GCN Circular 14697

D. James, C. Foster, P. Taylor, M. Carroll, A. Trotter, D. Reichart, A. 
LaCluyze, J. Haislip, T. Berger, H. T. Cromartie, R. Egger, A. Foster, 
N. Frank, K. Ivarsen, M. Maples, J. Moore, M. Nysewander, E. Speckhard, 
and J. A. Crain report

Skynet observed the Swift/BAT localization of GRB 130521A (Pagani et 
al., GCN 14691
Not found
 
 
, Swift trigger #556344) with four 16" telescopes of the 
PROMPT array at CTIO, Chile.  Starting at 2013-05-21, 22:49:16 UT and 
continuing until 23:01:04 UT (t=49.2s-11.8m post-trigger), it took 66 
exposures in the BVRI bands. We did not detect a fading afterglow within 
the 3 arcmin radius of the Swift/BAT error circle, which was centered on 
RA 05h50m14.2s, Dec +14d27m08.6s (J2000.0).

A plot of the 3-sigma limiting magnitudes in each exposure, calibrated 
to six USNO-B1/NOMAD stars in the field, is here:
http://skynet.unc.edu/grb/grb130521a.png

We stacked all the images in each band and obtained 3-sigma limiting 
magnitudes on any afterglow of:
Filter       B       V       R       I
Mag       >18.29  >18.53  >18.13  >17.07

Magnitudes are Vega magnitudes, and have not been corrected for the 
expected line-of-sight Milky Way dust extinction E(B-V)=0.38 (Schlegel 
et al. 1998).

No further Skynet observations are scheduled.