2010/07/07 by LAT Collaboration, M. Ackermann, A. A. Abdo +98 · 1 citation
Physics and Astronomy · #Astronomy #Astrophysical Phenomena and Observations #Astrophysics #Astrophysics and Cosmic Phenomena #Fermi Gamma-ray Space Telescope #Flux (metallurgy) #Gamma ray #Optics #Photon #Physics #Pulsar #Pulsars and Gravitational Waves Research #Spectral index #Spectral line #astro-ph.HE
paper · pdf · doi:10.1088/0004-637x/720/1/272
32 pages, 12 figures, 3 tables. Accepted for publication in The Astrophysical Journal. Corresponding authors: Denis Dumora ([email protected]), Fabio Gargano ([email protected]), Massimiliano Razzano ([email protected])
arxiv created 2010/07/07 · openalex publication_date 2010/08/09 · arxiv updated 2016/04/13 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We report on the Fermi -LAT observations of the Geminga pulsar, the second brightest non-variable GeV source in the γ-ray sky and the first example of a radio-quiet γ-ray pulsar. The observations cover one year, from the launch of the Fermi satellite through 2009 June 15. A data sample of over 60,000 photons enabled us to build a timing solution based solely on γ-rays. Timing analysis shows two prominent peaks, separated by Δϕ = 0.497 ± 0.004 in phase, which narrow with increasing energy. Pulsed γ-rays are observed beyond 18 GeV, precluding emission below 2.7 stellar radii because of magnetic absorption. The phase-averaged spectrum was fitted with a power law with exponential cutoff of spectral index Γ = (1.30 ± 0.01 ± 0.04), cutoff energy E 0 = (2.46 ± 0.04 ± 0.17) GeV, and an integral photon flux above 0.1 GeV of (4.14 ± 0.02 ± 0.32) × 10 −6 cm −2 s −1 . The first uncertainties are statistical and the second ones are systematic. The phase-resolved spectroscopy shows a clear evolution of the spectral parameters, with the spectral index reaching a minimum value just before the leading peak and the cutoff energy having maxima around the peaks. The phase-resolved spectroscopy reveals that pulsar emission is present at all rotational phases. The spectral shape, broad pulse profile, and maximum photon energy favor the outer magnetospheric emission scenarios.