MODELS FOR THE TYPE Ⅰc HYPERNOVA SN 2003lw ASSOCIATED WITH GRB 031203

摘要

The gamma-ray burst GRB 031203 at a redshift z = 0.1055 revealed a highly reddened Type Ⅰc supernova, SN 2003lw, in its afterglow light. This is the third well-established case of a link between a long-duration GRB and a Type Ⅰc SN. The SN light curve is obtained by subtracting the galaxy contribution and is modeled together with two spectra at near-maximum epochs. A red VLT grism 1501 spectrum of the SN near peak is used to extend the spectral coverage, and in particular to constrain the uncertain reddening, the most likely value for which is E_(G+H)(B-V) approx = 1.07 ± 0.05. Accounting for reddening, SN 2003lw is ～0.3 mag brighter than the prototypical GRB-SN 1998bw. Light curve models yield a ~(56)Ni mass of ～0.55 solar mass. The optimal explosion model is somewhat more massive (M_(ej) ～ 13 solar mass)and more energetic (E ～ 6 x 10~(52) ergs) than the model for SN 1998bw, implying a massive progenitor (40-50 solar mass). The mass at high velocity is not very large (1.4 solar mass above 30,000 km s~(-1), but only 0.1 solar mass above 60,000 km s~(-1)), but it is sufficient to cause the observed broad lines. The similarity of SNe 2003lw and 1998bw and the weakness of their related GRBs, GRB 031203 and GRB 980425, suggest that both GRBs may be normal events viewed slightly off-axis or a weaker but possibly more frequent type of GRB.