GRB 081203A: Swift UVOT captures the earliest ultraviolet spectrum of a gamma-ray burst

N.~P.~M. Kuin, W. Landsman, M.~J. Page, P. Schady, M. Still, A.~A. Breeveld, M. de Pasquale, P.~W.~A. Roming, P.~J. Brown, M. Carter, C. James, P.~A. Curran, A. Cucchiara, C. Gronwall, S.~T. Holland, E.~A. Hoversten, S. Hunsberger, T. Kennedy, S. Koch, H. LamoureuxF.~E. Marshall, S.~R. Oates, A. Parsons, D.~M. Palmer, P.~J. Smith

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32 Citations (Scopus)

Abstract

We present the earliest ultraviolet (UV) spectrum of a gamma-ray burst (GRB) as observed with the Swift Ultra-Violet/Optical Telescope (UVOT). The GRB 081203A spectrum was observed for 50 s with the UV-grism starting 251 s after the Swift-Burst-Alert-Telescope (BAT) trigger. During this time, the GRB was ≈13.4 mag (u filter) and was still rising to its peak optical brightness. In the UV-grism spectrum, we find a damped Lyα line, Lyβ and the Lyman continuum break at a redshift z= 2.05 ± 0.01. A model fit to the Lyman absorption implies a gas column density of log NH i= 22.0 ± 0.1 cm−2, which is typical of GRB host galaxies with damped Lyα absorbers. This observation of GRB 081203A demonstrates that for brighter GRBs (v≈ 14 mag) with moderate redshift (0.5 < z < 3.5) the UVOT is able to provide redshifts, and probe for damped Lyα absorbers within 4–6 min from the time of the Swift-BAT trigger.
Original languageEnglish
Pages (from-to)L21-L24
JournalMonthly Notices of the Royal Astronomical Society
Volume395
Issue number1
DOIs
Publication statusPublished - 1 May 2009

Keywords

  • instrumentation: spectrographs, gamma-rays: bursts, Astrophysics

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