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

2. 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
Pisa - 21/05/02

3. 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.
Pisa - 21/05/02

4. 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
Pisa - 21/05/02

5. 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 !!
Pisa - 21/05/02

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

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

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

9. 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…
Pisa - 21/05/02

10. 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
Pisa - 21/05/02

11. 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”
Pisa - 21/05/02

12. 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
Pisa - 21/05/02

13. 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!!
Pisa - 21/05/02

14. 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
Pisa - 21/05/02

15. 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 ( 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
Pisa - 21/05/02