Catia Grimani

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Antimatter origin and average pulsar parameters
from e measurements

• Catia Grimani
• University of Urbino - INFN Florence

ECRS Lisbona September 5th - September 8th 2006
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Positron fraction observations before 1995
CG, AA, 418, 649, 2004
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Positron production models

• Primordial Black Hole Annihilation
• 56Co decay in Supernova Remnants
• Supersymmetric particle annihilation
• gg interaction
• Pulsar magnetosphere
• (Polar Cap - Outer Gap Models)

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POLAR CAP MODEL
Goldreich Julian, 1969 Harding Ramaty, 1987
Strong electric fields are induced by the
rotating neutron star Electrons are extracted
from the star outer layer and accelerated
Open field lines originate at polar caps (rpc
8 x 102 m)
Figure from http//cossc.gsfc.nasa.gov/images/epo/
gallery/pulsars/
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OUTER GAP MODEL
Cheng, Ho Ruderman, 1986
Electrons are accelerated in the outer
magnetosphere in vacuum gaps within a charge
separated plasma Electrons interact through
syncrotron radiation or inverse Compton
scattering ee- pairs are produced by gg
interactions
Figures from http//cossc.gsfc.nasa.gov/images/epo
/gallery/pulsars/
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Positron Flux from Young Pulsar Polar Caps
Harding Ramaty, 1987
Maximum pulsar age for e production 104
years 1/PB30 years Crab and Vela pulsar
parameters
Rate of positron emission per pulsar
Le (E) ? B12 P-1.7 E-2.2 s-1 GeV-1
Measurements before 1995 1/PB60 years CG,
ApSS, 241, 295, 1996
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Positron observations after 1995
Average value above 7 GeV 0.064 0.003
CG et al., AA, 2002
Figure from CG, AA, 418, 649, 2004
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Positron observations compared to the secondary
AND polar cap components
Harding Ramaty, 1987
Top region corresponds to the secondary
component HR with a 1/PB of 30 yrs
Dashed region corresponds to the secondary
component HR with a 1/PB of 200 yrs
Bottom region corresponds to the secondary
component HR with a 1/PB of 250 yrs
CG, AA, 418, 649, 2004
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Solar polarity and low energy e measurements
Thick dot-dashed lines Protheroe, 1982 SLBM Clem
Evenson, 2004 Thin dot-dashed line Protheroe,
1982 Diff. Mod. Dashed line Stephens, 2001 Dotted
line MS, 1998
Agt0
Alt0
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LEE and AESOP data
Agt0
Thick dot-dashed lines Protheroe, 1982 SLBM Clem
Evenson, 2004
Alt0
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HEAT data
Open symbols Agt0 Solid simbols Alt0
Thick dot-dashed lines Protheroe, 1982
SLBM Beatty et al., astro-ph/0412230
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ANTIPROTON DATA
Open symbols Agt0 Solid simbols Alt0
Alt0
Agt0
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Electron flux Measurements and calculations
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Upper limit (continuous thick line) to the
e flux excess with respect to the secondary
component (dot-dashed line -MoskalenkoStrong,
1998) same trend than HR87 with 1/PB35 years
(dotted line)
CG, ICRC2005
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CG, AA, 418, 649, 2004
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PULSAR BIRTHRATE ESTIMATES
LMT-1985 Lyne, Manchester Taylor, 1985 L-1993
Lorimer, 1993 H-1999 Hansen, 1999 R-2001
Regimbeau, 2001 CET-1999 Cappellaro, Evans
Turatto, 1999
35.7 years
Fucher-Giguère and Kaspi, astro-ph/0512585
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However middle aged pulsars are favoured over
young ones in producing positrons reaching the
interstellar medium as an increasing fraction of
them lies outside their host remnants as a
function of age.
0.0625 of pulsars have an age ranging between
0 and 104 years
Rate of positron emission per pulsar
Le (E) ? B12 P-1.7 E-2.2 s-1 GeV-1
Arzoumanian, astro-ph/0106159
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Observed gamma-ray pulsar characteristics
Pulsar Age (years) Magnetic Field B (1012 G) Period (ms)
Crab 1300 3.8 33
B1509-58 1500 15.4 150
Vela 11000 3.4 89
B1706-44 17000 1.165 102
B195132 110000 1.1 40
Geminga 340000 1.6 237
B1055-52 530000 0.97 197
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3.8 ? 1012 G HR87
Radio pulsar observed magnetic field distribution
Observed gamma-ray pulsar magnetic field (3.92 ?
1.97) ? 1012 G
Figure from Gonthier et al., 2002
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Gamma-ray Pulsars from e measurements 200-300 ms
Radio pulsar observed period distribution
Average observed gamma-ray pulsar period 121 ? 29
ms
Figure from Gonthier et al., 2002
Gamma-ray pulsars from HardingRamaty 33 ms
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PAMELA expected measurements (secondary e
Moskalenko Strongpolar cap Production)
CG, PUNE ICRC 2005

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Different cut-off energies are predicted by polar
cap and outer gap models in the pulsed
gamma-ray spectra (GLAST)!
Figure from http//cossc.gsfc.nasa.gov/images/epo/
gallery/pulsars/
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Fit function Fit result dof c2/dof
Constant Value (k) (6.23.2)10-2 18 0.74
Power-law (A E-g) 0.0796 E-0.112 17 0.76
Stephens calculations --- 19 0.70
Moskalenko Strong calculations --- 19 6.59
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CONCLUSIONS

• An upper limit to the cosmic-ray positron flux in
• excess with respect to the secondary component
  has
• been determined.

• This upper limit shows the same trend of the e
  flux
• generated at the polar cap of middle aged
  pulsars with
• 1/PB35 years when, on average, a pulsar period
  
• of 200-300 ms is considered.

• Future experiments such as PAMELA and GLAST
• will allow us to clarify the role of e and e-
  
• production in the pulsar magnetosphere.