[vsnet-grb-info 10533] GRB 110422A: TNG optical observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  11963
SUBJECT: GRB 110422A: TNG optical observations
DATE:    11/04/23 00:25:49 GMT
FROM:    Andrea Melandri at Liverpool John Moores U  <axm at astro.livjm.ac.uk>

A. Melandri, P. D'avanzo, D. Fugazza (INAF-OAB) and E. Palazzi (INAF- 
IASFBo)
on behalf of a larger collaboration report:


We observed the field of GRB 110422A (Mangano et al. GCN 11957) with  
the 3.6m
TNG equipped with the Dolores camera. Few sets of unfiltered images  
were acquired
starting on Apr 22.89 UT (i.e. ~5.7 hours after the burst event).

The optical afterglow (Elunko et al. GCN 11958; Gres et al. GCN  
11960;  Xu et al.
GCN 11961, Moskvitin GCN 11962) is clearly detected in all our  
frames. The observed
magnitudes (calibrated with respect to the same star used in GCN  
11961) are


Dt_start  t_exp    R_mag   err
   [hr]            [s]
---------------------------------------------
  5.777      60.0    20.17   0.03
  5.934      60.0    20.24   0.05
  5.998      60.0    20.03   0.05
  8.052      60.0    20.24   0.04

Our observations, coupled with previous observations reported on GCNs  
imply a
power-law decay index for the optical afterglow of ~0.55.

Further observations are ongoing.