[vsnet-grb-info 8024] GRB 090621B: GRT Optical Observation

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  9565
SUBJECT: GRB 090621B: GRT Optical Observation
DATE:    09/06/23 02:18:16 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), T.N. Ukwatta (GWU/GSFC), Y. Urata (NCU),  
C.A. Wallace (FGCU) 
  
We observed the field of GRB 090621B detected by Swift 
(trigger #355359; Curran et al., GCN #9545) with the 14-inch 
Goddard Robotic Telescope (GRT) located at the Goddard Geophysical 
and Astronomical Observatory (http://cddisa.gsfc.nasa.gov/ggao/).   

100 set of 30 sec exposures were taken in the R filter starting 
from June 22 01:51:44 (UT) about 3.7 hours after the trigger and 
stopped on June 22 02:47:51 (UT).  We do not detect the optical 
afterglow both in the individual images and the combined image 
inside the XRT position (Beardmore et al., GCN #9550).  The 
estimated three sigma upper limit of the combined image (total 
exposure of 2880 sec; excluding four bad quality images) is 
~17.8 mag using the USNO-B1 catalog.