[vsnet-grb-info 9180] GRB 100420A: GRT Optical Observation

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  10666
SUBJECT: GRB 100420A: GRT Optical Observation
DATE:    10/04/24 01:26:57 GMT
FROM:    Takanori Sakamoto at NASA/GSFC  <takanori.sakamoto-1 at nasa.gov>

T. Sakamoto (UMBC/GSFC), D. Donato (ORAU/GSFC), N. Gehrels (GSFC),
T. Okajima (JHU/GSFC), Y. Urata (NCU), C.A. Wallace (FGCU)

We observed the field of GRB 100420A detected by Swift
(trigger #419932; Baumgartner et al., GCN Circ. 10628) with the 14-inch
Goddard Robotic Telescope (GRT) located at the Goddard Geophysical
and Astronomical Observatory (http://cddisa.gsfc.nasa.gov/ggao/).

Total 435 images of 5 sec (200 images), 30 sec (80 images), 
60 sec (120 images) and 100 sec (35 images) exposures were taken in 
the R filter starting from April 20 05:26:53 (UT) about 4.2 minutes after 
the trigger and stopped on April 20 09:49:15 (UT).  We do not detect 
the optical afterglow both in the individual images and the stucked 
image, which only combined good quality 400 images, inside the XRT 
position (Rowlinson et al., GCN #10639).  The estimated three sigma 
upper limit of the combined image (total exposure of 10600 sec) is ~18.9  
mag using the USNO-B1 catalog.