4 PI SKY goes hunting for more transients

This week, members from the 4 PI SKY team visited the AMI telescope in Cambridge, UK, in search of even more transients.

Members of the 4 PI SKY team visiting the AMI teelscope

Members of the 4 PI SKY team visiting the AMI telescope. Shown (from left to right): Clare Rumsey, Richard Saunders, Anthony Rushton, Tim Staley, Kunal Mooley, Rob Fender and Richard Armstrong.

The Universities of Oxford and Cambridge already have a very succesful partnership of following up astronomical transients at 15 GHz using the AMI large array. Gamma-ray alerts from the Swift-BAT space telescope robotically send messages back to earth-based servers, which in-turn automatically command AMI to slew to transient location in the sky (effectively eliminating the need of human intervention). However, when the array isn’t chasing high-energy explosions it spends a significant amount of time surveying galaxy clusters looking for Sunyaev-Zel’dovich (SZ) effects.

AMI recently completed the Tenth Cambridge Survey (10C; AMI Consortium: Davies et al. 2011; AMI Consortium: Franzen et al. 2011) at 15.7 GHz creating the deepest high-frequency (10 GHz) radio survey, complete to 1mJy in 10 different fields covering a total of≈27 deg^2. These data could contain radio transients that haven’t previously been found at other wavelengths and it is our goal to search the entire archive for historic events.

AMI-SA correlator

A new correlator that will power high-spectral resolution observations with AMI

In the mean-time, the AMI telescope is undergoing a major upgrade to the correlator. The original correlator was a lag-based system, which suffered from large errors in correlator lag spacing  and was prone to man-made radio frequency interferences (RFI) particularly at low declinations due to geostationary satellites.

The new AMI Digital Correlator (AMIDC), pictured right, will have a highly channelized digital correlator system giving more flexibility within the radio band and a much more uniform response across it, which would provide the potential to avoid or mitigate to a large extent many of the problems with the current system. This will significantly improve the sensitivity of the array.

Ultimately, we would like to use the new system to detect radio transients in near real-time and produce rapid VOEvent alerts that can help coordinate follow-up observations.