TITLE:   GCN CIRCULAR
NUMBER:  8382
SUBJECT: GRB 081016B: ROTSE-III Optical Limits
DATE:    08/10/16 20:14:33 GMT
FROM:    Brad Schaefer at LSU  <schaefer@grb.phys.lsu.edu>

B. E. Schaefer (Louisiana State), E.S. Rykoff (UCSB), and H. Swan (U.  
Mich.) report on behalf of the ROTSE collaboration:

ROTSE-IIIc, located at the H.E.S.S. site at Mt. Gamsberg, Namibia, 
responded to GRB 081016B (Swift trigger 331856), producing images 
beginning 6.4 s after the GCN notice time. An automated response took the 
first image at 19:47:59.4 UT, 44.9 s after the burst, under excellent 
conditions. We took 10 5-sec, 10 20-sec and 20 60-sec exposures. These 
unfiltered images are calibrated relative to USNO A2.0 (R). Imaging is on 
going.

Comparison to the DSS (second epoch) reveals no new sources within the 
3-sigma Swift/BAT error circle or the XRT error circle, for both single 
images and coadding into sets of 10; the field is not crowded. Individual 
images have limiting magnitudes ranging from 15.8-17.1; we set the 
following specific limits.

start UT       end UT      t_exp(s)   mlim   t_start-tGRB(s)  Coadd?
--------------------------------------------------------------------
19:47:59.4   19:48:04.4         5     15.8           44.9       N
19:47:59.4   19:49:15.5        76     17.5           44.9       Y

[GCN OPS NOTE(17oct08): Per author's request, the burst name was changed
from "A" to "B".]