Difference: GCNCIRCULAR21625 ( vs. 1)

D. Dobie (University of Sydney), A. Hotan (CSIRO), K. Bannister (CSIRO), D. Kaplan (UWM), T. Murphy (University of Sydney), C. Lynch (University of Sydney), on behalf of the ASKAP/VAST collaboration.

We are observing the LIGO localisation region (LVC GCN 21513) with the Australian Square Kilometre Array Pathfinder (ASKAP) at a central frequency of 1345 MHz with a bandwidth of 192 MHz. As the array is still undergoing commissioning, we are using a nominal 12 (of 36) antennas, although other site activities may cause that number to vary from one observation to the next.

Our observing strategy consists of 3 pointings containing approximately 90% of the LIGO localisation region. Each pointing consists of a 5.5 x 5.5 degree square grid of 36 beams, though the exact number captured may also vary. The first pointing is centered at

RA = 13:09:21.60
Dec = -25:00:00.00

and contains ~48% of the localisation region and the positions of 35 target galaxies (Cook et al. LVC GCN 21519) including NGC 4993, the host of the possible optical counterpart SSS17a (Coulter et al. LVC GCN 21529). Observations began at 2017-08-19 05:34:32 (UT) and are ongoing.

Processing and analysis of the first pointing is underway.

Thank you to CSIRO staff for supporting these observations.

-- ThomasKupfer - 21 Aug 2017