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LOFAR LBA Single Pulse Study of the PSR B0809+74

transientskp
December 04, 2012

LOFAR LBA Single Pulse Study of the PSR B0809+74

Vlad Kondratiev

transientskp

December 04, 2012
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  1. LOFAR LBA single­pulse study of
    the PSR B0809+74
    Vlad Kondratiev
    (ASTRON)
    Jason Hessels, Ben Stappers, Tom Hassall,
    Aris Karastergiou, Anya Bilous, Michael Kramer, Patrick Weltevrede,
    and the LOFAR Pulsar Working Group,
    and the LOFAR TKP

    View Slide

  2. Observations
    Variety of pulsar radio emission
    Drifting subpulses,
    nulling, mode changing
    Giant pulses and
    micropulses
    Spiky
    emission
    (Weltevrede et
    al. 2006)
    high frequencies
    Dec 4, 2012 TKP, Amsterdam

    View Slide

  3. Observations
    Variety of pulsar radio emission
    Drifting subpulses,
    nulling, mode changing
    Giant pulses and
    micropulses
    Spiky
    emission
    (Weltevrede et
    al. 2006)
    ?
    ?
    high frequencies
    Strong pulses
    @ 111 MHz, BSA
    (Kuzmin & Ershov)
    Strong pulses
    @ 110-180 MHz
    WSRT
    (Karuppusamy et al. 2011)
    low frequencies
    Dec 4, 2012 TKP, Amsterdam

    View Slide

  4. Observations
    Variety of pulsar radio emission
    Drifting subpulses,
    nulling, mode changing
    Giant pulses and
    micropulses
    Spiky
    emission
    (Weltevrede et
    al. 2006)
    Anomalously
    Intensive Pulses
    @ 18-30 MHz, UTR-2
    (Ulyanov et al. 2006)
    ?
    ?
    high frequencies
    Strong pulses
    @ 111 MHz, BSA
    (Kuzmin & Ershov)
    Strong pulses
    @ 110-180 MHz
    WSRT
    (Karuppusamy et al. 2011)
    low frequencies
    ?
    Dec 4, 2012 TKP, Amsterdam

    View Slide

  5. 62 MHz
    15 MHz
    B0809+74
    By studying pulsar emission at the
    lowest accessible frequencies, can
    we learn something new and
    fundamental?
    LOFAR provides full coverage of the
    10–90 MHz window.
    Dec 4, 2012 TKP, Amsterdam

    View Slide

  6. Dec 4, 2012 TKP, Amsterdam
    Observations

    LBA Superterp

    15–62 MHz

    1 hour

    ∆f ≈ 6 kHz

    ∆t = 491.52 μs

    Stokes I

    View Slide

  7. Bright narrow­band pulses
    Kondratiev et al.
    (in prep)
    B1133+16
    B0809+74
    Dec 4, 2012 TKP, Amsterdam

    View Slide

  8. Bright narrow­band pulses
    Kondratiev et al.
    (in prep)
    B1133+16
    B0809+74
    Dec 4, 2012 TKP, Amsterdam

    View Slide

  9. Pulse energy distribution
    Kondratiev et al. (in prep)
    B0809+74

    Energies < 10 ‹E›

    Can't diffirentiate
    between Log­Norm
    and PL

    In general, Log­Norm
    fits better

    PL works better for
    high­energy tail
    Dec 4, 2012 TKP, Amsterdam

    View Slide

  10. Kondratiev et al. (in prep)
    B0809+74
    Peak flux densities
    Dec 4, 2012 TKP, Amsterdam

    View Slide

  11. Pulse spectra
    Kondratiev et al. (in prep)
    B0809+74

    ∆f ~ 1 – 16 MHz
    peaking at 3 MHz

    For B1133+16
    emission is much
    broader
    Dec 4, 2012 TKP, Amsterdam

    View Slide

  12. ≤ 30 MHz vs. >30 MHz
    Kondratiev et al. (in prep)
    B0809+74
    Energies Peak flux densities
    Dec 4, 2012 TKP, Amsterdam

