Journal articles

A large light-mass component of cosmic rays at 1017–1017.5 electronvolts from radio observations

S. Buitink ¹ A. Corstanje ¹ H. Falcke ^{1, 2} J. R. Hörandel ¹ T. Huege ³ A. Nelles ¹ J. P. Rachen ¹ L. Rossetto ¹ P. Schellart ¹ O. Scholten ⁴ S. ter Veen ⁵ S. Thoudam ¹ T. N. G. Trinh ⁶ J. Anderson ⁷ A. Asgekar ² I. M. Avruch ⁸ M. E. Bell ⁹ M. J. Bentum ² G. Bernardi P. Best ¹⁰ A. Bonafede ¹¹ F. Breitling ¹² J. W. Broderick ¹³ W. N. Brouw ¹⁴ M. Brüggen ¹¹ H. R. Butcher ² D. Carbone ¹⁵ B. Ciardi ¹⁶ J. E. Conway ¹⁷ F. de Gasperin ¹⁸ E. de Geus ¹⁹ A. Deller ² R.-J. Dettmar ²⁰ G. van Diepen ² S. Duscha ² J. Eislöffel ²¹ D. Engels ¹⁸ J. E. Enriquez ²² R. A. Fallows ²³ R. Fender ¹³ C. Ferrari ²⁴ W. Frieswijk ² M. A. Garrett ^{25, 2} Jean-Mathias Griessmeier ^{26, 27} A. W. Gunst ² M. P. van Haarlem ² T. E. Hassall ²⁸ G. Heald ² J. W. T. Hessels ¹⁵ M. Hoeft ²¹ A. Horneffer ²⁹ M. Iacobelli ²⁵ H. Intema ²⁵ E. Juette ³⁰ A. Karastergiou ³¹ V. I. Kondratiev ² M. Kramer ^{29, 32} M. Kuniyoshi ²⁹ G. Kuper ² J. van Leeuwen ¹⁵ G. M. Loose ² P. Maat ² G. Mann ¹² S. Markoff ³³ R. Mcfadden ² D. Mckay-Bukowski ³⁴ J. P. Mckean ² M. Mevius ² D. D. Mulcahy ¹³ H. Munk ² M. J. Norden ² E. Orru ² H. Paas ³⁵ M. Pandey-Pommier ³⁶ V. N. Pandey ³⁷ M. Pietka ³⁸ R. Pizzo ² A. G. Polatidis ² W. Reich ²⁹ H. J. A. Röttgering ²⁵ A. M. M. Scaife ³⁹ D. J. Schwarz ⁴⁰ M. Serylak ^{26, 27} J. Sluman ² O. Smirnov ⁴¹ B. W. Stappers ²⁸ M. Steinmetz ⁴² A. Stewart ⁴³ J. Swinbank ³³ Michel Tagger ²⁶ Y. Tang ⁴⁴ C. Tasse ^{45, 46} M. C. Toribio ⁴⁷ R. Vermeulen ² C. Vocks ¹² C. Vogt ² R. J. van Weeren ² R. A. M. J. Wijers ¹⁵ S. J. Wijnholds ² M. W. Wise ^{33, 2} O. Wucknitz ⁴⁸ S. Yatawatta ² P. Zarka ^{49, 50} J. A. Zensus ²⁹

