The Fraction The Fraction Alice K. Harding Alice K. Harding NASA NASA Goddard Space Flight Center Goddard Space Flight Center • How many UnID -ray sources are radio-quiet pulsars? • Recent revision of radio and -ray beam geometries • Re-assess fraction of radio-quiet -ray pulsars (Gemingas) Isabelle Grenier Isabelle Grenier CEA-Saclay CEA-Saclay Peter Gonthier Peter Gonthier Hope College Hope College
Geminga. The Fraction. Alice K. Harding NASA Goddard Space Flight Center. Isabelle Grenier CEA-Saclay. Peter Gonthier Hope College. How many UnID g -ray sources are radio-quiet pulsars? Recent revision of radio and g -ray beam geometries - PowerPoint PPT Presentation
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The FractionThe Fraction
Alice K. HardingAlice K. Harding NASA Goddard Space Flight NASA Goddard Space Flight CenterCenter
• How many UnID-ray sources are radio-quiet pulsars?
• Recent revision of radio and -ray beam geometries
• Re-assess fraction of radio-quiet -ray pulsars (Gemingas)
-ray pulsar age distribution-ray pulsar age distribution
EGRET
GLAST
1yr LAT
RL and RQ
-ray pulsar distance distribution-ray pulsar distance distribution
EGRET
GLAST
1yr LAT
RL and RQ
-ray pulsar solid angle distribution-ray pulsar solid angle distribution
EGRET
GLAST
1yr LAT
RL and RQ
Slot gap Geminga fractionSlot gap Geminga fraction
Fraction of Gemingas = RQ/(RL + RQ)
= 0.86 EGRET
= 0.89 1 yr LAT
Outer gap Geminga fractionOuter gap Geminga fraction
Fraction of Gemingas = RQ/(RL + RQ)
= 0.98 EGRET
= 0.96 1 yr LAT
Outer gap population studies Outer gap population studies comparedcompared
Jiang et al. 2006
EGRET
8 RL
24 RQ
Our study
GLAST
78 RL
740 RQ
GLAST
9 RL
362 RQ
EGRET
3 RL
170 RQ
Recent change in outer gap geometryRecent change in outer gap geometry
Takata et al. 2006
Outer gap exists below the null surface
visible emission from both poles
More like extended slot gap!
Improved profile for Crab
ConclusionsConclusions
• Geminga fraction is large for models where -ray emission occurs at high altitude in the pulsar magnetosphere (e.g. extended slot gap and outer gap models)– 86% for slot gap, 98% for outer gap– Slot gap has (slightly) higher correlation with radio beams
• Even larger radio beams for young pulsars do not produce a small fraction of Gemingas– size of radio beam decreases rapidly for P < 50 ms
• Large spread in -ray emission solid angles and L vs Lsd
– Assumption of 1 sr is not accurate • Radio loud pulsars are closer and have larger solid
angles• If many EGRET sources are radio loud pulsars, the
emission must some from pair cascades of the low altitude slot gap (Gonthier talk)