[vsnet-grb-info 13873] GRB 130907A: NOT redshift

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  15187
SUBJECT: GRB 130907A: NOT redshift
DATE:    13/09/07 23:44:37 GMT
FROM:    Antonio de Ugarte Postigo at IAA-CSIC  <deugarte at iaa.es>

A. de Ugarte Postigo (IAA-CSIC, DARK/NBI), D. Xu (DARK/NBI), D. Malesani (DARK/NBI), 
J. Gorosabel (IAA-CSIC/UPV-EHU), P. Jakobsson (U. Iceland) and J. Kajava (NOT) report 
on behalf of a larger collaboration:

We observed the optical afterglow of GRB 130907A (Page et al., GCN 15183; Gorbovskoy
et al., GCN 15184) with the NOT equipped with the AlFOSC spectrograph and camera. 
The transient is clearly detected in our acquisition images, taken in a clear filter, at the 
following coordinates:

RA(J2000) = 14:23:34.08
Dec(J2000) = +45:36:26.7

Using R-band values from nearby USNO stars, we get a magnitude R = 16.7 +- 0.1 at a 
mean time of 0.41 hr after the GRB, where the error is dominated by calibration 
uncertainties.

A single spectrum of 900 s covering the range from 3800 to 8000 AA, with a resolution of 
~700, was obtained with a mean epoch of 0.598 hr after the burst. The spectrum presents 
a strong continuum with deep spectral features of AlIII, FeII, MgII and MgI at a common 
redshift of z=1.238 (wavelength calibration based on archival data), which we identify as 
the redshift of the GRB.