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Title: Constraints on axions and axionlike particles from Fermi Large Area Telescope observations of neutron stars

We present constraints on the nature of axions and axion–like particles (ALPs) by analyzing gamma–ray data from neutron stars using the Fermi Large Area Telescope. In addition to axions solving the strong CP problem of particle physics, axions and ALPs are also possible dark matter candidates. We investigate axions and ALPs produced by nucleon–nucleon bremsstrahlung within neutron stars. We derive a phenomenological model for the gamma–ray spectrum arising from subsequent axion decays. By analyzing 5 years of gamma-ray data (between 60 MeV and 200 MeV) for a sample of 4 nearby neutron stars, we do not find evidence for an axion or ALP signal, thus we obtain a combined 95% confidence level upper limit on the axion mass of 7.9×10-2 eV, which corresponds to a lower limit for the Peccei-Quinn scale fa of 7.6×107 GeV. Our constraints are more stringent than previous results probing the same physical process, and are competitive with results probing axions and ALPs by different mechanisms.
 [1] ;  [2] ;  [3]
  1. California State Univ. (CalState), Los Angeles, CA (United States)
  2. Univ. of Amsterdam (Netherlands)
  3. Stockholm Univ. (Sweden); Oskar Klein Centre for Cosmoparticle Physics (Sweden)
Publication Date:
OSTI Identifier:
Grant/Contract Number:
AC02-76SF00515; PF1-120089; NAS8-03060; PIIF-GA-2013-628997
Accepted Manuscript
Journal Name:
Physical Review D
Additional Journal Information:
Journal Volume: 93; Journal Issue: 4; Journal ID: ISSN 2470-0010
American Physical Society (APS)
Research Org:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org:
USDOE; National Aeronautics and Space Administration (NASA)
Country of Publication:
United States