TITLE: GCN GRB OBSERVATION REPORT NUMBER: 1651 SUBJECT: GRB 020813; likely host galaxy. DATE: 02/10/23 10:39:19 GMT FROM: Javier Gorosabel at LAEFF-INTA, Madrid J. Gorosabel* (IAA-CSIC, Granada), J.P.U. Fynbo* (Univ. of Aarhus), J. Hjorth, H. Pedersen, B.L. Jensen (Univ. of Copenhagen), S.T. Holland* (Notre Dame), J.M. Castro Cerón* (ROA, San Fernando), M. Andersen (AIP, Potsdam), A.J. Castro-Tirado (IAA-CSIC, Granada) report: We have imaged the GRB 020813 (GCN 1471) optical afterglow (GCN 1470) with the 1.54-m Danish Telescope (+DFOSC) as follows: =================================================================== Date Filter Seeing Exp.Time Time Since Mag (UT) (") (s) GRB (days) ------------------------------------------------------------------- 10.01-10.13/10/2002 R 1.0 2x1200+8x900 58.0 23.90+/-0.14 09.02-09.17/10/2002 B 1.7 10x1200 57.0 24.46+/-0.19 ------------------------------------------------------------------- The calibration is based on the photometric standards given in GCN 1503. The B-R colour of our measurements (B-R=0.56+/-0.24) is bluer than the ones reported for the afterglow to date (constant around B-R ~ 1, see GCN 1513). This "blueing" could be due to a change of spectral slope in the afterglow or the presence of an underlying blue host galaxy. Given the epoch of our observations (~60 days after the gamma-ray event) we consider the second possibility more likely. The faintness of our detection does not allow us to see any extended structure. Two gifs of the potential host galaxy can be seen at: http://www.dsri.dk/~jgu/grb020813/GCN/grb020813R.gif http://www.dsri.dk/~jgu/grb020813/GCN/grb020813B.gif ----------------------------------------------------- * Visitors at the Copenhagen University Observatory.