GCN Circular 16279
A. de Ugarte Postigo (IAA-CSIC, DARK/NBI), J. Gorosabel (IAA-CSIC, UPV-EHU), C.C. Thoene (IAA-CSIC), A. Cabrera-Lavers, D. Reverte and C. Alvarez (IAC-ULL) report on behalf of a larger collaboration: We have obtained spectroscopic observations of the afterglow of GRB 140415A (D'Avanzo et al., GCN 16267; Chornock et al. GCN 16269; Fong et al. GCN 16274; de Ugarte Postigo et al. GCN 16278) using the 10.4m GTC telescope (+OSIRIS). Our observation started at 22:37 UT (13.41 hr after the burst), with a seeing of 0.6", and consisted of 3x1800s exposures using grism R2500I, which covers the range between 7330 and 10000 A at a resolution of ~2500. In a preliminary reduction we detect a strong continuum above 8900 A, with no significant absorption features. The sharp decay below 8900 A is consistent with Ly-alpha absorption at the redshift of 6.32 suggested by Chornock et al. (GCN 16269). The transmission of the Ly-forest is low, but some emission is detected down to the blue limit of our spectrum.