1. Pulsar modeling and simulations Gamma-ray Large Area Space Telescope Massimiliano Razzano Nicola Omodei LAT Collaboration Meeting (SLAC, August 29 th - September 1 th 2005)

2. Outline The PulsarSpectrum simulator; The phenomenological model; The EGRET pulsars: some first analysis of simulated data; Simulation and generation of pulsar catalogs; Some first results on catalogs; Conclusions and future developments;

3. PulsarSpectrum simulator Crab and Geminga seen by EGRET Simulation of Crab and Geminga Key features:  The simulator engine is designed to make easy the creation of pulsar sources;  Spectra and lightcurves are simulated according to observed pulsars through a phenomenological model;  Simulation of timing effects due to period changes and motion of GLAST and Earth in the Solar System;  Interface with a new tool for creating catalog of pulsars  Compatibily with LAT software (Gleam, observationSim);

4. An overview of PulsarSpectrum Pulsar model Simulator Engine Model parameters (phenomenological, physical) ( XML File ) Pulsar Data (Flux,Period,…) (Ascii datafile) StandaloneLAT software (ObsSim,Gleam) 2Dim ROOT hist

5. The simulation of the lightcurves Lightcurves can be random generated or read from a profile Random curves (Lorentz peaks); Existing TimeProfiles are useful for simulating known pulsars; Random peaks Vela Time Profile Crab Time Profile The current default model is a phenomenological one

6. The simulation of spectra We choose this analytical spectral shape: (Nel and De Jager,1995): Description of the high energy cutoff; Parameters are obtained from fits on the known  ray pulsars (e.g. ref. N,DJ95, and DJ 2003); Flux normalisation based on 3 rd EGRET catalog (ph/cm 2 /s, E>100MeV); Example for Vela-like PSR F(E>100) ~9*10 -6 ph/cm2/s, E n =1GeV,E 0 =8GeV; g=1.62 B=1.7 Data fit b=1 Different scenarios b=2

7. We combine lightcurve and spectrum:  TH2D ROOT histogram Now multiplication, but more complex combination laws are not too difficult to simulate; (goal for phase-resolved analysis) The phenomenological model (III) the final product According to the flux the photons are extracted and then the photon arrival times are de-corrected LightcurveSpectrum

8. Barycentric decorretions The analysis procedure on pulsars starts by perfoming the barycentering, i.e. transform the photon arrival times at the spacecraft to the Solar System Barycenter, located near the surface of the Sun In order to be more realistic for the simulations we then must de-correct Several effects that contribute to the barycentering, mainly: Geometrical delays (due to light propagation); Relativistic effects (i.e “Shapiro delay” due to gravitational wall of Sun)

9. Period change with time Phase assignment in analysis: # of rotations: Integrating and taking the fractional part: We know that pulsar period changes with time because of loss of rotational energy: We must take this effect into account The interval between 2 photons is expanded according to the period variation.  We switch between the “reference systems” S (P dot is = 0, period constant) S ~ (P dot is not 0, period not constant, the real world)

10. Pulsar database PulsarDataListXML file For each pulsar simulated in DC2 there must be an entry in the pulsar database (D4) PulsarSpectrum creates an output file that can be converted through gtpulsardb to a FITS file compatible with the D4 database PulsarSpectrum ASCII ephem file gtpulsardb Ephemerides fits file

11. Advertisement Create your own pulsar with only 2 easy steps! 1 - Edit the PulsarDataList.txt file (located in /Pulsar/vXrYpZ/data), where are stored the general parameters of the pulsars know by the simulator Flux E>100MeV Ephem. validity rangeT(>t0) where phi(t) = 0.0 Period (or frequency) and derivatives For more informations, please see at: www.pi.infn.it/~razzanoPulsar/PulsarSpTutor/PulsarSpTutor.htm 2 – Create an XML source entry in a xml file, where are stored the position, energy range and model- dependent parameters of the pulsar Name as in Datalist Emax,Emin RA,dec Model (=1) & random seed Model parameters

12. An example of simulation: the EGRET pulsars This is a one-week simulation of: EGRET pulsars; galactic diffuse emission; extragalactic background; Geminga Crab VelaB1706-44 B1055-52 B1951+32 On the road to DC2 we have updated EGRET pulsars with more detailed data

13. First results on simulated Vela Plotting the PULSE_PHASE entries in the Vela_1week_bari.fits (after barycentering and phase assignment) The real Vela observed by Egret (Kanbach et al.,1994)

14. Analysis of simulated data:Crab Cut of 2° around Crab position After applying barycentric corrections and phase assigment EGRET lightcurve (from J.M.Fierro thesis,1995) For all these pulsars we perform periodicity tests

15. Analysis of simulated data:Geminga After applying barycentric corrections and phase assigment EGRET lightcurve (from J.M.Fierro thesis,1995) Cut of 2° around Geminga position

16. Simulating pulsar catalogs PulsarSpectrum can also simulate different pulsars placed in the sky. For each pulsar a log file is produced in order to keep track of the simulated pulsars This tool is now at a good point of development and it’s working with basic features 1-day catalog simulation of a catalog We designed a tool that manage catalog of pulsars and can be interfaced with PulsarSpectrum. This will be useful for several purposes: Create catalogs for checkouts and for the next Data Challenge; Provide synthetic catalogs from existing ones; Make studies on LAT pulsar capabilities;

17. An example of Pulsar Catalog We started to take pulsar data from the database of the Australian Telescope National Facility. http://www.atnf.csiro.au/research/pulsar/

18. Synthetized pulsars Starting from an observed population we extract the characteristic of the population we want to simulate. Galactic positions (The distribution of distance in the galaxy are also considered)

19. Period-Pdot diagram Also the period vs. period derivative is derived (Here we didn’t show the millisecond pulsars) This first approach has a limitation: our empirical catalog didn’t mimic the distribution of radio quiet pulsars. ATNF pulsars Synthetized pulsars

20. Spectral modeling Spectrum and flux depends on the theoretical model you choose to adopt We start from Polar Cap model, as in Harding & Zhang (2000), and Gonthier et al. (2002) We obtain the luminosity L gamma, the spectral index and an estimate of the cutoff energy for the power law. Then we slightly modify the spectra in order to have an exponential cutoff of ≈2. LAT sensitivity EGRET sensitivity This is very,very,…,very preliminar estimate!

21. Rumors from 3° Checkout… Some pulsars in the 3° Checkout will be near EGRET sources… …and much more surprises have to come!

22. Conclusions Where we are…  The PulsarSpectrum simulator is stable and working;  The phenomenological model included can reproduce observed pulsars and used with theoretical models;  Most of the timing effects are simulated (i.e. barycentering);  An updated set of data for simulating EGRET pulsars is now available;  PulsarSpectrum is being used during Science Tools Checkouts for testing the Pulsar Analysis Tools;  A tool for managing and simulating pulsar catalogs is under development, we will include more theoretical models;  All this tools are suitable for modeling pulsars for DC2 and to study pulsar science with LAT; …and where we go!  Include more realistic timing effects (timing noise, glitches,etc.);  Develop the simulation of binary pulsar systems;  Add more theoretical model to the simulations (i.e. outer gap);  Develop and optimize the simulated catalogs managers;  Provide a set of pulsars for DC2 and the relative ephemerides database;