TITLE: GCN CIRCULAR NUMBER: 7629 SUBJECT: GRB 080413B: Rapid PROMPT Observations DATE: 08/04/17 17:02:01 GMT FROM: Thomas Summers Brennan at UNC/GRB Group T. Brennan, D. Reichart, M. Nysewander, A. LaCluyze, K. Ivarsen, J. A. Crain, M. Schubel, A. Foster, J. Haislip, J. Styblova, and A. Trotter report: Skynet observed the localization of GRB 080413B (Stamatikos et al., GCN 7598) with four of the 16" PROMPT telescopes at CTIO beginning 27 seconds after the trigger (10 seconds after notification) in UBVRz' We detect the afterglow (Stamatikos et al., GCN 7598) in BVRz'. At 42 seconds after the burst we measure B ~ 15.7 mag (calibrated to 2 USNO B1 stars), at 55 seconds we measure V ~ 15.4 mag (calibrated to 2 USNO B1 stars), and at 87 seconds we measure R ~ 15.4 mag (calibrated to 2 NOMAD stars).