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Pulsar observations with LOFAR

Pulsar observations with LOFAR

Joeri van Leeuwen
LOFAR and the Transient Radio Sky, Amsterdam, December 2008

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transientskp

June 18, 2012
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  1. Radio pulsar surveys with LOFAR Joeri van Leeuwen (ASTRON) +

    PWG
  2. Introduction 1 second of Crab-pulsar data with WSRT+PuMaII

  3. Galactic longitude (degrees) 270 -500 0 z (pc) 500 180

    90 0 Why look for more pulsars? Young pulsars tell about birth location, velocities supernova mechanism Known proper motions of pulsars younger than 1Myr (Hobbs et al. 2005)
  4. 12 13 11 -2 -1 0 1 Log period (s)

    Log magnetic field (G) Why look for more pulsars? Number of dim pulsars reveals supernova rates and minimum masses Clarify why long-period pulsars stop emitting Pulsar period versus magnetic field
  5. Why look for more pulsars? Pulsars 'time' the relativistic effects

    caused by a possible companion (neutron star / black hole) measures masses and spin pulse arrival time residual (µs)
  6. Why look with an interferometer? Time-based (vs. image-based) astronomy uses

    beam-forming, not interferometry Field of view dictated by largest separation, but sensitivity by total area: sparse Potentially form many parallel beams each with own periodicity-search back end Computationally challenging 8GR8; LOFAR; SKA (cf. Backer 1999)
  7. Why look with an interferometer? Beam-forming pulsar survey WSRT, at

    ~1000 beams First ever pulsars discovered from NL Can find ~10s of new pulsars 28 28.5 29 29.5 30 30.5 292 292.5 293 293.5 294 294.5 295 295.5 DEC (deg, J2000) R A (deg, J2000)
  8. LOFAR Pulsar survey Trade off between large FoV and high

    sensitivity. Supercore/core/entire LOFAR Different sparseness and total area
  9. LOFAR Pulsar survey Theoretical gains Core, coherent: 8.8 K/Jy Core+NL

    incoherent: 1.8 K/Jy Supercore: 2.9 K/Jy van Leeuwen & Stappers (2009)
  10. LOFAR Pulsar survey First station beam forming & tracking at

    Pulsar Busy Week Nov09:
  11. LOFAR Pulsar survey Theoretical gains Pointings for all-sky Core, coherent:

    8.8 K/Jy 3.000.000 @ 2min Core+NL incoherent: 1.8 K/Jy 1.000 @ 1hr Supercore: 2.9 K/Jy van Leeuwen & Stappers (2009)
  12. LOFAR Pulsar survey Simulate birth rates, evolution, selection effects for

    1e7 pulsars and 8 surveys: Survey Real Sim Jodrell (1972) 51 20 UMass-Arecibo (1974 50 39 MolongloII (1978) 224 227 UMass-NRAO (1978) 50 54 Parkes II (1991) 298 335 Cambr 80MHz (1993) 20 27 Parkes MB (1999) 1005 801 LOFAR (2009-2011)
  13. LOFAR Pulsar survey Simulate birth rates, evolution, selection effects for

    1e7 pulsars and 8 surveys: Survey Real Sim Jodrell (1972) 51 20 UMass-Arecibo (1974 50 39 MolongloII (1978) 224 227 UMass-NRAO (1978) 50 54 Parkes II (1991) 298 335 Cambr 80MHz (1993) 20 27 Parkes MB (1999) 1005 801 LOFAR (2009-2011) 1200
  14. LOFAR Pulsar survey Relatively robust; different luminosity and gain models:

  15. LOFAR Pulsar survey Surveyed volume limited by multi-path scattering on

    ISM. van Leeuwen & Stappers (2009)
  16. LOFAR Pulsar survey Can however see all radio pulsars within

    ~2kpc -10 5 10 0 position (kpc) 15 -5 0 position (kpc) 5 10 Lofar detection Sun Galactic Centre -2 -1 position (kpc) 0 position (kpc) 2 1 -2 -1 0 2 1
  17. LOFAR Pulsar survey Can see very far out of galactic

    plane birth velocities: supernova kicks
  18. LOFAR Pulsar survey Measuring velocities, ages, magnetic fields, etc takes

    pulsar timing Initial positions: run incoherent beam forming + 10ms per second correlation in parallel Optimizing detected pulsars within station beam: 44% of pulsars are in pairs in station beam -- 20% in triples -- 19% in 4+ Coherent beamforming on those: 10hr total to get detection SNR on all sources
  19. Conclusions Computationally overcoming interferometer draw-backs (cf. SKA). Can find entire

    local population and measure velocity distribution infer supernova mass ranges, energetics