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GCN Circular 2107

Subject
GRB 030329: Supernova Spectrum Emerging
Date
2003-04-07T01:54:45Z (21 years ago)
From
Krzysztof Z. Stanek at CfA <kstanek@cfa.harvard.edu>
T. Matheson (CfA), P. Garnavich (Notre Dame), N. Hathi, R. Jansen,
R. Windhorst, L. Echevarria (ASU), J. Lee (Arizona), W. Brown,
N. Caldwell, P. Berlind. M. Calkins and K. Z. Stanek (CfA) report:

We obtained spectra of the afterglow of GRB 030329 (Peterson & Price,
GCN 1985; Torii: GCN 1986) with the 6.5-m MMT and Blue-Channel
spectrograph each night from March 30.12 to April 6.15 (UT). The
spectra cover a wavelength range of 350 nm to 850 nm with a resolution
of 0.6 nm (FWHM). The early spectra consist of a power-law continuum
with narrow emission lines originating from HII regions in the host
galaxy (Martini et al. GCN 2013; Della Ceca et al. GCN 2015; Greiner
et al. GCN 2020; Caldwell et al. GCN 2053).  However, our spectrum
taken Apr. 6.15 (UT) shows a broad peak in flux at approximately 570
nm and another weak deviation from a power-law near 470nm that were
not evident in the earlier spectra.

The April 6 spectrum is well reproduced by adding a spectrum of SN
1998bw (Patat et al. 2001, ApJ, 555, 900) seven days before maximum
light to a power-law distribution. We conclude that a supernova
spectrum is emerging from the afterglow light.  The brightness of the
supernova is approximately V=22 based on the strengths of the broad
features relative to a pure power-law. Further spectroscopy is
planned.

A plot of the spectrum compared with SN 1998bw is available at:
http://cfa-www.harvard.edu/~tmatheson/grb030329_sn.jpg

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