SEARCH FOR NEW COSMIC-RAY ACCELERATION SITES WITHIN THE 4FGL CATALOG GALACTIC PLANE SOURCES

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https://iopscience.iop.org/article/10.3847/1538-4357/ac704f/meta

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http://hdl.handle.net/11603/24885
 https://doi.org/10.3847/1538-4357/ac704f

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UMBC Physics Department
UMBC Center for Space Sciences and Technology (CSST) / Center for Research and Exploration in Space Sciences & Technology II (CRSST II)
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Author/Creator ORCID

https://orcid.org/0000-0002-7021-5838
 https://orcid.org/0000-0002-8090-6528

Date

2022-07-14

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journal articles
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Citation of Original Publication

Abdollahi, S. et al. "Search for New Cosmic-Ray Acceleration Sites within the 4FGL Catalog Galactic Plane Sources." The Astrophysical Journal, 933, no. 2 (2022 July 14). https://doi.org/10.3847/1538-4357/ac704f

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This work was written as part of one of the author's official duties as an Employee of the United States Government and is therefore a work of the United States Government. In accordance with 17 U.S.C. 105, no copyright protection is available for such works under U.S. Law.
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Abstract

Cosmic rays are mostly composed of protons accelerated to relativistic speeds. When those protons encounter interstellar material, they produce neutral pions which in turn decay into gamma rays. This offers a compelling way to identify the acceleration sites of protons. A characteristic hadronic spectrum, with a low-energy break around 200 MeV, was detected in the gamma-ray spectra of four Supernova Remnants (SNRs), IC 443, W44, W49B and W51C, with the Fermi Large Area Telescope. This detection provided direct evidence that cosmic-ray protons are (re-)accelerated in SNRs. Here, we present a comprehensive search for low-energy spectral breaks among 311 4FGL catalog sources located within 5◦ from the Galactic plane. Using 8 years of data from the Fermi Large Area Telescope between 50 MeV and 1 GeV, we find and present the spectral characteristics of 56 sources with a spectral break confirmed by a thorough study of systematic uncertainty. Our population of sources includes 13 SNRs for which the proton-proton interaction is enhanced by the dense target material; the high-mass γ-ray binary LS I +61 303; the colliding wind binary η Carinae; and the Cygnus star-forming region. This analysis better constrains the origin of the γ-ray emission and enlarges our view to potential new cosmic-ray acceleration sites.