[vsnet-grb-info 15592] GRB 141004A: TNG photometric and spectroscopic observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  16881
SUBJECT: GRB 141004A: TNG photometric and spectroscopic observations
DATE:    14/10/05 02:49:18 GMT
FROM:    Valerio D'Elia at ASDC  <delia at asdc.asi.it>

V. D'Elia (INAF/OAR & ASI/ASDC), S. Covino (INAF/OAB), M. Cecconi and  
Carmen Padilla (INAF/TNG) report on behalf of the CIBO collaboration:


We observed the optical afterglow of GRB 141004A (D'Elia et al., GCN  
16878; Mereghetti et al. GCN 16879) on 2014 October 5 with the 3.6m  
TNG telescope located in the Canary Islands, equipped with the DOLORES  
operated in both imaging and spectroscopic mode. The observations were  
carried out under good weather conditions (seeing about 1.5) at high  
airmass.

In a 180 s image started at 01:41 UT (~2.3 hr after the GRB), the  
afterglow has a magnitude r = 20.9 +/- 0.1 (AB), calibrated against  
the APASS catalog. No correction has been applied for the Galactic  
extinction. The position of the afterglow is
RA: 05:06:56.17
Dec: 12:49:10.54,
consistent with the UVOT detection (D'Elia et al. GCN 16878) and with  
the CAHA observation (Gorosabel et al., GCN 16880). We also detect a  
fainter object (possibly extended) 5" eastward to the afterglow.


We also obtained two optical spectra, each one lasting 1200 s, using  
the grism LR-B covering the wavelength range 3000 - 8000 AA. The  
observations started at 01:00 UT (~1.7 hr after the GRB). Using a  
preliminary wavelength calibration, in the co-added spectrum we detect  
a faint continuum extending down to 4000 A. No obvious absorption or  
emission features are detected in our preliminary analysis of the  
afterglow spectrum.