[vsnet-grb-info 13877] GRB 130907A: Skynet DSO-14/Yerkes-41 detections of a possible afterglow

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  15191
SUBJECT: GRB 130907A: Skynet DSO-14/Yerkes-41 detections of a possible afterglow
DATE:    13/09/08 02:40:43 GMT
FROM:    Adam S. Trotter at UNC-Chapel Hill/PROMPT/Skynet  <atrotter at physics.unc.edu>

A. Trotter, J. Haislip, A. LaCluyze, J. Moore, N. Frank, D. Reichart, A. 
Smith, D. Caton, L. Hawkins, V. Hoette, D. Harper, R. Kron, K. Cudworth, 
E. Struble, R. Russell, T. Linder, T. Berger, H. T. Cromartie, R. Egger, 
A. Foster, K. Ivarsen, M. Maples, M. Nysewander, and J. A. Crain report:

Skynet observed the Swift/XRT localization of GRB 130907A (Page et al., 
GCN 15183, Swift trigger 569992) with the 14" telescope at the 
Appalachian State University Dark Sky Observatory (DSO-14) in NC, USA (R 
and I bands), and with the 41" telescope of Yerkes Observatory in WI, 
USA (r' and i' bands).

Starting at 2013-09-08, 00:43 UT (t=3.03h post-trigger) and continuing 
until 17:41 UT (t=35.5m-4.65h post-trigger), Skynet took a total of 42 
160s exposures. We detect an uncatalogued optical source in stacked 
images at RA 14:23:34.03, Dec +45:36:26.7 (J2000.0), consistent with the 
afterglow position reported by de Ugarte Postigo et al. (GCN 15187), and 
~8" south of the Swift-XRT localization. At t=3.4h post-trigger, R~19.6 
mag. The time range of our observations is not sufficient to confirm 
whether the source is indeed fading.

A preliminary light curve is at:
http://skynet.unc.edu/grb/grb130907a.png

R and I magnitudes are in the Vega system, and r' and i' are in the AB 
system, calibrated to 5 APASS stars in the field. Magnitudes have not 
been corrected for line-of-sight Milky Way dust extinction with expected 
E(B-V)=0.011 (Schlegel et al. 1998).

Skynet observations are ongoing.