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

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 • Pulsar Surveys • RRATs • Giant Pulses • LMC/SMC Pulsar Survey • An enormous pulse • Location • Potential • Future directions

Pulse Dispersion D ∫ DM = n e dl 0

Standard pulsar search

Single pulse search

The RRATs • McLaughlin et al. (2006) – Discovered repeating impulsive bursts at the same DM – Gap ~4->120 minutes

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

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

Pulsar Surveys with Parkes Swinburne Surveys Burgay Burgay MB Survey Survey Survey Swinburne Surveys SMC/LMC surveys

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 -3 pc!

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) − 4.8 ⎛ ⎞ υ W = 5ms ⎜ ⎟ ⎝ ⎠ 1400 MHz

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

Where? x X x

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)!!

If it is a PSR or RRAT • Should repeat • Original pulse 100x detection threshold! • 40 hours of follow-up @ 20cm • Nothing!

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! – 10 40 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

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

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)

A dedicated search • Green Bank Extragalactic Radio Transient Experiment (GERTIE) – 3x 85’ telescopes (3 square degree coverage)