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Evidence for supernova-synthesized dust from the rising afterglow of GRB 071025 at z∼ 5

D. A. PerleyDepartment of Astronomy, University of California, Berkeley, CA, 94720-3411, USAJ. S. BloomDepartment of Astronomy, University of California, Berkeley, CA, 94720-3411, USACourtney KleinDepartment of Astronomy, University of California, Berkeley, CA, 94720-3411, USAS. CovinoINAF – Osservatorio Astronomico di Brera, Via Bianchi 46, 23807 Merate (LC), ItalyTakeo MinezakiInstitute of Astronomy, School of Science, University of Tokyo, Mitaka, Tokyo 181‐0015, JapanP. R. WoźniakLos Alamos National Laboratory, Los Alamos, NM 87545, USAW. T. VestrandLos Alamos National Laboratory, Los Alamos, NM 87545, USAG. G. WilliamsSteward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ, 85721 USAPeter MilneSteward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ, 85721 USAN. ButlerDepartment of Astronomy, University of California, Berkeley, CA, 94720-3411, USAA. C. UpdikeDepartment of Physics and Astronomy Clemson University Clemson SC 29634-0978 USAT. KrühlerHigh Energy Astrophysics, MPI for Extraterrestrial Physics, Max Planck SocietyP. AfonsoHigh Energy Astrophysics, MPI for Extraterrestrial Physics, Max Planck SocietyL. A. AntonelliINAF/Rome Astronomical Observatory, Via Frascati 33, 00044 Monte Porzio (Roma), ItalyL. L. CowieP. FerreroInstituto de Astrofisica de Canarias, Via Lactea, s/n, 38200 La Laguna, Tenerife, SpainJ. GreinerMax Planck Institut für Extraterrestrische Physik, Giessenbachstraße, D-85748 Garching, GermanyD. H. HartmannDepartment of Physics and Astronomy Clemson University Clemson SC 29634-0978 USAY. KakazuInstitut d’Astrophysique de Paris, 98bis Bd Arago, F-75014, Paris, FranceA. YoldaşEuropean Southern Observatory, Karl-Schwarzschild Str.2, 85748 Garching, GermanyA. N. MorganDepartment of Astronomy, University of California, Berkeley, CA, 94720-3411, USAP. A. PriceJ. X. ProchaskaUCO/Lick Observatory, Department of Astronomy and Astrophysics, University of California, 1156 High Street, Santa Cruz, CA 95064, USAYuzuru YoshiiInstitute of Astronomy, School of Science, University of Tokyo, Mitaka, Tokyo 181‐0015, Japan

2010en

ABI

Annotatsiya

We present observations and analysis of the broad-band afterglow of Swift GRB 071025. Using optical and infrared (RIYJHK) photometry, we derive a photometric redshift of 4.4 < 5.2; at this redshift our simultaneous multicolour observations begin at ∼30 s after the gamma-ray burst trigger in the host frame, 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 0 ∼ 200. The red spectral energy distribution (even in regions not affected by the Lyman α break) provides secure evidence of a large dust column. However, the inferred extinction curve shows a prominent ﬂat component between 2000 and 3000 Å in the rest frame, inconsistent with any locally observed template but well ﬁtted 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 A3000 < 0.54 mag after t = 50 s in the rest frame. Together with studies of high-z quasars, our observations suggest a transition in dust properties in the early Universe, possibly associated with a transition between supernova-dominated and asymptotic giant branch-dominated modes of dust production.

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DOI: 10.1111/j.1365-2966.2010.16772.x

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