Gamma-ray Large Area Space Telescope

Gamma-ray Large Gamma-ray Large Area Space Area Space TelescopeTelescope Timing activities at Timing activities at

Bordeaux Bordeaux

Bordeaux group in ManchesterBordeaux group in Manchester

October 2007October 2007

Lucas Guillemot

OutlineOutline

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L. Guillemot, Manchester, October 23 2007

• Validation of the GLAST software, using real data from other wavelengths (radio, X)

• The October Test (simulation of first GLAST data)

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GLAST softwareGLAST software

In a few words, pulsar-related Science Tools that needed to be tested are:

gtbary: computation of the barycentric correction, knowing event times, and spacecraft position

gtpphase: calculation of the pulsar phase, knowing pulsar ephemerides

And also:

gtpulsardb: tool that produces D4 files => GLAST format for ephemeris databases


Validation of the softwareValidation of the software

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We have been able to test GLAST tools using real data:

Giant pulses from the Crab (Nançay): barycentering phase folding (no binary companion) absolute phase

Giant pulses from 1937+21 (Nançay): barycentering phase folding (still no binary companion) but: fewer events, on a larger timescale absolute phase

J0218+4232 X-ray data (XMM): barycentering phase folding (with a binary companion !) absolute phase


Bordeaux-Nançay collaborationBordeaux-Nançay collaboration

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We’re in charge of producing ephemerides for the not-too difficult pulsars observed by Nançay. They gave us a computer account, so that we can use their tools and data:

us Nançay Radio Telescope

You know this better than we do…You know this better than we do…


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GRPs from the Crab: some screenshotsGRPs from the Crab: some screenshots

GRP times

FT1 file with the event times

D4.fits with Nançay ephemerides


GRPs from the CrabGRPs from the Crab

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Data:Data:

4 sets of GRPs, for MJD = 54175, 54178, 54180, 54181 (16, 19, 21 and 22 of March 2007) => 2769 events over 30 σ, recorded at the Nançay radiotelescope (Ismael Cognard) at 1400 MHz.

They occur in phase with the main pulse or the interpulse (see e.g. Shearer et al., Science, 2003).

GRPs are folded with ephemerides from Nançay.

Procedure:Procedure:• Get the event times, convert them into the right time format (namely MJD UTC to Mission Elapsed TT)• Calculate exact positions of the Nançay telescope as a function of time in the Celestial Reference System• Build an ephemeris using Nançay data• Run the tools !


ResultsResults

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Template radio profile at 1400 MHz of the Crab pulsar, derived from the Nançay radiotelescope data.

GRPs from the crab, folded with ephemerides from Nançay.

The main component is in phase with the main radio pulse.

The tested timing chain (barycentering + phase folding) is satisfying at the µs scale.


GRPs from 1937+21GRPs from 1937+21

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B1937+21: P ≈ 1.56 ms, no binary companion

Data:Data:

3 sets of GRPs, for MJD = 54172, 54178, 54197 (13, 19 of March and 7 of April 2007) => 251 event times over 30 σ, recorded at the Nançay radiotelescope (Ismael Cognard). About 10 times less TOAs, for a longer period !

The main component occurs after the main pulse, with a delay of 58 µs (see Soglasnov et al., 2004).

GRPs are folded with ephemerides from Nançay.

Procedure:Procedure: same as for GRPs from the Crab pulsar


ProblemProblem

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In the first version of the ephemeris we had a proper motion and a parallax, with POSEPOCH=46024 !

PM and PX are handled by TEMPO, not by ST…

If we launch gtpphase with no consideration of this PM, we obtain a 12 µs deviation over the 25 days !

2 solutions: • Have POSEPOCH as close as possible to event times• Modify gtbary so that it takes PM into account


ResultsResults

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Both methods were tested. This plot = obtained by modifying gtbary (but this won’t be implemented !).

Once again, we have good results at the µs scale.

Whole timing chain tested ? No ! What about binary pulsars ?

