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- Pulsed Gamma-rays from PSR J2021+3651 with the Fermi Large Area Telescope doi link

Author(s): Abdo A. A., Ackermann M., Ajello M., B. Atwood W., Ballet J., Bogaert G., Bruel P., M. Casandjian J., Cognard I., Cohen-Tanugi J., Dumora D., Farnier C., Giebels B., A. Grenier I., Grondin M.-H., Guillemot L., Guiriec Sylvain, Knodlseder J., Komin Nukri, Lemoine-Goumard M., Lott B., Nuss E., Parent D., Piron F., Reposeur T., Sanchez D., A. Smith D., Starck J.-L., Theureau G., Vilchez N.

(Article) Published: The Astrophysical Journal / The Astrophysical Journal Letters, vol. 700 p.1059-1066 (2009)
Links openAccess full text : arxiv


Ref HAL: in2p3-00394148_v1
Ref Arxiv: 0905.4400
DOI: 10.1088/0004-637X/700/2/1059
Ref. & Cit.: NASA ADS
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36 citations
Abstract:

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^{-8} /cm2/s. The photon spectrum is well-described by an exponentially cut-off power law of the form dF/dE = kE^{-\Gamma} e^(-E/E_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_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^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.



Comments: Accepted by the Astrophysical Journal, 25 May 2009