The net optical light curves and spectra of the supernova ( SN ) 2003dh are obtained from the published spectra of GRB 030329 , covering about 6 days before SN maximum to about 60 days after .
The bulk of the U -band flux is subtracted from the observed spectra using early-time afterglow templates , because strong line blanketing greatly depresses the UV and U -band SN flux in a metal-rich , fast-moving SN atmosphere .
The blue-end spectra of the gamma-ray burst ( GRB ) connected hypernova SN 1998bw is used to determine the amount of subtraction .
The subtraction of a host galaxy template affects the late-time results .
The derived SN 2003dh light curves are narrower than those of SN 1998bw , rising as fast before maximum , reaching a possibly fainter maximum , and then declining \sim 1.2 - 1.4 times faster .
We then build UVOIR bolometric SN light curve .
Allowing for uncertainties , it can be reproduced with a spherical ejecta model of M _ { ej } \sim 7 \pm 3 M _ { \sun } , E _ { K } \sim 3.5 \pm 1.5 \times 10 ^ { 52 } ergs , with E _ { K } / M _ { ej } \sim 5 following previous spectrum modeling , and M ( ^ { 56 } { Ni } ) \sim 0.4 _ { -0.1 } ^ { +0.15 } M _ { \sun } .
This suggests a progenitor main-sequence mass of \sim 25 - 40 M _ { \sun } , lower than SN 1998bw but significantly higher than normal Type Ic SNe and the GRB-unrelated hypernova SN 2002ap .