[vsnet-grb-info 2971] GRB 060218: Decline in r-band flux

[GCN Circulars]

TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  4808
SUBJECT: GRB 060218: Decline in r-band flux
DATE:    06/02/21 22:58:14 GMT
FROM:    Edo Berger at Carnegie Obs  <eberger at ociw.edu>

E. Berger (Carnegie), B. P. Schmidt (ANU), and A. M. Soderberg (Caltech)
report on behalf of a larger collaboration:

"As part of our spectroscopic observations with GMOS on Gemini-south (GCN
4804) we obtained a single 30-sec r-band image of the field on 2006, Feb
21.01 UT.  Calibration against 9 nearby stars from SDSS (GCN 4777) yields
r = 17.92+/-0.12 mag for the afterglow+SN+host.  Subtracting off the
contribution of the host (r = 19.93+/-0.03; GCN 4777) we find that the
afterglow+SN faded by 0.43+/-0.22 mag compared to the measurement by
Mirabal (GCN 4784).  This corresponds to a decay rate of -0.4+/-0.2, which
is relatively shallow compared to typical optical afterglows, and
furthermore indicates a turnover in the flux evolution following the
initial period of brightening in the B,V bands observed with UVOT (GCN
4800)."