[vsnet-grb-info 8023] GRB 090621A: GRT Optical Observation

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  9564
SUBJECT: GRB 090621A: GRT Optical Observation
DATE:    09/06/23 02:08:36 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 090621A detected by Swift 
(trigger #355303; Curran et al., GCN #9540) 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 21 05:00:15 (UT) about 37.3 min after the trigger and 
stopped on June 21 05:56:22 (UT).  We do not detect the optical 
afterglow both in the individual images and the combined image 
inside the XRT position (Page et al., GCN #9543).  The estimated 
three sigma upper limit of the combined image (total exposure 
of 2850 sec; excluding five bad quality images) is ~17.9 mag using 
the USNO-B1 catalog.