Fermi Large Area Telescope Observations of the Vela Pulsar

• Published in: The Astrophysical journal 2009-05, Vol.696 (2), p.1084-1093
• Main Authors: Abdo, A. A, Atwood, W. B, Ballet, J, Baring, M. G, Baughman, B. M, Bloom, E. D, Bogart, J. R, Borgland, A. W, Burnett, T. H, Caliandro, G. A, Camilo, F, Caraveo, P. A, Casandjian, J. M, Ceccanti, M, Chiang, J, Ciprini, S, Cognard, I, Cohen-Tanugi, J, Cominsky, L. R, Conrad, J, Corbet, R, de Angelis, A, Digel, S. W, Dormody, M, Silva, E. do Couto e, Dubois, R, Dumora, D, Espinoza, C, Farnier, C, Focke, W. B, Frailis, M, Fukazawa, Y, Funk, S, Fusco, P, Gehrels, N, Giebels, B, Grondin, M.-H, Haller, G, Hart, P. A, Hartman, R. C, Hays, E, Hobbs, G, Hughes, R. E, Jóhannesson, G, Johnson, A. S, Johnson, R. P, Johnson, W. N, Kamae, T, Kanbach, G, Kataoka, J, Kelly, H, Kiziltan, B, Klamra, W, Landriu, D, Latronico, L, Lemoine-Goumard, M, Longo, F, Loparco, F, Lyne, A. G, Makeev, A, Marangelli, B, Mazziotta, M. N, McEnery, J. E, Michelson, P. F, Mitthumsiri, W, Mongelli, M, Moretti, E, Moskalenko, I. V, Murgia, S, Nakamori, T, Nolan, P. L, Nuss, E, Orlando, E, Paccagnella, A, Panetta, J. H, Pepe, M, Piron, F, Rainò, S, Rapposelli, E, Razzano, M, Reposeur, T, Rochester, L. S, Ryde, F, Sadrozinski, H. F.-W, Saggini, N, Sanchez, D, Sgrò, C, Siskind, E. J, Smith, D. A, Stecker, F. W, Stephens, T. E, Takahashi, T, Thayer, J. B, Thayer, J. G, Tibaldo, L, Turri, M, Vigiani, L, Vitale, V, Wang, P, Ylinen, T
• Format: Article
• Language: English
• Subjects: Astronomy; discovery; Earth, ocean, space; emission; Exact sciences and technology; Fysik; gamma rays: observations; gamma-ray pulsars; light curves; magnetospheres; Physics; polar-cap; pulsars: individual (PSR B0833-45); radiation; slot gaps; timing package
• ISSN: 0004-637X; 1538-4357; 1538-4357
• DOI: 10.1088/0004-637X/696/2/1084

The Vela pulsar is the brightest persistent source in the GeV sky and thus is the traditional first target for new g-ray observatories. We report here on initial Fermi Large Area Telescope observations during verification phase pointed exposure and early sky survey scanning. We have used the Vela signal to verify Fermi timing and angular resolution. The high-quality pulse profile, with some 32,400 pulsed photons at E >= 0.03 GeV, shows new features, including pulse structure as fine as 0.3 ms and a distinct third peak, which shifts in phase with energy. We examine the high-energy behavior of the pulsed emission; initial spectra suggest a phase-averaged power-law index of = 1.51+0.05 -0.04 with an exponential cutoff at Ec = 2.9 ± 0.1 GeV. Spectral fits with generalized cutoffs of the form require b