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Early Fermi LAT observations of the Vela pulsar

Early Fermi LAT observations of the Vela pulsar. Massimiliano Razzano on behalf of the Fermi LAT Collaboration. INFN-Pisa massimiliano.razzano@pi.infn.it. ID of Vela pulsar. Radio pulsation discovered in 1968 in the Vela SNR, bright pulsar: S 1.4Ghz ~1.5 Jy

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Early Fermi LAT observations of the Vela pulsar

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  1. Early Fermi LAT observations of the Vela pulsar Massimiliano Razzano on behalf of the Fermi LAT Collaboration INFN-Pisa massimiliano.razzano@pi.infn.it M.Razzano - 44th Rencontres de Moriond

  2. ID of Vela pulsar • Radio pulsation discovered in 1968 in the Vela SNR, bright pulsar: S1.4Ghz~1.5 Jy • Located RA=08:35:20.61,dec=-45:10:34.87 (near the Galactic plane @b~-2.8˚) • D~287+19-17 pc (VLBI parallax in 2003)‏ • P:~89 ms; Pdot ~3x10-13 s/s • Young pulsar tc~11 kyr • Energetic Edot~7x1036 erg/s • Bsurf ~3.4x1012 G 7 high confidence gamma-ray pulsars Low confidence gamma-ray pulsars (D. Thompson, 2003)‏

  3. A huge gamma-ray telescope ! Kanbach et al. 1980 Kanbach et al. 1994 Thompson et al. 1975 Pellizzoni et al. 2008 Abdo et. al 2008

  4. A huge teamwork ! • Large collaborative effort of scientific/instrumental analysis! • See Abdo et al. 2009 ApJ in press,arXiv:0812.2960

  5. Point Spread Function Excellent agreement with pre-launch expectations below few GeV Stefano Germani’s talk about on-orbit performance verifications & monitoring Flight data on Vela used for testing the pre-launch expectations The PSF is very sharp at high energy

  6. First Fermi Vela light curve 100 MeV < E < 10 GeV ~50000 photons ! Remarkably sharp peaks; features to ~0.3 ms Turns almost completely off between the double pulses

  7. Light curve evolution with energy Large LAT energy window puts Vela pulsar in multiwavelength context !

  8. Vela in Radio Coherent radio emission Parkes 64m telescope RMS residuals 90s log nFn (Jy Hz) log E2 dN/dE (erg cm-2 s-1)

  9. Synchrotron optical/uv HST STIS/MAMA 4.1-6.5 eV (Romani et al., ApJ 2005) Vela in UV log nFn (Jy Hz) log E2 dN/dE (erg cm-2 s-1)

  10. Thermal soft X-rays XMM PN Soft X-rays log nFn (Jy Hz) log E2 dN/dE (erg cm-2 s-1)

  11. Synchrotron hard X-rays RXTE PCA (Harding et al., ApJ 2002) Hard X-rays log nFn (Jy Hz) log E2 dN/dE (erg cm-2 s-1)

  12. Vela in g-rays • Curvature g-rays • Fermi LAT • Energy dependent pulses • First peak softer than second • Known from EGRET log nFn (Jy Hz) log E2 dN/dE (erg cm-2 s-1)

  13. Vela in g-rays • Curvature g-rays • Fermi LAT • Energy dependent pulses • First peak softer than second • Known from EGRET log nFn (Jy Hz) log E2 dN/dE (erg cm-2 s-1)

  14. Vela in g-rays • Curvature g-rays • Fermi LAT • Energy dependent pulses • First peak softer than second • Known from EGRET • 3rd Peak, which shift in energy • New result ! log nFn (Jy Hz) log E2 dN/dE (erg cm-2 s-1)

  15. Vela in g-rays • Curvature g-rays • Fermi LAT • Energy dependent pulses • First peak softer than second • Known from EGRET • 3rd Peak, which shift in energy • New result ! log nFn (Jy Hz) log E2 dN/dE (erg cm-2 s-1)

  16. Vela in g-rays • Curvature g-rays • Fermi LAT • Energy dependent pulses • First peak softer than second • Known from EGRET • 3rd Peak, which shift in energy • New result ! log nFn (Jy Hz) log E2 dN/dE (erg cm-2 s-1)

  17. Vela in g-rays • Curvature g-rays • Fermi LAT • Energy dependent pulses • First peak softer than second • Known from EGRET • Trailing peak survives (known from EGRET) log nFn (Jy Hz) log E2 dN/dE (erg cm-2 s-1)

  18. Phase-averaged spectrum Consistent with b=1 (simple exponential) b=2 (super-exponential) rejected at 16.5s No evidence for magnetic pair attenuation: Near-surface emission ruled out

  19. The Vela pulsar movie • E<300MeV (red) • 300MeV<E<1GeV(Green) • E>1GeV (blue)

  20. Summary of key results Vela pulsar Phase-averaged spectrum Simple exponential cutoff Ec = 2.9 ± 0.1 GeV Inconsistent with magnetic pair attenuation, thus favoring outer magnetosphere emission models Energy-dependent pulse profile First peak is softer than second peak (confirming EGRET) Sharpest features to ~0.3 ms. Peak in bridge region (phase ~ 0.3) shifts to later phase with increasing g-ray energy Upper limit on unpulsed emission (>100 MeV) 1.8x10-7 ph/cm2/s 95% C.L. upper limit on unpulsed emission, e.g. PWN (Talk of Marie-Helene Grondin) Stringent limits or measurement will be available with more livetime See Abdo et al. 2009 ApJ in press, arXiv:0812.2960 Contact authors R. Romani and M. Razzano Fermi LAT & Vela Working as designed, performance as expected e.g. Vela results demonstrate timing and angular resolution below few GeV (Talk of Stefano Germani)

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