* Astronomy

Title: The Optical SN 2012bz Associated with the Long GRB 120422A
Authors: A. Melandri, E. Pian, P. Ferrero, P. D'Avanzo, E. S. Walker, G. Ghirlanda, S. Covino, L. Amati, V. D'Elia, P. A. Mazzali, M. Della Valle, C. Guidorzi, L. A. Antonelli, M. G. Bernardini, F. Bufano, S. Campana, A. J. Castro-Tirado, G. Chincarini, J. Deng, A. V. Filippenko, D. Fugazza, G. Ghisellini, C. Kouveliotou, K. Maeda, G. Marconi, N. Masetti, K. Nomoto, E. Palazzi, F. Patat, S. Piranomonte, R. Salvaterra, I. Saviane, R. L. C. Starling, G. Tagliaferri, M. Tanaka, S. D. Vergani

The association of Type Ic supernovae (SNe) with long-duration gamma-ray bursts (GRB) is well established. GRB 120422A was a low-redshift (z=0.283) event that allowed an extensive ground-based observational campaign to monitor the light curve of the associated SN 2012bz. We obtained a series of photometric and spectroscopic observations of SN 2012bz associated with the long-duration GRB 120422A using the 3.6-m TNG and the 8.2-m VLT telescopes during the time interval between 4 and 36 days after the burst. We characterised the optical light curve of SN 2012bz and compared its shape with other GRB/SNe. Peak brightness was reached ~18 days after the burst, corresponding to ~14 days in the rest-frame. A general resemblance between the spectra of SN 2012bz and SN 1998bw at similar epochs is noticed, but the spectra are too noisy for detailed analysis. The shape and maximum of the bolometric light curve (M ~ -18.7) are very similar to those of other known GRB/SNe, suggesting comparable explosion conditions and parameters. GRB 120422A may lie slightly above the 2\sigma confidence region of the Epeak-Eiso relation.

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D. Malesani, DARK Cosmology Centre, Niels Bohr Institute, University of Copenhagen; S. Schulze, University of Iceland; T. Kruehler, J. P. U. Fynbo, J. Hjorth, B. Milvang-Jensen, and D. Watson, DARK Cosmology Centre, Niels Bohr Institute, University of Copenhagen; A. de Ugarte Postigo, Instituto de Astrofisica de Andalucia and Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen; N. R. Tanvir, University of Leicester; G. Tagliaferri, Osservatorio Astronomico di Brera; J. Sollerman, Oskar Klein Centre, Stockholm University; D. Xu, Weizmann institute, Israel; M. D. Stritzinger, Institute of Physics and Astronomy, Aarhus University; and A. De Cia, University of Iceland, on behalf of the X-shooter GRB "guaranteed time observation" collaboration, report on monitoring the afterglow of the gamma-ray burst GRB 120422A (located at R.A. = 9h07m38s.38, Decl. = +14d01'07".5, equinox 2000.0; Troja et al., GCN 13243, accessible at website 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.
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