    View Slide

  13. Pulse ''super­sequence''
    B0809+74
    Kondratiev et al.
    (in prep)
    Dec 4, 2012 TKP, Amsterdam

    View Slide

  14. ''super­sequence'' (afterglow)
    Kondratiev et al.
    (in prep)
    Dec 4, 2012 TKP, Amsterdam
    B0809+74

    View Slide

  15. Pulse ''super­sequence''
    Kondratiev et al.
    (in prep)
    Dec 4, 2012 TKP, Amsterdam
    B0809+74

    View Slide

  16. Pulse ''super­sequence''
    Dec 4, 2012 TKP, Amsterdam
    B0809+74

    downward motion of plasma
    enhancement along the magnetic field
    line (+radius-to-frequncy mapping,
    +geometry)

    connection to frequency-dependent
    drifting subband (see Tom's talk),
    frequency drift rates are harmonically
    related??

    ...

    View Slide

  17. ISM scintillations are
    averaged out (frequency
    resolution of 400 kHz)
    ∆ν
    d
    ~ 7 kHz @60 MHz
    ∆ν
    d
    ~ 2 kHz @40 MHz
    In agreement with BSA
    and DKR­1000
    observations (Smirnova
    & Shishov 2008)
    Narrow­band origin? ISM?
    Kondratiev et al. (in prep)
    Dec 4, 2012 TKP, Amsterdam
    B0809+74

    View Slide

  18. ISM scintillations are
    averaged out (frequency
    resolution of 400 kHz)
    ∆ν
    d
    ~ 7 kHz @60 MHz
    ∆ν
    d
    ~ 2 kHz @40 MHz
    In agreement with BSA
    and DKR­1000
    observations (Smirnova
    & Shishov 2008)
    Narrow­band origin? ISM?
    Kondratiev et al. (in prep)
    Dec 4, 2012 TKP, Amsterdam
    B0809+74
    Must be intrinsic to the pulsar ?..

    View Slide

  19. Kondratiev et al. (in prep)
    Strong plasma turbulence?

    ∆f/f
    c
    ~ 0.15

    Strong plasma
    turbulence model
    (SPT, Weatherall 1998)
    predicts ∆f/f ~ 0.1–0.2

    SPT plasma flow in

    the radio emission
    region is likely to be
    unsteady
    Dec 4, 2012 TKP, Amsterdam
    B0809+74

    View Slide


  20. We observe occasional bright narrow­band pulses from the PSR B0809+74 at
    frequencies 15–62 MHz. Their spectra can be as narrow as 1 MHz and tend to have a
    width of 3 MHz.

    We identified pulse sequences from the PSR B0809+74 where narrow patch of emission
    is drifting up in frequency from pulse to pulse. We see evidence for similar frequency
    drift for at least one other pulsar, B1919+21.

    The origin of these narrow­band pulses is likely to be pulsar­intrinsic rather than due to
    propagation effects in ISM or ionosphere.

    At the moment observed pulse properties of the PSR B0809+74 do not allow us to relate
    low­frequency bright narrow­band pulses to ``spiky emission'', or to giant pulses or
    regular emission.

    Spectral width of strong emission patches scales with increasing frequency as f/f

    c
    ~0.15
    for the PSR B0809+74 and qualitatively agrees with the prediction of the SPT model.
    This supports the relation between bright narrow­band pulses at low frequencies and
    giant pulses.
    Summary
    Dec 4, 2012 TKP, Amsterdam

    View Slide

  21. Dec 4, 2012 TKP, Amsterdam
    LBA, 19 CS
    1 h
    8 bit
    15–93 MHz
    Δt = 655 µs
    Δf ≈ 3 kHz

    View Slide

  22. Dec 4, 2012 TKP, Amsterdam
    LBA, 19 CS
    1 h
    8 bit
    15–93 MHz
    Δt = 655 µs
    Δf ≈ 3 kHz

    View Slide

  23. View Slide

  24. Dec 4, 2012 TKP, Amsterdam

    View Slide