Difference: GCNCIRCULAR21559 ( vs. 1)

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

We observed 54 candidate host galaxies in the LIGO/Virgo G298048 localisation volume with the Australia Telescope Compact Array (LVC GCN 21513, sky map; LVC GCN 21519, 54 nearby galaxies). Observations started at 2017-08-18 01:00 UT and ended at 2017-08-18 09:14:15 UT with approximately 1-2 minutes of on-source time for each target.

We detect an unresolved radio source coincident with NGC 4993. The best-measured position was at 8.5 GHz:

RA = 13:09:47.7
Dec = -23:22:59.1

(J2000) with positional errors of 1” in RA and 4” in declination.

This position is in agreement with the VLA detection of a radio source (Alexander et al. LVC GCN 21548) within the stated errors of each observation.

We report preliminary flux densities of:

~0.6 mJy at 8.5 GHz

~0.5 mJy at 10.5 GHz

~0.4 mJy at 16.7 GHz

~0.4 mJy at 21.2 GHz

We find no evidence for any radio emission at the position of the optical transient (Coulter et al. LVC GCN 21529).

Analysis of the full dataset is underway. Subsequent epochs are planned.

Thank you to CSIRO staff for supporting these observations.

-- Keith Bannister

-- ShaonGhosh - 18 Aug 2017