Inferred cosmic-ray spectrum from fermi large area telescope -Ray Observations of Eartha's Limb

M. Ackermann, M. Ajello, A. Albert, A. Allafort, L. Baldini, G. Barbiellini, D. Bastieri, K. Bechtol, R. Bellazzini, R. D. Blandford, E. D. Bloom, E. Bonamente, E. Bottacini, A. Bouvier, T. J. Brandt, M. Brigida, P. Bruel, R. Buehler, S. Buson, G. A. CaliandroR. A. Cameron, P. A. Caraveo, C. Cecchi, E. Charles, R. C.G. Chaves, A. Chekhtman, J. Chiang, G. Chiaro, S. Ciprini, R. Claus, J. Cohen-Tanugi, J. Conrad, S. Cutini, M. Dalton, F. Dammando, A. De Angelis, F. De Palma, C. D. Dermer, S. W. Digel, L. Di Venere, E. Do Couto E Silva, P. S. Drell, A. Drlica-Wagner, C. Favuzzi, S. J. Fegan, E. C. Ferrara, W. B. Focke, A. Franckowiak, Y. Fukazawa, S. Funk, P. Fusco, F. Gargano, D. Gasparrini, S. Germani, N. Giglietto, F. Giordano, M. Giroletti, T. Glanzman, G. Godfrey, G. A. Gomez-Vargas, I. A. Grenier, J. E. Grove, S. Guiriec, M. Gustafsson, D. Hadasch, Y. Hanabata, A. K. Harding, M. Hayashida, K. Hayashi, J. W. Hewitt, D. Horan, X. Hou, R. E. Hughes, Y. Inoue, M. S. Jackson, T. Jogler, G. Jóhannesson, A. S. Johnson, T. Kamae, T. Kawano, J. Knödlseder, M. Kuss, J. Lande, S. Larsson, L. Latronico, F. Longo, F. Loparco, M. N. Lovellette, P. Lubrano, M. Mayer, M. N. Mazziotta, J. E. McEnery, J. Mehault, P. F. Michelson, W. Mitthumsiri, T. Mizuno, A. A. Moiseev, C. Monte, M. E. Monzani, A. Morselli, I. V. Moskalenko, S. Murgia, R. Nemmen, E. Nuss, T. Ohsugi, A. Okumura, M. Orienti, E. Orlando, J. F. Ormes, D. Paneque, J. H. Panetta, J. S. Perkins, M. Pesce-Rollins, F. Piron, G. Pivato, T. A. Porter, S. Rainò, R. Rando, M. Razzano, S. Razzaque, A. Reimer, O. Reimer, S. Ritz, M. Roth, M. Schaal, A. Schulz, C. Sgrò, E. J. Siskind, G. Spandre, P. Spinelli, A. W. Strong, H. Takahashi, Y. Takeuchi, J. G. Thayer, J. B. Thayer, D. J. Thompson, L. Tibaldo, M. Tinivella, D. F. Torres, G. Tosti, E. Troja, V. Tronconi, T. L. Usher, J. Vandenbroucke, V. Vasileiou, G. Vianello, V. Vitale, M. Werner, B. L. Winer, K. S. Wood, M. Wood, Z. Yang

Research output: Contribution to journalArticlepeer-review

33 Citations (Scopus)

Abstract

Recent accurate measurements of cosmic-ray (CR) species by ATIC-2, CREAM, and PAMELA reveal an unexpected hardening in the proton and He spectra above a few hundred GeV, a gradual softening of the spectra just below a few hundred GeV, and a harder spectrum of He compared to that of protons. These newly discovered features may offer a clue to the origin of high-energy CRs. We use the Fermi Large Area Telescope observations of the -ray emission from Earthas limb for an indirect measurement of the local spectrum of CR protons in the energy range 90GeV-6TeV (derived from a photon energy range 15 GeV-1 TeV). Our analysis shows that single power law and broken power law spectra fit the data equally well and yield a proton spectrum with index 2.68±0.04 and 2.61±0.08 above 200GeV, respectively.

Original languageEnglish
Article number151103
JournalPhysical Review Letters
Volume112
Issue number15
DOIs
Publication statusPublished - 17 Apr 2014

ASJC Scopus subject areas

  • General Physics and Astronomy

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