1. Early Fermi LAT observations of the Vela pulsar
Massimiliano Razzano
on behalf of the Fermi LAT Collaboration
INFN-Pisa
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
D~ 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 !
Thompson et al. 1975
Kanbach et al. 1980
Kanbach et al. 1994
Pellizzoni et al. 2008
Abdo et. al 2008

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

5. 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 Germani’s talk about on-orbit performance verifications & monitoring

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. 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)

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

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

12. Vela in g-rays Fermi LAT Curvature g-rays 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 Fermi LAT Curvature g-rays 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 Fermi LAT Curvature g-rays 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 Fermi LAT Curvature g-rays 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 Fermi LAT Curvature g-rays 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 Fermi LAT Curvature g-rays 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 ApJ in press, arXiv:
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)