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In-flight measurement of the absolute energy scale of the Fermi Large Area Telescope

  • M. Ackermann
  • , M. Ajello
  • , A. Allafort
  • , W. B. Atwood
  • , M. Axelsson
  • , L. Baldini
  • , G. Barbiellini
  • , D. Bastieri
  • , K. Bechtol
  • , R. Bellazzini
  • , B. Berenji
  • , E. D. Bloom
  • , E. Bonamente
  • , A. W. Borgland
  • , A. Bouvier
  • , J. Bregeon
  • , A. Brez
  • , M. Brigida
  • , P. Bruel
  • , R. Buehler
  • S. Buson, G. A. Caliandro, R. A. Cameron, P. A. Caraveo, J. M. Casandjian, C. Cecchi, E. Charles, A. Chekhtman, J. Chiang, S. Ciprini, R. Claus, J. Cohen-Tanugi, S. Cutini, F. De Palma, C. D. Dermer, S. W. Digel, E. Do Couto E Silva, P. S. Drell, A. Drlica-Wagner, R. Dubois, T. Enoto, L. Falletti, C. Favuzzi, S. J. Fegan, W. B. Focke, P. Fortin, Y. Fukazawa, S. Funk, P. Fusco, F. Gargano, N. Gehrels, S. Germani, N. Giglietto, F. Giordano, M. Giroletti, T. Glanzman, G. Godfrey, I. A. Grenier, J. E. Grove, S. Guiriec, D. Hadasch, M. Hayashida, E. Hays, R. E. Hughes, G. Jóhannesson, A. S. Johnson, T. J. Johnson, T. Kamae, H. Katagiri, J. Kataoka, J. Knödlseder, M. Kuss, J. Lande, L. Latronico, S. H. Lee, F. Longo, F. Loparco, M. N. Lovellette, P. Lubrano, G. M. Madejski, M. N. Mazziotta, J. E. McEnery, P. F. Michelson, T. Mizuno, A. A. Moiseev, C. Monte, M. E. Monzani, A. Morselli, I. V. Moskalenko, S. Murgia, T. Nakamori, M. Naumann-Godo, P. L. Nolan, J. P. Norris, E. Nuss, T. Ohsugi, A. Okumura, N. Omodei, E. Orlando, J. F. Ormes, M. Ozaki, D. Paneque, J. H. Panetta, D. Parent, M. Pesce-Rollins, M. Pierbattista, F. Piron, S. Rain, R. Rando, M. Razzano, A. Reimer, O. Reimer, T. Reposeur, S. Ritz, L. S. Rochester, C. Sgr, E. J. Siskind, P. D. Smith, G. Spandre, P. Spinelli, D. J. Suson, H. Takahashi, T. Tanaka, J. G. Thayer, J. B. Thayer, D. J. Thompson, L. Tibaldo, G. Tosti, E. Troja, T. L. Usher, J. Vandenbroucke, V. Vasileiou, G. Vianello, N. Vilchez, V. Vitale, A. P. Waite, P. Wang, B. L. Winer, K. S. Wood, Z. Yang, S. Zimmer
  • Kavli Institute for Particle Astrophysics and Cosmology
  • University of California at Santa Cruz
  • Stockholm University
  • Oskar Klein Centre
  • KTH Royal Institute of Technology
  • Istituto Nazionale di Fisica Nucleare, Sezione di Pisa
  • INFN Sezione di Trieste
  • University of Trieste
  • INFN
  • University of Padova
  • INFN Sezione di Perugia
  • University of Perugia
  • Naval Research Laboratory
  • Politecnico di Bari
  • INFN Sezione di Bari
  • University of Sheffield
  • INAF Istituto di Astrofisica Spaziale e Fisica Cosmica, Milan
  • Universite Paris-Saclay
  • Artep Inc.
  • ASI Science Data Center
  • Laboratoire Univers et Particules de Montpellier
  • Science and Research Directorate
  • Ip Paris
  • Hiroshima University
  • NASA Goddard Space Flight Center
  • INAF Istituto di Radioastronomia
  • Center for Space Plasma and Aeronomic Research
  • The Ohio State University
  • University of Iceland
  • National Research Council
  • Ibaraki University
  • Waseda University
  • IRAP/CNRS
  • Yukawa Institute for Theoretical Physics
  • University of Maryland
  • Sezione di Roma
  • University of Denver
  • ISAS/JAXA
  • Max Planck Institut für Extraterrestrische Physik
  • Max-Planck-Institut für Physik
  • George Mason University
  • Medical University of Innsbruck
  • Univ. Bordeaux
  • NYCB Real-Time Computing Inc.
  • Purdue University Northwest
  • Consorzio Interuniversitario per la Fisica Spaziale (CIFS)
  • University of Rome “Tor Vergata”

Research output: Contribution to journalArticlepeer-review

Abstract

The Large Area Telescope (LAT) on-board the Fermi Gamma-ray Space Telescope is a pair-conversion telescope designed to survey the gamma-ray sky from 20 MeV to several hundreds of GeV. In this energy band there are no astronomical sources with sufficiently well known and sharp spectral features to allow an absolute calibration of the LAT energy scale. However, the geomagnetic cutoff in the cosmic ray electron-plus-positron (CRE) spectrum in low Earth orbit does provide such a spectral feature. The energy and spectral shape of this cutoff can be calculated with the aid of a numerical code tracing charged particles in the Earth's magnetic field. By comparing the cutoff value with that measured by the LAT in different geomagnetic positions, we have obtained several calibration points between ∼6 and ∼13 GeV with an estimated uncertainty of ∼2%. An energy calibration with such high accuracy reduces the systematic uncertainty in LAT measurements of, for example, the spectral cutoff in the emission from gamma ray pulsars.

Original languageEnglish
Pages (from-to)346-353
Number of pages8
JournalAstroparticle Physics
Volume35
Issue number6
DOIs
Publication statusPublished - 1 Jan 2012

Keywords

  • Absolute energy scale
  • Cosmic-rays
  • Fermi Large Area Telescope
  • Geomagnetic cutoff

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