GCN Circular 30432
P. D'Avanzo (INAF-OAB), V. D'Elia (ASI-SSDC), S. Campana (INAF-OAB), M. De Pasquale (Istanbul Univ.), A. Melandri (INAF-OAB), A. Rossi (INAF-OAS), R. Salvaterra (INAF-IASF Mi), G. Tagliaferri (INAF-OAB), M. Cecconi, A. Garcia de Gurtubai Escudero (INAF-TNG) on behalf of the CIBO collaboration report: We carried out further observations of the optical afterglow of GRB 210704A (Kim et al. GCN Circ. 30384; D'Avanzo et al. GCN Circ. 30385) with the Italian 3.6m TNG telescope equipped with the optical camera DOLORES. A series of images were obtained with the i-sdss and r-sdss filters on 2021-07-08 from 21:22:44 UT to 22:36:58 UT (i.e. about 4.1 days after the burst) under non optimal seeing conditions (2"). A faint source, possibly extended, is detected at the optical afterglow position. With preliminary photometry we derive the following magnitudes: r = 23.35 +/- 0.16 i = 23.39 +/- 0.14 (AB; calibrated against the SDSS catalogue). Because of the seeing conditions and the source faintness we cannot definitely confirm if the source is extended or point-like. Further deep optical observations are encouraged to monitor the light curve evolution and to check if there is any contribution from an underlying host galaxy.