GCN Circular 21676

J.W. Broderick (ASTRON), A. Rowlinson (UvA, ASTRON), P.G. Jonker (SRON, RU), R.P. Fender (Oxford), R.A.M.J. Wijers (UvA), B.W. Stappers (Manchester), S. ter Veen (ASTRON), S. Nissanke (RU) and A. Shulevski (ASTRON) report on behalf of the LOFAR Transients Key Science Project

On 2017 August 22, we conducted a LOFAR follow-up observation of the Advanced LIGO/Virgo trigger G298048 with the ILT (International Low-Frequency Array [LOFAR] Telescope). This is a highly experimental observation to assess whether images of sufficient quality can be obtained at very low elevations. The observation began at 14:05:00 UTC, near transit, with any useable data likely only within the first hour. We placed two beams on the most northerly part of the probability distribution, as determined from the preliminary LALInference map. The bandwidth for each beam is 47.5 MHz, spread over the frequency range 120-187 MHz. The beam centres (RA/Dec), in degrees, are as follows:

1) 192.4167   -15.8333
2) 193.1875   -17.0000

where the field of view per beam is 11.35 deg^2 at 150 MHz. Analysis is ongoing, with the possibility of further observations if this test run is deemed to have been successful.  
  
We thank the ASTRON Radio Observatory for rapidly scheduling the observations.