Search for millisecond pulsars at the GMRT and the exotic discoveries !!

1. Search for millisecond pulsars at the GMRT and the exotic discoveries !! Jayanta Roy NCRA- TIFR SINP, 18th October 2012

2. People involved Jayanta Roy (NCRA) Bhaswati Bhattacharyya (IUCAA) Paul Ray (NRL) Yashwant Gupta (NCRA)‏ Dipankar Bhattacharya (IUCAA) Roger Romani (Stanford) Michael T. Wolff (NRL) Fermi Pulsar Search Consortium Fermi Pulsar Timing Consortium Fermi LAT team ‏

3. OUTLINE • Pulsars classifications on diagram • Challenges for searching of millisecond pulsars (MSP) • Observational • Pre-requisite • Fermi LAT gamma-ray triggered surveys for MSPs • Pulsar Search Consortium • GMRT discoveries of 6 MSPs and its impact • State-of-art pulsar studies using interferometric array • Prospect of the on-going survey

4. Young pulsars Regular pulsars Millisecond (mostly binary) pulsars Pulsar classifications based on simple period and slow-down rate

5. MSP as Galactic GPS PSR J0437-4715 on 23rd Aug 2012 @ 14:40 UTC P = 5.7574518556687 ms +/- 0.0000000000001 ms Taken from Handbook of Pulsar Astronomy by Lorimer and Kramer

6. Challenges for searching of MSP

7. Observational Dispersion removal : dedispersed the data many “trial” DMs Scattering : survey at higher frequency near the Galactic plane

8. Observational Scintillation : survey the sky multiple times Binary motion : carry out “acceleration” searches

9. Instrumental High resolution back-end receiver to hunt for nearby fast pulsar GMRT Software Back-end developed by Roy et al 2010 using High Performance Computer GSB : a 2.5 Tflops Linux cluster sample the universe @ 61 us 30% improvement in search sensitivity for 1ms pulsar with DM of 20 pc/cc

10. 3-D pulsar search A Large HPC problem • 3-D search pipeline : • search in dispersion delay in order to compensate ISM effect • searching for periodicity in time-series data using spectral domain search algorithm (64 M point FFT + harmonic summing using power spectrum)‏ • search in acceleration (required in case of binary objects)‏ • In 2-D search real-time compute requirements for the pipeline parallelized over the dispersion grid (~ 1200) is 150 Gflops • 3-D search is very expensive ~ 3.5 Tflops • over the same range of DM grid • On a single Desktop 1hr of data (~ 60 GB) • takes ~ 1280 hours • On IUCAA HPC 1hr of data takes ~ 5 hrs • using 256 CPUs

11. 26 Aug NASA renamed GLAST to Fermi in honour of Prof. Enrico Fermi (1901-1954)‏ Fermi LAT Space mission devoted to study of High-Energy gamma rays from Universe • KEY FEATURES • Huge field of view • – LAT: 20% of the sky at any • instant; in sky survey mode, • expose all parts of sky for • every 3 hours. • GBM: whole sky at any time. • Broad energy range. • Large effective area. • Excellent time resolution • (microseconds UTC).

12. Fermi Bright source catalog ‏ 630 unassociated sources LAT source as pulsar search targets

13. Fermi pulsar search consortium (PSC)‏ Low frequency facility GMRT

14. GMRT as a PSC telescope • NCRA has set up a unique facility for radio astronomical research known as GMRT • Located at 80 km north to Pune • Consists 30 fully steerable gigantic parabolic dishes, each of 45m diameter spread over distances of upto 25 km Low-radio frequency (325 MHz and 610 MHz) pulsar search : Steep spectral nature Large FOV : easily cover the positional error boxes of Fermi sources (18’) High resolution search : high sensitivity of nearby MSP ~ 100 μJy Simultaneous dual beam search Large declination coverage for southern sky

15. GMRT discovery of 6 MSPs

17. MSPs discovered at the GMRT are pushing boundaries of known parameter space • J1544+4937 : Black widow pulsar • Eclipse seen • 3rd of its kind • 2.16ms @ 23.2 DM • Bhaswati’s talk for details J1828+0625: featureless profile International pulsar timing array candidate : 3.07ms @ 22.4 DM J1536-4948 : Widest profile MSP 3.16ms @ 38.0 DM J1646-2142 : considerable profile evolution between 325 and 610 MHz short eclipse 5.84ms @ 29.7 DM J1120-3618: In beam binary MSP outside HPBW 5.55ms @ 45.1 DM J1207-5050: Isolated MSP 4.84ms @ 50.6 DM

18. Success of pulsar search efforts at the GMRT First GMRT observation Follow up of Fermi LAT sources have resulted in discovery of 43 MSPs 33 % increase in population of disk MSPs GMRT Joined PSC GMRT contribution • PSC was formed • : August 2008 • GMRT joined PSC • : July 2010 • Fermi MSPs discovered • before July 2010 : 22 • Fermi MSPs discovered • after July 2010 till now 21 • GMRT discovered :6 ~33% of the Fermi MSP discoveries after GMRTjoined PSC are contributed by GMRT

19. State-of-art pulsar studies using interferometer Precise localization (<10”) of the MSP within the Fermi error box ~ 18’ using GMRT interferometer A multi-pixel beamformer PSR J1544+4937 is localized in the image plane (with an accuracy of 8”) at an offset of 4’ from the search beam center Roy et al 2012

20. State-of-art pulsar studies using interferometer Precise localization (<10”) of the MSP within the Fermi error box ~ 18’ using GMRT interferometer A multi-pixel beamformer PSR J1536-4948 is localized in the image plane (with an accuracy of 12”) at an offset of 2’ from the search beam center Roy et al 2012

21. State-of-art pulsar studies using interferometer (Roy et al 2012) A coherently dedispersed MSP gating correlator

22. ON-OFF gating image of Fermi MSPs 5σ @ 6’ from search centre 12σ @ 10’ from search centre 6σ @ 26’ from search centre 11σ @ 19’ from search centre 4σ @ 57’ from search centre

23. Coming future .... There are till lot to be discovered : MSP-MSP, NS-BH, Sub-MSP, Diamond Planet system, RRATs …… On-going GMRT survey holds promises to keep increasing the nos (so stay tuned)

24. Thank you Jayanta Roy NCRA-TIFR jroy@ncra.tifr.res.in