1 Radboud university [Nijmegen]

2 ASTRON - Netherlands Institute for Radio Astronomy

3 Institute for Nuclear Physics (IKP), Karlsruhe Institute of Technology (

4 University of Groningen [Groningen]

5 IMAPP - Institute for Mathematics, Astrophysics and Particle Physics

6 LAGA - Laboratoire Analyse, Géométrie et Applications

7 Institute for Mathematics Applied to Geoscience

8 SRON - SRON Netherlands Institute for Space Research

9 ATNF - Australia Telescope National Facility

10 University of Edinburgh

11 Jacobs University [Bremen]

12 AIP - Leibniz-Institut für Astrophysik Potsdam

13 University of Southampton

14 Kapteyn Astronomical Institute [Groningen]

15 UvA - University of Amsterdam [Amsterdam]

16 Max Planck Institute for Astrophysics

17 Onsala Space Observatory, Dept. of Radio and Space Science, Chalmers University of Technology

18 Hamburger Sternwarte/Hamburg Observatory

19 Medstar Research Institute

20 Astronomisches Institut der Ruhr-Universität Bochum

21 TLS - Thüringer Landessternwarte Tautenburg

22 SETI Institute

23 Institute of Mathematical and Physical Sciences

24 Département de Géologie

25 Leiden Observatory [Leiden]

26 LPC2E - Laboratoire de Physique et Chimie de l'Environnement et de l'Espace

27 USN - Unité Scientifique de la Station de Nançay

28 Jodrell Bank Centre for Astrophysics

29 MPIFR - Max-Planck-Institut für Radioastronomie

30 Ruhr-Universität Bochum [Bochum]

31 Oxford Astrophysics

32 CAL - Columbia Astrophysics Laboratory

33 AI PANNEKOEK - Astronomical Institute Anton Pannekoek

34 University of Oulu

35 Center for Information Technology CIT

36 CRAL - Centre de Recherche Astrophysique de Lyon

37 NRAO - National Radio Astronomy Observatory [Charlottesville]

38 University of Oxford [Oxford]

39 School of Physics and Astronomy [Southampton]

40 Interactions Son Musique Mouvement

STMS - Sciences et Technologies de la Musique et du Son

41 Rhodes University, Grahamstown

42 DSMZ - Leibniz-Institut DSMZ-Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH / Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures

43 LASP - Laboratory for Atmospheric and Space Physics [Boulder]

44 UP11 - Université Paris-Sud - Paris 11

45 SKA South Africa

46 GEPI - Galaxies, Etoiles, Physique, Instrumentation

47 Finca El Encin

48 AlfA - Argelander-Institut für Astronomie

49 OP - Observatoire de Paris - Site de Paris

50 LESIA - Laboratoire d'études spatiales et d'instrumentation en astrophysique

Abstract : Cosmic rays are the highest-energy particles found in nature. Measurements of the mass composition of cosmic rays with energies of 1017–1018 electronvolts are essential to understanding whether they have galactic or extragalactic sources. It has also been proposed that the astrophysical neutrino signal1 comes from accelerators capable of producing cosmic rays of these energies2. Cosmic rays initiate air showers—cascades of secondary particles in the atmosphere—and their masses can be inferred from measurements of the atmospheric depth of the shower maximum3 (Xmax; the depth of the air shower when it contains the most particles) or of the composition of shower particles reaching the ground4. Current measurements5 have either high uncertainty, or a low duty cycle and a high energy threshold. Radio detection of cosmic rays6, 7, 8 is a rapidly developing technique9 for determining Xmax (refs 10, 11) with a duty cycle of, in principle, nearly 100 per cent. The radiation is generated by the separation of relativistic electrons and positrons in the geomagnetic field and a negative charge excess in the shower front6, 12. Here we report radio measurements of Xmax with a mean uncertainty of 16 grams per square centimetre for air showers initiated by cosmic rays with energies of 1017–1017.5 electronvolts. This high resolution in Xmax enables us to determine the mass spectrum of the cosmic rays: we find a mixed composition, with a light-mass fraction (protons and helium nuclei) of about 80 per cent. Unless, contrary to current expectations, the extragalactic component of cosmic rays contributes substantially to the total flux below 1017.5 electronvolts, our measurements indicate the existence of an additional galactic component, to account for the light composition that we measured in the 1017–1017.5 electronvolt range.

Keywords : Particle astrophysics High-energy astrophysics

Document type :

Journal articles

Domain :

Sciences of the Universe [physics]

Complete list of metadata

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Submitted on : Tuesday, February 14, 2017 - 2:18:44 PM
Last modification on : Saturday, September 24, 2022 - 12:02:05 PM
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