Marie-H l ne Grondin Marianne Lemoine-Goumard CEN Bordeaux-Gradignan on behalf of the Fermi-LAT Collaboration and the

2. The Crab Nebula and Pulsar Pulsar Wind Nebula G184.6-5.8 aka Crab Nebula, powered by the Crab Pulsar (B0531+21, dE/dt = 4.6x1038 erg/s)? No SNR shell detected Remnant of a supernova explosion, occurred in 1054 A.D. Distance = (2.0 �0.2) kpc, characteristic pulsar age = 1240 yr Spectrum of the nebula spanning 21 decades in frequency, from radio to ~80 TeV, emission predominantly by non-thermal processes Crab Pulsar detected and studied in all wavelength bands from the radio to high energy gamma-rays

3. Earlier gamma-ray observations of the Crab region Crab Nebula: EGRET observations of the synchrotron/Inverse Compton spectrum in the 70 MeV � 30 GeV energy band (De Jager et al., ApJ 457:253, 1996): Large uncertainties on the spectrum shapes for both components

4. Crab Pulsar: EGRET observations (Nolan et al., ApJ 409:697, 1993; Fierro et al., ApJ 494:734, 1998; Kuiper et al., A&A 378:918,2001): Large uncertainties on the spectrum at high energy No cut-off detected in the EGRET energy band Study of the pulsar spectroscopy Earlier gamma-ray observations of the Crab region

5. Analysis of the Fermi-LAT data Event selection: 20�circular region around the Crab Pulsar radio position 8 months of data in survey mode Photons above 100 MeV ��diffuse�� class events (highest quality photon data)? Temporal analysis: Timing solution built with the TEMPO2 timing package (Hobbs et al., MNRAS 369:655, 2006), using observations made with the Jodrell Bank (England) and Nan�ay (France) radio telescopes Spectral analysis: Sources with a statistical significance larger than 5? (after 6 months of survey) are taken into account Galactic diffuse background modelled using GALPROP (Strong et al ApJ 613:962, 2004)? Extragalactic and residual backgrounds assumed as isotropic and described with a power-law spectrum

6. Fermi-LAT light curve above 100 MeV Events in an energy-dependent circular region are selected (optimized for the Crab case)? 14563 � 240 pulsed photons above the background level The radio main pulse lags the first gamma-ray peak by ~0.014 in phase ?~280 �s ? implications on the emitting region

7. Fermi-LAT light curves above 100 MeV The peaks are asymmetric The positions of the peak are stable with energy The peak half-widths and the P1/P2 ratio decrease with energy The off-pulse window is defined as the 0.52-0.87 phase interval A 2.3? significant enhancement is observed above 10 GeV at phase ~0.74, coincident with a radio feature (HFC2) reported by Moffett and Hankins (ApJ 468:77, 1996)?

8. Spectral analysis of the Crab Nebula Analysis in the off-pulse window Synchrotron and inverse Compton (IC) components are resolved Crab Nebula spectral parameters (renormalized to the total phase):

11. Spectral analysis of the Crab Pulsar Analysis in the whole phase interval Best fit above 100 MeV obtained with a power-law with an exponential cut-off An hyper exponential cut-off (b=2) spectrum is excluded at ~ 5? Crab Pulsar spectral parameters:

12. Summary Large photon counts number obtained in 8 months of survey Analysis of the gamma-ray pulse profile with unprecedented precision Detailed analysis of the nebular spectrum between 100 MeV and 300 GeV, covering the falling edge of the synchrotron and the rising edge of the IC components implications on physical parameters such as the mean magnetic field strength First measurement of the cut-off energy of the Crab Pulsar implications on the models of pulsed emission Results are reported in an upcoming paper (to be submitted), including a detailed phase-resolved spectroscopic study of the pulsed emission