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Eight-meter-wavelength Transient Array (ETA) Project Update. Steve Ellingson (on behalf of the Virginia Tech ETA Group) Low Frequency Software Workshop – Chicago – Aug 10, 2008. ETA Science. Single dispersed pulses , including:

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Eight meter wavelength transient array eta project update

Eight-meter-wavelength Transient Array (ETA) Project Update

Steve Ellingson (on behalf of the Virginia Tech ETA Group)Low Frequency Software Workshop – Chicago – Aug 10, 2008


ETA Science

  • Single dispersed pulses, including:

  • Exploding primordial black holes (PBHs): detection and/or improved limits (27 hours so far)

  • GRB prompt emission: GCN-triggered search; detection and limits for both pulse- and maser-type emission (7 usable trigger events so far)

  • Pulsars in 29-47 MHz:

    • Crab Giant Pulses (22 h so far, 3 probable detections in 7 h processed)

    • Periodic emission of strong pulsars below turnover.

      • Requires roughly 10x collecting area to do well … ETA-2, ultimately LWA-1)

  • 10-100 pc/cm3 “source agnostic” search

    • PBH phase transition revealing scale of extra dimension(s): astro-ph/0801.4023

    • “Sparks” from cosmic strings

    • LIGO associations

    • Other exotica


RF

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A/D-RX

Node

A/D-RX

A/D-RX

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A/D-RX

A/D-RX

Node

A/D-RX

A/D-RX

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PC

Node

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A/D-RX

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PC

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Node

Instrument

  • 35°12’ N, 82°52’ W (remote mountainous region in Western NC, USA)

  • 12 dual-polarization active dipoles, Galactic noise-limited over 29-47 MHz

4-Node

PC Cluster

w/ 400 GB x 4

LTO3 Array

(Continuous recording to disk for up to 2 hours)

“Reconfigurable

Computing

Cluster” (RCC)

(16 Xilinx XC2VP30s)

Dipole Array

3.125 Gb/s Serial Interconnect Matrix

Output is 8 streams of beams or dipoles in any combination

Long

Coax

I-Q

(12 Altera EP1S25s)

“Active

Baluns”

“ARXs”

ETA-2 replaces each dipole with a 4 element array (10x increase in collecting area)

120 MSPS x 12b direct sampling

3.75 MHz processed bandwidth (7.5 MSPS 7b+7b)


Active Balun

Analog Receiver (ARX)

A/D-RX (Altera EP1S25) Cluster

RCC (Xilinx XC2VP30) Cluster

PC Cluster & Tape Drive Array


Crab giant pulse experiment
Crab Giant Pulse Experiment

22.1 hours collected;

Roughly ~½ of data is usable

3 pulses of ~1 kJy (4-6 s) / ~7 h so far. (38 MHz x 3.75 MHz)

Plan to repeat over 27 - 49 MHz.

(LWA-1 will be able to do this up to about 80 MHz)

ETA

Freq

Range

Bhat et al. (2007), ApJ, 665, 618.


Exploding Primordial Black Holes

  • Formed in very early universe, evaporation, explosive self-annihilation expected in current epoch (Hawking 1974).

  • Compelling argument for very strong pulse emission below 1 GHz (Rees 1977, Blandford 1977)

  • Observing frequency & collecting area select range of observable fireball Lorentz factor gf.

  • Previous searches:

    • Phinney & Taylor 1979, 430 MHz (Sensitive to gf > 105), 2 x 10-9 pc3 yr-1

    • Benz & Paesold 1998, 40-1000 MHz (Sensitive to gf > 104), 5 x 10-3 pc3 yr-1

  • ETA is sensitive to PBH explosions with 104.4 > gf > 106 over kpc distances and can efficiently improve on existing rates, owing to the very large FOV


ETA PBH Search Status

  • Methodology:

    • 1 hour acquisition at same local sidereal time each night.

    • Search over DM and pulse duration.

  • Status:

    • 27.2 hours collected, preliminary examination of first 3 hours

    • For 104.4 we have improved limits by orders of magnitude already

    • For 105 we start improving on existing limits after about 1000 hours

gf = 106.0

gf = 104.4


Project Past, Present, Future

  • Aug 2005: Start

  • Apr 2006: First array streaming acquisition

  • Jul 2006: Lightning strike destroys front end electronics; rebuilding

  • Sep 2006: Positive detection of periodic emission from B0950+08

  • Feb 2007: First (probable) Crab GP detection

  • Mar 2008: System control computer “zapped”

  • July 2008: Decommissioning of PARI site (except antennas)

  • Currently buried in data! (over 16 TB; 67 hours of observations)

  • Restarted data reduction to account for antenna/cable dispersion, site multipath; improved RFI mitigation

  • 2nd (mobile) system, being developed

  • 1st system being refurbished

  • Anticoincidence

  • New antenna system; 10x increase in collecting area

    using same electronics, albeit with FOV penalty


VT ETA Group:

Steve Ellingson EE

John Simonetti Phys

Cameron Patterson CpE

Zack Boor Phys

Sean Cutchins Phys

Kshitija Deshpande EE

Mahmud Harun EE

Mike Kavic Phys

Anthony Lee EE

Kyehun Lee EE

Brian Martin CpE

Wyatt Taylor EE

Vivek Venugopal CpE

Pisgah Astronomical Research Institute

Supported by:

AST-

0504677

http://www.ece.vt.edu/swe/eta


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