- p. 3215-3221
- Sponsoring Org:
- National Science Foundation
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