TITLE:   GCN CIRCULAR
NUMBER:  14436
SUBJECT: GRB 130420A: Early RAPTOR Simultaneous Multi-Color Observations
DATE:    13/04/22 17:34:49 GMT
FROM:    James Wren at LANL  <jwren@nis.lanl.gov>

J. Wren, W.T. Vestrand, P. Wozniak, and H. Davis,
of Los Alamos National Laboratory report:

The RAPTOR network of robotic optical telescopes made follow-up observations
of Swift trigger 553977 (Page, et al., GCN 14406).  Our RAPTOR-S and RAPTOR-T
robotic telescopes located in Los Alamos, NM, began imaging at 07:29:52.95 UTC,
83.4 s after the Swift BAT trigger and continued during the entire period the
BAT was detecting the dominant gamma-ray pulse (Lien, et al., GCN 14419).  We
detect optical emission during the gamma-ray emitting interval at the location
of the counterpart reported by the Faulkes team (Guidorzi, et al., GCN 14405).
In subsequent images we see a rapid rise in brightness at the same location,
peaking at about T+300s.  These observations were made simultaneously using
SDSS g', r', i', z' and clear filters.  Our unfiltered observations are
consistent with the lightcurve published by the ISON team (Elenin, et al.,
GCN 14428).