We report on analysis of timing and spectroscopy of the Vela pulsar using 11 months of observations with the Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope. The intrinsic brightness of Vela at GeV energies combined with the angular resolution and sensitivity of the LAT allows us to make the most detailed study to date of the energy-dependent light curves and phase-resolved spectra, using a LAT-derived timing model. The light curve consists of two peaks (P1 and P2) connected by bridge emission containing a third peak (P3). We have confirmed the strong decrease of the P1/P2 ratio with increasing energy seen with EGRET and previous Fermi LAT data, and observe that P1 disappears above 20 GeV. The increase with energy of the mean phase of the P3 component can be followed with much greater detail, showing that P3 and P2 are present up to the highest energies of pulsation. We find significant pulsed emission at phases outside the main profile, indicating that magnetospheric emission exists over 80% of the pulsar period. With increased high-energy counts the phase-averaged spectrum is seen to depart from a power law with simple exponential cutoff, and is better fit with a more gradual cutoff. The spectra in fixed-count phase bins are well fit with power laws with exponential cutoffs, revealing a strong and complex phase dependence of the cutoff energy, especially in the peaks. By combining these results with predictions of the outer magnetosphere models that map emission characteristics to phase, it will be possible to probe the particle acceleration and the structure of the pulsar magnetosphere with unprecedented detail.
|Autori:||Abdo AA; Ackermann M; Ajello M; Allafort A; Atwood WB; Baldini L; Ballet J; Barbiellini G; Baring MG; Bastieri D; Baughman BM; Bechtol K; Bellazzini R; Berenji B; Blandford D; Bloom ED; Bonamente E; Borgland AW; Bouvier A; Bregeon J; Brez A; Brigida M; Bruel P; Burnett TH; Buson S; Caliandro GA; Cameron RA; Caraveo PA; Carrigan S; Casandjian JM; Cecchi C; Celik O; Chekhtman A; Cheung CC; Chiang J; Ciprini S; Claus R; Cohen-Tanugi J; Conrad J; Dermer CD; de Luca A; de Palma F; Dormody M; Silva EDE; Drell PS; Dubois R; Dumora D; Farnier C; Favuzzi C; Fegan SJ; Focke WB; Fortin P; Frailis M; Fukazawa Y; Funk S; Fusco P; Gargano F; Gasparrini D; Gehrels N; Germani S; Giavitto G; Giebels B; Giglietto N; Giordano F; Glanzman T; Godfrey G; Grenier IA; Grondin MH; Grove JE; Guillemot L; Guiriec S; Hadasch D; Harding AK; Hays E; Hobbs G; Horan D; Hughes RE; Jackson MS; Johannesson G; Johnson AS; Johnson TJ; Johnson WN; Kamae T; Katagiri H; Kataoka J; Kawai N; Kerr M; Knodlseder J; Kuss M; Lande J; Latronico L; Lee SH; Lemoine-Goumard M; Garde ML; Longo F; Loparco F; Lott B; Lovellette MN; Lubrano P; Makeev A; Manchester RN; Marelli M; Mazziotta MN; McConville W; McEnery JE; McGlynn S; Meurer C; Michelson PF; Mitthumsiri W; Mizuno T; Moiseev AA; Monte C; Monzani ME; Morselli A; Moskalenko IV; Murgia S; Nakamori T; Nolan PL; Norris JP; Noutsos A; Nuss E; Ohsugi T; Omodei N; Orlando E; Ormes JF; Ozaki M; Paneque D; Panetta JH; Parent D; Pelassa V; Pepe M; Pesce-Rollins M; Pierbattista M; Piron F; Porter TA; Raino S; Rando R; Ray PS; Razzano M; Reimer A; Reimer O; Reposeur T; Ritz S; Rochester LS; Rodriguez AY; Romani RW; Roth M; Ryde F; Sadrozinski HFW; Sander A; Parkinson PMS; Sgro C; Siskind EJ; Smith DA; Smith PD; Spandre G; Spinelli P; Starck JL; Strickman MS; Suson DJ; Takahashi H; Takahashi T; Tanaka T; Thayer JB; Thayer JG; Thompson DJ; Tibaldo L; Torres DF; Tosti G; Tramacere A; Usher TL; Van Etten A; Vasileiou V; Venter C; Vilchez N; Vitale V; Waite AP; Wang P; Watters K; Weltevrede P; Winer BL; Wood KS; Ylinen T; Ziegler M|
|Titolo:||THE VELA PULSAR: RESULTS FROM THE FIRST YEAR OF FERMI LAT OBSERVATIONS|
|Anno del prodotto:||2010|
|Digital Object Identifier (DOI):||10.1088/0004-637X/713/1/154|
|Appare nelle tipologie:||1.1 Articolo in rivista|