Diapositiva 1

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Early Fermi LAT observations of the Vela pulsar
Massimiliano Razzano on behalf of the Fermi LAT
Collaboration
INFN-Pisa massimiliano.razzano_at_pi.infn.it
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ID of Vela pulsar

• Radio pulsation discovered in 1968 in the Vela
  SNR, bright pulsar S1.4Ghz1.5 Jy
• Located RA083520.61,dec-451034.87 (near the
  Galactic plane _at_b-2.8)
• D28719-17 pc (VLBI parallax in 2003)?

• P89 ms Pdot 3x10-13 s/s
• Young pulsar tc11 kyr
• Energetic Edot7x1036 erg/s
• Bsurf 3.4x1012 G

7 high confidence gamma-ray pulsars Low
confidence gamma-ray pulsars (D. Thompson, 2003)?
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A huge gamma-ray telescope !
Thompson et al. 1975
Kanbach et al. 1980
Kanbach et al. 1994
Pellizzoni et al. 2008
Abdo et. al 2008
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A huge teamwork !

• Large collaborative effort of scientific/instrumen
  tal analysis!
• See Abdo et al. 2009 ApJ in press, arXiv0812.2960

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Point Spread Function

• Flight data on Vela used for testing the
  pre-launch expectations
• The PSF is very sharp at high energy

Excellent agreement with pre-launch expectations
below few GeV
Stefano Germanis talk about on-orbit performance
verifications monitoring
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First Fermi Vela light curve
100 MeV lt E lt 10 GeV 50000 photons !
Remarkably sharp peaks features to 0.3
ms Turns almost completely off between
the double pulses
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Light curve evolution with energy
Large LAT energy window puts Vela pulsar in
multiwavelength context !
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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)
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Vela in UV

• Synchrotron optical/uv
• HST STIS/MAMA
• 4.1-6.5 eV
• (Romani et al., ApJ 2005)

log nFn (Jy Hz)
log E2 dN/dE (erg cm-2 s-1)
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Soft X-rays

• Thermal soft X-rays
• XMM PN

log nFn (Jy Hz)
log E2 dN/dE (erg cm-2 s-1)
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Hard X-rays

• Synchrotron hard X-rays
• RXTE PCA
• (Harding et al., ApJ 2002)

log nFn (Jy Hz)
log E2 dN/dE (erg cm-2 s-1)
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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)
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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)
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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)
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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)
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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)
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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)
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Phase-averaged spectrum
Consistent with b1 (simple exponential)
b2 (super-exponential) rejected at 16.5s
No evidence for magnetic pair attenuation Near-su
rface emission ruled out
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The Vela pulsar movie

• Elt300MeV (red)
• 300MeVltElt1GeV(Green)
• Egt1GeV (blue)

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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 (gt100 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,
  arXiv0812.2960
• 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)