{
  "bibcode": "2002GCN..1518....1L",
  "body": "A.J. Levan, A.S. Fruchter, I. Burud and J.E. Rhoads (STScI)\nreport for the larger GOSH collaboration:\n\nThe field containing the optical counterpart of GRB 020813 was imaged by\nHST using ACS/HRC, ACS/WFC and NICMOS on 17th August beginning at 04:00 UT\napproximately 98 hours after the burst.\n\nThe optical counterpart is clearly visible in our images. Using the\nzeropoints for the filters on ACS/WFC, as given below, we find the\nmagnitude of the counterpart to be:\n\nFILTER    Z_P(AB) OT MAG(AB)\n==========================\nF435W     25.47     23.20\nF606W     26.35     22.71\nF814W     25.86     22.33\n\nThis is consistent with a spectral slope of beta =-0.8.\n\nComparing to early, 3 hour I Band observations (GCN 1513) gives\nan approximate slope of ~t^-1.07. Comparing to observations taken after\n23 hours (also GCN 1513) indicates a somewhat faster (broken) slope\nof t^-1.35.\n\nThe OT appears largely point like, however a PSF subtraction reveals some\nevidence for a possible 25th magnitude host galaxy underlying the OT.\n\nImages of the field of GRB 020813 may be found at\n\nhttp://www.stsci.edu/~fruchter/GRB/020813\n\nAnalysis is continuing and further observations are planned.",
  "circularId": 1518,
  "createdOn": 1030035895000,
  "email": "anl@star.le.ac.uk",
  "subject": "GRB 020813 : HST observations",
  "submitter": "Andrew Levan at U.of Leicester  <anl@star.le.ac.uk>",
  "eventId": "GRB 020813"
}