Status of pulsar simulation for DC 2 Gamma-ray Large Area Space Gamma-ray Large Area Space

TelescopeTelescope

Massimiliano RazzanoNicola Omodei

GLAST DC II Software Workshop

(Goddard Space Flight Center, June 27th-29th 2005)

ray pulsar simulation for

GLASTPulsarSpectrum is a simulator

developed in Pisa used for simulating gamma ray emission

from pulsars

Key features:

It can reproduce spectra and lightcurves of known ray pulsars;Flexible architecture to facilitate creation of pulsar sources;Advanced simulation of timing effects due to period changes and motion of GLAST and Earth in Solar System;Full phenomenological model now implemented;Pulsar parameters easy to implement;Capability of simulation of pulsar catalogs;Fully compatible with GLAST-LAT standard software environment (Gleam, observationsSim);

An overview of PulsarSpectrum

Pulsar model

Simulator Engine

Model parameters(phenomenological, physical)

( XML File )

Pulsar Data(Flux,Period,…)

(Ascii file)Standalone

LAT software framework

(ObsSim,Gleam)

2Dim ROOT histo

The phenomenological model (I)lightcurve

Different alternatives for lightcurves:

Random curves (2 Lorentz peaks);From existing TimeProfiles (useful for simulating known pulsars);For diagnostic purposes is possible to generate a -Dirac shaped profile;

An output TimeProfileData file is created !

The phenomenological model (II)spectrum

Example for Vela-like PSRF(E>100) ~9*10-6 ph/cm2/s,•En=1GeV,E0=8GeV;•g=1.62,b=1.7;

We choose this analytical spectral shape:(Nel and De Jager,1995):

Description of the high energy cutoff; Parameters are obtained from fit on the known ray pulsars (ref. N,DJ95, and DJ 2003);Flux normalisation based on 3rdEGRET catalog (ph/cm2/s, E>100MeV);By changing values of the parameters we can simulate different pulsars;

We combine lightcurve and spectrum:

TH2D ROOT histogram

•Now multiplication, but more complicated combination laws are not so difficult to achieve;

The phenomenological model (III)the final product

According to the flux the photons are then

extracted and the time arrivals of photons are

de-corrected

Lightcurve Spectrum

The extraction of the photons:the SpectObj package

SpectObj transforms N (ph/keV/s/m2) into ph

N N*Adet*t*E

Compute also the cumulative function of Nv values in the choosen spectral range

P(tk) = N(tk,Ek) Next photon is at tN when P(tN ) = 1

T1 T2 T3

Period derivativesPhase assignment in analysis:•# of rotations:

•Integrating and taking the fractional part:

ttttftttftfttf d...))((21))(()(d)(dN 2

00000

...)(61)(

21)()φ()φ( 3

022

01000 ttfttfttftt

)( 00 tff )( 01 tff )( 02 tff )(

1)(tP

tf

The Nv is computed is a system where period is constantWe should switch between the “reference systems”

S (Pdot is = 0, period constant)

S~ (Pdot is not 0, period not constant, e.g. the real world)

Barycentric decorretionsThe first step in data analysis is to transform the photon arrival time at the spacecraft (expressed in MET) to the Solar System Barycenter (expressed in TDB):

The simulator must de-correct for these effects: At present 3 main effects are taken into account:

Conversion TTTDB;Geometric corrections due to lighttravel time from GLAST to Solar System BarycenterRelativistic delay due to gravitaional field of Sun (Shapiro delay)

Simulating pulsar catalogs

PulsarSpectrum is also been tested for simulation of many pulsar in the sky. This features allow the possibility to simulate entire pulsar catalog.

For each pulsar a log file is produced in order to keep track of the simulated pulsars

Up to now:•simulated catalog of EGRET pulsars

•Tests with catalog provided by A.Harding with more than 1k pulsars

A tools for managing catalogs (population plots, creation of xml files, etc.) is under development

1-day catalog simulation

Pulsar databaseFor each pulsar simulated in DC2 there must be a correspondant entry in the pulsar database (D4)

PulsarSpectrum next implemented features (under tests) are devoted to interfacing with database:

•Multiple entries (that allows the possibility to insert different ephemerides for different periods as in observations)•Output txt file that can be converted with gtpulsardb in a FITS file compatible with SAE standard.

