1 / 19

Simulations of Thermal GRBs as observed by GLAST GBM+LAT

Simulations of Thermal GRBs as observed by GLAST GBM+LAT. Milan Battelino Stockholm Observatory DC2 Closeout Meeting 31 May - 2 June 2006. Outline. Background The Hybrid Model Simulation flow Results. a. b. GRB Standard Model. Band, D. et al.:1993 ApJ 413 , 281.

vine
Download Presentation

Simulations of Thermal GRBs as observed by GLAST GBM+LAT

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Simulations of Thermal GRBs as observed by GLAST GBM+LAT Milan Battelino Stockholm Observatory DC2 Closeout Meeting 31 May - 2 June 2006

  2. Outline • Background • The Hybrid Model • Simulation flow • Results

  3. a b GRB Standard Model Band, D. et al.:1993 ApJ413, 281 Excellent fit for majority of GRB spectra in BATSE energy window a, b, Ec , Aband

  4. Fermi-shock-accelerated e– distribution: p ~ 2.2 Ne g-p Observed region BATSE logg Low energies Self absorption High energies Cut off Characteristic synchrotron frequency Cooling frequency Optically Thin Synchrotron Spectrum FC: s = -1.5 s = -2/3 s = -2.1 SC: s = -1.6

  5. Time-resolved spectra from 57 bright BATSE bursts A substantial fraction of the time-resolved spectra from bright BATSE bursts show hard sub-peak spectra! -2/3 Line of Death Crider et al: 1997, ApJ479, L39+ Preece et al: 1998, ApJ506, L23 Hard to explain with optically thin synchrotron model! This has to be considered when implementing a model. Also high energy components in the MeV – GeV band...

  6. Other Models...Review paper by GRB Group, 2006 • Synchrotron and Inverse Compton • Electron IC Scattering • Synchrotron Self-Compton • Proton Synchrotron Emission • Thermal Components + Synchrotron • Pion production and cascades • Hadronic Cascades • Neutron-proton decoupling

  7. Bose-Einstein function + Powerlaw(s) GRB 911016 Hybrid Model Ryde, F: 2004, ApJ614, 827 m = 0 : Planck spectrum : a = 1 m >> 0 : Wien spectrum : a = 2 Blackbody + Powerlaw kT, AkT, s, Apow

  8. -2/3 -1.6 ...also: a peak at s = -1.6, close to s = -1.5 LOD not a problem in Hybrid Model LOD not a problem with

  9. How to simulate Hybrid Model? • Model independent simulator software (C++) producing photon histogram files • Extend gtobssim software (C++): • New celestialSource class: GRBtemplateManager (by Nicola Omodei) that reads photon histogram files • Extend GBM Tools package (IDL): • Read photon histogram files

  10. N(E,t) Model PlotDevice 1 C(E,t) 1..n Component 1 1 P(t) ComponentList Parameter 1..n Blackbody Powerlaw 1 Hybrid ParameterList Lightcurve Breakpoint Simple Burst Modeler

  11. Hybrid Model Parameters Blackbody Component • Lightcurve (Flux) • Temperature (kT) • Normalization Powerlaw Component • Lightcurve (Flux) • Spectral index/indices • Breakpoints • Normalization

  12. BATSE window High energy cut-off Competition between the acceleration (heating) of the electrons and the radiative cooling leads to a maximal energy that the electrons can be accelerated to. Blackbody component Broken power-law : synchrotron emission spectrum Hybrid Model Simulation GRB 911016 ~ 3 GeV based on results by de Jager et al, 1996, ApJ457, 253

  13. File Header GRBtemplateManagerNicola Omodei • Photon Histogram: • Number of energy bins (columns): • Min Energy: • Max Energy: • Number of time bins (rows): • Timebinwidth: • Energy binning:

  14. GBM Tools extensions • GRBtemplate photon histogram file • populate energy bins from LAT photon histogram file with internal energy binning defined by energy grid • Energy grid photon histogram file • GBM Simulator reads definition file, determines energy grids for NaI and BGO detectors and saves energy grids as files • SBM reads energy grid files and produces histogram files • GBM Simulator reads SBM histogram files to produce, apportion photons and create TTE files.

  15. BATSE Trigger Data GLAST Definition file XSPEC GBM Simulator 1 5 Model Parameter Values + guesses NaI/BGO Energy Grid SBM 2 6 LAT lightcurve histogram file Separate NaI and BGO lightcurve histogram files gtobssim gtselect gtrspgen 3 GBM Simulator 7 LAT FITS and response files NaI/BGO TTE, background and response files gtbin 4 8 XSPEC 9 Simulation Flow

  16. q = 27.1o, f = 95.3o NaI #2 + NaI #9 + BGO #1 + LAT XSPEC Model Resolution : 1 x 5.0 s Blackbody + (Broken Powerlaw x High Energy Cutoff) s1 = -1.30 +/- 0.04 Resolution : 5 x 1.0 s c2n= 0.9 s1 = -1.33 +/- 0.02 s2 = -1.71 +/- 0.02 s2 = -1.81 +/- 0.08 Joint Spectral AnalysisGRB 911016 XSPEC Result SBM input s1 = -1.3 s2 = -1.7

  17. XSPEC Result SBM Input = 0.78 S1 = -1.6 S1 = -1.7 +/- 0.03 S2 = -2.1 S2 = -2.1 +/- 0.2 GRB 941026 Time integrated: 0.0 - 5.0 s q = 27.1o, f = 95.3o NaI #2 + NaI #9 + BGO #1 + LAT

  18. Conclusion • Hard to determine high energy cutoff in time-resolved spectra above 3 GeV • Blackbody component easily detected if it is the cause of spectral hardness • Position of powerlaw breakpoint hard to determine when strong blackbody component

  19. The End Thanks to: Nicola Omodei, Valerie Connaughton and Felix Ryde

More Related