Discovery of high-energy Gamma-Ray pulsations from PSR J2021+3651 with AGILE

J. P. Halpern, F. Camilo, A. Giuliani, E. V. Gotthelf, M. A. Mclaughlin, R. Mukherjee, A. Pellizzoni, S. M. Ransom, M. S.E. Roberts, M. Tavani

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Discovered after the end of the Compton Gamma-Ray Observatory mission, the radio pulsar PSR J2021 + 3651 was long considered a likely counterpart of the high-energy γ-ray source 2CG 075 + 00=3EG J2021+3716=GeV J2020 + 3658, but it could not be confirmed due to the lack of a contemporaneous radio pulsar ephemeris to fold the sparse, archival γ-ray photons. Here, we report the discovery of γ-ray pulsations from PSR J2021 + 3651 in the 100-1500 MeV range using data from the AGILE satellite gathered over 8 months, folded on a densely sampled, contemporaneous radio ephemeris obtained for this purpose at the Green Bank Telescope. The γ-ray pulse consists of two sharp peaks separated by 0.47 ± 0.01 cycles. The single radio pulse leads the first γ-ray peak by 0.165 ± 0.010 cycles. These properties are similar to those of other γ-ray pulsars, and the phase relationship of the peaks can be interpreted in the context of the outer-gap accelerator model for γ-ray emission. Pulse-phase-resolved images show that there is only one dominant source, AGL J2020.5+3653=PSR J2021+3651, in the region previously containing confused sources 3EG J2021+3716 and 3EG J2016+3657.

Original languageEnglish (US)
Pages (from-to)L33-L36
JournalAstrophysical Journal
Issue number1 PART 2
StatePublished - 2008


  • Gamma rays
  • Observations-pulsars

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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    Halpern, J. P., Camilo, F., Giuliani, A., Gotthelf, E. V., Mclaughlin, M. A., Mukherjee, R., Pellizzoni, A., Ransom, S. M., Roberts, M. S. E., & Tavani, M. (2008). Discovery of high-energy Gamma-Ray pulsations from PSR J2021+3651 with AGILE. Astrophysical Journal, 688(1 PART 2), L33-L36.