Limits on millisecond transients with ARTEMIS on LOFAR

Aris Karastergiou

Transcript

1. Limits on millisecond
   transients with
   ARTEMIS on LOFAR
   Wednesday, 8 January 14
   

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2. ARTEMIS has no
   confirmed detections yet...
   Lorimer 2007 Keane 2012
   Wednesday, 8 January 14
   

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3. LOFAR international
   stations
   • Large collecting area, high sensitivity
   • 96 coherently added dipoles x 2 pol
   • Very fast sampling rate, 5.12μs voltage data
   • Large fields of view, e.g. 30 sq.deg in 8x6MHz
   beams at ~150 MHZ
   • Large amounts of available time
   Wednesday, 8 January 14
   

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4. Griffin Foster
   Wednesday, 8 January 14
   

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5. Dell Poweredge C6100
   Dell Poweredge C410x
   Stef
   Salvini
   Wes Armour
   Dalal
   Ait Allal
   Mike Giles
   Chris Williams Steve Roberts
   Fred
   Dulwich
   Ben Mort
   Alessio
   Magro
   Aris
   Karastergiou
   hardware
   Wednesday, 8 January 14
   

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6. Frequency (MHz)
   Time (ms)
   8000 8200 8400 8600 8800 9000
   143
   144
   145
   146
   147
   148
   149
   20
   30
   40
   50
   60
   200 400 600 800
   0
   2000
   4000
   6000
   8000
   Time bin
   40 60
   100
   200
   300
   400
   500
   600
   700
   800
   900
   dB
   Frequency channels
   Pulse
   Wednesday, 8 January 14
   

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7. Frequency (MHz)
   Time (ms)
   8000 8200 8400 8600 8800 9000
   143
   144
   145
   146
   147
   148
   149
   16
   18
   20
   22
   24
   26
   28
   30
   200 400 600 800
   0
   200
   400
   Time bin
   22 24 26
   100
   200
   300
   400
   500
   600
   700
   800
   900
   dB
   Frequency channels
   Wednesday, 8 January 14
   

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8. dynamic noise
   modelling
   for effective RFI
   removal and
   transient detection
   filterbank noise
   pre-filtering
   filterbank noise
   post-filtering
   Wednesday, 8 January 14
   

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9. DM
   time (s)
   GPU dedispersion test:
   1500 measures searched in real-time, only pulses from
   B0329+54 detected, no spurious signals
   Wednesday, 8 January 14
   

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10. Real time detection system which
    would easily detect RRATs and Lorimer
    burst as they happened.
    Affordable and scalable hardware
    26 December 2011
    drift scan with beam at Dec=+21º
    B1919+21
    Crab
    time (s)
    Crab
    B1919+21
    Wednesday, 8 January 14
    

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11. Wednesday, 8 January 14
    

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12. ARTEMIS survey I
    • 1000 h of observations
    • 8 beams on Greenwich meridian
    • 143 - 149 MHz
    • ~2000 x 3.05 kHz channels
    • ~40 Jy (at 8σ) over 2ms integrations
    • DMmax = 150 pc / cm3, δDM = 0.1
    • Sampling local Galactic population (really?)
    Wednesday, 8 January 14
    

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13. ARTEMIS survey I
    For 40 Jy (8σ) sources in 2ms integrations:
    R < 1/1000h/30deg2 ≈ 30 sources / sky / day
    ≈ 3x10-5 sources / deg2 / hour
    Wednesday, 8 January 14
    

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14. Scattering
    Bhat et al. 2004
    Wednesday, 8 January 14
    

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15. DM (pc/cm3)
    log10(o
    sc
    ) (ms)
    100
    101
    102
    103
    −10
    −8
    −6
    −4
    −2
    0
    2
    4
    6
    Pulsars
    Extragalactic FRBs
    o
    sc
    = 10ms at 1GHz
    o
    sc
    = 10ms at 350MHz
    o
    sc
    = 10ms at 150MHz
    A peculiar population
    FastRadioBursts
    Wednesday, 8 January 14
    

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16. Galactic & Extragalactic
    scattering
    Maximum scattering occurs when midway between the
    pulsar and Earth
    Lorimer et al. 2013
    Wednesday, 8 January 14
    

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17. DM (pc/cm3)
    log10(o
    sc
    ) (ms)
    100
    101
    102
    103
    −10
    −8
    −6
    −4
    −2
    0
    2
    4
    6
    Pulsars
    Extragalactic FRBs
    o
    sc
    = 10ms at 1GHz
    o
    sc
    = 10ms at 350MHz
    o
    sc
    = 10ms at 150MHz
    DM ~ 1200 z pc/cm3
    z ~ 0.1
    z ~ 0.5
    Lorimer et al. 2013
    Wednesday, 8 January 14
    

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18. ARTEMIS survey I
    R < 1/1000h/30deg2 ≈ 30 sources / sky / day
    Assuming:
    • z = 0.1 and limit at 40 Jy
    • some cosmological expansion
    • rates of fast transients from high frequency surveys
    • high frequency surveys probe much greater volumes
    we can extract some limits on the spectra of these objects
    Wednesday, 8 January 14
    

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19. Standard candle model
    Uniformly distributed, 1Jy peak flux at z = 0.75
    Artemis 1
    Artem
    is I1
    (prediction)
    0.75
    events per day
    Wednesday, 8 January 14
    

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20. ARTEMIS survey II
    Wednesday, 8 January 14
    

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21. ARTEMIS survey II
    • Out to DM of 320 pc / cm3
    • 288 hours completed on 30 deg2
    • Upper limit of 111 sources/sky/day
    • 10 times less than Extragalactic standard
    candle prediction
    Wednesday, 8 January 14
    

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22. The hundred
    tied-array-beams
    realtime processor
    LOFAR APERTIF MeerKAT
    SKA-I SKA-II
    RFI-excision dedispersion folding detection
    CPU - GPU cluster
    Slide from
    Oxford
    TKSP
    meeting
    Wednesday, 8 January 14
    

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