Gamma-ray Large Area Space Telescope

1. Gamma-ray Large Area Space Telescope Timing activities at Bordeaux Bordeaux group in Manchester October 2007 Lucas Guillemot

2. L. Guillemot, Manchester, October 23 2007 Outline • Validation of the GLAST software, using real data from other wavelengths (radio, X) • The October Test (simulation of first GLAST data) • 2

3. L. Guillemot, Manchester, October 23 2007 GLAST 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 • 3

4. L. Guillemot, Manchester, October 23 2007 Validation of the software 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 • 4

5. L. Guillemot, Manchester, October 23 2007 Bordeaux-Nançay collaboration 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… • 5

6. L. Guillemot, Manchester, October 23 2007 GRPs from the Crab: some screenshots GRP times FT1 file with the event times D4.fits with Nançay ephemerides • 6

7. L. Guillemot, Manchester, October 23 2007 GRPs from the Crab • Data: • 4 sets of GRPs, for MJD = 54175, 54178, 54180, 54181 (16, 19, 21 and 22 of March 2007) => 2769 events over 30 σ, recordedat 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: • 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 ! • 7

8. L. Guillemot, Manchester, October 23 2007 Results 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. • 8

9. L. Guillemot, Manchester, October 23 2007 GRPs from 1937+21 B1937+21: P ≈ 1.56 ms, no binary companion 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: same as for GRPs from the Crab pulsar • 9

10. L. Guillemot, Manchester, October 23 2007 Problem 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 • 10

11. Slogasnov et al., 2004 • L. Guillemot, Manchester, October 23 2007 Results 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 ? • 11

12. L. Guillemot, Manchester, October 23 2007 J0218+4232 with XMM 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 system Data set: 40000 s of observation, in February 2002 Ephemeris 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 ! • 12

13. L. Guillemot, Manchester, October 23 2007 Phasogram 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 • 13

14. L. Guillemot, Manchester, October 23 2007 The October Test • 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: • Detection of Vela, and validation of its absolute phase • Detection of other bright pulsars as well • 14

15. L. Guillemot, Manchester, October 23 2007 A quick look at the results (I) phase is stable with time 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. • 15

16. L. Guillemot, Manchester, October 23 2007 A quick look at the results (II) Vela Crab 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. Geminga 1951+32 1706-44 1055-52 (from Damien) • 16

17. L. Guillemot, Manchester, October 23 2007 Backup Slides • 17

18. L. Guillemot, Manchester, October 23 2007 D4.fits work in progress 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) • 18

19. L. Guillemot, Manchester, October 23 2007 Web database login web pages & functions data submission Pulsar toplist browse database build custom D4 Public content Private content ephemeris database(s) Legend: Ephemeris providers Ephemeris clients • 19

20. L. Guillemot, Manchester, October 23 2007 Sexiest pulsars In May 07, M. Lopez & D. Parent : ~ 30 very interesting among the 215 with Ė>1034 erg/s. Marginal EGRET detection Associated with a 3EG source and a PWN Associated with a 3EG source, without PWN Associated with a PWN, without 3EG High Ė • 20