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The Fraction Alice K. Harding NASA Goddard Space Flight Center Alice K. Harding NASA Goddard Space Flight Center How many UnID  -ray sources are radio-quiet.

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Presentation on theme: "The Fraction Alice K. Harding NASA Goddard Space Flight Center Alice K. Harding NASA Goddard Space Flight Center How many UnID  -ray sources are radio-quiet."— Presentation transcript:

1 The Fraction Alice K. Harding NASA Goddard Space Flight Center Alice K. Harding NASA 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 CEA-Saclay Peter Gonthier Hope College

2 Traditional radio beam geometry  core B  Model of Arzoumanian, Chernoff & Cordes (2002) – 400 MHz Frequency dependent cone width of Mitra & Deshpande (1999)

3 Radio polarization of young pulsars One of two pulse components Flat polarization swings (RVM) High linear polarization (> 70%) Emission height 1-10% R LC (Kijak & Gil 2003) Wide cone beams Johnston & Weisberg 2006, Crawford et al. 2003)  = -3 0  =  = 3 0  = 9 0

4 Studies of 3-peak pulsars Gonthier et al. 2006

5 Revised radio beam geometry P = 50 ms

6 Traditional radio beam geometry Model of Arzoumanian, Chernoff & Cordes, 2002 P = 50 ms 

7 New radio beam - phase plots P = 50 ms, 400 MHz  =10 0  =40 0  =30 0  =20 0  =90 0  =80 0  =70 0  =60 0  =50 0 Phase  Observer angle 

8 Pulsar simulations Evolve neutron stars using population synthesis (Gonthier talk) Assign radio flux using revised emission cone/cone model RADIO LOUD if > S min for any of 9 radio surveys Assign  -ray flux using slot gap or outer gap models  -RAY LOUD if > F min for EGRET, AGILE, GLAST SLOT GAPOUTER GAP Low-altitude pair cascade emission not included

9 Phase plots RADIO (50 ms, 400 MHz)  -RAY SLOT GAP  -RAY OUTER GAP 

10 Slot gap model Pair-free zone near last open field-line (Arons 1983, Muslimov & Harding 2003, 2004) Slower acceleration Pair formation front at higher altitude Slot gap forms between conducting walls E || acceleration is not screened

11 Which pulsars have slot gaps? Only the younger pulsars above the death line for production of curvature radiation pairs will have SLOT GAPS Harding, Muslimov & Zhang 2002 Older pulsars below the death line for production of curvature radiation pairs will have unscreened E || and NO SLOT GAPS

12 High-altitude slot gap model Normalize phase plots Average flux derived from profile, given  and  Two-pole caustic geometry (Dyks & Rudak 2003, Dyks et al. 2004) Muslimov & Harding 2003, 2004

13 High energy “luminosity” from slot gaps For  =0 0

14 Outer gap model Dependence of OG  -ray luminosity on inclination angle  f is fractional gap size (  ) is average emission radius in gap f determined by location of pair formation front wrt last open field line PFF determined by pair production condition E X is the self consistent PC temperature from heating by OG particles Zhang et al. 2004

15 Outer gap model Normalize phase plots f is fractional gap size Average flux derived from profile, given  and  Zhang et al. 2004, Jiang et al. 2006

16 Outer gap luminosity Zhang et al This simulation

17  -ray pulsar flux distribution EGRET GLAST 1yr LAT RL and RQ 32 pulsed RQ 157 pulsed RQ

18  -ray pulsar spin-down luminosity EGRET GLAST 1yr LAT RL and RQ

19  -ray pulsar age distribution EGRET GLAST 1yr LAT RL and RQ

20  -ray pulsar distance distribution EGRET GLAST 1yr LAT RL and RQ

21  -ray pulsar solid angle distribution EGRET GLAST 1yr LAT RL and RQ

22 Slot gap Geminga fraction Fraction of Gemingas = RQ/(RL + RQ) = 0.86 EGRET = yr LAT

23 Outer gap Geminga fraction Fraction of Gemingas = RQ/(RL + RQ) = 0.98 EGRET = yr LAT

24 Outer gap population studies compared Jiang et al EGRET 8 RL 24 RQ Our study GLAST 78 RL 740 RQ GLAST 9 RL 362 RQ EGRET 3 RL 170 RQ

25 Recent change in outer gap geometry Takata et al Outer gap exists below the null surface visible emission from both poles More like extended slot gap! Improved profile for Crab

26 Conclusions 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 L sd –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)


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