{
  "bibcode": "2010GCN.10666....1S",
  "body": "T. Sakamoto (UMBC/GSFC), D. Donato (ORAU/GSFC), N. Gehrels (GSFC),\nT. Okajima (JHU/GSFC), Y. Urata (NCU), C.A. Wallace (FGCU)\n\nWe observed the field of GRB 100420A detected by Swift\n(trigger #419932; Baumgartner et al., GCN Circ. 10628) with the 14-inch\nGoddard Robotic Telescope (GRT) located at the Goddard Geophysical\nand Astronomical Observatory (http://cddisa.gsfc.nasa.gov/ggao/).\n\nTotal 435 images of 5 sec (200 images), 30 sec (80 images), \n60 sec (120 images) and 100 sec (35 images) exposures were taken in \nthe R filter starting from April 20 05:26:53 (UT) about 4.2 minutes after \nthe trigger and stopped on April 20 09:49:15 (UT).  We do not detect \nthe optical afterglow both in the individual images and the stucked \nimage, which only combined good quality 400 images, inside the XRT \nposition (Rowlinson et al., GCN #10639).  The estimated three sigma \nupper limit of the combined image (total exposure of 10600 sec) is ~18.9  \nmag using the USNO-B1 catalog.",
  "circularId": 10666,
  "createdOn": 1272072417000,
  "email": "takanori.sakamoto-1@nasa.gov",
  "subject": "GRB 100420A: GRT Optical Observation",
  "submitter": "Takanori Sakamoto at NASA/GSFC  <takanori.sakamoto-1@nasa.gov>",
  "eventId": "GRB 100420A"
}