K. P. Mooley (Hintze Fellow, Oxford), T. D. Staley, R. P. Fender
(Oxford), G. E. Anderson (Curtin), T. Cantwell (Manchester), D.
Titterington, S. H. Carey, J. Hickish, Y. C. Perrott, N. Razavi-Ghods,
P. Scott (Cambridge), K. Grainge, A. Scaife (Manchester)
The AMI Large Array robotically triggered on the Swift alert for the
short GRB 170728B (Cenko et al., GCN 21371) as part of the 4pisky
program, and subsequent follow up observations were obtained up to 3
days post-burst. Our observations at 15 GHz on 2017 Jul 29.00, Jul
29.80, Jul 30.80 and Jul 31.76 (UT) do not reveal any radio source at
the XRT location (Osborne et al., GCN 21377), with 3sigma upper limits
of 258 uJy, 201 uJy, 171 uJy and 108 uJy respectively. This upper limit
is consistent with the radio afterglow detection on 2017 Jul 29.81
reported by Fong et al. (GCN 21395; much fainter than 300 uJy at 6 GHz).
We thank the AMI staff for scheduling these observations. The AMI-GRB
database is a log of all GRB follow up observations with the AMI, and is
available at http://4pisky.org/ami-grb/.