P. Clark (QUB), O. McBrien (QUB), D. Malesani (DAWN, DARK), P. D'Avanzo (INAF-OAB), E. Kankare (QUB),
M. T. Botticella (INAF Capodimonte), K. Maguire (QUB), M. Dennefeld (IAP, Paris), C. Inserra (Southampton),
S. J. Smartt (QUB), O. Yaron (Weizmann), D. R. Young (QUB), I. Manulis (Weizmann) report:
We observed the field of GRB 180504A (Lien et al., GCN Circ. 22682) under the extended Public ESO Spectroscopic
Survey for Transient Objects (ePESSTO; see Smartt et al. 2015, A&A, 579, 40 http://www.pessto.org <http://www.pessto.org/> ). The observations
were performed on the ESO New Technology Telescope at La Silla with the SofI instrument in imaging mode starting from
2018-05-05 at 08:37:49 UT (i.e. about 12.9 hours from the burst) and consisted of 15 images obtained with the J filter,
each one lasting 90s.
The afterglow candidate reported by Malesani et al. (GCN Circ. 22684) is clearly detected. From preliminary photometry,
we estimate a magnitude of J ~ 21.3 (Vega, calibrated against the 2MASS catalogue).