[vsnet-grb-info 8205] GRB 090727: GRT Optical Observation

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  9735
SUBJECT: GRB 090727: GRT Optical Observation
DATE:    09/07/29 19:19:45 GMT
FROM:    Takanori Sakamoto at NASA/GSFC  <takanori at milkyway.gsfc.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 090727 detected by Swift
(trigger #358520; Evans et al., GCN Circ. 9718) with the 14-inch
Goddard Robotic Telescope (GRT) located at the Goddard Geophysical
and Astronomical Observatory (http://cddisa.gsfc.nasa.gov/ggao/).

77 set of 30 sec exposures (excluding the bad quality images) were 
taken in the R filter starting from July 28 01:57:45 (UT) about 
3.2 hours after the trigger and stopped on July 28 02:40:50 (UT).  
We do not detect the optical afterglow (Smith et al., GCN Circ. 
9719; Gorosabel et al., GCN Circ. 9728; Moskvitin et al., GCN Circ. 
9733) both in the individual images and the combined image.  The 
estimated three sigma upper limit of the combined image (total 
exposure of 2310 sec) is ~16.6 mag using the USNO-B1 catalog.