PULSAR SURVEYS (AO

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PULSAR SURVEYS(AO GBT)

• Why?
• How deep can we go? (Dmax, Vmax)
• Example surveys
• Hardware
• Funding

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Why more pulsars?

• Extreme Pulsars
• P lt 1 ms P gt 5 sec
• Porb lt hours B gt 1013 G
• V gt 1000 km s-1

• Population Stellar Evolution Issues
• Physics payoff (GR, LIGO, GRBs)
• Serendipity (strange stars, transient sources)
• New instruments (AO, GBT, SKA) can dramatically
  increase the volume
  searched (galactic extragalactic)

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Simulated DM vs l histogram (50k pulsars)
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How Low Can We Go?
Dmax D (S / Smin1 )1/2 Nh1/4 Smin1
single harmonic threshold m Ssys /(Dn T)1/2
m no. of sigma Nh no. of harmonics
that maximize harmonic sum Nh ? 0
for heavily broadened pulses Regimes Luminosity
limited Dmax ? Smin1 -1/2 DM/SM limited
Dmax ? Smin1 -x , xlt1/2
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Finding Dmax

• beam luminosity
• beam widths (core,cone)
• orientation angles (a,b)
• pulse shape at nominal distance (1 kpc)
• Dmax Dnom H(Nh)/Smin11/2
• H(Nh)
• max Nh-1/2 ? Wi WORB WDM WSM WTC WHPF
• Dmax Dmax (DM, SM) ? iterate

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SEARCH VOLUME VS ? ?S D3max DETECTION
VOLUME Vd ?S
?0Dmax dD D2np/np(sun)
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Regimes for Dmax
Luminosity limited (r -2 law) Dispersion
limited ?t ? ??ch DM / ?3 Scattering limited
?t ? SM5/6 / ?4.4 Time constant limited
?tTC ?tTC(min) (??ch)-1
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Dmax example
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Dmax vs Lp
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Dmax vs. P (0.43 GHz)
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Dmax vs. P (larger Lp)
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Dmax vs. P (1.4 GHz)
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Dmax for B193316 (L band)
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Implications

• After maximizing ??T (RFI,TAC constraints), the
  control parameters for Dmax are l,b,?,Nch
• ? optimal directions to search
  (modulo
  RF and where pulsars are)
• Coherent dedispersion for searches? (not worth
  it if scattering limited better to put
  processing power into binary searches)

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AO, GBT, Parkes
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Compare AO,GBT Parkes(Lband)
Ssys Dn Nch T Smin1
d?/dT (Jy) (MHz)
(s) (?Jy) (hr/deg2) AO 3.6 400 1024 300
73 42/Nb GBT 16 400 1024
900 190 4.5/Nb Parkes 36 288 96 2100 360 1 (Nb13)
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Compare AO,GBT Parkes(Lband)
DMc Dmax for Lp10 mJy kpc2
,l30,b5 0.5
ms 33 ms 89 ms AO 27 3 kpc 8 kpc
8 kpc GBT 54 2.8 5
5 Parkes 28 1.3 4
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Strawman AO Surveys

• L band
• 7 beams
• 400 MHz/512 channels/beam (multi WAPP)
• 300 s/beam ? 6 hr/deg2
• 3000 hr ? 500 deg2
• Search volume ? 3 to 20 x Parkes MB
• (l,b,P dependent)
• S band? Advantage for very fast,weak pulsars
• flat spectrum pulsars at low b

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AO at S,L,P bands
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OPTIMAL DIRECTIONS

• AO advantage collecting area
  smaller channel bandwidths
• ? choose directions where Parkes MB is
  luminosity or DM limited. (SM limited ? less
  advantage per decrease in Smin1)
• e.g. along spiral arm tangents Cygnus
  region b gt few degrees (period
  dependent)

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Shopping List

• Multibeam system (Feeds/Rx) e.g. 7 _at_ L
• Digital backends (multi WAPP)
• Data storage
• Processing
• Followup
• for all of the above

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Ideas

• Multibeam systems e.g. Rick Fishers focal
  plane sampling beamforming system
• Digital backends AO WAPP x 4 x
  Nbeams GBT GBT correlator fast dump
• Storage/processing Moores law
• Followup dedicated timing telescopes (85ft,
  1HT, 100ft _at_ AO?)
• NSF MRI consortium proposal, private
  funding?

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