A gamma-ray signature of energetic sources of cosmic-ray nuclei

Alexander Kusenko, M. B. Voloshin

Research output: Contribution to journalArticlepeer-review

6 Scopus citations


Astrophysical sources of nuclei are expected to produce a broad spectrum of isotopes, many of which are unstable. An unstable nucleus can beta-decay outside the source into a single-electron ion. Heavy one-electron ions, thus formed, can be excited in their interactions with cosmic microwave background photons, in which case they relax to the ground state with the emission of a gamma ray. Repetitive cycles of excitation and gamma-ray emission can produce an observable feature in the gamma-ray spectrum with a maximum around 8 GeV (for iron). We find that the observed spectrum of Centaurus A is consistent with a substantial flux of nuclei accelerated to 0.1 EeV. A characteristic 5-10 GeV (iron) shoulder in the gamma-ray spectra of various sources can help identify astrophysical accelerators of nuclei or set upper limits on nuclear acceleration.

Original languageEnglish (US)
Pages (from-to)255-258
Number of pages4
JournalPhysics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
Issue number2
StatePublished - Jan 20 2012

Bibliographical note

Funding Information:
The authors thank C. Dermer, J. Beacom, W. Essey, P. Mészáros, and S. Razzaque for discussions. A.K. and M.B.V. were supported in part by DOE grants DE-FG03-91ER40662 and DE-FG02-94ER40823 , respectively. The authors appreciate hospitality of the Aspen Center for Physics, supported by NSF grant 1066293 , where this work was done.


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