------------------------------------------------------------------- THE ASTRONOMER Electronic Circular No 2914 2013 May 17 19.01UT Ed:Guy M Hurst, 16,Westminster Close, Kempshott Rise, Basingstoke, Hants, RG22 4PP,England.Telephone/FAX(01256)471074Int:+441256471074 INTERNET: GUY@TAHQ.DEMON.CO.UK Backup: gmh@wdcc1.bnsc.rl.ac.uk WORLD WIDE WEB http://www.theastronomer.org ------------------------------------------------------------------- GRB 130427A Further to E-Circulars 2909 and 2910, the editor has received further enquiries about the development of this unusual gamma ray burster. We have published a graph of 49 reported results and general comments in the May magazine of TA. Since then has come notice of the spectroscopic detection of the emerging supernova (GCN 14646) from A. de Ugarte Postigo (IAA-CSIC0 et. al., as follows: "We obtained spectroscopy of the optical counterpart and host galaxy of GRB 130427A with the 10.4m GTC telescope, 16.7 days after the GRB onset. This is 12.5 days in the host galaxy rest-frame (z = 0.34; Levan et al. GCN 14455, Xu et al. GCN 14478 and Flores et al. GCN 1449). Observations consisted of 4x1200s with the R500R grism, covering the range between 4800 and 10000 AA with a resolution of ~600. The slit was oriented to cover both the afterglow and the host galaxy centre. The spectrum has a strong contribution from the host galaxy. To overcome this, we built a synthetic host galaxy spectrum based on the SDSS (DR9) photometry using LePhare. We then subtracted this host galaxy template from the GTC spectrum to obtain a "clean" spectrum of the counterpart associated to GRB 130427A. The resulting spectrum is that of a broad-lined Ic SN, with a prominent bump at ~6800 A observer frame. In particular, we obtain an excellent match with the spectrum of SN 2010bh at 12.7 days after GRB 100316D. We stress that this conclusion is independent of the host galaxy model adopted. By running SNID on the original spectrum, we still obtain good matches with a series of broad-lined Type Ic SNe, including SNe 1998bw, 1997ef, 2002ap and 2006aj, albeit at a lower redshift. The fact that SNID suggests a lower redshift is explained by the fact that SN 2010bh had high expansion velocities, reaching ~34000 km/s at similar phases, which we suggest is also the case for the SN associated with GRB 130427A. A figure of our preliminary analysis can be seen at: http://www.iaa.es/~deugarte/GRBs/130427A/130427A_GTC.jpg Guy M Hurst OPEN OUTLOOK MAIL AND SET TO FORMAT TEXT, PLAIN TEXT TO AVOID MIME