Transcript Progress on Pulsar Tools Development Masaharu Hirayama James Peachey (GLAST SSC, GSFC/UMBC)

Progress on Pulsar Tools Development
Masaharu Hirayama (GLAST SSC, GSFC/UMBC)
James Peachey (GLAST SSC, HEASARC)
June 29, 2005
http://glast.gsfc.nasa.gov/ssc/dev/psr_tools/
DC2 Software Workshop — 1
Typical Pulsar Analysis
1. Download data and screen events.
For maximum pulse-detection sensitivity, select only events
within a small region, typically size of a couple of PSFs.
2. Correct event times – barycentric correction.
To cancel Doppler effect resulting from the orbital motions of the
Earth and the spacecraft.
3. Find pulsar ephemeris at the time of observation.
Option 1: Use a radio ephemeris as is.
Option 2: Scan pulse frequencies around extrapolation of radio
ephemeris.
Option 3: Search for pulsations even if no radio ephemeris is
available.
4. Calculate pulse phase for each photon.
5. Use pulse phases in your analysis.
•
•
•
June 29, 2005
Pulse shape (or pulse profile)
Phase-resolved spectrum
Phase-resolved image
http://glast.gsfc.nasa.gov/ssc/dev/psr_tools/
DC2 Software Workshop — 2
Pulsar Tools Components
• Pulsar ephemerides database (D4)
– List of pulsar timing solution maintained during the mission
for potential LAT sources.
– Downloadable as a FITS file.
• Pulsar ephemeris extractor gtpsearch (U11)
– Basic front end to the pulsar ephemerides database.
• Photon arrival time converter glbary/gtbary (U10)
– Converts photon arrival times in a photon list to those at the
solar system barycenter.
• Pulsar phase assignment pulsePhase/gtpulsephase (U12)
– Assigns pulse phase to each photon in a photon list.
• Pulsar profile & periodicity tests gtpsearch (A3)
– Epoch-folds photon arrival times at trial pulse frequencies and
estimate significance of pulsation at each frequency.
• Pulsar period search gt??? (A4)
– Searches for periodic emission from a point source.
June 29, 2005
http://glast.gsfc.nasa.gov/ssc/dev/psr_tools/
DC2 Software Workshop — 3
Pulsar Tools In Action
gtpulsardb
Pulsar
ephemerides (D4)
Ephemeris
extract (U11)
gtpulsephase
Pulsar phase
assign (U12)
Satellite position
history (D2)
TIME
•••••
fv
PULSE_PHASE • • •
Arrival time
correction (U10)
gtbary
Event Summary
FITS File (D1)
gtpsearch
June 29, 2005
Periodicity
test (A3)
Pulsar period
search (A4)
gt???
http://glast.gsfc.nasa.gov/ssc/dev/psr_tools/
Pulse
profile (A3)
Data subselection (U2)
Likelihood (A1)
DC2 Software Workshop — 4
Major Design Changes Since 9/2002 Review
• Binary demodulation (arrival time correction for binary
pulsars) will be performed on the fly.
– Originally this task was assigned to photon arrival time
converter (U10). This had the following problems:
• The FITS standards for photon lists have no support for binarydemodulated times.
• For U10 an existing tool (FAXBARY in FTOOLS) was adopted for
use with GLAST data, and it does not support binary
demodulation.
– As of the end of build 9 it is performed in pulse phase
assignment (U12), periodicity tests (A3), and period search
(A4).
• Single TIME column in an event file.
– Original plan was to include multiple time columns in event
files, in order to preserve original event times while performing
time corrections. This had the following problems:
• The HEASARC standards for an event file assume a single time
column. (Desired HEASARC compliance).
• Existing analysis tools may recognize TIME column only.
