A bright millisecond
radio burst of Extragalactic
originDuncan Lorimer, Matthew Bailes, Maura McLaughlin, David Narkevic and Froney
CrawfordScience (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
€
DM = ne0
D
∫ dl
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
MB Survey
Swinburne Surveys
Swinburne Surveys
BurgaySurvey
BurgaySurvey
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-3pc!
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 = 5msυ
1400 MHz
⎛
⎝ ⎜
⎞
⎠ ⎟−4.8
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!
– 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
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)