TITLE:   GCN CIRCULAR
NUMBER:  18987
SUBJECT: GRB 160203A: Skynet PROMPT-CTIO observations of the optical afterglow
DATE:    16/02/03 18:50:26 GMT
FROM:    Adam S. Trotter at UNC-Chapel Hill/PROMPT/Skynet  <atrotter@physics.unc.edu>

A. Trotter, D. Reichart, J. Haislip, J. Moore, N. Frank, M. Maples, E. Johnson, R. Joyner, J. Martin, C. Salemi, J. A. Crain, K. Ivarsen, A. LaCluyze, and M. Nysewander report:

Skynet observed the Swift BAT/XRT localization of GRB 160203A (D'Avanzo et al., GCN 18979, Swift trigger=672525) with with one 16" telescope (P5) and two 24" telescopes (P1 and P8) of the PROMPT array at CTIO, Chile. Starting at 2016-02-03 02:17:18 UT and continuing until 09:26 UT (t=4.1m-7.2h post-trigger), Skynet took a total of 353 exposures ranging from 20-160s. Between t=4.1m and t=61m, both P5 and P8 observed in the I band. Between t=78m and t=7.2h, P1 cycled through the V, R and I filters, while P8 cycled through the B, V and R filters.

We clearly detect an optical afterglow at the position first reported by Kruehler et al. (GCN 18980). The OT exhibits a rising light curve at early times, peaking at I~17 at t~8m, and fades thereafter, with I~20 at t~5h.

A preliminary light curve is at:
http://www.skynet.unc.edu/grb/grb160203a.png

Magnitudes are in the Vega System, calibrated to 8 APASS DR9 stars in the field.  Magnitudes have not been corrected for line-of-sight Milky Way dust extinction, with expected E(B-V)=0.06 (Schlafly & Finkbeiner 2011).

No further Skynet observations are scheduled.