June 29, 2005
http://glast.gsfc.nasa.gov/ssc/dev/psr_tools/
DC2 Software Workshop — 5
Current Status of Development
Design
Existing
Implementation
counterparts
Testing
Ephemerides
database
Defined in
detail
Identified
Examples
available
Used in ST
checkout 2
Ephemeris
extractor
Complete
None
Complete
Done
Arrival time
converter
Algorithms
identified
Identified
Complete
Done
Phase
assignment
Algorithms
identified
Identified
Complete for
solitary pulsars
Done
Pulse profile & Algorithms
period scan
identified
Identified
Complete for
solitary pulsars
Done
Period search
Identified
After DC2
Not yet
June 29, 2005
Algorithms
identified
http://glast.gsfc.nasa.gov/ssc/dev/psr_tools/
DC2 Software Workshop — 6
Data Challenge 2
• Ready for Data Challenge 2
– Pulsar ephemerides database (D4)
• Database format defined and examples available.
• Ingest protocol defined.
• Extractor (U11) available.
– Photon arrival time converter (U10)
– Pulse phase assignment (U12) for solitary pulsars
– Pulsar periodicity tests (A3) for solitary pulsars
• Will be ready by Data Challenge 2
– Arrival time corrections for binary pulsars
• Pulsar periodicity tests (A3)
• Pulse phase assignment (U12)
• Major tasks beyond Data Challenge 2
– Pulsar period search (A4) – re-use of FTOOLS counterparts?
– Bayesian approach for periodicity tests (A3)
June 29, 2005
http://glast.gsfc.nasa.gov/ssc/dev/psr_tools/
DC2 Software Workshop — 7
Further Developments
• Ephemeris computer
– Reads pulsar ephemerides database (D4) and compute pulsarrelated 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).
• User-interface
– GUI under development for all SAE tools.
– Web interface for database extractor?
• Orbital phase assignment
– 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.
June 29, 2005
http://glast.gsfc.nasa.gov/ssc/dev/psr_tools/
DC2 Software Workshop — 8
Backup Slides
June 29, 2005
http://glast.gsfc.nasa.gov/ssc/dev/psr_tools/
DC2 Software Workshop — 9
Pulsar Tools
Pulsar
ephem. (D4)
Data in
Level 0.5
Level 1 (D1)
Pointing/livetime
history (D2)
Alternative source
for testing highlevel analysis
Event
display (UI1)
Pulsar period
search (A4)
Ephemeris
extract (U11)
Arrival time
correction (U10)
Pulsar phase
assign (U12)
Data extract
(U1)
Pt.ing/livetime
extractor (U3)
Alternative for
making additional
cuts on alreadyretrieved event data
Observation
simulator (O2)
Data subselection (U2)
Pt.ing/livetime
simulator (O1)
Pt.ing/livetime
extractor (U3)
Exposure
calc. (U4)
Source model
def. tool (U7)
Catalog
Access (U9)
Likelihood (A1)
Astron.
catalogs (D6)
Src. ID (A2)
Interstellar em.
model (U5)
Map gen
(U6)
IRFs (D3)
IRF visualization (U8)
GRB spectral
analysis (A8)2
GRB event
binning (A5)
GRB unbinned
spectral analysis (A9)
GRB spectral-temporal
modeling (A10)
GRB LAT DRM
gen. (U14)
June 29, 2005
LAT Point source
catalog (D5)
Pulsar
profiles (A3)1
GRB rebinning
(A6)2
GRB visualization (U13)
GRB temporal
analysis (A7)2
http://glast.gsfc.nasa.gov/ssc/dev/psr_tools/
DC2 Software Workshop — 10
Algorithms
• Periodicity tests
– Chi-squared test (Leahy et al. 1983, ApJ 266, 160; Vaughan et
al. 1994, ApJ 435, 362)
– Zn2 test (Buccheri et al. 1983, A&A 128, 245)
– Rayleigh test (equivalent to Zn2 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)
June 29, 2005
http://glast.gsfc.nasa.gov/ssc/dev/psr_tools/
DC2 Software Workshop — 11
Pulsar Ephemerides Database (D4, U11)
• Full definition of D4 FITS file complete.
