[vsnet-grb-info 3133] GRB 060418, SMARTS optical/IR afterglow observations

[GCN Circulars]

TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  4970
SUBJECT: GRB 060418, SMARTS optical/IR afterglow observations
DATE:    06/04/18 05:05:45 GMT
FROM:    Bethany Cobb at Yale U  <cobb at astro.yale.edu>

B. E. Cobb (Yale), part of the larger SMARTS                 
consortium, reports:

Using the ANDICAM instrument on the 1.3m telescope at CTIO, we
obtained optical/IR imaging of the error region of GRB 060418
(Falcone et al. GCN 4966) beginning ~1 hours post-burst   
(2006-04-18 04:05 UT).  Several dithered images                
were obtained in each filter, with total summed exposure times
of 180s in each of BRIYJK and 120s in each of H and V.

The afterglow candidate reported by Falcone et al. and
confirmed by Covino et al. (GCN 4967) and Melandri et al. (GCN 4968)
is visible in all wavebands, from B to K.  At a mid-exposure
time of 1.2 hrs post-burst, the preliminary K-band magnitude
of the afterglow candidate is K = 14.1 +/- 0.1.  This value is obtained 
by comparison with nearby 2MASS standards.  The lack of a Lyman-alpha
forest absorption break suggest this GRB has a redshift of z<~3.