TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3680 SUBJECT: GRB 050724: J-band observations DATE: 05/07/26 01:21:06 GMT FROM: Javier Gorosabel at LAEFF-INTA, Madrid A. de Ugarte Postigo, J. Gorosabel, A.J. Castro-Tirado, M. Jelinek, S. Guziy (IAA-CSIC), H.-J. Roeser (MPI Heidelberg), A. Aguirre, S. Pedraz (CAHA), O. Bogdanov (Nikolaev State Univ.), report: "We have observed the field of GRB 050724 (GCN Circ. 3665) in the J-band with the 3.5m Calar Alto telescope (mean observing epoch July 25.86 UT, Texp=45 min). A comparison with the images taken yesterday with the same telescope (mean observing epoch July 24.87 UT, Texp=15 min) did not reveal any variable source in the reported XRT error boxes (GCN Circ. 3678, 3665, 3669) down to J~20. At first epoch we note the presence of a possible object on our detection limit (J~20.5) located at RA(J2000)=16:24:45.02, DEC(J2000)=-27:32:29.1. However, the worse seeing on July 25.86 UT prevented us from confirming its potential variability." This message can be cited.