Evidence for Supernova-Synthesised Dust from the Rising Afterglow of GRB 071025 at z~5

Daniel A. Perley; J. S. Bloom; C. R. Klein; S. Covino; T. Minezaki; P. Wozniak; W. T. Vestrand; G. G. Williams; P. Milne; N. R. Butler; A. C. Updike; T. Krühler; P. Afonso; A. Antonelli; L. Cowie; P. Ferrero; J. Greiner; D. H. Hartmann; Y. Kakazu; A. Küpcü Yoldas; A. N. Morgan; P. A. Price; J. X. Prochaska; Y. Yoshii

doi:10.1111/j.1365-2966.2010.16772.x

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arXiv · 0912.2999

Evidence for Supernova-Synthesised Dust from the Rising Afterglow of GRB 071025 at z~5

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Abstract

We present observations and analysis of the broadband afterglow of Swift GRB 071025. Using optical and infrared (RIYJHK) photometry, we derive a photometric redshift of 4.4 < z < 5.2; at this redshift our simultaneous multicolour observations begin at ~30 s after the GRB trigger in the host frame and during the initial rising phase of the afterglow. We associate the light curve peak at 580 s in the observer frame with the formation of the forward shock, giving an estimate of the initial Lorentz factor Gamma_0 ~ 200. The red spectral energy distribution (even in regions not affected by the Lyman-alpha break) provides secure evidence of a large dust column. However, the inferred extinction curve shows a prominent flat component between 2000-3000 Angstroms in the rest-frame, inconsistent with any locally observed template but well-fit by models of dust formed by supernovae. Time-dependent fits to the extinction profile reveal no evidence of dust destruction and limit the decrease in the extinction column to Delta A_3000 < 0.54 mag after t = 50 s in the rest frame. Our observations provide evidence of a transition in dust properties at z~5, in agreement with studies of high-z quasars, and suggest that SN-formed dust continues to dominate the opacity of typical galaxies at this redshift.

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Daniel A. Perley, J. S. Bloom, C. R. Klein, S. Covino, T. Minezaki, P. Wozniak, W. T. Vestrand, G. G. Williams, P. Milne, N. R. Butler, A. C. Updike, T. Krühler, P. Afonso, A. Antonelli, L. Cowie, P. Ferrero, J. Greiner, D. H. Hartmann, Y. Kakazu, A. Küpcü Yoldas, A. N. Morgan, P. A. Price, J. X. Prochaska, Y. Yoshii. 2010-01-27. Evidence for Supernova-Synthesised Dust from the Rising Afterglow of GRB 071025 at z~5. https://doi.org/10.1111/j.1365-2966.2010.16772.x

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