TITLE: GCN GRB OBSERVATION REPORT NUMBER: 374 SUBJECT: GRB990704 radio and optical observations DATE: 99/07/06 19:26:40 GMT FROM: Paul Vreeswijk at U of Amsterdam E. Rol, P. Vreeswijk, T. Galama (U. of Amsterdam), N. Masetti, E. Palazzi, E. Pian, F. Frontera (ITESRE, CNR, Bologna), J. van Paradijs (U. of Amsterdam and U. of Alabama in Huntsville), C. Kouveliotou (USRA/MSFC), R. Strom (NFRA and U. of Amsterdam), G. de Bruyn (NFRA and U. of Groningen) and T. Augusteijn (ESO) report: We have observed the BeppoSAX NFI error circle of GRB 990704 (Gandolfi 1999, GCN 364) with the Westerbork Synthesis Radio Telescope (WSRT). We observed for 9.2 hours at 4.88 GHz centered on July 5.75 UT, 1999. Within the error circle we detect two sources at 4.88 GHz. Their fluxes and positions are given below: flux (mJy) RA(J2000) Decl.(J2000) 0.68 12:19:27.2 -03:51:38.5 0.35 12:19:31.0 -03:52:05.3 The error in the flux is 0.065 mJy. The error in the RA and Decl. are 0.5" and 5", respectively. We have also observed the error circle in the R band with the ESO 2.2m (La Silla) and VLT-UT1 Antu (Paranal) telescopes, 6.5 and 30.5 hours after the burst, respectively. We calibrated these images with the Landolt SA104 field (stars 350 and 456; Landolt 1992, AJ, 104, 340). We detect an object at RA 12:19:27.20, Decl. -3:51:39.7 (J2000; positional accuracy of about 2"), coincident with the first radio source. We measure the following magnitudes for this object: UT Date R err. telescope July 4.96 22.05 0.16 2.2m July 6.01 22.00 0.05 VLT-UT1 July 6.07 21.87 0.07 VLT-UT1 The error in the absolute calibration (estimated to be 0.2 mag.) is not included in the error listed above. The object is constant within the measurement errors and it is therefore not likely the counterpart of GRB990704. At the position of the second radio source, no object is detected. The 5 sigma limiting magnitudes of the 2.2m and the co-added VLT-UT1 images are R=22.2 and R=23.5, respectively. This message is citeable.