TITLE: GCN GRB OBSERVATION REPORT NUMBER: 1491 SUBJECT: GRB020813: optical observations; possible host galaxy DATE: 02/08/14 18:19:47 GMT FROM: Weidong Li at UC Berkeley KAIT/LOSS W. D. Li, R. Chornock, and A. V. Filippenko (UC Berkeley) report on behalf of the Lick Observatory and Tenagra Observatory Supernova Search (LOTOSS; see IAU Circ. 7906): "We have obtained additional observations of the optical afterglow of GRB020813 with the 0.8-m Katzman Automatic Imaging Telescope (KAIT) at Lick Observatory. We continue to detect the object first reported by Fox et al. (GCN 1470) and also observed by us (GCN 1473). An unfiltered observation (600 s) obtained at 14 Aug 04:36 UT shows an extended object at the position of the afterglow. Another image (600 s unfiltered) obtained at 06:56 UT under better conditions shows two unresolved objects at that position separated by about 3.7". We identify one of these objects with the fading GRB afterglow, and suggest that the other object is a possible host galaxy (although it could be an unrelated faint object). We measured the following unfiltered magnitudes, in addition to those reported in GCN 1473: 13 Aug 8.3542 UT, mag 18.55 +/- 0.05 14 Aug 4.5972 UT, mag 20.55 +/- 0.25 (host?+GRB) 14 Aug 6.9333 UT, mag 21.08 +/- 0.30 (GRB only) host? = 20.70 +/- 0.25. We note that the first and third observations imply a power-law decay index of about -1.44. This is substantially steeper than the decay rate implied by the early observations (GCN 1473, 1474), supporting the hypothesis of Bloom et al. (GCN 1476) that the object may have undergone a temporal break." This message may be cited.