TITLE:   GCN CIRCULAR
NUMBER:  14747
SUBJECT: GRB 130603B: optical follow-up and independent GTC redshift  determination and afterglow spectrum
DATE:    13/06/04 03:05:17 GMT
FROM:    Alberto Castro-Tirado at Inst.de Astro. de Andalucia  <ajct@iaa.es>

R. Sánchez-Ramírez, A. J. Castro-Tirado (IAA-CSIC), J. Gorosabel
(IAA-CSIC, UPV-EHU), F. J. Aceituno (IAA-CSIC), E. Sonbas (Adiyaman
Univ.), E. Gogus, T. Güver (Sanbaci Univ.), H. Kirbiyik (TUG) and D.
García-Alvárez (GTC) on behalf of a larger collaboration, report:

“We have observed the optical afterglow of the short-duration GRB 130603B
(Melandri  et al. GCNC  14735, Norris et al. GCNC 14746). Optical images
have been obtained with the 1.0m telescope at the Tübitak National
Observatory (Antalya, Turkey) in the R-band and with the 1.5m telescope at
Observatorio de Sierra Nevada (Granada, Spain) in the I-band, starting on
June 3. 771 and June 3.854 UT (2.69 hr and 4.69 hr post burst)
respectively. Spectra covering the range 3500-10000 A  were obtained  with
the 10.4m GTC (+OSIRIS) starting on June 3.993 UT (i.e. 8 hr post burst). 
At the position of the optical afterglow (Levan et al. GCNC  14742) the
afterglow spectrum shows Ca II in absorption, and we detect significant
contribution of the underlying host galaxy (eg. [OII], [OIII], H-beta and
H-alpha emission lines about 1” off), implying altogether a redshift of z
= 0.356, consistent with the values provided by Thoene et  al. (GCNC 
14744) and Foley et al. (GCNC 14745)“.