TITLE:   GCN CIRCULAR
NUMBER:  9937
SUBJECT: GRB 090926A: Skynet/PROMPT Discovery of the Optical Afterglow
DATE:    09/09/27 01:36:29 GMT
FROM:    Josh Haislip at U.North Carolina  <haislip@physics.unc.edu>

J. Haislip, D. Reichart, K. Ivarsen, A. LaCluyze, A. Foster, J. Moore, A. 
Oza, M. Schubel, J. Styblova, A. Trotter, J. A. Crain, and M. Nysewander 
report:

Skynet observed the Fermi/LAT localization of GRB 090926A (Uehara et al., 
GCN 9934) with four of the 16" PROMPT telescopes at CTIO beginning 19.0 
hours after the trigger in UBVRI.

We detect an optical source within the Swift/XRT localization (Vetre et 
al., GCN 9936) that is not in the DSS (POSS-II Red), at

RA = 23:33:36.02
DEC = -66:19:26.5

Stacking only images that increase the limiting magnitude yields:

mean
time
since                                              cal.
trig.  tel.      exp.     fil.  magnitude          stars
(h)              (# x s)

19.9   PROMPT-2  22 x 80  V     18.81 +0.10 -0.09  52 NOMAD
20.0   PROMPT-5  22 x 80  I     18.24 +0.04 -0.04  165 USNO B1
20.0   PROMPT-4  24 x 80  R     18.06 +0.03 -0.03  230 USNO B1