[vsnet-grb-info 13119] GRB 130427A: Continued P60 follow-up of an extremely bright optical afterglow
GCN Circulars
gcncirc at capella2.gsfc.nasa.gov
Sat Apr 27 20:52:52 JST 2013
TITLE: GCN CIRCULAR
NUMBER: 14456
SUBJECT: GRB 130427A: Continued P60 follow-up of an extremely bright optical afterglow
DATE: 13/04/27 11:52:44 GMT
FROM: S. Bradley Cenko at Caltech <cenko at srl.caltech.edu>
D. A. Perley (Caltech) and S. B. Cenko (UC Berkeley) report:
We have continued observations of the afterglow of GRB130427A (Maselli et
al., GCN 14448) with the Palomar 60-inch telescope until the field set.
Relative to SDSS reference stars in the field, in some select recent
images we estimate afterglow magnitudes of:
r' = 14.86 mag (t = 1.40 hours)
r' = 15.32 mag (t = 2.31 hours)
r' = 15.55 mag (t = 3.10 hours)
This is brighter (by about 1 mag) than any other Swift burst as measured
at similar epoch (as of 2010; Kann et al. ApJ 720:1513), though still
significantly fainter than GRB 030329 which reached approximately 13 mag
at 0.1 day. The rate of fading corresponds to a relatively shallow decay
index of approximately alpha~-0.85, suggesting that this afterglow will
remain bright for an extended period. Worldwide small-telescope follow-up
(including by amateurs) is strongly encouraged.
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