A bright millisecond radio burst of Extragalactic origin Duncan - - PowerPoint PPT Presentation

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A bright millisecond radio burst of Extragalactic origin Duncan - - PowerPoint PPT Presentation

Sep 24, 2023 175 likes •394 views

A bright millisecond radio burst of Extragalactic origin Duncan Lorimer, Matthew Bailes, Maura McLaughlin, David Narkevic and Froney Crawford Science (in press) astro-ph/0709.4301 Talk Outline Dispersion by the interstellar medium

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SLIDE 1

A bright millisecond radio burst of Extragalactic origin

Duncan Lorimer, Matthew Bailes, Maura McLaughlin, David Narkevic and Froney Crawford Science (in press) astro-ph/0709.4301

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SLIDE 2

Talk Outline

  • Dispersion by the interstellar medium
  • Pulsar Surveys
  • RRATs
  • Giant Pulses
  • LMC/SMC Pulsar Survey
  • An enormous pulse
  • Location
  • Potential
  • Future directions
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SLIDE 3

Pulse Dispersion

DM = ne

D

∫

dl

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SLIDE 4

Standard pulsar search

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SLIDE 5

Single pulse search

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SLIDE 6

The RRATs

  • McLaughlin et al. (2006)

– Discovered repeating impulsive bursts at the same DM – Gap ~4->120 minutes

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SLIDE 7

RRAT Properties

  • Power law distribution of energies
  • Regular gaps between pulses
  • Associated with

– Rotating – Radio – Transients

  • Another manifestation of neutron stars
  • Luminosity not enough to see beyond Milky

Way Galaxy

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SLIDE 8

Giant Pulses

  • Unresolved on us timescales
  • From young or millisecond pulsars
  • Power-law distribution of energies
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SLIDE 9

Pulsar Surveys with Parkes

MB Survey Swinburne Surveys Swinburne Surveys Burgay Survey Burgay Survey SMC/LMC surveys

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SLIDE 10

LMC/SMC bursts?

  • Searched DM 0-5000 cm-3 pc.
  • Found 3 giants from one pulsar

– Seen already by Johnston & Romani

  • Der Wunderpuls…
  • DM=375 cm-3pc!
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SLIDE 11
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SLIDE 12

Giant Pulse Characteristics

  • Seen in 3/13 beams
  • Side-lobes suggest 20 Jy intensity
  • Analog level setting suggests 40 Jy
  • Adopt (30+/-10) Jy.

– Width fn(frequency)

W = 5ms υ 1400 MHz ⎛ ⎝ ⎜ ⎞ ⎠ ⎟

−4.8

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SLIDE 13

An astrophysical origin

  • Knows about Cold Plasma Dispersion law
  • Knows about Kolmogorov Scattering law
  • Appears only in 3 adjacent beams out of 13

– From the sky direction

  • Doesn’t repeat in 20 days of observing
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SLIDE 14

Where?

X x x

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SLIDE 15

SMC Pulsar DMs

  • 70 pc/cc (far from H-alpha)
  • 76 pc/cc (far from H-alpha)
  • 105 pc/cc (Near H-alpha)
  • 125 pc/cc (Near H-alpha)
  • 201 pc/cc (Near H-alpha emission)
  • 375 pc/cc (far from any H-alpha)!!
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SLIDE 16

If it is a PSR or RRAT

  • Should repeat
  • Original pulse 100x detection threshold!
  • 40 hours of follow-up @ 20cm
  • Nothing!
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SLIDE 17

What then?

  • Points to a one-off event?
  • Distance?

– If DM (MWG+SMC ~ 70 units) – Up to 1 Gpc! – Adopt 500 Mpc - first detection ionized IGM! – 1040 ergs in radio required!

  • Event rate (1/20 days/5 sq deg)

– Could be SNe, GRB or ns+ns coalescence – Also Hyperflares on Magnetars? – 100s per day and still invisible

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SLIDE 18

Worrying bits

  • 100x detection threshold

– Might expect power law distribution – More distant events fainter – Different orientations fainter too?

  • Proximity to SMC

– Only place people have looked!

  • Re-processing in progress…
  • Swinburne Surveys
  • SMC/LMC Surveys
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SLIDE 19

If we find more

  • Great synergy with other wavebands
  • Sub-arcsec position from VLBI

– “Host Galaxy” Redshift Determination – Integrated baryonic content of Universe

  • ~100% ionised
  • Many VLBI events

– Baryonic density of the Universe(Z)

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SLIDE 20

A dedicated search

  • Green Bank Extragalactic Radio Transient

Experiment (GERTIE)

– 3x 85’ telescopes (3 square degree coverage)