Dust properties in afterglow of GRB 071025 at z~5
  At high redshift, the universe was so young that core-collapse supernovae
(SNe) are suspected to be the dominant source of dust production. However, some
observations indicate that the dust production by SNe is an inefficient
process, casting doubts on the existence of abundant SNe-dust in the early
universe. Recently, Perley et al. (2010) reported that the afterglow of GRB
071025 - an unusually red GRB at z ~ 5 - shows evidence for the SNe-produced
dust. Since this is perhaps the only high redshift GRB exhibiting compelling
evidence for SNe-dust but the result could easily be affected by small
systematics in photometry, we re-examined the extinction properties of GRB
071025 using our own optical/near-infrared data at a different epoch. In
addition, we tested SNe-dust models with different progenitor masses and dust
destruction efficiencies to constrain the dust formation mechanisms. By
searching for the best-fit model of the afterglow spectral energy distribution,
we confirm the previous claim that the dust in GRB 071025 is most likely to
originate from SNe. We also find that the SNe-dust model of 13 or 25M_{\odot}
without dust destruction fits the extinction property of GRB 071025 best, while
pair-instability SNe (PISNe) models with a 170M_{\odot} progenitor poorly fit
the data. Our results indicate that, at least in some systems at high redshift,
SNe with intermediate masses within 10 - 30M_{\odot} were the main contributors
for the dust enrichment, and the dust destruction effect due to reverse shock
was negligible.
