TITLE:   GCN CIRCULAR
NUMBER:  10494
SUBJECT: GRB 100316B: Skynet/PROMPT Observations of Fading
DATE:    10/03/16 10:13:19 GMT
FROM:    Josh Haislip at U.North Carolina  <haislip@physics.unc.edu>

J. Haislip, K. Ivarsen, D. Reichart, A. LaCluyze, R. Egger, A. Foster, J. 
Moore, A. Oza, M. Schubel, J. Styblova, A. Trotter, J. A. Crain, and M. 
Nysewander report:

Skynet observed the Swift/BAT localization of GRB 100316B (Baumgartner et 
al., GCN 10489) with four of the 16" PROMPT telescopes at CTIO beginning 32 
seconds after the trigger (19 seconds after notification) in BVRI.

We detect the afterglow (Baumgartner et al., GCN 10489) in all filters.

At 34 seconds after the trigger, the afterglow's magnitude was I = 15.61 
+0.16 -0.14 (statistical) +/- 0.20 (systematic; calibrated to 56 USNO B1 
stars).

Between 34 seconds and 2.1 minutes after the trigger, the afterglow faded 
with a power-law index of about -1.0.

Between 2.1 and 35 minutes after the trigger, the afterglow faded more 
slowly, with a power-law index of about -0.3.

Between 35 and 41 minutes after the trigger, the afterglow suddenly 
rebrightened, with a power-law index of about +5.4.

Between 41 and 49 minutes after the trigger, the afterglow faded with a 
power-law index of about -0.6.

Between 49 and 95 minutes after the trigger, the afterglow faded more 
rapidly, with a power-law index of about -1.7.

At 95 minutes after the trigger, the afterglow's magnitude was R = 19.51 
+0.33 -0.26 (statistical) +/- 0.28 (systematic; calibrated to 40 USNO B1 
stars).

Skynet's most recent BVRI light curve, calibrated to USNO B1 and NOMAD 
stars, can be found here:

http://skynet.unc.edu/grb/grb100316b.png