ABSTRACT. We present early observations of the afterglow of GRB 030329 and the spectroscopic discovery of its associated supernova SN 2003dh. We obtained spectra of the afterglow of GRB 030329 each night from March 30.12 (0.6 days after the burst) to April 8.13 (UT) (9.6 days after the burst). The spectra cover a wavelength range of 350-850 nm. The early spectra consist of a power-law continuum (F_ν ν^-0.9) with narrow emission lines originating from H II regions in the host galaxy, indicating a low redshift of z = 0.1687. However, our spectra taken after 2003 April 5 show broad peaks in flux characteristic of a supernova. Correcting for the afterglow emission, we find that the spectrum of the supernova is remarkably similar to the Type Ic "hypernova" SN 1998bw. While the presence of supernovae has been inferred from the light curves and colors of gamma-ray burst afterglows in the past, this is the first direct, spectroscopic confirmation that a subset of classical gamma-ray bursts originate from supernovae.

Subject headings: galaxies: distances and redshifts; gamma rays: bursts; supernovae: general; supernovae: individual (SN 2003dh)

^* Based on data from the Multiple Mirror Telescope Observatory 6.5 m telescope, the Magellan 6.5 m Clay telescope, and the Fred Lawrence Whipple Observatory 1.5 m telescope.

Print publication: Issue 1 (2003 July 1)
Received 2003 April 13, accepted for publication 2003 May 20
Published 2003 June 6