2012CBET.3098....1F

Johan Fynbo, Dark Cosmology Centre, Niels Bohr Institute, reports on monitoring the afterglow of the gamma-ray burst GRB 120422A (located at R.A. = 9:07:38.38, Decl. = +14:01:07.5, equinox 2000.0; Troja et al., GCN 13243, accessible at URL http://gcn.gsfc.nasa.gov/gcn3/13243.gcn3; position and magnitude i = 19.0 via the Gemini-North 8-m telescope on Apr. 22.3 UT from Cucchiara et al., GCN 13245) with the Nordic Optical Telescope (NOT) since the burst. Imaging that was secured in the i-band, with the NOT on Apr. 30.90 showed that the afterglow was found to have re-brightened (to i = 21.3, from i = 22.1 five days earlier; Malesani et al., GCN 13275). Subsequent spectroscopy was secured with the X-shooter spectrograph starting on May 1.0 (8.7 days after the GRB), for a total exposure time of 80 min in each of the UVB, VIS, and NIR arms, covering the wavelength range 300-2500 nm. The slit was aligned to cover both the galaxy at z = 0.28 (as visible in the Sloan Digital Sky Survey; Cucchiara et al., GCN 13245; Tanvir et al., GCN 13251) and the optical counterpart (Cucchiara et al., GCN 13245). The spectrum exibits a broad emission peak centred at 630 nm, similar to what was found in a Keck-telescope spectrum taken on Apr. 27 (Perley et al., GCN 13267). Blueward of the peak, the spectrum drops steeply down to around 400 nm, and beyond that there is no detection of flux. Comparison with a library of supernova spectra using the "Supernova Identification" tool (SNID; Blondin and Tonry 2007, Ap.J., 666, 1024) gives good matches with both type-Ib and type-Ic supernovae at about a week before maximum.