– Similar to the CGRO catalog, with some improvements.
– Ephemerides ingest protocol defined.
– Ephemerides extractor tool (U11) available.
• Examples of D4 FITS file available.
– Contents based on the CGRO catalog.
– To be used in Data Challenge 2.
• Action items:
– Discuss on ephemerides data ingest with the pulsar IDS.
June 29, 2005
http://glast.gsfc.nasa.gov/ssc/dev/psr_tools/
DC2 Software Workshop — 12
Photon Arrival Time Converter (U10)
• Existing counterparts identified.
– FAXBARY seems to be “re-usable” for GLAST.
– FAXBARY: FTOOLS originally developed for XTE, now
available for other missions such as Swift.
• FAXBARY modified to adopt to GLAST data.
– Tested with simulated data in Science Tools checkout 2.
– To be used in Data Challenge 2.
• Action items:
– Deliver to the LAT team as a part of the HEADAS package.
June 29, 2005
http://glast.gsfc.nasa.gov/ssc/dev/psr_tools/
DC2 Software Workshop — 13
Pulsar Phase Assignment (U12)
• Basic functionality implemented and tested.
–
–
–
–
Single set of frequency ephemeris can be given.
Multiple ephemerides can be read from database (D4).
Probably already good enough for Data Challenge 2.
To be used in Data Challenge 2.
• Action items:
– Implement arrival time corrections for binary pulsars.
June 29, 2005
http://glast.gsfc.nasa.gov/ssc/dev/psr_tools/
DC2 Software Workshop — 14
Pulsar Profile & Periodicity Tests (A3)
• Basic functionality implemented and tested.
– Single set of initial frequency ephemeris can be given by a
user or read from database (D4).
– Good enough for Data Challenge 2.
– To be used in Data Challenge 2.
• Most of periodicity tests implemented and tested.
– Chi-squared test (Leahy et al. 1983, ApJ 266, 160; Vaughan et
al. 1994, ApJ 435, 362)
– Zn2 test (Buccheri et al. 1983, A&A 128, 245)
– Rayleigh test (equivalent to Zn2 test for n = 1)
– H test (De Jager et al. 1989, A&A 221, 180)
• Action items:
– Implement arrival time corrections for binary pulsars.
– Identify periodicity tests to be implemented (if any).
June 29, 2005
http://glast.gsfc.nasa.gov/ssc/dev/psr_tools/
DC2 Software Workshop — 15
Pulsar Period Search (A4)
• Suggested algorithms for 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)
• Existing counterparts identified.
– “powspec” (XRONOS) calculates power spectrum density
– “perdgrm” (FTOOLS) computes Lomb-Scargle periodogram
• Action items:
– Test existing tools with GLAST data format.
– Implement Python wrapper if needed.
June 29, 2005
http://glast.gsfc.nasa.gov/ssc/dev/psr_tools/
DC2 Software Workshop — 16
Pulsars for GLAST LAT
• Pulsars are point sources
• GLAST expected to detect
pulsations from 50-100
pulsars
Plot by D.J. Thompson
– 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
June 29, 2005
http://glast.gsfc.nasa.gov/ssc/dev/psr_tools/
DC2 Software Workshop — 17
What Pulsar Tools Are Needed?
•
Barycentric corrector
Photon arrival time converter glbary/gtbary (U10)
•
Pulsar ephemeris “finder”
Case 1: use a radio ephemeris as is.
Pulsar ephemerides database (D4)
Pulsar ephemeris extractor gtpulsardb (U11)
Case 2: scan around a radio ephemeris.
Pulsar profile & periodicity tests gtpsearch (A3)
Case 3: search for pulsations.
Pulsar period search gt??? (A4)
•
Pulse phase calculator
Pulsar phase assignment pulsePhase/gtpulsephase (U12)
June 29, 2005
http://glast.gsfc.nasa.gov/ssc/dev/psr_tools/
DC2 Software Workshop — 18