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 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) pc/cm 3 “source agnostic” search –PBH phase transition revealing scale of extra dimension(s): astro-ph/ –“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 MHz Instrument PC Node A/D-RX RF Dipole Array AB x2 Node Gb/s Serial Interconnect Matrix Long Coax “Reconfigurable Computing Cluster” (RCC) (16 Xilinx XC2VP30s) 4-Node PC Cluster w/ 400 GB x 4 LTO3 Array (Continuous recording to disk for up to 2 hours) 120 MSPS x 12b direct sampling 3.75 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) Cluster PC Cluster & Tape Drive Array

Crab Giant Pulse Experiment Bhat et al. (2007), ApJ, 665, 618. ETA Freq 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 MHz. (LWA-1 will be able to do this up to about 80 MHz)

Exploding Primordial Black Holes l Formed in very early universe, evaporation, explosive self-annihilation expected in current epoch (Hawking 1974). l 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. l Previous searches: –Phinney & Taylor 1979, 430 MHz (Sensitive to  f > 10 5 ), 2 x pc 3 yr -1 –Benz & Paesold 1998, MHz (Sensitive to  f > 10 4 ), 5 x pc 3 yr -1 ETA is sensitive to PBH explosions with >  f > 10 6 over kpc distances and can efficiently improve on existing rates, owing to the very large FOV

ETA PBH Search Status l Methodology: –1 hour acquisition at same local sidereal time each night. –Search over DM and pulse duration. l Status: –27.2 hours collected, preliminary examination of first 3 hours –For we have improved limits by orders of magnitude already –For 10 5 we start improving on existing limits after about 1000 hours  f =  f =

l Aug 2005: Start l Apr 2006: First array streaming acquisition l Jul 2006: Lightning strike destroys front end electronics; rebuilding l Sep 2006: Positive detection of periodic emission from B l Feb 2007: First (probable) Crab GP detection l Mar 2008: System control computer “zapped” l July 2008: Decommissioning of PARI site (except antennas) l Currently buried in data! (over 16 TB; 67 hours of observations) l Restarted data reduction to account for antenna/cable dispersion, site multipath; improved RFI mitigation l 2 nd (mobile) system, being developed l 1 st system being refurbished l Anticoincidence l New antenna system; 10x increase in collecting area using same electronics, albeit with FOV penalty Project Past, Present, Future

VT ETA Group: Steve EllingsonEE John Simonetti Phys Cameron Patterson CpE Zack Boor Phys Sean Cutchins Phys Kshitija DeshpandeEE Mahmud HarunEE Mike KavicPhys Anthony LeeEE Kyehun LeeEE Brian MartinCpE Wyatt Taylor EE Vivek VenugopalCpE Pisgah Astronomical Research Institute AST Supported by: