Transient Sources Simulation and “GRBSpectrum” Nicola Omodei INFN Pisa & University of Siena 1 Pisa - 21/05/02

On Going activities Status of the GRB package Visualization of the Results & Validation of the model “Expected” flux Sampled flux Reconstructed flux (not yet available) Extension of the Model Simulations and the GRB & Solar Flares Working Group 2 Pisa - 21/05/02

Status of GRB pakage GRB is an independent package, available from the repository Needs FluxSvc & ROOT It has 2 Test programs Visualize the expected flux Samples photons (this test can be used with every “Spectrum” objects) and save the result in a root tree. Viewed using a rootmacro. 3 Pisa - 21/05/02

Save the Results in a TTree Scheme of the classes GRBTest Save the Results in a TTree Spectrum GRBTest1 Energy(time) Rate(Time) Flux(Time) Interval(Time) Direction(time) GRBSpectrum GRBSim GRBSim GRBShell GRBShell GRBShock GRBShock Compute Flux(e,t) Compute Flux Plot the Result 4 Pisa - 21/05/02

Output GRBTest Calculates some quantities to test the physics of the model: Light Curve, Spectrum… GRBTest1 can also “sample” the photon extracted from the spectrum. They are the same photons that reach the detector in the Montecarlo simulation !! 5 Pisa - 21/05/02

Light Curves Short Bursts & Long Bursts 6 Pisa - 21/05/02

Spectrum Different Emission processes are included. The Shape of the spectrum will be a key study to understand the nature of this phenomenon. 7 Pisa - 21/05/02

Waves, Mountains ? No GRBs !! 8 Pisa - 21/05/02

How to sample photons from a time dependent spectrum “Draw photon from spectrum” Common problem for every kind of spectrum (static and transient) Given a spectrum -> randomly extracts a photon using the spectrum as probability function… “Interval” to wait before the next iteration Is a problem only for transient sources The default definition Interval = 1/Rate can not work for transient sources… 9 Pisa - 21/05/02

The problem of the “Interval” In the general definition of the Spectrum object (see ISpectrum.h) the interval to wait before the next event is 1/Rate. For transient sources the Rate depends on the time… Rate Time The solution we adopt is compute the integral of 1/Rate 10 Pisa - 21/05/02

The Photons that reach GLAST… With a rootmacro the information about the extracted photons are plotted Spectrum of sampled Photons !! Light curves in different energy bands “Sky map” 11 Pisa - 21/05/02

Combined Sources Galactic Electromagnetic Galactic Electromagnetic GRBTest use the General definition of the Spectrum object: It can test all the sources available from FluxSvc Galactic Electromagnetic Emission of HE Protons + GRB Time = 5 sec Galactic Electromagnetic emissionof HE Protons Time = 100 s 12 Pisa - 21/05/02

Extension of the model Some Astrophysical transient objects have common characteristics “Geometry”: Jets,relativistic blastwaves, blobs, accretion discs “Accelerators”: Shocks, Magnetic Acceleration… “Emission processes”: Synchrotron, Inverse Compton, External Compton, Bremsstrahlung… Special relativistic transformations. Common framework to extend the description to other celestial objects!! 13 Pisa - 21/05/02

HE transients classes User Requirements Structure and Usage This category should be interfaced with the Ground Software (I.e. FluxSvc) but should be internally coherent and consistent to be used as standalone package. There should be a common analysis package relevant to HE transient study There should be a GUI for the usage of these series of classes by a generic user The light Simulator should provide a simulation of astrophysical objects using a phenomenological description (like the simulator proposed by J.Norris) The physical simulator should include the full physics involved in the model 14 Pisa - 21/05/02

Conclusions and “to do” list The “GRB & SF Science Team” (= GLAST GRB and Solar flare working group) is formed ! Actually 2 models for GRB are available, and both will be taken into account for the simulations Phenomenological (J.Norris) Theoretical (Our!) Both depend on some hypothesis : Validation and comparison with the BATSE data (50-300 KeV) Include different emission models (External shock scenario, external Compton) and study their signatures in the detection of GRB signals. Study the detector in the observation of transients Comparison between the input spectrum(t) from a simulated GRB and the reconstructed particles Study the trigger capability (especially for the low energy part) and study the trigger algorithm 15 Pisa - 21/05/02