Pulsed gamma-rays from PSR j2021+3651 with the Fermi large area telescope

A. A. Abdo, M. Ackermann, M. Ajello, W. B. Atwood, L. Baldini, J. Ballet, G. Barbiellini, D. Bastieri, M. Battelino, B. M. Baughman, K. Bechtol, R. Bellazzini, B. Berenji, E. D. Bloom, G. Bogaert, A. W. Borgland, J. Bregeon, A. Brez, M. Brigida, P. BruelT. H. Burnett, G. A. Caliandro, R. A. Cameron, F. Camilo, P. A. Caraveo, J. M. Casandjian, C. Cecchi, E. Charles, A. Chekhtman, A. W. Chen, C. C. Cheung, J. Chiang, S. Ciprini, I. Cognard, J. Cohen-Tanugi, L. R. Cominsky, J. Conrad, S. Cutini, P. Demorest, C. D. Dermer, A. De Angelis, A. De Luca, F. De Palma, S. W. Digel, M. Dormody, E. Do Couto E Silva, P. S. Drell, R. Dubois, D. Dumora, C. Espinoza, C. Farnier, C. Favuzzi, W. B. Focke, M. Frailis, P. C.C. Freire, Y. Fukazawa, S. Funk, P. Fusco, F. Gargano, D. Gasparrini, N. Gehrels, S. Germani, B. Giebels, N. Giglietto, F. Giordano, T. Glanzman, G. Godfrey, I. A. Grenier, M. H. Grondin, J. E. Grove, L. Guillemot, S. Guiriec, Y. Hanabata, A. K. Harding, M. Hayashida, E. Hays, R. E. Hughes, G. Jóhannesson, A. S. Johnson, R. P. Johnson, T. J. Johnson, W. N. Johnson, S. Johnston, T. Kamae, H. Katagiri, J. Kataoka, N. Kawai, M. Kerr, B. Kiziltan, J. Knödlseder, N. Komin, M. Kramer, F. Kuehn, M. Kuss, J. Lande, L. Latronico, S. H. Lee, M. Lemoine-Goumard, F. Longo, F. Loparco, B. Lott, M. N. Lovellette, P. Lubrano, A. G. Lyne, A. Makeev, R. N. Manchester, M. Marelli, M. N. Mazziotta, W. McConville, J. E. McEnery, M. A. McLaughlin, C. Meurer, P. F. Michelson, W. Mitthumsiri, T. Mizuno, A. A. Moiseev, C. Monte, M. E. Monzani, A. Morselli, I. V. Moskalenko, S. Murgia, P. L. Nolan, A. Noutsos, E. Nuss, T. Ohsugi, N. Omodei, E. Orlando, J. F. Ormes, M. Ozaki, D. Paneque, J. H. Panetta, D. Parent, M. Pepe, M. Pesce-Rollins, F. Piron, T. A. Porter, S. Rainò, R. Rando, S. M. Ransom, M. Razzano, A. Reimer, O. Reimer, T. Reposeur, S. Ritz, L. S. Rochester, A. Y. Rodriguez, R. W. Romani, F. Ryde, H. F.W. Sadrozinski, D. Sanchez, P. M.Saz Parkinson, C. Sgrò, A. Sierpowska-Bartosik, E. J. Siskind, D. A. Smith, P. D. Smith, G. Spandre, P. Spinelli, B. W. Stappers, J. L. Starck, M. S. Strickman, D. J. Suson, H. Tajima, H. Takahashi, T. Takahashi, T. Tanaka, J. B. Thayer, J. G. Thayer, G. Theureau, D. J. Thompson, S. E. Thorsett, L. Tibaldo, D. F. Torres, G. Tosti, A. Tramacere, Y. Uchiyama, T. L. Usher, A. Van Etten, N. Vilchez, V. Vitale, A. P. Waite, E. Wallace, K. Watters, P. Weltevrede, K. S. Wood, T. Ylinen, M. Ziegler

Research output: Contribution to journalArticlepeer-review

40 Citations (Scopus)


We report the detection of pulsed gamma-rays from the young, spin-powered radio pulsar PSR J2021+3651 using data acquired with the Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope (formerly GLAST). The light curve consists of two narrow peaks of similar amplitude separated by 0.468 0.002 in phase. The first peak lags the maximum of the 2 GHz radio pulse by 0.162 ± 0.004±0.01 in phase. The integral gamma-ray photon flux above 100 MeV is (56±3±11) × 10-8 cm-2 s-1. The photon spectrum is well described by an exponentially cut-off power law of the form , where the energy E is expressed in GeV. The photon index is Γ = 1.5±0.1±0.1 and the exponential cut-off is Ec = 2.4±0.3±0.5 GeV. The first uncertainty is statistical and the second is systematic. The integral photon flux of the bridge is approximately 10% of the pulsed emission, and the upper limit on off-pulse gamma-ray emission from a putative pulsar wind nebula is < 10% of the pulsed emission at the 95% confidence level. Radio polarization measurements yield a rotation measure of RM = 524±4 rad m-2 but a poorly constrained magnetic geometry. Re-analysis of Chandra X-ray Observatory data enhanced the significance of the weak X-ray pulsations, and the first peak is roughly phase aligned with the first gamma-ray peak. We discuss the emission region and beaming geometry based on the shape and spectrum of the gamma-ray light curve combined with radio and X-ray measurements, and the implications for the pulsar distance. Gamma-ray emission from the polar cap region seems unlikely for this pulsar.

Original languageEnglish
Pages (from-to)1059-1066
Number of pages8
JournalAstrophysical Journal
Issue number2
Publication statusPublished - 2009
Externally publishedYes


  • Gamma rays: observations pulsars: general pulsars: individual

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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