PulsarDataList XML file

PulsarSpectrum

ASCII ephem filegtpulsardb

Ephemerides

fits file

PulsarSpectrum and Science Tools

Thanks to the simulation of timing effects, like

barycentric decorrections) PulsarSpectrum is useful

for testing Pulsar Analysis Tools in the SAE

(glbary, pulsePhase, gtpulsarDb, stpsearch)

Simulations and

ScienceTools report in Science Tools 1st

Checkout (Oct,12-Oct 29 2004) and 2nd Checkout

(Mar,21-Apr,8)

1-day simulation of EGRET pulsar + diffuse emission

Testing the SAE Pulsar Analysis Tools

Some screenshots from Checkout 2

1-week of Crab

1-week of 1706-44 (artificial lightcurve )

1-week of Vela

Summary for DC2What to simulate Priority Remark PulsarSpectrum

simulations

Light travel time between the spacecraft and the solar system barycenter

Must have in DC2 Those effects must be taken into account in pulsar simulations to match the barycentric correction tool to be used in DC2. See also note on barycentric "de-correction" in pulsar simulation below.

Implemented and tested

Difference between TDT and TDB Must have in DC2 Implemented and tested

Shapiro delay in the solar system Must have in DC2 Implemented and tested

Pulsars for periodicity tests with known ephemerides Must have in DC2 To simulate studies of known radio

pulsars Ok, also with catalogs

Pulsars for blind periodicity searches

Good to have in DC2

To simulate blind searches for Geminga-like pulsars using A4

Ok, also with catalogs

Variety of pulse profiles Good to have in DC2

Duplicate the light curves of the EGRET pulsars?

Implemented random and user-defined (e.g. EGRET pulsars)

Realistic energy spectra Good to have in DC2 Such as spectral cutoffs, etc. Parameterized power

law with cutoff

Pulse phase dependent energy spectra

Nice to have sometime

Power-law index and/or cut-off energy changes with pulse phase?

To be implemented

Binary pulsars Nice to have sometime

Related effects include: light travel time in a binary system, gravitational time dilation in a binary system, and Shapiro delay in a binary system.

To be implemented

Glitches and timing noise Nice to have sometime

Similar to the Vela and the Crab pulsars?

Multiple ephemerides implemented and under tests.

From http://glast.gsfc.nasa.gov/ssc/dev/psr_tools/testplanDC2.html

Summary on Pisa activities on pulsarsStatus of work

Full simulation code implemented and tested;Phenomenological model included;Simulation of period change with time;Effects of GLAST and Earth motion and of gravitational field of Sun on timing (barycentric de-corrections)Simulation of EGRET pulsars;Use of PulsarSpectrum for testing the LAT Analysis Tools for pulsars;Participation to Science Tools Checkouts. Up to now 1st and 2nd Checkout;Development of visualization and analysis tool (not included is the Analysis Tool suite);Work on simulating catalogs of pulsars in preparation for DC2

Work in progress and plans for future…Inclusion of more realistic timing effects (timing noise, glitches,etc.);Development of simulation of binary pulsar systems;Work with LAT Pulsar Science Group for studying GLAST performances on pulsar science;Study of analysis techniques for pulsar blind searches;Work on the development to fit optimally the requirements for DC2 (start January 2006);Provide output ephemerides database of the simulated pulsars to the DC2 users;

backup

On going Pisa activities (Pulsars)Pulsar simulations:

Refine the model;Optimize algorithms (simulating pulsars requires lot of time to simulate all timing effects);Adding more realistic timing effects (multiple ephemerides, timing noise, etc…);Use EGRET data to simulate known gamma ray pulsars;

Pulsar Data Analysis:Test Pulsar Analysis Tools for crosscheck the simulationanalysis chain;Interface with Science Tools group to know simulation requirements and refine the model;Partecipation to Science Tools Checkout as reviewers for the pulsar tools;Development of visualisation and analysis tools ( e.g. spectral) as for GRBs.

LAT Pulsar Science:Partecipation to the PSR/PWN/SNR Science Group;Plan to work for pre-lauch papers on:

LAT performances on the observation of pulsars;Expected LAT sensitivity for different pulsars emission scenarios;

Pulsars in DC2:Development of PulsarSpectrum in order to fit the simulation requirements for DC2 (now this simulator is considered as basis for the pulsars simulation in DC2) Test of simulation of an extended catalog of fake pulsars;Include realistic observation conditions (multiple ephemerides, pulsar database);Provide the ephemerides database of the simulates pulsars to the DC2 users;