TITLE:   GCN CIRCULAR
NUMBER:  33834
SUBJECT: LIGO/Virgo/KAGRA S230518h: ATCA follow-up of candidate counterparts
DATE:    23/05/20 14:56:35 GMT
FROM:    Dougal Dobie at VAST <ddobie94@gmail.com>

D. Dobie (Swinburne/OzGrav), A. Gulati (USyd/OzGrav), T. Murphy
(USyd/OzGrav)
and the JAGWAR collaboration.

We have conducted observations of the three candidate optical counterparts
to
S230518h (GCN 33829) and the X-ray source S230518h_X8 (GCN 33824) with the
Australia Telescope Compact Array.

Observations were carried out on 2023-05-20 between 02:40 and 13:30 UTC
with 2x2048 MHz bands centered on 5.5 and 9 GHz. The array is currently in
the compact EW352 configuration and hence we discarded all data from CA06,
resulting in a FWHM angular resolution of approximately 30" and 20" at
5.5 GHz and 9 GHz respectively.

We detect no radio emission at the location of the optical candidates
with the following preliminary 3-sigma upper limits:

|      Source | 5.5 GHz (uJy) | 9 GHz (uJy) |
|      SSS23a |           <90 |         <50 |
|      SSS23b |          <120 |         <90 |
|      SSS23c |          <120 |         <60 |

We detect a radio source consistent with the position of S230518h_X8 with
preliminary flux densities of ~350 uJy and ~500 uJy at 5.5 GHz and 9 GHz.
This source was also detected by the Rapid ASKAP Continuum Survey in
observations on 2019-08-03, suggesting it is unrelated to S230518h.

Thank you to CSIRO staff for supporting these observations.