Perley 2009 GRB 071025 的光学余辉观测

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可能有超新星成分。
红移为5

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Title:		Evidence for Supernova-Synthesised Dust from the Rising Afterglow of GRB 071025 at z~5
Authors:		Perley, Daniel A.; Bloom, J. S.; Klein, C. R.; Covino, S.; Minezaki, T.; Wozniak, P.; Vestrand, W. T.; Williams, G. G.; Milne, P.; Butler, N. R.; Updike, A. C.; Krühler, T.; Afonso, P.; Antonelli, A.; Cowie, L.; Ferrero, P.; Greiner, J.; Hartmann, D. H.; Kakazu, Y.; Küpcü Yoldas, A.; Morgan, A. N.; Price, P. A.; Prochaska, J. X.; Yoshii, Y.
Publication:		eprint arXiv:0912.2999
Publication Date:		12/2009
Origin:		ARXIV
Keywords:		Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Cosmology and Extragalactic Astrophysics
Comment:		Resubmitted to MNRAS following referee report. Contains additional figure and some extra analysis/discussion
Bibliographic Code:		2009arXiv0912.2999P

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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