{
  "bibcode": "2013GCN.14646....1D",
  "body": "A. de Ugarte Postigo (IAA-CSIC, DARK/NBI), D. Xu (DARK/NBI), \nG. Leloudas (OKC, Stockholm, DARK/NBI),  T. Kruehler, \nD. Malesani (DARK/NBI), J. Gorosabel (IAA-CSIC, UPV/EHU), Z. Cano (U. Iceland),\nC.C. Thoene, R. Sanchez-Ramirez (IAA-CSIC), S. Schulze (PUC and MCSS), \nJ.P.U. Fynbo, J. Hjorth (DARK/NBI), P. Jakobsson (U. Iceland) and \nA. Cabrera-Lavers (IAC-ULL) report on behalf of a larger collaboration:\n\nWe obtained spectroscopy of the optical counterpart and host galaxy of \nGRB 130427A (Maselli et al., GCN 14448; Elenin et al., GCN 14450) with the \n10.4m GTC telescope, 16.7 days after the GRB onset. This is 12.5 days in the \nhost galaxy rest-frame (z = 0.34; Levan et al. GCN 14455, Xu et al. GCN 14478 \nand Flores et al. GCN 1449). Observations consisted of 4x1200s with the \nR500R grism, covering the range between 4800 and 10000 AA with a \nresolution of ~600. The slit was oriented to cover both the afterglow and the \nhost galaxy centre.\n\nThe spectrum has a strong contribution from the host galaxy. To overcome this, \nwe built a synthetic host galaxy spectrum based on the SDSS (DR9) photometry \nusing LePhare (version 2.2, Arnouts et al. 1999, MNRAS, 310, 540; Ilbert et al. \n2006, A&A, 457, 841). We then subtracted this host galaxy template from the \nGTC spectrum to obtain a \"clean\" spectrum of the counterpart associated to GRB \n130427A.\n\nThe resulting spectrum is that of a broad-lined Ic SN, with a prominent bump at \n~6800 A observer frame. In particular, we obtain an excellent match with the \nspectrum of  SN 2010bh at 12.7 (rest-frame) days after GRB 100316D \n(Bufano et al. 2012, ApJ 753, 67).\n\nWe stress that this conclusion is independent of the host galaxy model \nadopted. By running SNID (Blondin & Tonry 2007, ApJ, 666, 1024) on the \noriginal spectrum (i.e. including host contamination), we still obtain good \nmatches with a series of broad-lined Type Ic SNe, including SNe 1998bw, \n1997ef, 2002ap and 2006aj, albeit at a lower redshift. The fact that SNID \nsuggests a lower redshift  is explained by the fact that SN 2010bh had high \nexpansion velocities, reaching ~34000 km/s at similar phases (Bufano et al. \n2012, ApJ 753, 67), which we suggest is also the case for the SN associated \nwith GRB 130427A.\n\nA figure of our preliminary analysis can be seen at:\n\nhttp://www.iaa.es/~deugarte/GRBs/130427A/130427A_GTC.jpg\n\nWe acknowledge excellent support from the GTC staff.\n\n[GCN OPS NOTE(14may13): Per author's request, ZCwas added to the author list.]",
  "circularId": 14646,
  "createdOn": 1368566493000,
  "email": "deugarte@iaa.es",
  "subject": "GRB 130427A: Spectroscopic detection of the SN from the 10.4m GTC",
  "submitter": "Antonio de Ugarte Postigo at IAA-CSIC  <deugarte@iaa.es>",
  "eventId": "GRB 130427A"
}