LOFAR LBA Single Pulse Study of the PSR B0809+74

Vlad Kondratiev

Transcript

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
   

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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
   

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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
   

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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
   

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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
   

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6. Dec 4, 2012 TKP, Amsterdam
   Observations
   ●
   LBA Superterp
   ●
   15–62 MHz
   ●
   1 hour
   ●
   ∆f ≈ 6 kHz
   ●
   ∆t = 491.52 μs
   ●
   Stokes I
   

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

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

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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
   

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

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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
    

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

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

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

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

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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??
    ●
    ...
    

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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
    

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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 ?..
    

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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
    

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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
    

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

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

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23. View Slide

24. Dec 4, 2012 TKP, Amsterdam
    

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