Slogasnovet al., 2004


J0218+4232 with XMMJ0218+4232 with XMM

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In April, Natalie Webb (CESR, Toulouse) sent us J0218+4232 data from XMM. We tried to detect J0218+4232 in XMM data, but using the GLAST Tools.

J0218+4232: 2.3 ms pulsar, in a binary systemData set: 40000 s of observation, in February 2002Ephemeris used: taken from Kuiper et al., 2002; measured by Jodrell

The protocol is the same as in our study of GRPs apart from the XMM Spacecraft position that we needed to interpolate, based on XMM data.

This plot: difference between GLAST-barycentered times and XMM-barycentered times.

|Δt | < 120 ns : agreement !


PhasogramPhasogram

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If we plot the J0218+4232 phasogram, with events barycentered and folded with GLAST Tools (with binary demodulation) using the Kuiper et al. ephemeris (rough subtraction of the background):

Dashed line: peak positions in Webb et al., 2004

As for GRPs but also testing the binary demodulation, we have satistying results at the µs scale.

Webb et al., 2004


The October TestThe October Test

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15 simulated orbits (initially: 16, but 5th orbit has failed…) covering ~ 1 day.

GLAST was essentially in “scan mode”, except for orbits 9-12 where it pointed Vela.

Total observation: spans from 2009-01-03, 10:55:00 to 2009-01-04, 11:41:12.

What we did:What we did:

• Detection of Vela, and validation of its absolute phase• Detection of other bright pulsars as well


A quick look at the results (I)A quick look at the results (I)

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After 16 orbits, the Vela phasogram is well reproduced (but shifted !); P1, P2 and the bridge are clearly visible. The phase is stable with time => no obvious timing, ephemeris (apart from the shift) or position issue.

phase is stable with time


A quick look at the results (II)A quick look at the results (II)

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1055-52

1951+32

VelaCrab

Geminga

1706-44

Vela, Crab and Geminga are detected with high confidence. 1706-44 is detected with low-confidence. 1951+32 and 1055-52 are not clearly detected.

Vela, Crab, and 1706-44 phasograms are clearly shifted with respect to EGRET-based templates, whereas Geminga phasogram is OK => probably simulation features.

(from Damien)


Backup SlidesBackup Slides

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D4.fits work in progressD4.fits work in progress

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Simon Johnston recently suggested that it should be good to centralize ephemerides and observations informations in a common radio/X/gamma structure.

We have started building a web database (LG took a crash course in PHP & mySQL), in order to:

Centralise data and expertise Keep track of ephemerides, templates, residuals… in an other place than the incomplete D4.fits Know at a glance which pulsars need to be timed, or on the contrary which pulsars are over timed ! (for radio astronomers) Build custom D4, with selected ephemerides. (for gamma astronomers)


Web databaseWeb database

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login

data submission browse database

build custom D4

web pages & functions Pulsar toplist

Public content Private content

Legend:Ephemeris providersEphemeris clients

ephemeris database(s)


Sexiest pulsarsSexiest pulsars

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In May 07, M. Lopez & D. Parent : ~ 30 very interesting among the 215 with Ė>1034 erg/s.

Name Obs number @ Nançay since Sept 04 Obs time (s) @ Parkes in Oct 07

0656+14 92 01046-58 0 120

2229+6114 37 00218+4232 137 01747-2958 6 01718-3825 22 2401853+01 2 0

1420-6048 0 2401105-6107 0 3001016-5857 0 1202021+3651 15 0

1823-13 3 1201837-0604 2 4801637-4642 0 2401617-5055 0 12000205+6449 19 01930+1852 3 01124-5916 0 00537-6910 0 00540-69 0 0

1119-6127 0 2401811-1925 0 01846-0258 0 01833-1034 2 01338-62 0 1201643-43 0 1200740-28 4 120

1740+1000 6 0

Marginal EGRET detection

Associated with a 3EG source and a PWN

Associated with a 3EG source, without PWN

High Ė

Associated with a PWN, without 3EG


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