TITLE:   GCN CIRCULAR
NUMBER:  15369
SUBJECT: GRB 131024A: Skynet R-COP optical observations
DATE:    13/10/24 19:12:32 GMT
FROM:    Adam S. Trotter at UNC-Chapel Hill/PROMPT/Skynet  <atrotter@physics.unc.edu>

A. Trotter, J. Haislip, D. Reichart, A. Verveer, T. Spuck, A. LaCluyze, 
N. Frank, J. Moore, T. Berger, H. T. Cromartie, R. Egger, A. Foster, K. 
Ivarsen, M. Maples, M. Nysewander, E. Speckhard, and J. A. Crain report:

Skynet observed the Swift/XRT localization of the field of GRB 131024A 
(Racusin et al., GCN 15365, Swift trigger # 575707) with the 14-inch 
R-COP telescope at Perth Observatory, Australia, starting at 2013-10-24, 
12:28:14 UT and continuing until 14:25 UT (t=1.9-118m post trigger). 
R-COP took a total of 44x20-80s exposures simultaneously in the BRI bands.

In a stack of 2 early R-band images at a mean time t=6.9m we marginally 
detect (S/N~3.5 sigma) an uncataloged source in the R band within the 
XRT error circle, with R~18.9 mag. In later stacks at mean times 
~70-80m, we obtain only 3-sigma upper limits in all three bands:

band    t(mean) exp     mag
B       69m      9x80s  >19.2
R       80m     12x80s  >19.8
I       83m     16x80s  >18.9

Magnitudes are in the Vega system, calibrated to four APASS-DR7 stars in 
the field, and have not been corrected for line-of-sight Milky Way dust 
extinction, with expected E(B-V)=0.05 (Schlegel et al. 1998).

No further Skynet observations are scheduled.