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Science. 2013 Feb 15;339(6121):807-11. doi: 10.1126/science.1231160.

Detection of the characteristic pion-decay signature in supernova remnants.

Ackermann M1, Ajello M, Allafort A, Baldini L, Ballet J, Barbiellini G, Baring MG, Bastieri D, Bechtol K, Bellazzini R, Blandford RD, Bloom ED, Bonamente E, Borgland AW, Bottacini E, Brandt TJ, Bregeon J, Brigida M, Bruel P, Buehler R, Busetto G, Buson S, Caliandro GA, Cameron RA, Caraveo PA, Casandjian JM, Cecchi C, Celik O, Charles E, Chaty S, Chaves RC, Chekhtman A, Cheung CC, Chiang J, Chiaro G, Cillis AN, Ciprini S, Claus R, Cohen-Tanugi J, Cominsky LR, Conrad J, Corbel S, Cutini S, D'Ammando F, de Angelis A, de Palma F, Dermer CD, do Couto e Silva E, Drell PS, Drlica-Wagner A, Falletti L, Favuzzi C, Ferrara EC, Franckowiak A, Fukazawa Y, Funk S, Fusco P, Gargano F, Germani S, Giglietto N, Giommi P, Giordano F, Giroletti M, Glanzman T, Godfrey G, Grenier IA, Grondin MH, Grove JE, Guiriec S, Hadasch D, Hanabata Y, Harding AK, Hayashida M, Hayashi K, Hays E, Hewitt JW, Hill AB, Hughes RE, Jackson MS, Jogler T, Jóhannesson G, Johnson AS, Kamae T, Kataoka J, Katsuta J, Knödlseder J, Kuss M, Lande J, Larsson S, Latronico L, Lemoine-Goumard M, Longo F, Loparco F, Lovellette MN, Lubrano P, Madejski GM, Massaro F, Mayer M, Mazziotta MN, McEnery JE, Mehault J, Michelson PF, Mignani RP, Mitthumsiri W, Mizuno T, Moiseev AA, Monzani ME, Morselli A, Moskalenko IV, Murgia S, Nakamori T, Nemmen R, Nuss E, Ohno M, Ohsugi T, Omodei N, Orienti M, Orlando E, Ormes JF, Paneque D, Perkins JS, Pesce-Rollins M, Piron F, Pivato G, Rainò S, Rando R, Razzano M, Razzaque S, Reimer A, Reimer O, Ritz S, Romoli C, Sánchez-Conde M, Schulz A, Sgrò C, Simeon PE, Siskind EJ, Smith DA, Spandre G, Spinelli P, Stecker FW, Strong AW, Suson DJ, Tajima H, Takahashi H, Takahashi T, Tanaka T, Thayer JG, Thayer JB, Thompson DJ, Thorsett SE, Tibaldo L, Tibolla O, Tinivella M, Troja E, Uchiyama Y, Usher TL, Vandenbroucke J, Vasileiou V, Vianello G, Vitale V, Waite AP, Werner M, Winer BL, Wood KS, Wood M, Yamazaki R, Yang Z, Zimmer S.

Author information

1
Deutsches Elektronen Synchrotron (DESY), Zeuthen, Germany.

Abstract

Cosmic rays are particles (mostly protons) accelerated to relativistic speeds. Despite wide agreement that supernova remnants (SNRs) are the sources of galactic cosmic rays, unequivocal evidence for the acceleration of protons in these objects is still lacking. When accelerated protons encounter interstellar material, they produce neutral pions, which in turn decay into gamma rays. This offers a compelling way to detect the acceleration sites of protons. The identification of pion-decay gamma rays has been difficult because high-energy electrons also produce gamma rays via bremsstrahlung and inverse Compton scattering. We detected the characteristic pion-decay feature in the gamma-ray spectra of two SNRs, IC 443 and W44, with the Fermi Large Area Telescope. This detection provides direct evidence that cosmic-ray protons are accelerated in SNRs.

PMID:
23413352
DOI:
10.1126/science.1231160
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