TITLE: GCN CIRCULAR NUMBER: 22172 SUBJECT: LIGO/Virgo G299232: LOFAR follow-up DATE: 17/11/28 10:02:14 GMT FROM: Antonia Rowlinson at U van Amsterdam J.W. Broderick (ASTRON), K. Gourdji (UvA), 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), A. Shulevski (ASTRON) report on behalf of the LOFAR Transients Key Science Project From 2017 November 18-26, we observed a large fraction of the localisation region of the Advanced LIGO/Virgo trigger G299232 (LVC, GCN 21693) 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 225 min using a number of separate 25-min snapshots. The beam centres are given below (RA and Dec in degrees); the Bayestar-HLV localisation was used as a basis for calculating the coordinates of the beams. The setup is identical to the previous sets of LOFAR follow-up observations described in Broderick et al., GCN 21809 and GCN 21962. Two beams in separate pointings were centred on the IceCube neutrino candidate at RA = 28.2 deg, Dec = 44.8 deg (Bartos et al., GCN 21694; Bartos et al., GCN 21698). Furthermore, one beam was centred on the optical transient discovered by Swift/UVOT at RA = 25.035625 deg, Dec = 34.567667 deg (Emery et al., GCN 21733). Analysis is ongoing. We thank the ASTRON Radio Observatory for scheduling the observations. Pointing 1 (integration time 225 min over the period 2017-11-18 18:11 UTC - 2017-11-19 01:32 UTC) 1) 34.039151 46.299866 2) 35.248501 48.949799 3) 28.200000 44.800000 4) 31.322127 48.348415 5) 36.756176 44.251317 6) 37.965526 46.901250 Pointing 2 (integration time 225 min over the period 2017-11-18 18:37 UTC - 2017-11-19 01:58 UTC) 1) 35.780064 51.725205 2) 36.750925 54.437875 3) 31.502071 50.889684 4) 32.472933 53.602354 5) 39.087195 49.848056 6) 40.058057 52.560726 Pointing 3 (integration time 225 min over the period 2017-11-20 18:11 UTC - 2017-11-21 01:32 UTC) 1) 29.306644 35.778068 2) 30.478008 38.389034 3) 25.035625 34.567667 4) 27.105198 37.906547 5) 31.508089 33.649589 6) 32.679454 36.260555 Pointing 4 (integration time 225 min over the period 2017-11-20 18:37 UTC - 2017-11-21 01:58 UTC) 1) 31.825000 41.000000 2) 33.084178 43.610966 3) 28.199341 40.517513 4) 28.200000 44.800000 5) 34.191481 38.871521 6) 35.450659 41.482487 Pointing 5 (integration time 225 min over the period 2017-11-24 18:11 UTC - 2017-11-25 01:32 UTC) 1) 41.738945 68.095823 2) 43.350996 70.808493 3) 34.635623 67.260303 4) 36.247674 69.972972 5) 47.230217 66.218674 6) 48.842268 68.931344 Pointing 6 (integration time 225 min over the period 2017-11-24 18:37 UTC - 2017-11-25 01:58 UTC) 1) 44.937500 79.572222 2) 44.267884 76.796335 3) 31.320689 78.289239 4) 31.990306 81.065126 5) 57.884694 78.079318 6) 58.554311 80.855205 Pointing 7 (integration time 225 min over the period 2017-11-25 18:11 UTC - 2017-11-26 01:32 UTC) 1) 37.337896 57.197845 2) 38.228521 59.934164 3) 32.518303 56.247531 4) 33.408928 58.983851 5) 41.266865 55.411839 6) 42.157490 58.148159 Pointing 8 (integration time 225 min over the period 2017-11-25 18:37 UTC - 2017-11-26 01:58 UTC) 1) 39.119146 62.670484 2) 40.170071 65.406804 3) 33.432096 61.720170 4) 34.483021 64.456490 5) 43.755272 60.884478 6) 44.806196 63.620798