TITLE:   GCN CIRCULAR
NUMBER:  23467
SUBJECT: GRB 181123B: ATCA 5/9 GHz rapid-response radio observation
DATE:    18/11/28 01:16:17 GMT
FROM:    Gemma Anderson at Curtin U  <gemma.anderson@curtin.edu.au>

G. E. Anderson (Curtin), M. E. Bell (UTS), J. Stevens (CASS), P. J. Hancock (Curtin),
J. C. A. Miller-Jones (Curtin), A. Bahramian (Curtin), K. W. Bannister (CASS),
A. J, van der Horst (GWU), S. D. Ryder (Macquarie), J-P. Macquart (Curtin),
R. M. Plotkin (Curtin), A. Rowlinson (UvA)

We used the Australia Telescope Compact Array (ATCA) rapid-response mode
to perform a triggered radio observation of the short GRB 181123B. The ATCA
responded to the Swift-BAT detection (Lien et al., GCN 23432), automatically
scheduling observations to begin on 2018 Nov 23.753 UT for 8.5 hours
(12.5 hours post-burst), when the GRB had risen above the horizon. No radio
source was detected at the XRT/optical position (Evans et al., GCN 23433,
Fong et al., GCN 23439), with 3 sigma upper-limits of 66 microJy and 69 microJy
at 5 and 9 GHz, respectively.

We thank the ATCA and CSIRO Astronomy and Space Science (CASS) staff for
supporting this new mode of operation.