# Presentation: 401844

## Overview of Pulsar Tools

**Masaharu Hirayama ****(GLAST SSC, JCA/UMBC)**** **
**James Peachey ****(GLAST SSC, HEASARC)**** **

## Pulsars for GLAST LAT

**Pulsars are point sources**
**GLAST expected to detect pulsations from 50-100 pulsars**
**10-50% are predicted to be radio quiet like Geminga**
**Most need 1 year exposure for detection**
**Sparse data**
**One photon per 500 pulses (Crab 30 MeV – 300 GeV)**
**Scanning with large FOV**
**All sources get some exposure every day throughout a year**
**Large number of short observations**

## Typical Pulsar Analysis

**Download data and screen events.**
**Barycentric correction. ****gtbary**
**To cancel Doppler effect resulting from the orbital motions of the Earth and the spacecraft.**
**Find pulsar ephemeris at the time of observation. ****gtephcomp**
**Option 1: Use a radio ephemeris as is.**
**Option 2: Scan pulse frequencies around extrapolation of radio ephemeris. ****gtpsearch **
**Option 3: Search for pulsations even if no radio ephemeris is available. (New tool ****gtpsd****).**
**Calculate pulse phase for each photon. ****gtpphase**
**Epoch folding (pulse shape) using ****fv, fplot, etc.**
**Phase-resolved spectrum (or image) ****gtselect, gtlike**

- _[http://glast-ground.slac.stanford.edu/workbook/science-tools/sciTools_Home.htm](http://glast-ground.slac.stanford.edu/workbook/science-tools/sciTools_Home.htm)_

## Pulsar Tools In Action

**Pulsar**
**ephemerides  (D4)**

**Satellite position**
**history (FT2)**

**Pulsar period**
**search (A4)**

**Pulsar phase**
**assign (U12)**

**Periodicity**
**test (A3)**

**Arrival time**
**correction (U10)**

**Ephemeris**
**extract (U11)**

**     ****TIME ****     • • • • •     PULSE_PHASE    • • • **

**Event Summary**
**FITS File (FT1)**

** ****Data sub-**
**selection (U2)**

**Likelihood (A1)**

**Pulse**
**profile (A3)**

**gtpulsardb**

**gtpphase**

**gtbary**

**gtpsearch**

**fv**

**gtpsd**

## GUC Action Item 18

**The methodology will be described for the simple pulsar search tool provided by the standard analysis environment. **
**Standard Analysis Environment identifies two tools:**
**Periodicity tests (A3) ****gtpsearch already implemented **
**Previous measurements provide an estimate of the frequency that may not be accurate for the current data.**
**Blind period search (A4) ****gtpsd? under consideration**
**Source has not been identified as a pulsar.**
**Blind search methodologies are open ended and many are outside the scope of SAE.**
**Many techniques exist and are still being developed.**
**Best technique depends strongly on the scientific goal, and on personal preference.**
**Powerful techniques are too computationally intensive.**

## Algorithms

**Periodicity tests**
**Chi-squared test (Leahy et al. 1983, ApJ 266, 160; Vaughan et al. 1994, ApJ 435, 362) **
**Zn****2**** test (Buccheri et al. 1983, A&A 128, 245) **
**Rayleigh test (equivalent to Zn****2**** test for n = 1) **
**H test (De Jager et al. 1989, A&A 221, 180) **
**Bayesian approach (Gregory and Loredo 1992, ApJ 398, 146; Gregory and Loredo 1996, ApJ 473, 1059) **
**Period search**
**Discrete Fourier transforms (Ransom 2002, AJ 124, 1788) **
**Lomb-Scargle periodogram (Lomb 1976, Ap&SS 39, 447; Scargle 1982, ApJ 263, 835; Press & Rybicki 1989, ApJ 338, 277) **

## Pulsar period search tool (A4)

**Searches for periodic emission from a point source. **
**Position of the source is well-known.**
**No prior knowledge on pulse frequency.**
**The source is either not in a binary system, or in a binary system whose binary parameters are known.**
**Example case: **
**	****Search for pulsations from EGRET un-identified sources.**
**Recommended algorithm for period search.**
**Discrete Fourier transforms (Ransom 2002, AJ 124, 1788)**
**Implementation is FFTW (Fastest Fourier Transform in the West) **_**[http://www.fftw.org/](http://www.fftw.org/)**_

## Backup Slides

## Utility Tools

**Ephemeris computer ****gtephcomp**
**Reads pulsar ephemerides database (D4) and compute pulsar-related parameters (such as pulse frequency) at a given moment in time.**
**Also serves as a sanity checker for first-time users of our pulsar ephemerides database (D4).**
**Orbital phase assignment ****gtophase**
**To assign an orbital phase to each photon (just like a pulse phase for each photon).**
**Pulse phase assignment tool (U12) is a natural candidate to do this task.**
**Pulsar ephemerides extraction tool ****gtpulsardb**
**To sub-select pulsar ephemerides from a master database.**
**Also, used to create, modify, merge pulsar ephemerides database.**

## Pulsar Tools

- Pulsar
- ephem. (D4)

- Level 1 (D1)

- LAT Point source
- catalog (D5)

- Interstellar em.
- model (U5)

- Pointing/livetime
- history (D2)

- Astron.
- catalogs (D6)

- Level 0.5

- IRFs (D3)

- Alternative source for testing high-level analysis

- Alternative for making additional cuts on already-retrieved event data

- Pt.ing/livetime
- simulator (O1)

- Observation
- simulator (O2)

- Pt.ing/livetime
- extractor (U3)

-  Data sub-
- selection (U2)

- Data extract
- (U1)

- Exposure
- calc. (U4)

- Likelihood (A1)

- Map gen(U6)

- Src. ID (A2)

- Event
- display (UI1)

- Pulsar
- profiles (A3)1

- Catalog
- Access (U9)

- Pt.ing/livetime
- extractor (U3)

- Pulsar phase
- assign (U12)

- Pulsar period
- search (A4)

- GRB spectral-temporal
- modeling (A10)

- Source model
- def. tool (U7)

- Arrival time
- correction (U10)

- GRB temporal
- analysis (A7)2

- GRB LAT DRM
- gen. (U14)

- GRB spectral
- analysis (A8)2

- GRB event
- binning (A5)

- GRB unbinned
- spectral analysis (A9)

- GRB visual-
- ization (U13)

- IRF visual-
- ization (U8)

- Ephemeris
- extract (U11)

- GRB rebinning
- (A6)2

**Data in**