marcus ziegleraps april meeting 2006 1 gamma-ray pulsars in the glast era gamma-ray large area space...
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Marcus Ziegler APS April Meeting 2006 1
Gamma-Ray Pulsars in the Gamma-Ray Pulsars in the GLAST Era GLAST Era
Gamma-ray Large Gamma-ray Large Area Space Area Space TelescopeTelescope
Marcus Ziegler
Santa Cruz Institute for Particle PhysicsUniversity of California at Santa Cruz
GLAST LAT Collaboration
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GLAST basic principleGLAST basic principle
Space based pair conversion telescope
Energy range of the LAT 20 MeV – 300 GeV
Preferred interaction from Gamma-Rays
of this energy range is pair-production
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GLAST statusGLAST statusAll detector components of the LAT (Large area Telescope) are assembled
Tracker, Calorimeter, and Anti coincidence detector
Picture of the 16 Tracker tower modules of GLAST
Launch with Delta 2 rocket is scheduled for Fall 2007
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GLAST Science performanceGLAST Science performanceEffective Area 9 000 cm2 at 10 GeV PSF 68% 100 MeV < 3.5ºSource sensitivity 3x10-9cm-2s-1 PSF 68% 10 GeV < 0.15º
Field of View 2.4 sr
EGRET sky map Simulated LAT (>100 MeV, 1 yr)Simulated LAT (>1 GeV, 1 yr)
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Different pulsar modelsDifferent pulsar models
Polar Cap ModelsDaugherty & Harding 1982, 1996;
Usov &Melrose 1995
High energy spectrum is cut off by magnetic
pair production for young pulsars with large B
Outer Gap ModelsCheng, Ho & Ruderman 1986, Romani 1996
Hirotani & Shibata 1999
More gradual high-energy turnover at about 10 GeV
Inverse Compton component up to TeV
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Predictions for different ModelsPredictions for different Models
Polar Cap Outer Gap
Radio Quiet Radio Loud Radio Quiet Radio Loud
EGRET 8 25 22 10
GLAST 370 363 1100 80
A.K. Harding, Gamma-Ray Pulsars: Models and Population Studies
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Pulsar Blind SearchesPulsar Blind Searches
The third EGRET catalog contains 271 sources.
Over 60 sources in the galactic plane remain unidentified.
Efforts with super computers to perform periodicity searches
did not find new Gamma-Ray pulsarsA Search for Radio-Quiet Gamma-Ray Pulsars, A. M. Chandler et. al. APJ, 2001
At UC Santa Cruz we developed a method to reduce the computational power
needed to find pulsars.
Problems with blind pulsar searches- Long time spans between the detection of photons (~ 1 ph/h for strong sources)- because of the pulsar spin down a huge phase space has to be searched
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Truncated Discrete Auto CorrelationTruncated Discrete Auto Correlation
Frequency in H z
Pow
er (
AU
)
100 20 30 40 50
Frequency in Hz
Pow
er (
AU
)
100 20 30 40 50
Standard method for periodicity searches
FFT on EGRET data (one viewing period) for Vela
Computing time 260s
Truncated discrete auto correlation function
Computing time 2s
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Correcting for the spin downCorrecting for the spin down
Still, to find a Crab like pulsar with a fast
spin down of Search for the Crab Pulsar -
3.86 E-10 s-2 a scan in F1 is required.
The truncated discrete auto correlation function is not as sensitive to the frequency
derivative of a pulsar as a discrete Fourier transform is.
Frequency (F0) and Frequency-Derivative
(F1) scan in the EGRET data to find the
Crab pulsar.
The scan took 15min on a standard PC.
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Simulated GLAST DataSimulated GLAST Data
To test the developed science tools a
data set with 55 days of simulated
GLAST data was created (Data
Challenge 2).
Simulated GLAST SKY map with 380 sources
About 100 of the simulated sources
can be expected to be pulsars.
A rough scan of all sources found 12 Radio-Loud Gamma-Ray pulsars
Plans for the near future:
-> Take an other look at the old EGRET data
-> Prepare for the upcoming real GLAST Data