GCN Circular 18457

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

On Oct 23, 2015, starting at 11:01 (UTC), we observed a large fraction
of the localization error range of the Advanced LIGO trigger G194575
with the ILT (International Low-Frequency Array [LOFAR] Telescope) as
part of a test observation. Due to the low elevation and proximity to the
Sun of these observations, we note that LOFAR will not be at optimal
performance. The quality of these observations will determine the
feasibility of further LOFAR follow-up of Advanced LIGO trigger
G194575.

The observations were obtained with the High-Band Antennas (HBA) at a
centre frequency of 145 MHz (bandwidth 7.8 MHz). In this configuration,
the ILT can provide 8 simultaneous beams on the sky, where each beam
has a field of view of approximately 12 deg^2 (beam FWHM 3.9 degrees).
The beam centres are given below:

1) 204.648425	-4.457881 13:38:35.62 -04:27:28.4
2) 207.424367	-4.457881 13:49:41.85 -04:27:28.4
3) 201.872483	-4.457881 13:27:29.40 -04:27:28.4
4) 206.036396	-2.053845 13:44:08.74 -02:03:13.8
5) 203.260454	-2.053845 13:33:02.51 -02:03:13.8
6) 206.036396	-6.861917 13:44:08.74 -06:51:42.9
7) 203.260454	-6.861917 13:33:02.51 -06:51:42.9
8) 196.154938	-15.286953 13:04:37.19 -15:17:13.0

The observations cover roughly 50 square degrees in total.  Each field
was observed for a total of 0.5 hr with 10s time resolution after
pre-processing. Analysis is ongoing.