TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3673 SUBJECT: GRB 050724: optical and near-IR observations DATE: 05/07/25 02:38:16 GMT FROM: Javier Gorosabel at LAEFF-INTA, Madrid A.J. Castro-Tirado, J. Gorosabel, A. de Ugarte Postigo, S. Guziy and M. Jelínek (IAA-CSIC), M. Karrer (Obs. de Geneve), H.-J. Roeser (MPI Heidelberg), N. Elías-Rosa (Obs. Astr. di Padova), O. Bogdanov (Nikolaev State Univ.) and A. Aguirre (CAHA Almería) report: "We have imaged a 6' x 6' region centred on the SWIFT/BAT error box for the short/hard GRB 050724 (Covino et al. GCNC 3665) with the 1.2-m Mercator telescope (+ Merope) at the Observatorio del Roque de los Muchachos on La Palma starting on July 24.890 UT (i.e. 8.8 hours after the GRB) under good meteorological conditions. Within the refined SWIFT/XRT position (Romano et al. GCNC 3669), the co-added R-band image (5400 s exposure time) shows a source close to the center of the 6.3 arcsec radius error box, labelled as A by Bloom et al. (GCN Circ. 3672). Coordinates yield: RA(2000) = 16 24 44.96, Dec(2000) = -27 32 23.6 (+/- 0.5"). We measure R = 22.40 +/- 0.13 using the USNO-A2.0 star at RA(2000) = 16 24 44.55, Dec(2000) = -27 32 59.9. This source is blue, since it is barely detected in contemporaneous J- and K-band images obtained at the 3.5-m telescope (+ Omega2000) at the German-Spanish Calar Alto Observatory and in H-band frames obtained at the 3.5-m Telescope Nazionale Galileo (+ NICS) on La Palma. The colours of objects B and C are also consistent with being blue, in contrast to the redder galaxy labelled D. Further observations are needed to confirm whether any of these objects has any relationship to GRB 050724." This message can be quoted.