Electronic Telegram No. 2227 Central Bureau for Astronomical Telegrams INTERNATIONAL ASTRONOMICAL UNION CBAT Director: Daniel W. E. Green; Room 209; Dept. of Earth and Planetary Sciences; Harvard University; 20 Oxford St.; Cambridge, MA 02138; U.S.A. e-mail: cbat@iau.org; cbatiau@eps.harvard.edu URL http://www.cfa.harvard.edu/iau/cbat.html SUPERNOVA 2010bh = GRB 100316D F. Bufano, S. Benetti, and E. Cappellaro, Istituto Nazionale di Astrofisica (INAF), Osservatorio Astronomico di Padova (OAP); S. Covino, INAF, Osservatorio Astronomico di Brera (OAB); S. Vergani, Galaxie, Etoile, Physique, Instrumentation (GEPI), Observatoire de Paris, and Astroparticule et Cosmologie (APC), Universite Paris 7; P. Goldoni, APC, Universite Paris 7, and Service d'Astrophysique, Commissariat a l'Energie Atomique (CEA); M. Della Valle, INAF, Osservatorio di Capodimonte; E. Pian, INAF, Osservatorio Astronomico di Trieste; S. Campana and G. Tagliaferri, INAF, OAB; D. Malesani and J. Fynbo, Dark Cosmology Centre, University of Copenhagen; M. Turatto, INAF, Osservatorio Astronomico di Catania; F. Patat, European Southern Observatory (ESO); and P. Mazzali, INAF, OAP, on behalf of a larger collaboration, report that a high-dispersion optical spectrum (range 350-900 nm, resolution 0.02 nm) of the afterglow associated with GRB 100316D (cf. GCN 10496; visible at http://gcn.gsfc.nasa.gov/gcn3/10496.gcn3) was obtained with the Very Large Telescope (+ XShooter) at ESO/Paranal on Mar. 23.04 UT. The spectrum of the source located at R.A. = 7h10m31s.8 and Decl. = -56o15'20".2 (equinox 2000.0; as measured on the XShooter acquisition image) shows very broad bumps with peaks measured at about 430 and 670 nm, reminiscent of an emerging broadline type-Ic supernova (in agreement with Chornock et al., GCN 10541). Indeed, above 600 nm, the spectrum of this source shows some similarities with that of SN 1998bw (Patat et al. 2001, Ap.J. 555, 900) taken seven days after outburst. There are, however, major differences with the spectrum of this transient, showing a significant flux deficiency in the range 450-550 nm, in comparison with SN 1998bw. The designation 2010bh is assigned to this supernova. NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2010 CBAT 2010 March 24 (CBET 2227) Daniel W. E. Green