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Fermi LAT Monash University Nov 23-24, 2009 R.DuboisFermi LAT Science Analysis Tutorial1 LS I +61 303 Analysis In the galactic plane, but in the suburbs –Harder than 3C454, but much easier than galactic center Main differences: –Stronger diffuse response –More neighbouring sources –High latitude –Well… periodic as well as variable –Exponential cutoff model – how to decide that

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Fermi LAT Monash University Nov 23-24, 2009 R.DuboisFermi LAT Science Analysis Tutorial2 Spectral Analysis: exponential cutoff Most common form is power law: AE - Pulsars are usually exponential cutoffs: AE - exp(E/E cut ) Use likelihood ratio to distinguish: 2 ln(LL) ~ 2 Where the 2 models differ by one degree of freedom Power law fit Exp cutoff fit

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Fermi LAT Monash University Nov 23-24, 2009 R.DuboisFermi LAT Science Analysis Tutorial3 Source Model for LS I +61 303

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Fermi LAT Monash University Nov 23-24, 2009 R.DuboisFermi LAT Science Analysis Tutorial4 Timing Analysis: LC and folded LC Aperture photometry –AKA counting photons in a cone –Quick and easy –No modeling! –Folded LC is average of flux in phase bins Likelihood fits in time bins –Needs statistics –Time consuming to do

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Fermi LAT Monash University Nov 23-24, 2009 R.DuboisFermi LAT Science Analysis Tutorial5 LS I +61 303 Systematics Alternate fitting method “Bracketing” Aeff IRF Different diffuse model Vary lower energy cut

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