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%pylab inline
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rcParams['font.size'] = 20.
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from VOT import *
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from VOTPlot import Plot, PlotSpectrum
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baseline = VOT("custom", eMin=0.001, eMax=100000, Nbins=10000, redshift=4.35, eblModel='Dominguez', instrument='VERITAS', zenith=20,
spectralModel='Band', N0=1e-9,alpha=-0.65, beta=-2.22, Ep = (2 - 0.65)*(265./100000.))
You can see that if this GRB went off in the FoV of VERITAS at a good zenith angle it could be detected in ~12.5 hours. This is fine for a non-transient source but not that great for a GRB. What's really killing us here is the EBL. This GRB was at a redshift of 4.35. What if it was at a redshift of 1.0?
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baseline_z1 = VOT("custom", eMin=0.001, eMax=100000, Nbins=10000, redshift=1.0, eblModel='Dominguez', instrument='VERITAS', zenith=20,
spectralModel='Band', N0=1e-9,alpha=-0.65, beta=-2.22, Ep = (2 - 0.65)*(265./100000.))
This is much more promising. So if you had a burst like 080916C go off at a redshift of 1 and it was in a good location for a IACT then you would nail the detection in about 10 minutes.
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fig2 = pyplot.figure(figsize=(16,8))
fig2ax1 = fig2.add_subplot(111)
fig2ax1.set_ylabel(r'Differential Flux [cm$^{-2}$ s$^{-1}$ GeV$^{-1}$]')
fig2ax1.set_xlabel('Energy [GeV]')
fig2ax1.loglog(baseline.VS.EBins, baseline.VS.dNdE)
fig2ax1.loglog(baseline.VS.EBins, baseline.VS.dNdE_absorbed)
fig2ax1.loglog(baseline_z1.VS.EBins, baseline_z1.VS.dNdE_absorbed)
fig2ax1.set_ylim((1e-16,1e-6))
fig2ax1.set_xlim([1,1000])
fig2ax2 = fig2ax1.twinx()
fig2ax2.loglog((10**baseline.VR.EACurve[0:,0])[::2],(baseline.VR.EACurve[0:,1])[::2],'ko')
fig2ax2.set_ylabel(r'Effective Area [cm$^2$]')
fig2ax2.axvline(10**baseline.VR.EASummary['minSafeE'],color='k')
fig2ax2.axvline(10**baseline.VR.EASummary['maxSafeE'],color='k')
show()
This plot shows the effect of the EBL. The blue line is the raw band model, the red is the spectrum after accounting for a redshift of 4.35 and the green is for a redshift of 1.0. The black curve is the VERITAS EA at a zenith angle of 20 degrees. The vertical black lines are the low and high energy ranges for the VERITAS analysis.
Another issue is that most GRBs for occur at high zenith angles due to solid angle arguments and high zenith means high energy threashold for the Cherenkov technique. What if this GRB occurred at a zenith angle of 45 degrees.
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baseline_zenith50 = VOT("custom", eMin=0.001, eMax=100000, Nbins=10000, redshift=4.35, eblModel='Dominguez', instrument='VERITAS', zenith=50,
spectralModel='Band', N0=1e-9,alpha=-0.65, beta=-2.22, Ep = (2 - 0.65)*(265./100000.))
This thing is not detectable if it happened at a zenith angle of 50. In fact, it'll only be detectable at a zenith angle of 30 and if it was nearby.
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baseline_zenith30_z1 = VOT("custom", eMin=0.001, eMax=100000, Nbins=10000, redshift=1.0, eblModel='Dominguez', instrument='VERITAS', zenith=30,
spectralModel='Band', N0=1e-9,alpha=-0.65, beta=-2.22, Ep = (2 - 0.65)*(265./100000.))
This plot shows why...
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fig2 = pyplot.figure(figsize=(16,8))
fig2ax1 = fig2.add_subplot(111)
fig2ax1.set_ylabel(r'Differential Flux [cm$^{-2}$ s$^{-1}$ GeV$^{-1}$]')
fig2ax1.set_xlabel('Energy [GeV]')
fig2ax1.loglog(baseline.VS.EBins, baseline.VS.dNdE,'k')
fig2ax1.loglog(baseline.VS.EBins, baseline.VS.dNdE_absorbed,'k')
fig2ax1.loglog(baseline_z1.VS.EBins, baseline_z1.VS.dNdE_absorbed,'k')
fig2ax1.set_ylim((1e-16,1e-6))
fig2ax1.set_xlim([1,1000])
fig2ax2 = fig2ax1.twinx()
fig2ax2.set_ylabel(r'Effective Area [cm$^2$]')
fig2ax2.loglog((10**baseline.VR.EACurve[0:,0])[::2],(baseline.VR.EACurve[0:,1])[::2],'bo')
fig2ax2.axvline(10**baseline.VR.EASummary['minSafeE'],color='b')
fig2ax2.axvline(10**baseline.VR.EASummary['maxSafeE'],color='b')
fig2ax2.loglog((10**baseline_zenith30_z1.VR.EACurve[0:,0])[::2],(baseline_zenith30_z1.VR.EACurve[0:,1])[::2],'ro')
fig2ax2.axvline(10**baseline_zenith30_z1.VR.EASummary['minSafeE'],color='r')
fig2ax2.axvline(10**baseline_zenith30_z1.VR.EASummary['maxSafeE'],color='r')
show()
The black curves are what were shown before (band model, absorbed at z = 4.35, and absorbed at z = 1.0). The blue curve and vertical lines are the EA at a zenith angle of 20 while the red is the same at a zenith angle of 30. The high energy EA (above ~300 GeV) is the same but the low energy threshold changes by about 50 GeV which is huge at these redshifts.
Things we will do:
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baseline_hawc = VOT("custom", eMin=0.001, eMax=100000, Nbins=10000, redshift=4.35, eblModel='Dominguez', instrument='HAWC', zenith=20,
spectralModel='Band', N0=1e-9,alpha=-0.65, beta=-2.22, Ep = (2 - 0.65)*(265./100000.))
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