results of automatic, high time resolution grb follow-up with t he parkes 12 m

Results of automatic, high time resolution GRB follow-up with the Parkes 12 m

Keith Bannisterk.bannister@physics.usyd.edu.auSydney Institute for Astronomy (SIfA) University of SydneyCSIRO Astronomy and Space ScienceCAASTRO

Supervised By:Tara Murphy (USyd)Bryan Gaensler (USyd)Tim Cornwell (CASS)

Thanks To:CASS: John Reynolds , Chris Phillips, Sarah Burke-Spolaor, Mike Keith

Swinburne: Willem van Straten, Andrew Jameson,Matthew Bailes

HTRU Team

Gamma ray bursts

Long GRB (>2s) Collapse of massive star, orShort GRB (< 2s) Binary merger ?

Gamma rays

Gamma Ray Coordinate

Network (GCN)

CoordinatesParkes 12m

Internet

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Robotic follow-up

› Automatically slew the 12m to the GRB coordinate

› On source within 2 minutes

› 1.4 GHz, 250 MHz bandwidth

› 64us time resolution, 600 channels

› Searched for:

- Single pulses

- Repeating pulses (e.g. pulsars)

- Long time scale (>1s) variation

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Bucket Feed

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Installation

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Results

› Responded to 15 GCN events

› 9 GRBs

- Remainder where X-ray binaries or instrumental effects

› Two single pulse detections

› One repeating candidate

- probable high latitude pulsar

› Nothing in long time resolution

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Single pulse detection

6.6 σ pulse (~7 Jy), 25 ms wide, 524s after GRB 101011A

GRB 101011A

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Single pulse detection

6.2 σ pulse (~7 Jy), 6 ms wide, 1076 s after GRB 100704A

GRB 100704A

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Correspondence with X-ray break

GRB 101011A

Correspondence with X-ray break - 2

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Rates

› 2/9 GRBs have a single pulse detection

› 2/7 long GRBs have a single pulse detection

› Blind rate = 3.5 x 105 sky-1 day-1 at ~7 Jy

› GRB rate (2 sky-1 day-1) is compatible with ATA fly’s eye result (Simeon et. al. 2011) of < 24 sky-1 day-1at ~44 Jy

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Are they real?

› Could it be random chance?- Statistical argument rules out

with > 99.8% confidence- Null test rules out random pulse

with 99% confidence

› Rate incompatible with chance detection of all other known astrophysical sources

› 20% chance of random event falling on X-ray break

› Equipment bug› Just an unlucky bit of RFI junksbronews.com

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Conclusions

› Good things can be done with a small telescope

› Typically on source within 2 minutes

› Possible high latitude pulsar detected serendipitously

› Next: confirm with coincidence or interferometer experiment

Delayed GRB radio pulses› Delayed formation of a

black hole after magnetar spindown?

› Applications: - direct detection of the

intergalactic medium,

- distinguishing between reionisation models

- GRB physics

A shameless plug

Two new techniques for antenna-coherent detection of dispersed radio pulses:

The Chirpolator & The Chimageator

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2011 ApJS,196 16B

Chirpolator: de-disperse thyself

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y(t)=x1(t) x2*(t)

time

frequency

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Δf = ˙ f Δty(t)

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f = ˙ f ΔtFFT(y(t))

frequency

Y(f)time

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Δt€

˙ f

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Δf = ˙ f Δt

x1(t)B

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x2(t)

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x1(t) = exp( jπ˙ f t 2)

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x2(t) = exp( jπ˙ f (t − Δt)2)

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y(t) = x1(t)x2*(t) = exp( jπ˙ f (2tΔt − (Δt)2))

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Y ( f ) = D( f − Δf )Φ(Δf )

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Computational Costs

Pre integrator Post integrator

Data Rates

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