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Accession Number
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DE2012-1046390
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Title
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Pulsed Gamma-Rays from PSR J2021+3651 with the Fermi Large Area Telescope.
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Publication Date
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Apr 2012
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Media Count
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10p
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Personal Author
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A. A. Abdo J. Ballet L. Baldini M. Ackerman M. Ajello W. B. Atwood
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Abstract
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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) x 10(sup -8) cm(sup -2) s(sup -1). The photon spectrum is well-described by an exponentially cut-off power law of the form dF/dE = kE(sup -(Gamma))e(sup (-E/E(sub c))) where the energy E is expressed in GeV. The photon index is (Gamma) = 1.5 (+-) 0.1 (+-) 0.1 and the exponential cut-off is E(sub c) = 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(sup -2) but a poorly constrained magnetic geometry. Re-analysis of Chandra 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.
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Keywords
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Amplitudes
Detection
Gamma rays
Geometry
Photons
Polarization
Pulsars
Pulsations
Radio astronomy
Rotation
Shape
Telescopes
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Source Agency
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Technical Information Center Oak Ridge Tennessee
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NTIS Subject Category
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54C - Astrophysics
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Corporate Author
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Stanford Linear Accelerator Center, CA.
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Document Type
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Technical report
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Title Note
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N/A
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NTIS Issue Number
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1303
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Contract Number
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DE-AC02-76SF00515
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