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

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

ETA Science

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

Instrument

PC

PC

PC

PC

Node

Node

Node

Node

A/D-RX

A/D-RX

A/D-RX

A/D-RX

A/D-RX

A/D-RX

A/D-RX

A/D-RX

A/D-RX

A/D-RX

A/D-RX

A/D-RX

RF

RF

RF

RF

RF

RF

RF

RF

RF

RF

RF

RF

Dip

ole

Arr

ay

AB x2

AB x2

AB x2

AB x2

AB x2

AB x2

AB x2

AB x2

AB x2

AB x2

AB x2

AB x2

Node

Node

Node

Node

Node

Node

Node

Node

Node

Node

Node

Node

3.12

5 G

b/s

Ser

ial

Inte

rco

nn

ect

Mat

rix

LongCoax

“Reconfigurable Computing Cluster” (RCC)(16 Xilinx XC2VP30s)

4-NodePC Clusterw/ 400 GB x 4LTO3 Array(Continuous recording to disk for up to 2 hours)

120 MSPS x 12b direct sampling3.75 MHz processed bandwidth (7.5 MSPS 7b+7b)

Output is 8 streams of beams or dipoles in any combination

(12 Altera EP1S25s)

I-Q

“ARXs”“Active Baluns”

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

Active Balun Analog Receiver (ARX)

A/D-RX (Altera EP1S25) Cluster

RCC (Xilinx XC2VP30) ClusterPC Cluster & Tape Drive Array

Crab Giant Pulse Experiment

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

ETAFreq

Range

22.1 hours collected;

Roughly ~½ of data is usable

3 pulses of ~1 kJy (4-6 ) / ~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)

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 f.

Previous searches:

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

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

ETA is sensitive to PBH explosions with 104.4 > f > 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

f = 104.4

f = 106.0

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

Project Past, Present, Future

VT ETA Group:

Steve Ellingson EEJohn Simonetti PhysCameron Patterson CpE

Zack Boor PhysSean Cutchins PhysKshitija Deshpande EEMahmud Harun EEMike Kavic PhysAnthony Lee EEKyehun Lee EEBrian Martin CpEWyatt Taylor EEVivek Venugopal CpE

Pisgah Astronomical Research Institute

AST-0504677

Supported by:

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