GCN Circular 21355

A. Rowlinson (UvA, ASTRON), J.W. Broderick (ASTRON), A.J. Stewart
(Oxford), 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), A. Shulevski (ASTRON) report on behalf
of the LOFAR Transients Key Science project

From 2017 May 29 - June 2, we observed a large fraction of the
localization error range of the Advanced LIGO trigger G275697 with the
ILT (International Low-Frequency Array [LOFAR] Telescope). The
observations were obtained with the high-band antennas (HBA) at a
centre frequency of 145 MHz (bandwidth 15.8 MHz). We used 6
simultaneous beams on the sky, where each beam has a field of view of
approximately 12 deg^2 (beam FWHM 3.9 deg). The observations cover
roughly 300 deg^2 in total at optimum sensitivity. Each field was
observed for a total of up to 225 min using a number of separate 25
min snapshots.

The beam centres are given below (RA & Dec in degrees); analysis is
ongoing.

Pointing 1
(integration time 225 min over the period 2017-05-29 01:11-08:32 UTC)

1) 333.611809    51.066434
2) 336.179366    53.328480
3) 329.210699    51.332745
4) 331.778257    53.594791
5) 335.445360    48.538078
6) 338.012918    50.800124

Pointing 2
(integration time 225 min over the period 2017-05-29 01:37-08:58 UTC)

1) 8.225000    67.934722
2) 15.175293   68.885036
3) 2.559069    69.720728
4) 9.509362    70.671042
5) 6.940638    65.198402
6) 13.890931   66.148716

Pointing 3
(integration time 225 min over the period 2017-05-30 01:11-08:32 UTC)

1) 325.025000    41.804167
2) 326.746137    44.268755
3) 321.301114    41.682969
4) 323.022251    44.147557
5) 327.027749    39.460777
6) 328.748886    41.925365

Pointing 4
(integration time 225 min over the period 2017-05-30 01:37-08:58 UTC)

1) 328.920158    46.542342
2) 331.030859    48.911430
3) 324.881912    46.615076
4) 326.992613    48.984164
5) 330.847703    44.100521
6) 332.958404    46.469609

Pointing 5
(integration time 225 min over the period 2017-06-01 00:11-07:32 UTC)

1) 319.219737    31.633699
2) 320.468591    34.200728
3) 315.984241    31.271028
4) 317.233096    33.838057
5) 321.206377    29.429341
6) 322.455232    31.996370

Pointing 6
(integration time 225 min over the period 2017-06-01 00:37-07:58 UTC)

1) 321.874437    36.767756
2) 323.340302    39.285962
3) 318.419103    36.525591
4) 319.884968    39.043797
5) 323.863905    34.491716
6) 325.329771    37.009921

Pointing 7
(integration time 225 min over the period 2017-06-02 00:11-07:32 UTC)

1) 314.137598    21.441764
2) 315.303983    23.999416
3) 311.174714    21.103147
4) 312.341099    23.660799
5) 315.934097    19.222730
6) 317.100481    21.780382

Pointing 8
(integration time 225 min over the period 2017-06-02 00:37-07:58 UTC)

1) 316.565036    26.557069
2) 317.828472    29.095384
3) 313.475776    26.266633
4) 314.739212    28.804948
5) 318.390860    24.309189
6) 319.654296    26.847504