GCN Circular 21725

A. Rowlinson (UvA, ASTRON), J.W. Broderick (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 25, we conducted a LOFAR follow-up observation of the
Advanced LIGO/Virgo trigger G299232 with the ILT (International
Low-Frequency Array [LOFAR] Telescope). The observation began at
14:47:31 UTC. The observations were obtained with the high-band
antennas (HBA) at a centre frequency of 145 MHz (bandwidth 11.9
MHz). We used 8 simultaneous beams on the sky, where each beam has a
field of view of approximately 12 deg^2 (beam FWHM 3.9 deg at 150
MHz). The observations cover roughly 50 deg^2 in total at optimum
sensitivity. Each field was observed in both imaging and beamformed
modes for a total of 120 min.

The beam centres (RA/Dec), in degrees, are as follows:

1) 27.8625 50.4931
2) 30.6384 50.4931
3) 25.0866 50.4931
4) 29.2505 52.8971
5) 26.4745 52.8971
6) 29.2505 48.0890
7) 26.4745 48.0890
8) 28.6250 57.4389

Analysis is ongoing.

We thank the ASTRON Radio Observatory for rapidly scheduling the
observations.