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Evidence for PeV Proton Acceleration from Fermi-LAT Observations of SNR G106.3+2.7

Ke Fang, Matthew Kerr, Roger Blandford, Henrike Fleischhack, and Eric Charles
Phys. Rev. Lett. 129, 071101 – Published 10 August 2022
Physics logo See synopsis: Identifying a Galactic Particle Accelerator
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Abstract

The existence of a “knee” at energy 1PeV in the cosmic-ray spectrum suggests the presence of Galactic PeV proton accelerators called “PeVatrons.” Supernova remnant (SNR) G106.3+2.7 is a prime candidate for one of these. The recent detection of very high energy (0.1–100 TeV) gamma rays from G106.3+2.7 may be explained either by the decay of neutral pions or inverse Compton scattering by relativistic electrons. We report an analysis of 12 years of Fermi-LAT gamma-ray data that shows that the GeV-TeV gamma-ray spectrum is much harder and requires a different total electron energy than the radio and x-ray spectra, suggesting it has a distinct, hadronic origin. The nondetection of gamma rays below 10 GeV implies additional constraints on the relativistic electron spectrum. A hadronic interpretation of the observed gamma rays is strongly supported. This observation confirms the long-sought connection between Galactic PeVatrons and SNRs. Moreover, it suggests that G106.3+2.7 could be the brightest member of a new population of SNRs whose gamma-ray energy flux peaks at TeV energies. Such a population may contribute to the cosmic-ray knee and be revealed by future very high energy gamma-ray detectors.

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  • Received 22 December 2021
  • Revised 8 March 2022
  • Accepted 1 July 2022

DOI:https://doi.org/10.1103/PhysRevLett.129.071101

© 2022 American Physical Society

Physics Subject Headings (PhySH)

Gravitation, Cosmology & Astrophysics

synopsis

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Identifying a Galactic Particle Accelerator

Published 10 August 2022

An analysis of 12 years of gamma-ray observations has allowed researchers to pinpoint a Galactic source of high-energy cosmic rays.

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Authors & Affiliations

Ke Fang1, Matthew Kerr2, Roger Blandford3,4, Henrike Fleischhack5,6,7, and Eric Charles4,3

  • 1Department of Physics, Wisconsin IceCube Particle Astrophysics Center, University of Wisconsin, Madison, Wisconsin 53706, USA
  • 2Space Science Division, Naval Research Laboratory, Washington, D.C. 20375, USA
  • 3Kavli Institute for Particle Astrophysics and Cosmology, Stanford University, Stanford, California 94305, USA
  • 4SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA
  • 5Department of Physics, Catholic University of America, Washington, D.C. 20064, USA
  • 6NASA Goddard Space Flight Center, Greenbelt, Maryland 20771, USA
  • 7Center for Research and Exploration in Space Science and Technology, NASA/GSFC, Greenbelt, Maryland 20771, USA

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Issue

Vol. 129, Iss. 7 — 12 August 2022

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