TITLE: GCN CIRCULAR NUMBER: 12802 SUBJECT: GRB 111211A: Detection of the SN with the 10.4m GTC DATE: 12/01/03 23:30:26 GMT FROM: Antonio de Ugarte Postigo at IAA-CSIC A. de Ugarte Postigo (IAA-CSIC, DARK/NBI), C.C. Thoene and J. Gorosabel (IAA-CSIC) report on behalf of a larger collaboration: Using the 10.4m GTC telescope + OSIRIS, at the Roque de los Muchachos Observatory (La Palma, Spain), we obtained late imaging and spectroscopy of the SuperAGILE GRB 111211A (Lazzarotto et al. GCN 12666, Kann et al. GCN 12668), located at a redshift of 0.478 (Vergani et al. GCN 12677) at 2 epochs. On 27 December 2011 (15.3 days after the burst) we obtained imaging in r-band of 6x180s with a seeing of ~0.9". This image clearly shows the afterglow of GRB 111211A at a magnitude of r ~ 22.6 (compared to SDSS stars) superposed to its resolved host galaxy but slightly offset towards the North East. Spectroscopy of the afterglow was obtained on 1 January 2012 (20.3 days after the burst) under good seeing conditions (~1"). At that time, the afterglow was detected at r ~ 22.7 in the acquisition frame, implying an almost flat evolution since the previous epoch which indicates a possible supernova component contributing to the light curve. We obtained 3x1800s spectroscopy at a resolution of ~ 500 and wavelength coverage from ~ 5 000 to 10 000 Angstrom. The spectrum shows both emission from the GRB and the host galaxy. The host shows emission lines of [OII], H-beta, [OIII] and H-alpha at a redshift of 0.478, consistent with the redshift of the GRB (Vergani et al. GCN 12677). The spectrum at the position of the afterglow shows undulations typical of a SN spectrum similar to the spectrum of the type Ic SN 2006aj / GRB 060218 close to maximum. We acknowledge excellent support from the GTC staff, in particular D. Reverte, A. Cabrera Lavers and R. Rutten.