TITLE: GCN GRB OBSERVATION REPORT NUMBER: 1429 SUBJECT: GRB 020604, optical observations DATE: 02/06/13 18:38:21 GMT FROM: Javier Gorosabel at LAEFF-INTA, Madrid J. Gorosabel (IAA-CSIC Granada), J. Hjorth, B. L. Jensen, H. Pedersen, P. Jakobsson (Univ. of Copenhagen), J. Fynbo (IFA Aarhus), M. I. Andersen (Univ. of Oulu), report: We have carried out optical observations of the GRB 020604 IPN error box (GCN 1417) with the 1.54 Danish Telescope (+DFOSC) on three epochs; June 8, 9 and 10. The observations were done following a mosaic as detailed below: ===================================================================== Date UT Filter R.A. Dec Seeing Time since ExpTime June 2002 (J2000) (J2000) (") GRB (days) (s) --------------------------------------------------------------------- 8.07874--8.11230 R 16:27:42.0 -29:48:43 1.2 3.50 4x600 8.11259--8.14516 R 16:28:39.8 -29:43:44 1.2 3.54 4x600 8.14642--8.16250 R 16:29:19.8 -29:39:44 1.1 3.56 2x600 8.16629--8.21525 R 16:28:01.7 -29:48:22 1.2 3.60 6x600** 8.21554--8.23159 R 16:27:18.4 -29:55:38 1.1 3.63 2x600 8.23186--8.23973 R 16:26:45.4 -29:52:52 1.0 3.64 600 8.27211--8.31829 I 16:28:01.7 -29:48:22 1.1 3.70 6x500** 8.32037--8.34111 I 16:28:39.8 -29:43:44 1.4 3.74 3x500 8.34216--8.36298 I 16:27:18.4 -29:55:38 1.8 3.76 3x500 --------------------------------------------------------------------- 9.12684--9.21986 R 16:28:01.7 -29:48:22 1.1 4.58 10x600** 9.22098--9.26678 R 16:28:39.8 -29:43:44 1.2 4.65 4x600 9.27909--9.30354 R 16:27:18.4 -29:55:38 1.3 4.70 4x600 9.30392--9.31180 R 16:26:45.4 -29:52:52 1.3 4.72 600 9.31378--9.32165 R 16:27:42.0 -29:48:43 1.2 4.72 600 9.32416--9.33202 R 16:29:19.8 -29:39:44 1.5 4.74 600 --------------------------------------------------------------------- 10.16572--10.24745 R 16:28:01.7 -29:48:22 1.0 5.61 6x900** 10.26606--10.30406 R 16:28:39.8 -29:43:44 1.3 5.69 3x900 10.30569--10.34051 R 16:27:18.4 -29:55:38 1.5 5.73 4x600 --------------------------------------------------------------------- ** Central part ===================================================================== The first and the second epoch observations cover the whole error box, whereas the third epoch images contain ~80% of it. A gif of the performed mosaic can be seen at: http://www.dsri.dk/~jgu/grb020604/FCs/grb020604.R.8-9.06.02.1.54D.gif The limiting magnitude depends on the error box position. For the central pointing (covering ~50% of the error box), the R-band limiting magnitude (3 sigma) at the three epochs are R=24.5, R=24.7 and R=24.9. For the rest of the error box the limiting magnitude are R=23.8, R=23.6 and R=24.0, respectively. In the I-band the limiting magnitude ranges from I=22.5 to I=23.4. Albeit the severe Galactic extinction (AR=1.18, AI=0.86 mag), many extragalactic objects are detected in our images. Among the unsaturated objects, marginal variability (< 0.2 mag) is detected for 12 of them. None of these objects shows flux variability consistent with a decay, as expected for an optical afterglow 3.5-5.7 days after the gamma ray event.